KR20150008681A - Preparing method for polarizer - Google Patents

Abstract

The present invention relates to a polarizer manufacturing method. The polarizer manufacturing method includes a step of dry-stretching a polarizer forming film at the temperature of 50 to 150 °C by 2.5 to 6 times before a wet process during the manufacturing process of the polarizer to reduce the breakage and manufacture polarizers which have excellent heat resistance and moisture resistance and are capable of minimizing the color change under hot and humid conditions.

Description

[0001] Preparing method for polarizer [0002]

The present invention relates to a method for producing a polarizer.

In general, a polarizing plate used in an image display apparatus is required to have a high transmittance and a high degree of polarization in order to provide a bright and reproducible image with good color reproducibility. Such a polarizing plate is conventionally produced by dying a polyvinyl alcohol (PVA) film using dichromatic iodine or a dichroic dye, and orienting it by a method such as uniaxial drawing.

Conventionally, an image display apparatus using a polarizing plate is mainly used in small-sized products such as an electronic calculator and a clock, but recently it has been used in almost all industrial fields such as a television, a monitor, an automobile instrument panel, various office use, As the area of use is expanded, there are many cases where it is required to be used for a long time under severe conditions such as high temperature and high humidity. However, the polyvinyl alcohol polarizers of the polarizing plate are thermodynamically unstable, vulnerable to moisture, and may undergo dimensional changes and breakage. Since the TAC protective film has a large moisture absorption rate and moisture permeability, the polarizing function is degraded in a high temperature and high humidity environment .

Korean Patent Publication No. 2008-74511 discloses a polarizing element and a polarizing plate excellent in durability and a manufacturing method thereof.

Korean Patent Publication No. 2008-74511

SUMMARY OF THE INVENTION The present invention aims to provide a method of manufacturing a polarizer capable of minimizing the breakage of a polarizer.

An object of the present invention is to provide a method for producing a polarizer which is excellent in heat resistance and moisture resistance and can minimize color change under high temperature and high humidity conditions.

An object of the present invention is to produce a polarizer excellent in durability.

It is an object of the present invention to provide a method of manufacturing a polarizing plate including such a polarizer.

1. A process for producing a polarizer wherein a film for forming a polarizer is dry-stretched at a temperature of 50 to 150 DEG C at a temperature of 2.5 to 6 times before a wet process in the production process of the polarizer.

2. The method of producing a polarizer according to 1 above, wherein the dry stretching is performed by an inter-roll stretching method, a heating roll stretching method, or a compression stretching method.

3. The method of producing a polarizer according to item 1 above, wherein the stretching ratio in the dry stretching is 60% or more of the total cumulative stretching ratio in the manufacturing process.

4. The method of producing a polarizer according to 1 above, wherein the water content of the polarizer-forming film is 1 to 10% by weight.

5. The method of producing a polarizer according to 1 above, wherein the water content of the polarizer-forming film is 2 to 8 wt%.

6. The method of producing a polarizer according to 1 above, wherein the wet process comprises dyeing, crosslinking and stretching.

7. The method of producing a polarizer according to 6 above, wherein said crosslinking step is carried out by immersing in an aqueous crosslinking solution containing a metal nitrate.

8. The method of claim 7, wherein the metal is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, silver, magnesium, calcium, strontium, barium, copper, zinc, iron, cobalt, nickel, ruthenium, rhodium, palladium, zirconium, At least one polarizer selected from the group consisting of aluminum, gallium, indium, titanium, lanthanum, cerium, europium, gadolinium, yttrium, neodymium, samarium, praseodymium, thulium, erbium, tin, vanadium, chromium, molybdenum and manganese Gt;

9. The method of producing a polarizer according to 7, wherein the metal nitrate is contained in an amount of 0.1 to 10% by weight based on the total weight of the aqueous crosslinking solution.

10. The method of producing a polarizer according to 6 above, wherein said stretching is carried out at a stretching ratio of 1 to 1.5 times.

11. The method of manufacturing a polarizer according to claim 6, further comprising a swelling step performed before the dyeing step.

12. A method for producing a polarizer, comprising the steps of: preparing a polarizer by the method according to any one of claims 1 to 11; And bonding a protective film to at least one side of the polarizer.

The present invention can produce a polarizer with minimum breakage.

The present invention can produce a polarizer that is excellent in heat resistance and moisture resistance and can minimize color change under high temperature and high humidity conditions.

The present invention can produce a polarizer with improved crosslinking efficiency and improved durability.

The present invention relates to a process for producing a polarizer by dry stretching a film for forming a polarizer at a temperature of 50 to 150 DEG C 2.5 to 6 times prior to a wet process in a polarizer manufacturing process to suppress breakage and to exhibit excellent heat resistance and moisture resistance, To a method for producing a polarizer capable of producing a polarizer that can be minimized.

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

The polarizer-producing method of the present invention dry-stretches the polarizer-forming film 2.5 to 6 times before the wet process in the manufacturing process.

By performing dry stretching before the wet process, the present invention can suppress the breakage of the polarizer and significantly improve the heat resistance and moisture resistance of the polarizer, thereby minimizing color change under high temperature and high humidity.

The dry stretching according to the present invention can be carried out at a stretching ratio of 2.5 to 6 times, and preferably at a stretching ratio of 3 to 5 times. When dry stretching is carried out at a stretching ratio of 2.5 to 6 times, it is possible to maximize the effect of suppressing fracture, improving heat resistance and moisture resistance.

The ratio of the stretching ratio in the dry stretching to the total cumulative stretching ratio in the manufacturing process is not particularly limited and may be, for example, 60% or more, preferably 80% or more, and the upper limit is not particularly limited. When the elongation of 60% or more is carried out in dry stretching, the effect of suppressing breakage, heat resistance and moisture resistance can be maximized.

The dry stretching method is not particularly limited as long as the dry stretching can be performed by a dry method, and a dry method commonly used in the art can be used. For example, an inter-roll stretching method, a heating roll stretching method , A compression stretching method, and the like. The heating roll stretching method can be preferably used in view of easiness of stretching by applying heat directly to the film.

The first stretching according to the present invention may be carried out at 50 to 150 ° C, preferably at 80 to 150 ° C in view of maximizing the effect of suppressing breakage due to sufficient stretching, improving the heat resistance and moisture resistance.

When stretching by the heating roll stretching method, the temperature is the temperature of the roll.

In this respect, the moisture content of the film for forming a polarizer may be, for example, 1 to 10% by weight, preferably 2 to 8% by weight, more preferably 3 to 5% by weight. When the moisture content of the film for forming a polarizer is 1 to 10% by weight, it is possible to maximize the effects of suppressing breakage due to dry drawing, improving heat resistance and moisture resistance.

The type of the polarizer-forming film according to the present invention is not particularly limited as long as it is a dichroic substance, that is, a film which can be dyed with iodine. Examples thereof include 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 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 iodine.

The thickness of the film for forming a polarizer is not particularly limited, and may be, for example, 40 to 80 탆.

The method for producing the polarizer of the present invention includes a wet process performed after the dry stretching.

The wet process is not particularly limited and may be a wet process commonly used in the art for polarizer production, and may be a process including, for example, swelling, dyeing, crosslinking, stretching, washing, drying and the like. The order of each process, the number of repetitions, the process conditions, and the like are not particularly limited as long as they do not deviate from the object of the present invention. For example, the stretching step may be performed before, after, or after the dyeing step, and may be performed simultaneously with at least one step selected from the group consisting of a swelling step, a dyeing step and a crosslinking step.

Hereinafter, according to one embodiment of the present invention, the wet process will be described step by step in more detail.

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

Water (pure water, deionized water) can usually be used as a swelling aqueous solution, 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 and potassium iodide is not particularly limited and may be, for example, 5 wt% or less and 10 wt% or less, respectively, in the total weight of the aqueous swelling solution.

The temperature of the swelling bath is not particularly limited, and may be, for example, 20 to 70 캜, preferably 25 to 55 캜. When the temperature of the swelling bath is 20 to 70 캜, the stretching and dyeing efficiency is excellent thereafter, and expansion of the film due to excessive swelling can be prevented.

The execution time (swelling bath immersion time) of the swelling step is not particularly limited, and may be, for example, 180 seconds or less, preferably 90 seconds or less. It is possible to prevent excessive swelling and saturation when the immersion time is 180 seconds or less, to prevent breakage due to softening of the polyvinyl alcohol-based film and to improve the polarization degree by uniformly adsorbing iodine in the dyeing step have.

The swelling step may be omitted and the swelling may be performed simultaneously in the staining step.

The dyeing step is a step of dipping the polarizing film in a dyeing bath filled with a dyeing aqueous solution containing a dichroic substance, for example, iodine, to adsorb iodine to the polarizing film.

The dyeing aqueous solution may comprise water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine in the dyeing aqueous solution may be 0.4 to 400 mmol / L, preferably 0.8 to 275 mmol / L, more preferably 1 to 200 mmol / L.

The dyeing aqueous solution may further contain iodide as a solubilizing aid for improving the dyeing efficiency.

The kind of iodide is not particularly limited and includes, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like , And potassium iodide is preferred in view of high solubility in water. These may be used alone or in combination of two or more.

The content of iodide is not particularly limited and may be, for example, 0.01 to 10% by weight, preferably 0.01 to 5% by weight, based on the total weight of the dyeing aqueous solution.

The temperature of the dye bath is not particularly limited and may be, for example, from 5 to 42 캜, preferably from 10 to 35 캜.

The immersing time of the film for forming a polarizer in the dyeing tank is not particularly limited and may be, for example, 1 to 20 minutes, preferably 2 to 10 minutes.

The cross-linking step is a step of immersing the dyed polarizer-forming film in a crosslinking aqueous solution so as to fix the adsorbed iodine molecules so that the dyeability due to physically adsorbed iodine molecules is not lowered 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.

The aqueous solution for crosslinking may further comprise water as a solvent and a boron compound such as boric acid or sodium borate, and may further comprise an organic solvent mutually soluble with water.

The boron compound imparts rigidity to the polarizer-forming film to suppress the occurrence of wrinkles in the process, thereby improving the handling property and forming the iodine orientation.

The content of the boron compound is not particularly limited and may be, for example, 1 to 10% by weight, and preferably 2 to 8% by weight, based on the total weight of the aqueous crosslinking solution.

The aqueous crosslinking solution may further contain a small amount of iodide to obtain the uniformity of the degree of polarization in the plane of the polarizer.

The iodide may be the same as that used in the dyeing step.

The content of iodide is not particularly limited and may be, for example, 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on the total weight of the aqueous crosslinking solution. If the content of iodide is less than 0.05% by weight, iodide ions in the film may escape to increase the transmittance and change the color of the polarizer. If the content of iodide exceeds 15% by weight, iodide ions in the aqueous solution may permeate into the film, .

The aqueous crosslinking solution according to the present invention may further comprise a metal nitrate.

The metal nitrate improves the crosslinking efficiency by forming a chelate structure between the metal and the polyvinyl alcohol, thereby improving the durability of the polarizer and minimizing the color change under high temperature and high humidity.

The metal is not particularly limited as long as it can react with nitric acid to form a salt. Examples of the metal include lithium, sodium, potassium, rubidium, cesium, silver, magnesium, calcium, strontium, barium, copper, zinc, iron, cobalt, nickel A rare earth element such as ruthenium, rhodium, palladium, zirconium, platinum, aluminum, gallium, indium, titanium, lanthanum, cerium, europium, gadolinium, yttrium, neodymium, samarium, praseodymium, thulium, erbium, tin, vanadium, chromium, molybdenum, Copper, aluminum, magnesium, sodium, zirconium and the like in terms of economy and process efficiency. These may be used alone or in combination of two or more.

The content of the metal nitrate is not particularly limited and may be, for example, 0.1 to 10% by weight, preferably 0.5 to 7% by weight, based on the total weight of the aqueous crosslinking solution. When the content of the metal nitrate is 0.1 to 10% by weight, the effect of improving the durability of the polarizer can be maximized.

The temperature of the crosslinking bath is not particularly limited, and may be, for example, 20 to 75 캜.

The immersion time of the polarizer-forming film in the crosslinking bath may be from 1 second to 15 minutes, and preferably from 5 seconds to 10 minutes.

The order of the stretching step is not particularly limited, and may be performed before, after, or after the dyeing step, and may be performed simultaneously with at least one step selected from the group consisting of a swelling step, a dyeing step and a crosslinking step .

The stretching ratio of the stretching step is not particularly limited, and may be, for example, 1 to 1.5 times the cumulative stretching ratio in the wet process. When the cumulative stretching ratio is within the above range, the effect of suppressing breakage of the polarizer and improving the durability can be maximized. In the present specification, "cumulative stretching ratio" represents the value of the product of the stretching ratio at each step.

The method for producing a polarizer of the present invention may further include a washing step.

The washing step is a step of immersing the crosslinked and stretched polarizer forming film in a water bath filled with aqueous solution for washing to remove unnecessary residues such as boric acid attached to the polarizing film in the previous steps.

The aqueous solution for washing may be water (deionized water), and iodide may be further added thereto. As the iodide, those same as those used in the dyeing step can be used, and among them, sodium iodide or potassium iodide is preferably used. The content of iodide is not particularly limited and may be, for example, 0.1 to 10% by weight, preferably 3 to 8% by weight, based on the total weight of the aqueous solution for washing.

The temperature of the water bath is not particularly limited and can be, for example, 5 to 60 ° C, and preferably 10 to 40 ° C. When the temperature of the water bath is within the above range, the effect of suppressing breakage and improving durability can be maximized.

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

The method for producing the polarizer of the present invention may further comprise a drying step.

The drying step is a step of drying the washed polyvinyl alcohol-based film and further improving the orientation of the iodine molecules dyed by the necking by drying, thereby obtaining a polarizer excellent in optical characteristics.

Examples of the drying method include natural drying, air drying, heat drying, far-infrared drying, microwave drying, hot air drying and the like.

The drying temperature is not particularly limited and may be, for example, 20 to 90 ° C, preferably 30 to 80 ° C, more preferably 30 to 60 ° C. When the drying temperature is 20 to 90 ° C, the effect of improving the breakage suppression and improving the durability can be maximized.

The drying time is not particularly limited and can be suitably performed so that the polarizer can be sufficiently dried, and can be performed, for example, for 1 to 10 minutes.

The present invention also provides a method of manufacturing a polarizer, comprising: preparing a polarizer according to the method; And bonding a protective film to at least one surface of the polarizer.

The protective film is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. Specifically, polyester films such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate; Cellulose-based films such as diacetylcellulose and triacetylcellulose; Polycarbonate-based films; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene-based films such as polystyrene and acrylonitrile-styrene copolymer; Polyolefin films; Vinyl chloride film; Polyamide-based films such as nylon and aromatic polyamide; Imidazole film; Sulfone based films; Polyether ketone-based films; A sulfided polyphenylene-based film; Vinyl alcohol film; Vinylidene chloride films; Vinyl butyral film; Allylate-based films; Polyoxymethylene-based films; Urethane-based films; Epoxy-based films; Silicone-based films, and the like. Among them, a cellulose-based film having a surface saponified (saponified) by alkali or the like is preferable in consideration of polarization characteristics or durability. The protective film may also have an optical compensation function such as a retardation function.

The thickness of the protective film is not particularly limited, and may be, for example, 10 to 200 mu m.

The bonding may be made of an adhesive commonly used in the art of polarizing plate manufacture and may be at least one selected from the group consisting of isocyanate-based, polyvinyl alcohol-based, gelatin-based, vinyl polymer-based latex and water- May be an adhesive.

After the bonding, a drying step is carried out. The drying time is not particularly limited, and may be, for example, 20 to 1200 seconds.

The drying temperature is 60 to 90 占 폚, preferably 75 to 85 占 폚. When the drying temperature is within the above range, the durability is improved and the effect of minimizing the color change even under high temperature and high humidity is maximized.

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. Polarizer  Produce

An unstretched polyvinyl alcohol film (VF-PS, Kuraray Co., Ltd.) having a degree of saponification of 99.9% or more and a transparent thickness of 75 탆 was humidified to have a water content of 4%. Thereafter, the first stretching was conducted at a draw ratio of 4.5 times by a hot roll stretching method of 120 占 폚, followed by immersion in water (deionized water) at 50 占 폚 for one minute to swell. Then, it was dipped in an aqueous solution for dyeing at 30 DEG C containing 5.0 mmol / L of iodine and 4% by weight of potassium iodide for 1 minute for dyeing. At this time, stretching was performed at 0.9 times and 1.1 times at the swelling and dyeing steps, respectively.

Subsequently, the resultant was immersed in a crosslinking aqueous solution at 70 DEG C containing 10 wt% of potassium iodide and 7 wt% of boric acid for 3 minutes to crosslink. In the crosslinking step, it was stretched to 1.2 times. After the crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 70 DEG C for 4 minutes to prepare a polarizer.

Example  2. Polarizer  Produce

A polarizer was produced in the same manner as in Example 1 except that the stretching ratio of the first stretching step was 5 times.

Example  3. Polarizer  Produce

A polarizer was produced in the same manner as in Example 1, except that the polyvinyl alcohol film (VF-PS, Kuraray Co., Ltd.) was humidified to have a water content of 2%.

Example  4. Polarizer  Produce

A polarizer was produced in the same manner as in Example 1, except that the polyvinyl alcohol film (VF-PS, Kuraray Co., Ltd.) was humidified to have a water content of 6%.

Example  5. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1 except that the aqueous solution for crosslinking contained 3 wt% of zinc nitrate.

Example  6. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 5, except that the stretching was performed at the crosslinking step.

Example  7. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 5, except that the stretching was performed at the crosslinking step.

Example  8. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1 except that the aqueous solution for crosslinking contained 0.5 wt% of zinc nitrate.

Example  9. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the aqueous crosslinking solution contained 15 wt% of zinc nitrate.

Example  10. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the aqueous solution for crosslinking contained 3 wt% of sodium nitrate.

Example  11. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1 except that the aqueous solution for crosslinking contained 3 wt% of magnesium nitrate.

Example  12. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the aqueous crosslinking solution contained 0.05 wt% of zinc nitrate.

Example  13. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the polyvinyl alcohol film (VF-PS, Kuraray Co., Ltd.) was humidified to have a water content of 0.5%.

Example  14. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the polyvinyl alcohol film (VF-PS, Kuraray Co., Ltd.) was humidified to have a water content of 11%.

Comparative Example  One. Polarizer  Produce

Polarizers were prepared in the same manner as in Example 1, except that the first stretching was not performed, and the stretching was performed at 1.3 times, 1.3 times, and 3.17 times at the swelling, dyeing and crosslinking steps, respectively.

Comparative Example  2. Polarizer  Produce

Polarizers were prepared in the same manner as in Example 1, except that the stretching ratio in the first stretching step was doubled, and the stretching ratios in the swelling, dyeing and crosslinking stages were 1, 1.1, and 2.45 times, respectively.

Comparative Example  3. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1, except that the stretching ratio in the first stretching step was 7 times, the stretching ratio in the swelling, dyeing and crosslinking steps was 1, 1.1, and 1, respectively.

Comparative Example  4. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1 except that the temperature of the roll was changed to 40 캜 at the time of the first stretching.

Comparative Example  5. Polarizer  Produce

A polarizer was prepared in the same manner as in Example 1 except that the temperature of the roll was changed to 160 캜 during the first stretching.

Experimental Example  One.

(One) Break rate  evaluation

The processes of the above-described Examples and Comparative Examples were repeated 10 times to measure the number of times the polarizer was broken during 10 manufacturing processes to calculate the breaking rate. The results are shown in Table 1 below.

(2) Measurement of transmittance

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

[Equation 1]

 The degree of polarization P = [(T1 - T2) / (T1 + T2)] / 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 in a state in which the absorption axes are orthogonal).

This is shown in Table 1 below.

division Break frequency Breaking rate (%) Transmittance (%) Polarization degree (%) Example 1 0 0 42.5 99.992 Example 2 0 0 42.4 99.993 Example 3 0 0 42.1 99.993 Example 4 0 0 42.4 99.993 Example 5 0 0 42.5 99.992 Example 6 0 0 42.5 99.992 Example 7 One 10 41.4 99.993 Example 8 0 0 42.7 99.992 Example 9 0 0 42.7 99.992 Example 10 0 0 42.5 99.992 Example 11 0 0 42.4 99.993 Example 12 0 0 42.5 99.991 Example 13 One 10 42.7 99.991 Example 14 One 10 42.8 99.990 Comparative Example 1 4 30 43.0 99.992 Comparative Example 2 3 30 43.2 99.931 Comparative Example 3 4 40 41.1 99.922 Comparative Example 4 3 30 42.8 98.815 Comparative Example 5 3 30 42.9 99.991

Referring to Table 1, the polarizers of Examples 1 to 12 were not broken at all during the ten-time production process. In Examples 13 and 14 in which the moisture content of the polyvinyl alcohol film was outside the preferred range of the present invention, the breaking rate was excellent as 10%.

The transmittance and the degree of polarization were similar to those of the comparative example.

However, the polarizers of Comparative Examples 1 to 5 had a failure rate of 30 to 40%.

Experimental Example  2.

(1) Heat resistance / Humidity Durability  evaluation

The spectral transmittances τ (λ) of the polarizers of Examples 5 to 12 and Comparative Examples 1 to 5 before and after being left for 30 minutes at 105 ° C. and 85 ° C. humidity 85% were measured with a spectrophotometer (V7100, manufactured by Nippon Bunko K.K.) The spectral transmittance spectrum was obtained, and an orthogonal color b and an A700 expressed by the following formula (2) were obtained.

&Quot; (2) "

A700 = - Log ₁₀ {(TMD * TTD) / 10000}

(Wherein TMD is a parallel transmittance at a wavelength of 700 nm obtained when a pair of polarizing plates are arranged in parallel with the absorption axis, and TTD is a transmittance at a wavelength of 700 nm obtained when the pair of polarizing plates are arranged in a state in which the absorption axis is orthogonal Lt; / RTI >

(2) Evaluation of color change

Two polarizers prepared in Examples 5 to 12 and Comparative Examples 1 to 5 were perpendicularly crossed with each other and the backlight was turned on in the dark room to confirm the dark state at the initial stage. After standing at 105 ° C for 30 minutes, ) State, and visually confirmed whether the color change (occurrence of side effects) occurred.

The experimental results are shown in Table 2 below.

division Heat resistance Wet heat color
Change A700 △ Orthogonal b A700 △ Orthogonal b Example 5 0.5 0.4 0.4 0.4 radish Example 6 0.6 0.4 0.5 0.4 radish Example 7 0.5 0.3 0.4 0.3 radish Example 8 0.5 0.5 0.5 0.4 radish Example 9 1.0 0.8 1.0 0.8 radish Example 10 0.7 0.5 0.8 0.4 radish Example 11 0.8 0.4 1.0 0.5 radish Example 12 1.0 1.0 1.1 0.9 radish Comparative Example 1 1.5 1.2 1.7 1.2 U Comparative Example 2 1.5 1.0 1.7 1.1 U Comparative Example 3 1.2 1.0 1.3 1.0 U Comparative Example 4 2.0 1.0 2.1 1.0 U Comparative Example 5 1.3 1.1 1.4 1.1 U

Referring to Table 1, the polarizers of Examples 5 to 12 exhibited excellent heat resistance and heat and humidity resistance due to a small rate of change of orthogonal color even after the heat treatment, so that no side stiction occurred.

However, in the polarizers of Comparative Examples 1 to 5, the orthogonal hue greatly changed after the heat treatment, and the heat resistance and the heat and humidity resistance were poor, so that the red light occurred.

Claims (12)

Wherein the polarizer-forming film is dry-stretched at a temperature of 50 to 150 ° C at a temperature of 2.5 to 6 times before the wet process in the production process of the polarizer.
The method of claim 1, wherein the dry stretching is performed by an inter-roll stretching method, a heating roll stretching method, or a compression stretching method.
The method of manufacturing a polarizer according to claim 1, wherein the stretching ratio in the dry stretching is 60% or more of the total stretching ratio in the manufacturing process.
The polarizer according to claim 1, wherein the polarizer-forming film has a water content of 1 to 10% by weight.
The polarizer according to claim 1, wherein the polarizer-forming film has a moisture content of 2 to 8 wt%.
The method of claim 1, wherein the wet process comprises dyeing, crosslinking and stretching.
7. The method according to claim 6, wherein the crosslinking step is carried out by immersing in a crosslinking aqueous solution containing a metal nitrate.
The method of claim 7, wherein the metal is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, silver, magnesium, calcium, strontium, barium, copper, zinc, iron, cobalt, nickel, ruthenium, rhodium, palladium, zirconium, At least one polarizer selected from the group consisting of gallium, indium, titanium, lanthanum, cerium, europium, gadolinium, yttrium, neodymium, samarium, praseodymium, thulium, erbium, tin, vanadium, chromium, molybdenum and manganese .
[12] The method of claim 7, wherein the metal nitrate is contained in an amount of 0.1 to 10% by weight based on the total weight of the aqueous crosslinking solution.
7. The method of claim 6, wherein the stretching step is performed at a stretching ratio of 1 to 1.5 times.
7. The method of claim 6, further comprising a swelling step performed prior to the dyeing step.
A method for manufacturing a polarizer, comprising the steps of: preparing a polarizer by the method according to any one of claims 1 to 11; And
And bonding a protective film to at least one surface of the polarizer.