阅读说明：本技术 偏振板及包括其的光学显示装置 (Polarizing plate and optical display device including the same ) 是由 曹成万 高门甫 金起龙 罗莲周 赵恩率 于 2020-03-03 设计创作，主要内容包括：提供了：偏振板,其包括锌阳离子和包含化学式1的偏振器,并且其中式1的色差变化△E的量为约5.2或更小；和包括该偏振板的光学显示装置。(Provided is a method for producing: a polarizing plate comprising zinc cations and a polarizer comprising chemical formula 1, and wherein the amount of color difference change Δ E of chemical formula 1 is about 5.2 or less; and an optical display device including the polarizing plate.)

1. A polarizing plate, which includes a polarizer,

the polarizer includes zinc cations and a unit represented by the following formula 1:

[ formula 1]

(wherein is a site of attachment,

r is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

n is an integer of 10 to 100,000, m is an integer of 0 to 10),

wherein the polarizer has a color difference change Δ E of about 5.2 or less as calculated according to equation 1:

[ equation 1]

△E＝[(△L)²+(△a*)²+(△b*)²]^1/2

(wherein. DELTA.L is L₂-L₁(ii) a Δ a is (a)₂-(a*)₁(ii) a And Δ b is (b)_2-(b*)₁Wherein L is₁Is the L value of the initial polarizing plate; l is₂Is the L value of the polarizing plate after the polarizing plate is left at about 95 ℃ for about 500 hours; (a)₁Is the a value of the initial polarizing plate; (a)₂Is the a value of the polarizer plate after the polarizer plate is left at about 95 ℃ for about 500 hours; (b)₁Is the b value of the initial polarizing plate; and (b)₂Is b value of the polarizing plate after the polarizing plate is left at about 95 ℃ for about 500 hours).

2. The polarizing plate of claim 1 wherein the zinc cations comprise divalent zinc cations.

3. The polarizing plate of claim 1, wherein the zinc cations are present in the polarizer in an amount from about 10ppm to about 5,000 ppm.

4. The polarizing plate of claim 1, wherein the units represented by formula 1 are present in an amount greater than about 0 wt% and less than or equal to about 35 wt%.

5. The polarizing plate of claim 1, wherein the polarizer comprises a crosslinked product of a zinc salt of an organic acid.

6. The polarizing plate of claim 5, wherein the zinc cation and the unit represented by formula 1 are derived from a zinc salt of an organic acid or a crosslinked product of a zinc salt of an organic acid.

7. The polarizing plate of claim 5, wherein the zinc salt of an organic acid comprises a salt of a zinc cation and an organic acid anion represented by the following formula 2:

[ formula 2]

CH₂＝CR-(CH₂)_m-(C＝O)-O^-

(wherein R is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

m is an integer of 0 to 10).

8. The polarizing plate of claim 5, wherein the zinc salt of an organic acid comprises at least one of zinc (meth) acrylate and zinc 10-undecenoate.

9. The polarizing plate of claim 5, wherein the crosslinked product of the zinc salt of an organic acid comprises a UV cured product of the zinc salt of an organic acid.

10. The polarizing plate of claim 1, wherein the polarizer comprises a photo radical initiator.

11. The polarizing plate of claim 1, wherein the polarizer is free of at least one of zinc salts of inorganic acids, zinc halide salts, and zinc salts of organic acids having no photocurable functional group.

12. The polarizing plate of claim 1, wherein the polarizer is free of at least one of inorganic acid anions, halogenated anions, and organic acid anions having no photocuring functional groups.

13. The polarizing plate of claim 1, further comprising: a protective layer stacked on at least one side of the polarizer.

14. An optical display device comprising the polarizing plate according to any one of claims 1 to 13.

Technical Field

The present invention relates to a polarizing plate and an optical display device including the same. More particularly, the present invention relates to a polarizing plate having good properties in terms of durability, optical reliability and appearance even after being left at high temperature for a long period of time, and an optical display device including the same.

Background

The polarizing plate may include a polarizer and a protective layer stacked on at least one surface of the polarizer. Polarizing plates are used in optical display devices, and may be inevitably exposed to high temperature and/or high temperature/humidity conditions for long periods of time. The polarization of the polarizing plate is mainly achieved by a polarizer in the polarizing plate. The polarizer was manufactured by uniaxially stretching an iodine-colored polyvinyl alcohol film. However, when the polarizing plate is left to stand at high temperature for a long period of time, it may undergo yellowing and poor durability.

In order to improve heat resistance of the polarizing plate, zinc may be added to the polarizer. In this case, however, the polarizing plate may suffer deterioration of the degree of polarization and transmittance at high temperature due to migration of zinc to the surface of the polarizer. Alternatively, a crosslinking agent may be added to the polyvinyl alcohol film constituting the polarizer to crosslink the hydroxyl groups in the polyvinyl alcohol film. In this case, however, the stretched polyvinyl alcohol film may suffer from axial deformation, thereby causing deterioration of optical properties.

The background art of the present invention is disclosed in Korean patent laid-open No. 10-2016-.

Disclosure of Invention

Technical problem

It is an object of the present invention to provide a polarizing plate having good durability even after being left for a long period of time under high temperature and/or high temperature/high humidity conditions.

Another aspect of the present invention is to provide a polarizing plate having good optical properties and appearance even after being left for a long period of time under high temperature and/or high temperature/high humidity conditions.

Another aspect of the present invention is to provide a polarizing plate that can simply and economically realize good properties in terms of durability, optical properties, and appearance even after being left at high temperatures for a long period of time.

Technical solution

One aspect of the present invention is a polarizing plate.

1. The polarizing plate includes a polarizer including zinc cations and a unit represented by the following formula 1:

[ formula 1]

(wherein is a site of attachment,

r is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

n is an integer of 10 to 100,000, m is an integer of 0 to 10),

wherein the polarizing plate has a color difference change Δ E of about 5.2 or less as calculated according to equation 1:

[ equation 1]

△E＝[(△L)²+(△a*)²+(△b*)²]^1/2

(wherein. DELTA.L is L₂-L₁(ii) a Δ a is (a)₂-(a*)₁(ii) a And Δ b is (b)₂-(b*)₁Wherein L is₁Is the L value of the initial polarizing plate; l is₂Is the L value of the polarizing plate after the polarizing plate is left at about 95 ℃ for about 500 hours; (a)₁Is the a value of the initial polarizing plate; (a)₂Is the a value of the polarizing plate after the polarizing plate was left at about 95 ℃ for about 500 hours; (b)₁Is the b value of the initial polarizing plate; and (b)₂B x value of the polarizing plate after the polarizing plate was left at about 95 ℃ for about 500 hours).

2. In embodiment 1, the zinc cation may include a divalent zinc cation.

3. In embodiments 1 to 2, the zinc cations may be present in the polarizer in an amount of about 10ppm to about 5,000 ppm.

4. In embodiments 1 to 3, the unit represented by formula 1 may be present in an amount of more than about 0 wt% and about 35 wt% or less.

5. In embodiments 1 to 2, the polarizer may include a crosslinked product of a zinc salt of an organic acid.

6. In embodiment 5, the zinc cation and the unit represented by formula 1 are derived from a zinc salt of an organic acid or a crosslinked product of a zinc salt of an organic acid.

7. In embodiments 5 to 6, the zinc salt of an organic acid may include a salt of a zinc cation and an organic acid anion represented by the following formula 2:

[ formula 2]

CH₂＝CR-(CH₂)_m-(C＝O)-O^-

(wherein R is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

m is an integer of 0 to 10).

8. In embodiments 5 to 7, the zinc salt of an organic acid may include at least one of zinc (meth) acrylate and zinc 10-undecylenate.

9. In embodiments 5 to 8, the crosslinked product of the zinc salt of an organic acid may include a UV-cured product of the zinc salt of an organic acid.

10. In embodiments 1 to 9, the polarizer may include a photo radical initiator.

11. In embodiments 1 to 10, the polarizer may be free of at least one of an inorganic acid zinc salt, a zinc halide salt, and an organic acid zinc salt having no photocurable functional group.

12. In embodiments 1 to 11, the polarizer may be free of at least one of an inorganic acid anion, a halogenated anion, and an organic acid anion having no photocurable functional group.

13. In embodiments 1 to 12, the polarizing plate further includes a protective layer stacked on at least one side of the polarizer.

The optical display device of the present invention includes the above polarizing plate of the present invention.

Advantageous effects

The present invention provides a polarizing plate having good durability even after being left for a long period of time under high temperature and/or high temperature/high humidity conditions.

The present invention provides a polarizing plate having good optical properties and appearance even after being left for a long period of time under high temperature and/or high temperature/high humidity conditions.

The present invention provides a polarizing plate that can simply and economically realize good properties in terms of durability, optical properties, and appearance even after being left at high temperatures for a long period of time.

Best mode for carrying out the invention

Hereinafter, embodiments of the present invention will be described in detail with respect to the accompanying drawings so that those having ordinary knowledge in the art can easily implement the present invention. It is to be understood that the present invention is not limited to the following embodiments and may be embodied in various forms.

Herein, the color difference change (Δ E) is a value calculated according to equation 1:

[ equation 1]

△E＝[(△L)²+(△a*)²+(△b*)²]^1/2

(wherein. DELTA.L is L₂-L₁(ii) a Δ a is (a)₂-(a*)₁(ii) a And Δ b is (b)₂-(b*)₁Wherein L is₁Is the L value of the initial polarizing plate; l is₂Is the L value of the polarizing plate after the polarizing plate is left at about 95 ℃ for about 500 hours; (a)₁Is the a value of the initial polarizing plate; (a)₂Is the a value of the polarizing plate after the polarizing plate was left at about 95 ℃ for about 500 hours; (b)₁Is the b value of the initial polarizing plate; and (b)₂B x value of the polarizing plate after the polarizing plate was left at about 95 ℃ for about 500 hours).

Herein, the term "initial polarizing plate" means a polarizing plate before the polarizing plate is left at about 95 ℃ for about 500 hours. L, a and b represent color space values according to CIE1976 and can be measured using a spectrophotometer (e.g., CM-3600A, Konica Minolta Co., Ltd.), but is not limited thereto.

As used herein, "X to Y" is used to mean a numerical range of "X or more to Y or less" or "X ≦ and ≦ Y".

As used herein, the term "(meth) acryl" refers to acryl and/or methacryl.

The present inventors have found that the smaller the Δ E value according to equation 1 after the polarizer is left at a high temperature for a long time, the occurrence of yellowing of the polarizer at a high temperature can be minimized and the polarizing plate can have excellent durability, so that it can be suitably used for an optical display device.

Accordingly, the present inventors applied a polarizer containing zinc cations and a unit represented by the following formula 1 to a polarizing plate. The polarizing plate may achieve a color difference change Δ E of about 5.2 or less as calculated according to equation 1. The polarizing plate having Δ E of about 5.2 or less in equation 1 may have high reliability at high temperature and/or high temperature and high humidity. Further, the present inventors have completed the present invention by: it was confirmed that the orientation of the polyvinyl alcohol resin in the polarizer was not changed even after the polarizing plate was left to stand at a high temperature for a long time, whereby the polarizing plate had an extremely low polarization degree change and a low light transmittance change even after the polarizing plate was left to stand at a high temperature for a long time, and thus the polarizing plate could obtain excellent optical properties and reliability.

Hereinafter, a polarizing plate according to one embodiment of the present invention will be described.

The polarizing plate of the present invention includes a polarizer and a first protective layer stacked on an upper surface of the polarizer. The upper surface of the polarizer may be a light incident surface of the polarizer or a light exiting surface of the polarizer.

The polarizing plate has a color difference change Δ E of about 5.2 or less as calculated according to equation 1. Within this range, the polarizing plate may have good durability and may be suitably used in an optical display device, thereby improving the lifespan of the optical display device and providing economic benefits. For example, the polarizing plate may have a color difference change Δ E of about 0 to about 5.2 according to equation 1.

The polarizing plate may have a change in degree of polarization Δ P of about 1.5% or less, for example, about 0% to about 1.5% according to equation 2, and a change in light transmittance Δ T of about 2% or less, for example, about 0% to about 2% according to equation 3. Within this range, the polarizing plate may have good durability and may be suitably used in an optical display device, thereby improving the lifespan of the optical display device and providing economic benefits.

[ equation 2]

△P＝|P₂-P₁|

(wherein P is₁Is the degree of polarization of the initial polarizing plate, and P₂Is the polarization of the polarizing plate after the polarizing plate is left at about 95 ℃ for about 500 hoursVibration level).

[ equation 3]

△T＝|T₂-T₁|

(wherein T is₁Is the light transmittance of the initial polarizing plate, and T₂Is the light transmittance of the polarizing plate after the polarizing plate is left at about 95 c for about 500 hours).

In equations 2 and 3, the degree of polarization and the transmittance are expressed in%, respectively. Herein, the term "initial polarizing plate" means a polarizing plate before the polarizing plate is left at about 95 ℃ for about 500 hours.

In one embodiment, in equation 2, P₁And P₂Each of which may be about 90% or more, e.g., about 95% or more, about 95% to about 100%, respectively. In one embodiment, in equation 3, T₁And T₂Each of which may be about 40% or more, e.g., about 40% or more, about 40% to about 50%, respectively. Within these ranges, the polarizing plate may be suitably used in an optical display device, and the screen quality may not be deteriorated even after the polarizing plate is left at a high temperature.

Next, the polarizer of the present invention will be described in more detail.

When applied to an optical display, the polarizer polarizes light, thereby improving visibility and screen quality.

The polarizer may include a polarizer formed of a polyvinyl alcohol film. For example, the polarizer may include a polyvinyl alcohol-based polarizer obtained by dyeing a polyvinyl alcohol film with iodine or the like or a polyene-based polarizer obtained by dehydrating a polyvinyl alcohol film.

The polarizer may have a thickness of about 5 μm to about 50 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm, specifically, about 5 μm to about 30 μm. Within this thickness range, polarizers may be used in the optical display.

The polarizer contains zinc cations. The zinc cations have a function of blocking heat, and thus if the polarizer or polarizing plate is placed at a high temperature, the zinc cations can prevent external heat from being transferred to polarizationInside the device. In addition, zinc cations may form chelates with hydroxyl groups of the polarizer, thereby preventing iodide ion (I)₅ ^-Or I₃ ^-) Sublimes and thus prevents yellowing, so that the durability of the polarizing plate can be improved.

The zinc cation may be present at about 10ppm to 5,000ppm, for example, 10ppm, 50ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, 450ppm, 500ppm, 550ppm, 600ppm, 650ppm, 700ppm, 750ppm, 800ppm, 850ppm, 900ppm, 950ppm, 1000ppm, 1050ppm, 1100ppm, 1150ppm, 1200ppm, 1250ppm, 1300ppm, 1350ppm, 1400ppm, 1450ppm, 1500ppm, 1550ppm, 1600ppm, 1650ppm, 1700ppm, 1750ppm, 1800ppm, 1850ppm, 1900ppm, 1950ppm, 2000ppm, 2050ppm, 2100ppm, 2150ppm, 2200ppm, 2300ppm, 2400ppm, 2450ppm, 2500ppm, 2550ppm, 2600ppm, 2650ppm, 2700ppm, 2750ppm, 2800ppm, 2850ppm, 2900ppm, 2850ppm, 290 ppm, 2950ppm, 3000ppm, 3700ppm, 3200ppm, 3, 4000ppm, 4050ppm, 4100ppm, 4150ppm, 4200ppm, 4250ppm, 4300ppm, 4350ppm, 4400ppm, 4450ppm, 4500ppm, 4550ppm, 4600ppm, 4650ppm, 4700ppm, 4750ppm, 4800ppm, 4850ppm, 4900ppm, 4950ppm, or 5000ppm, specifically, 100ppm to 2,500ppm are present in the polarizer. Within these ranges, the polarizing plate may have improved durability by suppressing the occurrence of yellowing of the polarizing plate. Herein, the amount of zinc cations in the polarizer can be measured by ICP-OES (inductively coupled plasma-emission spectrometer) using Agilent 5100 series, but is not limited thereto.

The zinc cation can include monovalent zinc cations, divalent zinc cations, and trivalent zinc cations, for example, the zinc cation can be a divalent zinc cation (Zn)²⁺). Divalent zinc cations are preferred in case they can be easily incorporated into the polarizer.

Zinc cations may be contained in the polarizer or on the surface of the polarizer.

The amount of zinc cations in the polarizer can be adjusted by the amount of zinc salts of organic acids, which are introduced during the production process of the polarizer from the polyvinyl alcohol film, to be described below.

The polarizer includes a unit represented by formula 1 below:

[ formula 1]

(wherein is a site of attachment,

r is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

n is an integer of 10 to 100,000, and m is an integer of 0 to 10).

In formula 1, if n is less than 10, durability of the polarizer may not be improved. If n is greater than 100,000, miscibility with a polyvinyl alcohol chain is poor, and thus separation may occur between the polarizer and the first protective layer.

In formula 1, m is the number of repeating units between the main chain and the carbonyl group. If m is greater than 10, the organic acid zinc salt described below is insoluble in water, and thus it may not be used in the production process of the polarizer. In one embodiment, n may be 20 to 80,000.

The unit represented by formula 1 may be formed by UV-irradiating the photocurable adhesive during the bonding of the polarizer and the protective layer or crosslinking the photocurable functional group by UV-irradiating the organic acid zinc salt described below during the preparation of the polarizer.

The presence of the unit represented by formula 1 can be confirmed by FT-NMR (fourier transform-nuclear magnetic resonance, BRUKER, ULTRASHIELD 300) analysis of the polarizer, but is not limited thereto.

The unit represented by formula 1 may be present in an amount of greater than about 0 wt% and about 35 wt% or less, preferably, greater than about 0 wt% and about 20 wt% or less. Within this range, the effects of the present invention can be achieved.

The cell represented by formula 1 may be included in the polarizer or on the surface of the polarizer.

The unit represented by formula 1 may be derived from a zinc salt of an organic acid, which will be described below.

In general, in order to improve durability of a polarizing plate, an inorganic zinc salt (for example, a zinc halide such as zinc chloride, zinc iodide, zinc sulfate, or zinc acetate) has been added to a polarizer. However, in this case, zinc cations are unstable and migrate to the polarizer surface, and thus the durability is not sufficiently improved. On the other hand, according to the present invention, by co-introducing zinc cations and the unit represented by formula 1 and fixing the zinc cations and the unit represented by formula 1 in the polarizer by UV curing, the durability of the polarizer can be significantly improved.

The zinc salt of an organic acid is a salt of a zinc cation and an organic acid anion. The zinc cation is as described above. The organic acid anion may be represented by the following formula 2:

[ formula 2]

CH₂＝CR-(CH₂)_m-(C＝O)-O^-

(wherein R is hydrogen or C₁To C₅An alkyl group, a carboxyl group,

m is an integer of 0 to 10).

Because organic acid anions commonly contain- (C ═ O) -O^-Anionic and photocurable functional group CH₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl) and thus may be interrupted by- (C ═ O) -O^-The ionic bond between the anion and the zinc cation suppresses the movement of the zinc cation, and the polarizer can pass through the photocurable functional group CH even if the organic acid anion has a low weight average molecular weight₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl) and has improved heat resistance and mechanical properties by its function as a filler. In addition, due to CH₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl group) is not chemically cross-linked with the polyvinyl alcohol, and thus the orientation of the polyvinyl alcohol is not changed, whereby the polarizing plate can have an extremely low variation in degree of polarization and a low variation in light transmittance even after the polarizing plate is left at a high temperature for a long period of time.

When an organic acid (e.g., polyacrylic acid, etc.) in the form of a polymer having a high weight average molecular weight or a salt containing an organic acid anion in the form of a polymer having a high weight average molecular weight is used, it is difficult to permeate into the polarizer, so that an excessive amount is required, and permeation into the polarizer is not uniform, so that physical properties and appearance of the polarizer may be deteriorated.

Photocurable functional group CH₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl) can stabilize zinc cations from migrating to the polarizer surface, and improve the mechanical properties of the polarizer by crosslinking, and prevent iodide ions (I)₅ ^-Or I₃ ^-) Sublimed to improve durability of the polarizing plate.

The photocurable functional group CH in the organic acid anion can be made by a separate UV irradiation treatment method₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl) curing. Further, when the adhesive layer described below is formed, the photocurable functional group CH in the organic acid anion can be made by a UV irradiation treatment method₂(iii) CR- (. is a linking site, R is hydrogen or C)₁To C₅Alkyl) is cured simultaneously with the tie layer.

In formula 2, m may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

In formula 2, R may be hydrogen or methyl.

In the zinc salt of an organic acid, the number of anions of the organic acid may be 1 to 3, preferably 2, based on the oxidation state of the zinc cation.

In one embodiment, the organic acid zinc salt may include at least one of: zinc (meth) acrylates, e.g., [ (H)₂C＝CH-CO₂)^-]₂Zn²⁺、[(H₂C＝CCH₃-CO₂)^-]₂Zn²⁺10-undecylenic acid zinc salt, such as [ [ H ]₂C＝CH(CH₂)₈COO]^-]₂Zn²⁺But is not limited thereto.

In one embodiment, the polarizer may include a crosslinked product of a zinc salt of an organic acid. In one embodiment, the polarizer may include a UV cured product of a zinc salt of an organic acid.

In the process of preparing the polarizer, an initiator may be added to promote chemical crosslinking (e.g., photo-curing) of the zinc salt of an organic acid. The initiator may include at least one of a photo radical initiator and a photo cation initiator, but is not limited thereto. In one embodiment, the initiator may comprise a photo radical initiator. The photo radical initiator and the photo cation initiator may include conventional types known to those skilled in the art.

In one embodiment, the polarizer may include an initiator, for example, a photo radical initiator. The initiator may be included in the polarizer or on the surface of the polarizer.

The initiator may be present in an amount of about 1 wt% to about 10 wt%, preferably about 2 wt% to about 6 wt%. Within this range, the organic acid anion can be cured without deterioration of the polarizer light transmittance caused by the residual initiator.

The polarizer may be free of at least one of inorganic acid zinc salt, zinc halide salt, and organic acid zinc salt having no photocurable functional group. The polarizer may be free of at least one of: an inorganic acid anion derived from a zinc salt of an inorganic acid, a halide anion derived from a zinc halide salt, and an organic acid anion having no photocurable functional group derived from a zinc salt of an organic acid having no photocurable functional group. The polarizer of the present invention may have improved high temperature durability without using at least one of an inorganic acid zinc salt, a zinc halide salt, and an organic acid zinc salt having no photocurable functional group. The photocurable functional group may be CH₂(iii) CR-is a linking site, R is hydrogen or C₁To C₅Alkyl groups). As the zinc inorganic acid salt and the zinc halide salt, conventional types known to those skilled in the art can be used. For example, the polarizer can be free of zinc inorganic acid salts, such as zinc sulfate, zinc halide salts, such as zinc iodide and zinc chloride, organic acid zinc salts that do not have photocurable functional groups, such as zinc acetate, sulfate anions, halogensAnions, acetate anions, and the like.

The amount of zinc cations and the amount of units represented by formula 1 in the polarizer can be controlled by adjusting the timing of addition of the zinc salt of an organic acid and/or the amount of the zinc salt of an organic acid at each step of producing the polarizer from the polyvinyl alcohol film.

The zinc salt of an organic acid may be added to at least one of the dyeing treatment, the stretching treatment, the crosslinking treatment, and the complementary color (color compensation) treatment described below.

The polarizer may be produced through dyeing treatment, stretching treatment, crosslinking treatment, and complementary color treatment processes of a polyvinyl alcohol film. The order of the dyeing treatment and the stretching treatment is not particularly limited. In one embodiment, the polarizer may be produced without performing at least one of a cross-linking treatment and a complementary color treatment.

According to the method of producing the polarizer of the present invention, the order of dyeing and stretching is not limited. That is, the polyvinyl alcohol film may be dyed and then stretched, or stretched and then dyed, or the dyeing treatment and the stretching treatment may be performed simultaneously.

The polyvinyl alcohol film may be a typical polyvinyl alcohol film known to those skilled in the art. In one embodiment, the polyvinyl alcohol film may be a film formed of polyvinyl alcohol or a derivative thereof. The polyvinyl alcohol may have a degree of polymerization of about 1000 to about 5000, a degree of saponification of about 80 mol% to about 100 mol%, a thickness of about 1 μm to 100 μm, specifically about 10 μm to about 70 μm. Within these ranges, polyvinyl alcohol may be suitably used in the preparation of the thin polarizer.

The polyvinyl alcohol film may be subjected to water washing treatment and swelling treatment before dyeing and stretching. Foreign substances on the surface of the polyvinyl alcohol film can be removed by washing the polyvinyl alcohol film with water. The polyvinyl alcohol film may be subjected to an expansion treatment, so that the dyeing or stretching of the polyvinyl alcohol film may be better. The swelling treatment is carried out by placing the polyvinyl alcohol film in a swelling bath filled with an aqueous solution known to the person skilled in the art. The temperature of the expansion bath and the expansion treatment time are not particularly limited. The expansion bath may further include boric acid, inorganic acid, surfactant, etc., and their amounts may be adjusted.

The polyvinyl alcohol film may be dyed with the dichroic material in a dyeing bath containing the dichroic material. In the dyeing process, the polyvinyl alcohol film may be immersed in a dyeing solution, and the dyeing solution may be an aqueous solution containing a dichroic material. In one embodiment, the dichroic material may be an iodide including potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, cuprous iodide, and the like. The staining solution may be an aqueous solution containing from about 0.5mol/ml to about 10mol/ml of dichroic material. Within this range, the polarizer can obtain a suitable degree of polarization and can be used in an optical display device.

The dye bath may have a temperature of about 20 ℃ to about 45 ℃, and the immersion time of the polyvinyl alcohol film in the dye bath may be about 10 seconds to about 300 seconds. In this range, a polarizer having a high degree of polarization can be obtained.

During the dyeing of the polyvinyl alcohol film, the dyeing bath may also contain zinc salts of organic acids. In this case, the organic acid zinc salt may be present in the dyeing solution in an amount of about 1 wt% to about 30 wt%, for example, about 2 wt% to about 15 wt%. When the zinc salt of an organic acid is contained in the dyeing solution, the dyeing bath may have a temperature of about 20 ℃ to about 45 ℃, and the immersion time of the polyvinyl alcohol film in the dyeing bath may be about 10 seconds to about 300 seconds. Within this range, the zinc cation of the present invention can be immobilized.

The dyed polyvinyl alcohol film may be stretched in a stretching bath, whereby the dichroic material may be oriented, and thus the polyvinyl alcohol film may have polarization. Specifically, the stretching may be performed by either dry stretching or wet stretching. The dry stretching may be performed by roll-to-roll stretching, extrusion stretching, hot roll stretching, or the like, and the wet stretching may be performed in a wet stretching bath containing water at about 35 ℃ to 70 ℃. The wet stretching bath may also include boric acid to enhance the stretching effect.

The polyvinyl alcohol film can be stretched at a desired stretch ratio. Specifically, the polyvinyl alcohol film may be stretched at a total stretching ratio of about 5 times to about 7 times, for example, about 5.5 times to about 6.5 times. In this range, the polyvinyl alcohol film is not subjected to cutting or wrinkling, and the polarizer obtained thereby may have a high degree of polarization and transmittance. The stretching may be performed by uniaxial stretching, and the stretching may be performed in one-step stretching, but preferably, the stretching may be performed in multi-step stretching, such as 2-step or 3-step stretching, thereby preventing the breakage of the thin polarizer.

During the stretching of the polyvinyl alcohol film, the stretching bath may further contain a zinc salt of an organic acid. In this case, the organic acid zinc salt may be present in the wet-stretch bath in an amount of about 1 wt% to about 30 wt%, for example, about 2 wt% to about 15 wt%. When the zinc salt of an organic acid is added during the stretching of the polyvinyl alcohol film, the wet-stretching bath may have a temperature of about 35 ℃ to about 70 ℃, and the immersion time of the polyvinyl alcohol film in the wet-stretching bath may be about 10 seconds to about 300 seconds. Within this range, the polarizing plate may realize a color difference change Δ E of about 5.2 or less as calculated according to equation 1.

As described above, the polyvinyl alcohol film may be dyed and then stretched, but in another embodiment, the dichroic material dyeing and stretching of the polyvinyl alcohol film may be performed in the same bath.

The polyvinyl alcohol film may be subjected to a crosslinking treatment in a crosslinking bath before stretching the dyed polyvinyl alcohol film or after stretching the dyed polyvinyl alcohol film. The crosslinking treatment is a process in which a polyvinyl alcohol film is strongly dyed with a dichroic material, and boric acid may be used as a crosslinking agent. In order to enhance the crosslinking effect, a phosphoric acid compound, potassium iodide, or the like may be added. For example, the crosslinking bath may contain an aqueous solution comprising from about 1 wt% to about 10 wt%, preferably from about 2 wt% to about 6 wt%, boric acid.

During the crosslinking of the polyvinyl alcohol film, the crosslinking bath may also contain zinc salts of organic acids. In this case, the organic acid zinc salt may be present in the crosslinking bath in an amount of about 1 wt% to about 10 wt%, for example, about 2 wt% to about 5 wt%. When the zinc salt of an organic acid is added during the crosslinking of the polyvinyl alcohol film, the crosslinking bath may have a temperature of about 35 ℃ to about 70 ℃, and the immersion time of the polyvinyl alcohol film in the crosslinking bath may be about 10 seconds to about 300 seconds.

The dyed and stretched polyvinyl alcohol film may be subjected to a complementary color treatment in a complementary color bath.

The complementary color treatment may be performed by immersing the dyed and stretched polyvinyl alcohol film in a complementary color bath. By the complementary color treatment, the polarizer can have a reduced color value and improved durability. The color compensation bath may contain potassium iodide in an amount of greater than about 0 wt% and about 10 wt% or less, preferably from about 1 wt% to about 5 wt%.

In the complementary color process of the polyvinyl alcohol film, the complementary color bath can also contain zinc salt of organic acid. In this case, the organic acid zinc salt may be present in the complementary color bath in an amount of about 1 wt% to about 10 wt%, for example, about 2 wt% to about 5 wt%. When the zinc salt of an organic acid is used in the complementary color process of the polyvinyl alcohol film, the complementary color bath may have a temperature of about 35 ℃ to about 65 ℃, and the immersion time of the polyvinyl alcohol film in the complementary color bath may be about 10 seconds to about 300 seconds. Within this range, the desired polarizer of the present invention can be obtained.

First protective layer

A first protective layer may be formed on the upper surface of the polarizer to protect the polarizer while improving the mechanical strength of the polarizing plate. The first protective layer may include at least one of an optically transparent protective film and an optically transparent protective coating.

When the first protective layer is of a protective film type, the first protective layer may include a protective film formed of an optically transparent resin. The protective film may be formed by melting and extrusion of the resin. The resin may be further stretched as necessary. The resin may include at least one of: cellulose ester resins, including cellulose triacetate, cyclic polyolefin resins, including amorphous Cyclic Olefin Polymers (COP), polycarbonate resins, polyester resins, including polyethylene terephthalate (PET), polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, acyclic polyolefin resins, polyacrylate resins, including poly (methyl methacrylate), polyvinyl alcohol resins, polyvinyl chloride resins, and polyvinylidene chloride resins.

When the first protective layer is of a protective coating type, the protective coating can improve adhesion to the polarizer, transparency, mechanical strength, thermal stability, moisture resistance, and durability of the polarizer. In one embodiment, the protective coating layer of the first protective layer may be formed from an actinic radiation-curable resin composition including an actinic radiation-curable compound and a polymerization initiator. The actinic radiation-curable compound may include at least one of a cationically polymerizable curable compound, a radically polymerizable curable compound, a polyurethane resin, and a silicone resin. The cationically polymerizable curable compound may be an epoxy compound having at least one epoxy group therein or a propylene oxide compound having at least one propylene oxide ring therein. The radical polymerizable curable compound may be a (meth) acrylic compound having at least one (meth) acryloyloxy group therein.

The first protective layer may have a thickness of about 5 μm to about 200 μm, specifically about 30 μm to about 120 μm. The first protective layer of the protective film type may have a thickness of about 50 μm to about 100 μm, and the first protective layer of the protective coating type may have a thickness of about 5 μm to about 50 μm. Within this range, the first protective layer may be used in the polarizing plate.

The polarizing plate may further include a functional coating layer, for example, a hard coating layer, an anti-fingerprint layer, or an anti-reflection layer, on the upper surface of the first protective layer.

Adhesive layer

The first protective layer may be bonded to the polarizer by an adhesive layer. The adhesive layer may be formed of a typical adhesive for a polarizing plate known to those skilled in the art. For example, the adhesive layer may be formed of a water-based adhesive or a photocurable adhesive. Preferably, the adhesive layer is formed of a photocurable adhesive, whereby the chemical crosslinking degree of the organic acid anion in the zinc salt of an organic acid is increased, and thus an additional UV treatment method for the anionic crosslinking of an organic acid can be omitted, and thus the workability can also be improved.

The photocurable binder may include an initiator and at least one of an epoxy compound and a (meth) acrylate compound. The initiator may include at least one of a photo cation initiator and a photo radical initiator. The photocurable adhesive may also include typical additives such as antioxidants, pigments, and the like. The bonding layer may have a thickness of about 0.1 μm to about 10 μm. Within this thickness range, the adhesive layer may be used in an optical display device.

On the lower surface of the polarizer, an adhesive layer may be laminated to attach the polarizing plate to the liquid crystal panel. The adhesive layer may be formed of a Pressure Sensitive Adhesive (PSA), but is not limited thereto.

Next, a polarizing plate according to another embodiment of the present invention will be described.

The polarizing plate according to this embodiment is substantially the same as the polarizing plate according to the above embodiment except that the polarizing plate further includes a second protective layer on the lower surface of the polarizer.

A second protective layer may be laminated on the lower surface of the polarizer to protect the polarizer while improving the mechanical strength of the polarizing plate.

The second protective layer may be formed of the same composition as the first protective layer or a different composition. The second protective layer may have the same thickness as the first protective layer or a different thickness.

Next, an optical display according to the present invention will be described.

The optical display according to the present invention may include the polarizing plate according to the present invention.

The optical display may include at least one of a liquid crystal display and a light emitting device display. For a light emitting device display, the light emitting device includes an organic or organic-inorganic light emitting device and may mean a Light Emitting Diode (LED), an Organic Light Emitting Diode (OLED), a quantum dot light emitting diode (QLED), and other devices including a light emitting material such as a phosphor.

Then, the present invention will be described in more detail with reference to some examples. It should be understood that these examples are provided for purposes of illustration only and are not to be construed as limiting the invention in any way.

The detailed descriptions of the components used in the examples and comparative examples are as follows:

example 1: preparation of polarizing plate

(1) Preparation of polarizer

A polyvinyl alcohol film (VF-PS6000, Kuraray Co., Ltd., thickness: 60 μm) washed with water at 25 ℃ was swollen in a swelling bath filled with water at 30 ℃. Then, the swollen film was dyed in a dyeing bath filled with an aqueous solution containing 1ml/mol of potassium iodide at 30 ℃ for 65 seconds. The dyed film was passed through a wet crosslinking bath filled with an aqueous solution containing 3 wt% boric acid at 30 ℃. Thereafter, the film passed through the crosslinking bath was stretched to 6 times its original length in an aqueous solution containing 3 wt% of boric acid at 65 ℃.

The stretched film was subjected to color compensation for 10 seconds at 30 ℃ in a color compensation bath filled with a color compensation solution containing 4.5% by weight of potassium iodide and 3% by weight of zinc acrylate ([ (H)₂C＝CHCO₂)^-]₂Zn²⁺) And 1 wt% of a photo radical initiator (Darocur 1173; ciba Specialty Chemicals). Then, the film was washed and dried, thereby obtaining a polarizer (thickness: 22 μm).

(2) Preparation of polarizing plate

UV-curable adhesive was applied to both sides of the polarizer from above. A triacetyl cellulose (TAC) film (thickness: 80 μm, FujiTAC, Fuiji co., Ltd.) was bonded to one side of the polarizer, and another TAC film (thickness: 80 μm, FujiTAC, Fuiji co., Ltd.) was bonded to the other side of the polarizer to prepare a polarizing plate. For the UV-curable binder KRX-4024(ADEKA co., Ltd.) (comprising 40 wt% of bisphenol a diglycidyl ether, 30 wt% of neopentyl glycol diglycidyl ether, 23 wt% of (3-ethyl-3 [ [ (3-ethyloxetan-3-yl) methoxy ] methyl ] propylene oxide) and 7 wt% of an initiator) was used. The adhesive is cured by UV irradiation.

Examples 2 to 7

Each of the polarizer and polarizing plate was produced in the same manner as in example 1, except that the composition (unit: wt%) of the complementary color bath was changed as listed in table 1.

Comparative examples 1 to 4

Each of the polarizer and polarizing plate was produced in the same manner as in example 1, except that the composition (unit: wt%) of the complementary color bath was changed as listed in table 2.

The polarizers and polarizing plates of examples and comparative examples were evaluated for the following properties, and the evaluation results are shown in tables 1 and 2.

(1) Amount of zinc cation (unit: ppm): the amount of zinc cations in the polarizer was measured by ICP-OES measurement. The amount of zinc cations was measured using the Agilent 5100 series.

(2) Change in color difference (Δ E, no unit): the L, a, and b values of each polarizing plate were measured using a spectrophotometer (CM-3600A, Konica Minolta co., Ltd.). Then, the polarizing plate was left at 95 ℃ for 500 hours, and then the values of L, a, and b were measured in the same manner. Then, the measured values of L, a, and b are used to calculate the color difference change Δ E according to equation 1.

(3) Degree of polarization change (. DELTA.P, unit:%): the degree of polarization of each polarizing plate was measured at a wavelength of 380nm to 780nm using V-7100(JASCO co., Ltd.) before and after the polarizing plate was left at 95 ℃ for 500 hours. Then, the degree of polarization change Δ P is calculated according to equation 2.

(4) Change in light transmittance (. DELTA.T, unit:%): the light transmittance of each polarizing plate was measured at a wavelength of 380nm to 780nm using V-7100(JASCO co., Ltd.) before and after the polarizing plate was left at 95 ℃ for 500 hours. Then, the light transmittance change Δ T is calculated according to equation 3.

(5) Appearance: each polarizing plate was left at 95 ℃ for 500 hours and then observed with the naked eye to identify whether yellowing occurred in the polarizing plate. When yellowing was visually indistinguishable, it was evaluated as "OK". When yellowing was visually recognized, it was evaluated as "NG".

[ Table 1]

[ Table 2]

As shown in table 1, the polarizing plate according to the present invention shows excellent durability and appearance by a polarizer that is not yellowed even after being left at high temperature for a long time, and the present invention provides a polarizing plate having excellent optical characteristics and excellent optical reliability due to a low polarization degree change and a low light transmittance change even after being left at high temperature for a long time.

In contrast, as shown in table 2, the polarizers of comparative examples 1 and 2, which do not contain the unit represented by the following formula 1, and the polarizers of comparative examples 3 and 4, which do not contain zinc cations, may not achieve the desired effects.

It will be appreciated that numerous modifications, changes, variations, and equivalents may be made by those skilled in the art without departing from the spirit and scope of the invention.