KR102087398B1 - Polarizing film and polarizing plate comprising the same - Google Patents

Abstract

The present specification relates to a polarizing film and a polarizing plate including the same.

Description

POLARIZING FILM AND POLARIZING PLATE COMPRISING THE SAME}

The present invention relates to a polarizing film and a polarizing plate including the same.

The polarizing film is used in a display unit such as a liquid crystal display, an organic light emitting (EL) display, a plasma display panel (PDP), etc., and is required to have a high transmittance and a polarization degree in order to provide an image having excellent color reproducibility. Such a polarizing film may generally be prepared by dyeing a polyvinyl alcohol-based film using a dichroic dye or the like, crosslinking, and then oriented by a method such as uniaxial stretching.

Recently, image display apparatuses using polarizing films have been used in display units of televisions, monitors, automobile dashboards, computers, laptops, PDAs, telephones, TVs, audio / video devices, various office and industrial machines. As the use area of the display unit expands as described above, a case in which the display unit is used under severe conditions such as high temperature and high humidity is increasing. In addition, in order to improve the durability of the display unit, a cover glass is attached to the polarizing film as a protective glass. However, as the cover glass is attached, a heat flux applied to the polarizing film is increased, thereby causing a problem that the polarizing film with the cover glass is discolored in red color under high temperature conditions.

Therefore, in order to provide a display unit that can be continuously used even in high temperature conditions, a situation that requires a polarizing film having excellent durability and heat resistance.

The present invention relates to a polarizing film and a polarizing plate including the same.

One embodiment of the present invention is a polyvinyl alcohol-based polarizing film, is prepared by stretching an unstretched polyvinyl alcohol-based film, the polyvinyl alcohol-based polarizing film comprises potassium and zinc, satisfying the following equation It provides a polyvinyl alcohol polarizing film.

[Equation 1]

In Equation 1, d is the thickness of the unstretched polyvinyl alcohol-based film (μm) / 60 ㎛, r is potassium content (wt%) / the polyvinyl alcohol-based polarized light in the polyvinyl alcohol-based polarizing film When the zinc content (wt%) in the film, and d is 1 or more, the potassium content in the polyvinyl alcohol polarizing film is 0.5 wt% or more.

Another embodiment of the present invention is a polarizing film according to an embodiment of the present invention; It provides a polarizing plate comprising a; protective film provided on at least one surface of the polarizing film.

Another embodiment of the present invention includes a display panel and a polarizing plate according to another embodiment of the present invention, and provides a display unit having the polarizing plate on at least one surface of the display panel.

According to one embodiment of the present invention, by adjusting the content of potassium and zinc contained in the polarizing film, it can implement a polarizing film excellent in durability and heat resistance.

According to another embodiment of the present invention, the polarizing plate comprises a polarizing film according to an embodiment of the present invention, it can retain excellent optical properties, heat resistance, durability even at high temperature conditions.

When any part of the specification is to "include" any component, this means that it may further include other components, except to exclude other components unless specifically stated otherwise. In addition, when a member is located "on" another member, this includes not only when one member is in contact with another member but also when another member exists between the two members.

Hereinafter, this specification is demonstrated in detail.

One embodiment of the present invention is a polyvinyl alcohol-based polarizing film, is prepared by stretching an unstretched polyvinyl alcohol-based film, the polyvinyl alcohol-based polarizing film comprises potassium and zinc, satisfying the following equation It provides a polyvinyl alcohol polarizing film.

[Equation 1]

In Equation 1, d is the thickness of the unstretched polyvinyl alcohol-based film (μm) / 60 ㎛, r is potassium content (wt%) / the polyvinyl alcohol-based polarized light in the polyvinyl alcohol-based polarizing film When the zinc content (wt%) in the film, and d is 1 or more, the potassium content in the polyvinyl alcohol polarizing film is 0.5 wt% or more.

According to one embodiment of the present invention, by adjusting the content of potassium and zinc contained in the polyvinyl alcohol polarizing film, it can implement a polarizing film excellent in durability and heat resistance.

According to an embodiment of the present invention, by adjusting the content of potassium and zinc contained in the polyvinyl alcohol-based polarizing film, the thickness of the unstretched polyvinyl alcohol-based film, the value of the following equation 2 is 0.7 or more and 0.95 or less Can be adjusted to Specifically, the value of Equation 2 may be 0.8 or more and 0.95 or less, 0.85 or more and 0.9 or less, and more specifically 0.89 or more and 0.92 or less.

[Equation 2]

According to an embodiment of the present invention, the polyvinyl alcohol-based polarizing film satisfies Equation 1, it is possible to prevent the color of the polyvinyl alcohol-based polarizing film is changed even at high temperature, the polyvinyl alcohol-based It can prevent that the polarization degree of a polarizing film falls. Specifically, when the value of Equation 2 is less than 0.7, the polarization degree of the polyvinyl alcohol-based polarizing film is lowered, a problem may occur that the transmittance is increased. In addition, when the value of Equation 2 exceeds 0.95, a problem may occur in which the color of the polyvinyl alcohol polarizing film is rapidly changed under high temperature conditions.

According to an embodiment of the present invention, the polyvinyl alcohol-based polarizing film may be prepared by stretching the unstretched polyvinyl alcohol-based film. Specifically, the polyvinyl alcohol-based polarizing film may be prepared by performing a processing process such as a dyeing step, a crosslinking step, a stretching step, a washing step, a drying step, and a zinc salt treatment step on the unstretched polyvinyl alcohol-based film. Can be. However, the dyeing, crosslinking, and stretching steps may be performed individually or simultaneously, and the order of each step is also variable, and the order of the process steps is not fixed. By processing the unstretched polyvinyl alcohol-based film to prepare the polyvinyl alcohol-based polarizing film, potassium and zinc may be included in the polyvinyl alcohol-based polarizing film.

According to an embodiment of the present invention, the process of processing the unstretched polyvinyl alcohol-based film may include dyeing the unstretched polyvinyl alcohol-based film. Specifically, the dyeing step may dye the unstretched polyvinyl alcohol-based film with a dichroic dye containing iodine and potassium iodide. As the dichroic dye is dyed to the unstretched polyvinyl alcohol-based film, the unstretched polyvinyl alcohol-based film absorbs light vibrating in the stretching direction and transmits light vibrating in the vertical direction in a specific vibration direction. It can hold the polarization characteristic having. By dyeing the unstretched polyvinyl alcohol-based film with a dichroic dye, the polyvinyl alcohol-based polarizing film may contain iodine and potassium.

According to an embodiment of the present invention, the dyeing step may be immersed in the unstretched polyvinyl alcohol-based film in a dyeing solution containing a dichroic dye. The dye solution may include a solvent and a dichroic dye. Water may be used as the solvent, a mixture of water and an organic solvent having compatibility with water may be used. By adjusting the concentration of the dichroic dye contained in the dyeing solution, it is possible to control the content of iodine and potassium dyeing on the unstretched polyvinyl alcohol-based film, it is possible to control the transmittance of the polyvinyl alcohol-based polarizing film have.

According to an embodiment of the present invention, the content of iodine contained in the dyeing solution may be adjusted to 0.001% by weight or more and 0.3% by weight or less, and the content of potassium iodide to 0.3% by weight or more and 3.5% by weight or less. Specifically, the content of the iodine may be adjusted to 0.005% by weight or more and 0.2% by weight or less, and the content of the potassium iodide may be adjusted to 0.5% or more and 3.0% by weight or less.

The content of the iodine contained in the dye solution may be adjusted to 0.001% by weight or more and 0.3% by weight or less, so that the polyvinyl alcohol-based polarizing film may have an appropriate transmittance. In addition, by adjusting the content of the potassium iodide contained in the dyeing solution to 0.3% by weight or more and 3.5% by weight or less, the amount of potassium iodide is insufficient to prevent the problem that iodine and potassium are not properly dissolved in the dyeing solution and In addition, it is possible to prevent foreign substances from occurring in the dyeing solution due to the solubility of potassium iodide itself in water.

In addition, by further adding an adjuvant of a dichroic dye to the dyeing solution, the dyeing efficiency of the unstretched polyvinyl alcohol-based film can be improved. Iodine has a low solubility in water, and by adding an adjuvant such as an iodide compound that can improve the solubility of iodine, the dyeing efficiency of the unstretched polyvinyl alcohol-based film can be improved. The iodide compound which may be used as the adjuvant may include one or more selected from the group consisting of lithium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide.

According to one embodiment of the present invention, the step of dyeing may be immersed in the dyeing solution of the unstretched polyvinyl alcohol-based film 20 ° C or more and 40 ° C or less for 30 seconds or more and 120 seconds or less. By adjusting the temperature of the dyeing solution to 20 ° C or more and 40 ° C or less, the dyeing efficiency can be improved, and the amount of iodine can be reduced by preventing iodine from sublimation. Further, by immersing the unstretched polyvinyl alcohol-based film in the dyeing solution for 30 seconds or more and 120 seconds or less, dyeing of the unstretched polyvinyl alcohol-based film can be made uniform.

According to an embodiment of the present invention, the process of processing the unstretched polyvinyl alcohol-based film may include crosslinking the unstretched polyvinyl alcohol-based film. By crosslinking the unstretched polyvinyl alcohol-based film, a dichroic dye may be adsorbed onto the polyvinyl alcohol polymer matrix of the polyvinyl alcohol-based film. The crosslinking may be performed by immersing the unstretched polyvinyl alcohol-based film in a crosslinking solution containing boron and potassium iodide or by applying or spraying a crosslinking solution to crosslink the unstretched polyvinyl alcohol-based film. By adjusting the contents of boron and potassium iodide contained in the crosslinking solution, it is possible to prevent the deterioration of the stretchability of the unstretched polyvinyl alcohol-based film, and to prevent boron and potassium adsorbed onto the unstretched polyvinyl alcohol-based film. And iodine content.

According to one embodiment of the present invention, the content of boron contained in the crosslinking solution may be adjusted to 0.1 wt% or more and 2.0 wt% or less, and the content of potassium iodide to 1.0 wt% or more and 7.0 wt% or less. Specifically, the boron content may be adjusted to 0.2 wt% or more and 1.5 wt% or less, and the content of potassium iodide may be adjusted to 2.0 wt% or more and 5.0 wt% or less.

The content of the boron contained in the crosslinking solution is adjusted to 0.1 wt% or more and 2.0 wt% or less, so that the unstretched polyvinyl alcohol-based film is not sufficiently crosslinked, thereby reducing optical properties and durability of the polyvinyl alcohol-based polarizing film. Can be prevented. In addition, by adjusting the content of the potassium iodide included in the cross-linking solution to 1.0% by weight or more to 7.0% by weight or less, the phenomenon that the color of the polyvinyl alcohol-based polarizing film changes and the phenomenon that the polarization degree is lowered effectively can do.

According to one embodiment of the present invention, the step of crosslinking may be immersed in the cross-linking solution of the unstretched polyvinyl alcohol-based film 20 ° C or more and 40 ° C or less for 30 seconds or more and 120 seconds or less. By adjusting the temperature of the said crosslinking liquid to 20 degreeC or more and 40 degrees C or less, the stretchability of the said unstretched polyvinyl alcohol-type film can be improved. Further, by immersing the unstretched polyvinyl alcohol-based film in the crosslinking solution for 30 seconds or more and 120 seconds or less, crosslinking may be uniformly performed on the unstretched polyvinyl alcohol-based film, and the polyvinyl alcohol-based polarizing film It can prevent that optical property falls.

According to one embodiment of the present invention, the process of processing the unstretched polyvinyl alcohol-based film may include stretching the unstretched polyvinyl alcohol-based film. In the stretching step, the unstretched polyvinyl alcohol-based film may be stretched uniaxially so that the polyvinyl alcohol polymers of the unstretched polyvinyl alcohol-based film are oriented in a predetermined direction. As the unstretched polyvinyl alcohol-based film is stretched, molecules of dichroic dye are arranged side by side in the stretch direction in the polyvinyl alcohol-based film, and the stretched polyvinyl alcohol-based film vibrates in the stretch direction Absorbs light and vibrates in a vertical direction.

According to one embodiment of the present invention, the stretching may be performed by a conventional method of stretching an unstretched polyvinyl alcohol-based film in the art. Specifically, the stretching may be a wet stretching method or a dry stretching method, and may be used in combination if necessary. The dry stretching method may be an inter-roll stretching method, a heating roll stretching method, a compression stretching method, a tenter stretching method, or the like. As the wet stretching method, a tenter stretching method, Inter-roll stretching method etc. can be used.

According to one embodiment of the present invention, the stretching may be performed by stretching the unstretched polyvinyl alcohol-based film at a stretching ratio of 4.0 times to 6.5 times. If the stretching ratio of the unstretched polyvinyl alcohol-based film is less than 4 times, there is a problem that the stretching of the polyvinyl alcohol-based polarizing film is insufficient, and if the stretching ratio exceeds 6.5 times, the polyvinyl alcohol-based polarization due to excessive stretching. The film may be broken or the orientation of the polyvinyl alcohol molecules may be misaligned, thereby causing a problem of deterioration in optical properties of the polyvinyl alcohol polarizing film.

According to one embodiment of the present invention, the stretching may be performed simultaneously with the dyeing or crosslinking, or may be performed separately. When the stretching step is performed separately using a wet stretching method, the unstretched polyvinyl alcohol-based film may be immersed in a stretching solution of 35 ° C. or more and 65 ° C. or less and stretched for 60 seconds or more and 120 seconds or less. . By adjusting the temperature of the soft liquor to 35 ° C. or higher and 65 ° C. or lower, the stretching efficiency of the unstretched polyvinyl alcohol-based film can be improved.

When the stretching step is performed at the same time as the dyeing step, the unstretched polyvinyl alcohol-based film may be immersed in a dyeing solution to dye and stretch the unstretched polyvinyl alcohol-based film. In addition, when the stretching step is performed at the same time as the crosslinking step, the unstretched polyvinyl alcohol-based film may be immersed in a crosslinking solution to crosslink the stretched polyvinyl alcohol-based film.

According to one embodiment of the present invention, the zinc in the polyvinyl alcohol-based polarizing film is derived from a zinc salt containing one or more selected from the group consisting of zinc nitrate, zinc chloride, zinc iodide, zinc acetate and zinc sulfate It may have been. By including zinc in the polyvinyl alcohol polarizing film, the polyvinyl alcohol polarizing film may be improved in heat resistance and durability.

According to one embodiment of the present invention, the process of processing the polyvinyl alcohol-based film may include the step of adsorbing a zinc salt on the polyvinyl alcohol-based film. By adsorbing a zinc salt on the polyvinyl alcohol-based film, zinc may be adsorbed onto the polyvinyl alcohol polymer matrix of the polyvinyl alcohol-based film. The zinc salt may include one or more selected from the group consisting of zinc nitrate, zinc chloride, zinc iodide, zinc acetate and zinc sulfate.

The step of adsorbing the zinc salt may be carried out simultaneously with the step of dyeing, crosslinking or stretching, or may be performed separately. When the step of adsorbing the zinc salt is performed separately, the polyvinyl alcohol-based film may be immersed in the solution containing the zinc salt. The content of the zinc salt may be 0.4 wt% or more and 12 wt% or less with respect to the total weight of the solution. Specifically, the content of the zinc salt may be 1 wt% or more and 10 wt% or less, 1.5 wt% or more and 8 wt% or less, more specifically 1.5 wt% or more and 2.5 wt% or less, 7.5 wt% based on the total weight of the solution. It may be up to 9% by weight.

By adjusting the content of the zinc salt contained in the solution, it is possible to control the content of zinc adsorbed on the polyvinyl alcohol-based film. In addition, the amount of the zinc salt contained in the solution may be different depending on the type of the zinc salt. For example, when using zinc nitrate as the zinc salt and using zinc sulfate, even if the content of zinc nitrate contained in the solution and the content of zinc sulfate contained in the solution is different, the polyvinyl alcohol polarized light The amount of zinc contained in the film may be similar.

In addition, when the step of adsorbing the zinc salt is performed at the same time as the dyeing, crosslinking or stretching step, the zinc salt may be added to the above-described dyeing solution, crosslinking solution or stretching solution, the dyeing solution, crosslinking solution Alternatively, the zinc salt content in the stretching solution may be 0.4 wt% or more and 12 wt% or less.

According to one embodiment of the present invention, potassium in the polyvinyl alcohol-based polarizing film may be derived from a potassium salt containing potassium iodide. Specifically, the potassium in the polyvinyl alcohol polarizing film may be derived from potassium iodide contained in the dyeing solution and / or crosslinking solution. In the process of dyeing and crosslinking the unstretched polyvinyl alcohol-based film, potassium may be included in the unstretched polyvinyl alcohol-based film. In addition, potassium may be adsorbed to the polyvinyl alcohol-based film in the step of adsorbing the zinc salt to the polyvinyl alcohol-based film by adding potassium salt to the solution containing the zinc salt.

According to an embodiment of the present invention, the processing of the polyvinyl alcohol-based film may include washing the polyvinyl alcohol-based film. The washing may be performed after the dyeing, crosslinking, stretching and zinc salt treatment of the unstretched polyvinyl alcohol-based film. In the washing step, the polyvinyl alcohol-based film is immersed in ion-exchanged water or distilled water at 20 ° C. or higher and 30 ° C. or lower for 10 seconds to 30 seconds to remove foreign substances remaining on the surface of the polyvinyl alcohol-based film. can do.

According to an embodiment of the present invention, the processing of the polyvinyl alcohol-based film may include drying the polyvinyl alcohol-based film. After washing the polyvinyl alcohol-based film, the polyvinyl alcohol-based film may be dried. Specifically, the washed polyvinyl alcohol-based film may be placed in an oven, and dried at a temperature of 40 ° C. or more and 100 ° C. or less for 10 seconds or more and 500 seconds or less. By drying the polyvinyl alcohol-based film at a temperature of 40 ° C or more and 100 ° C or less, it is possible to prevent wrinkles from occurring in the polyvinyl alcohol-based film due to insufficient drying of moisture remaining in the polyvinyl alcohol-based film. In addition, the polyvinyl alcohol-based film is excessively dried can effectively prevent the durability is lowered.

According to one embodiment of the present invention, the thickness of the unstretched polyvinyl alcohol-based film may be 5 μm or more and 300 μm or less. Specifically, the thickness of the unprocessed polyvinyl alcohol-based film may be 10 μm or more and 200 μm or less, 15 μm or more and 100 μm or less. By using an unstretched polyvinyl alcohol-based film having a thickness of 5 µm or more and 300 µm or less, the polyvinyl alcohol-based film needs to be thin in the process of manufacturing the polarizing film by processing the polyvinyl alcohol-based film. The durability of the polarizing film can be prevented from being lowered.

According to an embodiment of the present invention, the potassium content may be 0.1 wt% or more and 2.0 wt% or less with respect to the total weight of the polyvinyl alcohol polarizing film. Specifically, the potassium content may be 0.3 wt% or more, 1.5 wt% or less, 0.4 wt% or more and 0.9 wt% or less, and more specifically 0.45 wt% or more and 0.55 wt% or less, based on the total weight of the polyvinyl alcohol polarizing film. 0.75 wt% or more and 0.85 wt% or less. By adjusting the content of the potassium contained in the polyvinyl alcohol-based polarizing film in the above range, it is possible to effectively prevent the color change of the polyvinyl alcohol-based polarizing film at a high temperature, the polyvinyl alcohol-based polarizing film The polarization degree can be prevented from falling.

According to an embodiment of the present invention, when d is 1 or more, the potassium content in the polyvinyl alcohol polarizing film may be 0.5 wt% or more. D is a value obtained by dividing the thickness (μm) of the unstretched polyvinyl alcohol-based film by 60 μm. When the thickness of the unstretched polyvinyl alcohol-based film used to prepare the polyvinyl alcohol-based polarizing film is 60 μm or more, the content of potassium contained in the polyvinyl alcohol-based polarizing film is determined by the polyvinyl alcohol-based polarizing film. By being 0.5 wt% or more with respect to the total weight, it is possible to prevent the durability and heat resistance of the polyvinyl alcohol-based polarizing film is reduced.

According to an embodiment of the present invention, the zinc content may be 0.1 wt% or more and 0.5 wt% or less with respect to the total weight of the polyvinyl alcohol polarizing film. Specifically, the zinc content may be 0.12 wt% or more, 0.3 wt% or less, 0.14 wt% or more and 0.2 wt% or less, and more specifically 0.14 wt% or more, based on the total weight of the polyvinyl alcohol polarizing film. 0.2 wt% or more and 0.35 wt% or less. By adjusting the content of the zinc contained in the polyvinyl alcohol-based polarizing film in the above range, the polyvinyl alcohol-based polarizing film can effectively prevent the color change at high temperature, excellent durability and heat-resistant polyvinyl alcohol The polarizing film can be provided.

According to an embodiment of the present invention, the polyvinyl alcohol polarizing film may have a thickness of 3 μm or more and 200 μm or less. The thickness of the polyvinyl alcohol-based polarizing film processed through the steps of dyeing, crosslinking, stretching, etc., from the unstretched polyvinyl alcohol-based film may be 3 μm or more and 200 μm or less. The polyvinyl alcohol polarizing film having a thickness of 3 μm or more and 200 μm or less has excellent durability.

According to one embodiment of the present invention, the polyvinyl alcohol polarizing film may have a light transmittance of 40% or more and 50% or less. Specifically, the polyvinyl alcohol-based polarizing film is excellent in heat resistance, even when exposed to 105 ℃ temperature conditions for 100 hours, may have a light transmittance of 40% or more and 50% or less, there is an advantage in excellent optical properties.

Another embodiment of the present invention is a polarizing film according to an embodiment of the present invention; It provides a polarizing plate comprising a; protective film provided on at least one surface of the polarizing film.

According to another embodiment of the present invention, the polarizing plate comprises a polarizing film according to an embodiment of the present invention, it can retain excellent optical properties, heat resistance, durability even at high temperature conditions.

According to another embodiment of the present invention, the protective film may be provided on one side or both sides of the polarizing film. The protective film is to protect the polarizing film from foreign matter or impact introduced from the outside, the protective film may be attached to one or both sides of the polarizing film through an adhesive film or an adhesive.

According to another embodiment of the present invention, the protective film may have a thickness of 10 μm or more and 200 μm or less. Specifically, the thickness of the protective film may be 20 ㎛ or more and 100 ㎛ or less. By providing a protective film having a thickness in the above range on one side or both sides of the polarizing film, the polarizing film can be protected from foreign matter or impact that can be introduced from the outside, it can provide a polarizing plate with excellent durability.

According to another embodiment of the present invention, the protective film may be any one selected from the group consisting of acrylic film, cellulose film, polyolefin film, polyester film. Specifically, a triacetyl cellulose film which is a cellulose-based film may be used as the protective film.

According to another embodiment of the present invention, the polarizing plate may be provided on at least one surface of the polarizing plate, and may include a cover glass having a thickness of 20 μm or more and 1,000 μm or less. The cover glass may be attached to one side or both sides of the polarizing plate through an adhesive film or an adhesive. Specifically, the cover glass may be attached on the protective film provided in the polarizing film. By adhering the cover glass whose thickness is 20 micrometers or more and 1,000 micrometers or less to one surface or both surfaces of the said polarizing plate, durability of the said polarizing plate can be improved more.

Another embodiment of the present invention includes a display panel and a polarizing plate according to another embodiment of the present invention, and provides a display unit having the polarizing plate on at least one surface of the display panel. The polarizing plate can be effectively suppressed from changing color even at high temperature, the display unit including the polarizing plate has an advantage of excellent heat resistance.

Hereinafter, the present invention will be described in more detail with reference to the following examples. These examples are merely illustrative and are not intended to limit the invention.

Preparation of Polarizing Film

Example  One

A polyvinyl alcohol (PVA) film having a thickness of 30 µm (Japan Synthetic Co., Ltd., M2004) was immersed in a dyeing solution at 30 ° C. containing 0.05% by weight of iodine and 1.5% by weight of potassium iodide for 60 seconds for dyeing treatment. . The dyed polyvinyl alcohol film was crosslinked by dipping for 60 seconds in a 30 ° C crosslinking solution containing 0.5% by weight of boron and 3.0% by weight of potassium iodide. Thereafter, the crosslinked polyvinyl alcohol film was stretched at a draw ratio of 5.5 times by using an inter-roll stretching method. The stretched polyvinyl alcohol film was washed with water for 20 seconds by immersion in 30 ° C. ion-exchanged water, and then immersed in a 30 ° C. solution containing 1.5% by weight of zinc nitrate and 4.0% by weight of potassium iodide for 10 seconds. Thereafter, the polyvinyl alcohol film was dried at a temperature of 80 ° C. for 200 seconds to prepare a polarizing film.

Example  2

A polarizing film was prepared in the same manner as in Example 1, except that a polyvinyl alcohol film having a thickness of 60 μm was prepared and a 30 ° C. solution containing 2.0% by weight of zinc nitrate and 5.5% by weight of potassium iodide was prepared.

Example  3

A polarizing film was prepared in the same manner as in Example 1, except that a solution including 8.0 wt% of zinc sulfate and 6.0 wt% of potassium iodide was prepared.

Comparative example  One

A polarizing film was prepared in the same manner as in Example 1, but the polarizing film was prepared by immersing in a 30 ° C. solution containing 5.0 wt% of potassium iodide without zinc salt for 10 seconds.

Comparative example  2

A polarizing film was prepared in the same manner as in Example 1, except that a polyvinyl alcohol film having a thickness of 60 μm was prepared and a solution containing 13.0 wt% of zinc nitrate and 3.5 wt% of potassium iodide was prepared.

Comparative example  3

A polarizing film was prepared in the same manner as in Example 1, except that a solution including 0.3 wt% zinc nitrate and 5.0 wt% potassium iodide was prepared.

Analysis of potassium and zinc content in polarizing film

Content of potassium and zinc contained in the polarizing films according to Examples 1 to 3 and the polarizing films according to Comparative Examples 1 to 3 using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) Was analyzed. The analysis results are shown in Table 1 below.

Heat resistance analysis of polarizing film

Attaching a triacetyl cellulose film having a thickness of 40 ㎛ on both sides of the polarizing film according to Examples 1 to 3 and the polarizing film according to Comparative Examples 1 to 3 as a protective film, the triacetyl cellulose film A cover glass having a thickness of 700 μm was attached onto the acrylic adhesive to form a polarizing plate.

The light transmittance of the prepared polarizing plate was measured, and the light transmittance after the prepared polarizing plate was placed in an oven at 105 ° C. for 100 hours was measured. The light transmittance of the polarizing film included in the polarizing plate was measured using V-7100 (JASCO Co., Ltd.). The light transmittance of the polarizing film is shown in Table 1 below.

In addition, the prepared polarizing plate was placed in an oven at a temperature of 105 ° C., and the time point at which the polarizing film contained in the polarizing plate was discolored was observed. The time point at which the polarizing film is discolored is shown in Table 1 below.

PVA
thickness
(Μm) potassium
content
(weight%) zinc
content
(weight%)

Early
% Light transmittance 105 ℃,
100 hours
% Light transmittance Discoloration
(day) Example 1 30 0.47 0.17 0.90 42.51 42.46 6 Example 2 60 0.80 0.17 0.89 42.76 42.53 6 Example 3 30 0.49 0.14 0.92 42.44 42.05 5 Comparative Example 1 30 0.73 0.00 - 42.63 6.97 2 Comparative Example 2 60 0.35 1.21 0.49 42.35 79.22 One Comparative Example 3 30 0.60 0.02 0.99 42.56 31.09 3

Referring to Table 1, the discoloration time of the polarizing film according to Examples 1 to 3 of the present invention is 5 days to 6 days, the discoloration time of the polarizing film according to Comparative Examples 1 to 3 is 1 day to It can be confirmed that it is 3 days. Accordingly, the polarizing films according to Examples 1 to 3 of the present invention have a later time of discoloration under high temperature conditions than the polarizing films according to Comparative Examples 1 to 3, thereby confirming excellent heat resistance.

In addition, referring to Table 1, the polarizing films according to Examples 1 to 3 of the present invention can be seen that the initial transmittance and the transmittance under high temperature conditions are not significantly different, Comparative Examples 1 to 3 The polarizing film according to the present invention can be seen that the transmittance at high temperature is much different from the initial light transmittance. Therefore, it can be confirmed that the polarizing films according to Examples 1 to 3 of the present invention have excellent optical properties even at high temperature conditions than the polarizing films according to Comparative Examples 1 to 3.

Claims (9)

As polyvinyl alcohol polarizing film,
Prepared by stretching an unstretched polyvinyl alcohol-based film,
The polyvinyl alcohol polarizing film includes potassium and zinc, polyvinyl alcohol polarizing film that satisfies the following equation 1:
[Equation 1]

In Equation 1,
d is the thickness of the unstretched polyvinyl alcohol-based film (μm) / 60 μm,
r is potassium content (wt%) in the polyvinyl alcohol polarizing film / zinc content (wt%) in the polyvinyl alcohol polarizing film,
When the d is 1 or more, the potassium content in the polyvinyl alcohol polarizing film is 0.5 wt% or more,
The zinc content is 0.14 wt% or more and 0.17 wt% or less with respect to the total weight of the polyvinyl alcohol polarizing film. The method according to claim 1,
The polyvinyl alcohol polarizing film of which the thickness of the unstretched polyvinyl alcohol-based film is 5 μm or more and 300 μm or less. The method according to claim 1,
The potassium content of the polyvinyl alcohol polarizing film is 0.1 wt% or more and 2.0 wt% or less with respect to the total weight of the polyvinyl alcohol polarizing film. delete The method according to claim 1,
The polyvinyl alcohol polarizing film is a polyvinyl alcohol polarizing film having a thickness of 3 ㎛ or more and 200 ㎛ or less. The method according to claim 1,
The polyvinyl alcohol polarizing film has a light transmittance of 40% or more and 50% or less,
The light transmittance is polyvinyl alcohol-based polarizing film measured by V-7100 (JASCO, Inc.). The method according to claim 1,
Zinc in the polyvinyl alcohol polarizing film is a polyvinyl alcohol polarizing film derived from zinc salt containing one or more selected from the group consisting of zinc nitrate, zinc chloride, zinc iodide, zinc acetate and zinc sulfate. . Polarizing film according to claim 1; And
And a protective film provided on at least one surface of the polarizing film. The method according to claim 8,
Polarizing plate further comprises a cover glass provided on at least one surface of the polarizing plate.