KR20220102520A - Adhesive composition for polarizing plate, polarizing plate and optical display apparatus - Google Patents

Abstract

Provided are an adhesive composition for a polarizing plate comprising an acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH_2) and/or a secondary amine group (-NH-), and a polyphenol-based compound, a polarizing plate, and an optical display device.

Description

Adhesive composition for a polarizing plate, a polarizing plate, and an optical display device TECHNICAL FIELD

The present invention relates to an adhesive composition for a polarizing plate, a polarizing plate, and an optical display device.

A light emitting display device including an organic light emitting display device does not need to include a polarizing plate. However, incident external light may be totally reflected by the panel in the light emitting display device, thereby reducing screen quality. Therefore, it is common for the light emitting display device to include a polarizing plate on the upper surface of the panel. A polarizing plate is composed of a polarizer and a retardation film. Although a polymer film may be used as the retardation film, a liquid crystal retardation film is used according to the recent trend toward thinning.

In the bonding of the polarizer and the liquid crystal retardation film, there were many cases of bonding between the polarizing plate and the liquid crystal retardation film and between the two liquid crystal retardation films using a pressure-sensitive adhesive layer, particularly while introducing a two-sheet liquid crystal retardation film. However, the pressure-sensitive adhesive layer has many disadvantages in terms of bending reliability required for a flexible display. Therefore, a method of using an adhesive layer formed of a photocurable adhesive instead of the adhesive layer is being considered.

However, the adhesive layer formed of the photocurable adhesive has a limit in thickness reduction compared to the water-based adhesive. However, when bonding the liquid crystal retardation film with a water-based adhesive, the liquid crystal retardation film is a non-adhesive film with low adhesion, so it was difficult to adhere the polarizer and the liquid crystal retardation film, the liquid crystal retardation film and the liquid crystal retardation film with high adhesive force.

Background art of the present invention is disclosed in Korean Patent Application Laid-Open No. 10-2006-0103451 and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between a polarizer and a surface and a rear surface of a liquid crystal retardation layer having low adhesion.

Another object of the present invention is to provide an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between liquid crystal retardation layers having low adhesion.

Another object of the present invention is to provide an adhesive composition for a polarizing plate having excellent applicability and forming an adhesive layer with a uniform surface.

Another object of the present invention is to provide an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between a liquid crystal retardation layer and a polarizer having low adhesion even at room temperature and ultra-low temperature conditions.

Another object of the present invention is to provide an adhesive composition for a polarizing plate that forms an adhesive layer having excellent high-temperature, high-humidity durability.

Another object of the present invention is to provide an adhesive composition for a polarizing plate that forms an adhesive layer having excellent bending reliability.

Another object of the present invention is to provide a polarizing plate and an optical display device including the above-described adhesive layer.

One aspect of the present invention is an adhesive composition for a polarizing plate.

1. The adhesive composition for a polarizing plate includes an acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH ₂ ) and/or a secondary amine group (-NH-), and a polyphenol-based compound.

In 2.1, the crosslinking agent having a primary amine group or a secondary amine group may include at least one ethyleneimine-based crosslinking agent.

In 3.1-2, the crosslinking agent: the polyphenol-based compound may be included in a weight ratio of 1:1 to 1:20.

In 4.1-3, the polyphenol-based compound may include tannic acid.

In 5.1-4, the acetoacetylated polyvinyl alcohol-based resin may have an acetoacetyl group modification degree of 1 mol% to 30 mol%.

In 6.1-5, the composition is 100 parts by weight of the polyvinyl alcohol-based resin, 0.1 parts by weight to 50 parts by weight of the crosslinking agent having a primary amine group or a secondary amine group, 1 part by weight to 100 parts by weight of the polyphenol-based compound may include

Another aspect of the present invention is a polarizing plate.

7. The polarizer is a polarizer; a first liquid crystal retardation layer laminated on a lower surface of the polarizer; and a first adhesive layer for bonding the polarizer and the first liquid crystal retardation layer, wherein the first adhesive layer is formed of the adhesive composition for a polarizing plate of the present invention.

In 8.7, the first liquid crystal retardation layer may include an aromatic-containing liquid crystal compound.

In steps 9.7-8, a second adhesive layer and a second liquid crystal retardation layer may be further laminated on the lower surface of the first liquid crystal retardation layer.

In 10.9, the second liquid crystal retardation layer may include an aromatic-containing liquid crystal compound.

In 11.9-10, the second adhesive layer is an acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH ₂ ) and/or a secondary amine group (-NH-) and a polyphenol-based compound. It may be formed of an adhesive composition for a polarizing plate comprising.

In 12.11, the crosslinking agent having a primary amine group or a secondary amine group may include at least one ethyleneimine-based crosslinking agent.

In 13.12, the polyphenol-based compound may include tannic acid.

Another aspect of the present invention is an optical display device.

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

The present invention provides an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between the surface and the rear surface of a liquid crystal retardation layer having low adhesiveness and a polarizer.

The present invention provides an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between liquid crystal retardation layers having low adhesion.

The present invention provides an adhesive composition for a polarizing plate having excellent applicability and forming an adhesive layer with a uniform surface.

The present invention provides an adhesive composition for a polarizing plate that forms an adhesive layer having excellent adhesion between a liquid crystal retardation layer and a polarizer having low adhesion even at room temperature and ultra-low temperature conditions.

The present invention provides an adhesive composition for a polarizing plate that forms an adhesive layer excellent in high temperature, high humidity durability.

The present invention provides an adhesive composition for a polarizing plate that forms an adhesive layer having excellent bending reliability.

The present invention provides a polarizing plate and an optical display device including the adhesive layer described above.

1 is an exploded view of a transfer type liquid crystal retardation film.
2 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
3 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.
4 is a schematic plan view of a specimen in high-temperature, high-humidity durability evaluation.
5 is a cross-sectional view of a specimen in flexural reliability evaluation.

With reference to the accompanying drawings, it will be described in detail so that a person of ordinary skill in the art can easily carry out the present invention by way of example. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same names are used for the same or similar components throughout the specification. The length and size of each component in the drawings are for explaining the present invention, and the present invention is not limited to the length and size of each component described in the drawings.

In this specification, "upper" and "lower" are defined based on the drawings, and depending on the perspective of the city, "upper" may be changed to "lower" and "lower" to "upper", and "on" or What is referred to as “on” may include cases in which other structures are interposed in the middle as well as immediately above. On the other hand, reference to "directly on" or "immediately on" or "directly formed" refers to no intervening other structures such as intermediates.

In the present specification, when describing a numerical range, "X to Y" means "X or more and Y or less" (X≤≤Y).

Hereinafter, the adhesive composition for a polarizing plate of an embodiment of the present invention (hereinafter referred to as 'adhesive composition') will be described.

The adhesive composition of an embodiment of the present invention includes an acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH ₂ ) and/or a secondary amine group (-NH-), and a polyphenol-based compound .

The adhesive composition may form an adhesive layer having excellent adhesion between a liquid crystal retardation layer having low adhesion and a polarizer. The above-mentioned excellent adhesion may be realized by including all of the acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group and/or a secondary amine group, and a polyphenol-based compound. In this regard, the acetoacetylated polyvinyl alcohol-based resin provides excellent adhesion to the polarizer by reacting with the cross-linking agent, and by reaction with the acetoacetylated polyvinyl alcohol-based resin, polyphenol-based compound and the cross-linking agent It is also possible to provide excellent adhesion to the liquid crystal retardation layer. In particular, the adhesive composition can implement excellent adhesion not only at room temperature but also in an ultra-low temperature state, for example, -10°C or less, specifically -200°C to -10°C.

In addition, the adhesive composition may form an adhesive layer having excellent adhesion to both the surface and the rear surface of the liquid crystal retardation layer.

The front and back surfaces of the liquid crystal retardation layer will be described with reference to FIG. 1 . 1 is an exploded view of a transfer type liquid crystal retardation film.

Referring to FIG. 1 , the transfer type liquid crystal retardation film includes a base film 1 and a liquid crystal retardation layer 2 formed on one surface of the base film 1 .

The transfer-type liquid crystal retardation film may be prepared by forming an alignment film on one surface of the base film 1 (the upper surface of the base film in FIG. 1 ), coating the composition for forming a liquid crystal retardation layer on the alignment film, aligning the composition, and then curing. The liquid crystal retardation layer has a 'back' on the side that was in contact with the alignment film (the lower surface of the liquid crystal retardation layer in FIG. 1) (3), and the side that was not in contact with the alignment film (the upper surface of the liquid crystal retardation layer in FIG. 1) (4)' called 'surface'. Unlike the surface, the back surface is derived from the portion where the alignment layer of the base film 1 was formed, and thus physical properties may be different from the surface.

The base film 1 may include a conventional resin film known to those skilled in the art. For example, the base film may include a cellulose ester-based film such as triacetylcellulose (TAC). The upper surface of the base film, that is, the surface on which the alignment layer is formed, may or may not be subjected to a release treatment.

The alignment layer may be formed of a composition including a polyvalent carboxylic acid-based compound, a polyhydric carboxylic acid anhydride-based compound, a diamine-based compound, or the like, but is not limited thereto.

The liquid crystal retardation layer 2 may be formed of a composition including an aromatic-containing liquid crystal compound described in detail below.

The rear surface and the surface of the liquid crystal retardation layer 2 may have different water contact angles depending on the presence or absence of the alignment layer. The surface of the liquid crystal retardation layer may be adhered to the polarizer or the back side may be adhered to the polarizer depending on the polarizing plate manufacturing process sequence, the type of base film and alignment film among the transfer type liquid crystal retardation film, the thickness of the liquid crystal retardation layer, and the type of liquid crystal included in the liquid crystal retardation layer. have. Therefore, it is necessary to form an adhesive layer having excellent adhesion to both the surface and the rear surface of the liquid crystal retardation layer. The adhesive composition of the present invention can form an adhesive layer having excellent adhesion to both the surface and the rear surface of the liquid crystal retardation layer.

In one embodiment, the rear surface and the surface of the liquid crystal retardation layer may have different water contact angles at 25° C. after corona treatment, respectively. For example, the rear surface of the liquid crystal retardation layer may have a water contact angle of 50° to 70° at 25° C. after corona treatment, and the surface of the liquid crystal retardation layer may have a water contact angle of 70° to 90° at 25° C. after corona treatment. The above 'corona treatment' refers to corona treatment at 10mpm speed and 1000W output. The 'water contact angle' may be measured by a conventional method known to those skilled in the art.

In addition, the adhesive composition may form an adhesive layer having excellent adhesion between liquid crystal retardation layers having low adhesiveness. Specifically, the adhesive composition may provide excellent adhesion to the surface and the surface between the liquid crystal retardation layers having low adhesion, the surface and the back surface, and/or the back surface and the back surface.

In addition, the adhesive composition may implement an adhesive layer capable of providing a polarizing plate having both excellent durability and bending reliability at high temperature and high humidity.

Hereinafter, each component in the adhesive composition will be described in detail.

Acetoacetylated polyvinyl alcohol-based resin

The acetoacetylated polyvinyl alcohol-based resin may form an adhesive layer having excellent adhesion to the polarizer by reacting with the crosslinking agent described in detail below. In addition, the acetoacetylated polyvinyl alcohol-based resin may form an adhesive layer having excellent adhesion between the liquid crystal retardation layer having low adhesiveness and the polarizer by hydrogen bonding with the polyphenol-based compound described in detail below.

The degree of acetoacetyl group modification of the acetoacetylated polyvinyl alcohol-based resin may be 1 mol% to 30 mol%, for example, 1 mol% to 10 mol%. In the above range, by providing a sufficient reaction point with the crosslinking agent, the adhesive force may come out, and the water resistance of the polarizing plate may also be improved. A method for preparing the acetoacetylated polyvinyl alcohol-based resin is not particularly limited. For example, a method of dispersing a polyvinyl alcohol-based resin in acetic acid and adding diketene may be considered, but is not limited thereto.

The average degree of polymerization and saponification of the acetoacetylated polyvinyl alcohol-based resin are not particularly limited, and the average degree of polymerization may be 100 to 3,000, and the average degree of saponification may be 85 mol% to 100 mol%. In the above range, adhesion between the polarizer and the first liquid crystal retardation layer may be further improved.

The acetoacetylated polyvinyl alcohol-based resin may be included in an amount of 1 to 20 parts by weight, specifically 1 to 10 parts by weight, based on 100 parts by weight of the aqueous solvent. In the above range, the adhesive force of the adhesive layer may come out, and the viscosity of the adhesive composition may not increase rapidly, and thus processability may be excellent.

A crosslinking agent having a primary amine group and/or a secondary amine group

A crosslinking agent having a primary amine group and/or a secondary amine group may provide adhesion by reacting with the acetoacetylated polyvinyl alcohol-based resin. The crosslinking agent may help improve adhesion by hydrogen bonding with the polyphenol-based compound described in detail below.

The crosslinking agent may have a plurality of primary amine groups and/or secondary amine groups as a linear, branched or dendrimer type to provide adhesion to the adhesive layer. In addition, the crosslinking agent was selected from among a plurality of crosslinking agents used in the water-based adhesive for a polarizing plate in that it can implement all of the above-mentioned effects of the present invention when combined with the polyphenol-based compound described in detail below.

In one embodiment, the crosslinking agent having a primary amine group or a secondary amine group may include at least one of ethylenimine-based crosslinking agents. The 'ethyleneimine-based crosslinking agent' may include a crosslinking agent synthesized by treating ethyleneimine with one or more types such as ring opening, polymerization, and derivatization by a known method. Specifically, the ethyleneimine-based crosslinking agent may include a poly(ethyleneimine)-based crosslinking agent.

The poly(ethyleneimine)-based crosslinking agent may include a straight-chain, branched-chain or dendrimer-type compound having a primary amine group and/or a secondary amine group at the terminal and a secondary amine group and/or a tertiary amine group in the main chain. can The primary amine group and/or the secondary amine group may increase adhesion by reacting with a functional group of the polyvinyl alcohol-based resin, specifically, a hydroxyl group or an acetoacetyl group.

As known to those skilled in the art, poly(ethyleneimine)-based crosslinking agents have an ethylene group (-CH ₂ CH ₂ -) connected to a secondary amine group and/or a tertiary amine group, and a primary amine group and/or secondary amine group at the terminal. It may contain a crosslinking agent having.

The weight average molecular weight of the crosslinking agent is not particularly limited, but may be 1,000,000 to 1,000,000. Within the above range, the effect of the adhesive layer of the present invention may be well obtained.

The crosslinking agent is 0.1 parts by weight to 50 parts by weight, specifically 0.5 parts by weight to 10 parts by weight, more specifically 1 part by weight to 10 parts by weight, 1 part by weight based on 100 parts by weight of the acetoacetylated polyvinyl alcohol-based resin to 5 parts by weight. Within the above range, the adhesive strength of the adhesive layer may be improved.

The crosslinking agent: The following polyphenol-based compound may be included in the adhesive composition in a weight ratio of 1:1 to 1:20, specifically 1:1 to 1:15, and more specifically 1:1 to 1:10. Within the above range, it is possible to achieve excellent adhesion even in an ultra-low temperature state, and excellent durability and flexural reliability in high temperature and high humidity.

polyphenolic compounds

The polyphenol-based compound may include a compound having a plurality of hydroxyl groups in a plurality of aromatic rings. The polyphenol-based compound may form an affinity bonding force with the aromatic ring of the liquid crystal retardation layer, and may provide a higher bonding force between the polarizer and the liquid crystal retardation layer by matching the hydroxyl group arrangement of the acetacetylated polyvinyl alcohol-based resin. In addition, the polyphenol-based compound can be easily dissolved in an aqueous solvent due to a plurality of hydroxyl groups.

The polyphenol-based compound may include tannic acid. Tannic acid has a pKa of 6, and when combined with the acetoacetylated polyvinyl alcohol-based resin and crosslinking agent of the present invention, the effects of the present invention can be well realized.

The polyphenol-based compound may be included in an amount of 1 to 100 parts by weight, specifically 1 to 50 parts by weight, more specifically 5 to 30 parts by weight, based on 100 parts by weight of the acetoacetylated polyvinyl alcohol-based resin. have. Within the above range, it is possible to achieve excellent adhesion even in an ultra-low temperature state, and excellent durability and flexural reliability in high temperature and high humidity.

The adhesive composition is a thermosetting composition, and may form an adhesive layer by thermal curing.

The adhesive composition may further include an aqueous solvent. The aqueous solvent may facilitate application of the adhesive composition to form a thin adhesive layer.

The aqueous solvent may be water including, but not limited to, ultrapure water and the like. The aqueous solvent may be included in the remaining amount in the adhesive composition.

The adhesive composition may further include conventional additives other than the acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group and/or a secondary amine group, and a polyphenol-based compound. For example, the additive may include one or more of a UV absorber, a heat stabilizer, a plasticizer, a surfactant, a reaction inhibitor, an adhesion enhancer, a thixotropic agent, a conductivity-imparting agent, an antioxidant, a leveling agent, a stabilizer, but , but not limited thereto.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIG. 2 .

Referring to FIG. 2 , the polarizing plate includes a polarizer 100 , a first adhesive layer 300 , a first liquid crystal retardation layer 200 , and a third protective layer 400 . A third protective layer 400 is laminated on the upper surface of the polarizer 100 , and the first adhesive layer 300 and the first liquid crystal retardation layer 200 are sequentially formed from the polarizer 100 on the lower surface of the polarizer 100 . are stacked.

polarizer

The polarizer 100 may include a conventional polarizer known to those skilled in the art. For example, the polarizer may include a polarizer made of a polyvinyl alcohol (PVA)-based resin film or a polypropylene (PP)-based resin film. Specifically, the polarizer may be a polyvinyl alcohol-based polarizer in which at least one of iodine and a dichroic dye is adsorbed onto a polyvinyl alcohol-based resin film, or a polyene-based polarizer manufactured by dehydrating a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin film may have a saponification degree of 85 mol% to 100 mol%, specifically 98 mol% to 100 mol%. The polyvinyl alcohol-based resin film may have a polymerization degree of 1,000 to 10,000, specifically 1,500 to 10,000. A polarizer can be manufactured from the said saponification degree and polymerization degree. The polarizer may be manufactured by a conventional method known to those skilled in the art.

The polarizer 100 may have a thickness of 5 μm to 30 μm, specifically 5 μm to 25 μm. In the above range, it may be used for a polarizing plate, and a thinning effect of the polarizing plate may be realized.

first liquid crystal retardation layer

The first liquid crystal retardation layer 200 prevents reflection of external light by circularly polarizing linearly polarized light emitted after external light passes through the polarizer 100 to improve screen quality.

In one embodiment, the first liquid crystal retardation layer 200 may have an in-plane retardation (Re) of 100 nm to 220 nm, specifically 100 nm to 180 nm, for example, λ/4 retardation at a wavelength of 550 nm. In the above range, it is possible to obtain an effect of improving screen quality by lowering the reflectance for external light.

In another embodiment, the first liquid crystal retardation layer 200 may have an in-plane retardation (Re) of 225 nm to 350 nm, specifically 225 nm to 300 nm, for example, a λ/2 retardation at a wavelength of 550 nm. In the above range, it is possible to obtain an effect of improving screen quality by lowering the reflectance for external light.

In the present specification, the 'in-plane retardation (Re)' is Re = (nx - ny) x d (nx, ny is the slow axis direction of the liquid crystal retardation layer at a wavelength of 550 nm, respectively, the refractive index of the fast axis direction, d may be calculated as the thickness (unit: nm) of the liquid crystal retardation layer.

The first liquid crystal retardation layer 200 may have a thickness of 0.1 μm to 30 μm, for example, 1 μm to 10 μm. Within the above range, the polarizing plate may be thinned and a target retardation may be realized.

The first liquid crystal retardation layer 200 has low adhesiveness. The low adhesion may be due to the first liquid crystal retardation layer being formed of the liquid crystal composition.

In one embodiment, the first liquid crystal retardation layer 200 may contain a hydrophobic aromatic-containing liquid crystal compound. In one embodiment, the aromatic-containing liquid crystal compound may be a polymer, oligomer, or monomer including a unit composed of an aromatic ring capable of imparting liquid crystallinity and a polymerizable functional group. The polymerizable functional group may be a (meth)acryloyl group, an epoxy group, or a vinyl ether group, and may be cured by heat or light to increase the strength of the first liquid crystal retardation layer.

The first liquid crystal retardation layer 200 may be formed of a composition including the above-described aromatic-containing liquid crystal compound. The composition may further include additives such as a leveling agent, a polymerization initiator, an orientation aid, a heat stabilizer, a lubricant, a plasticizer, an antistatic agent, and the like, and these detailed types refer to those known to those skilled in the art.

Although not shown in FIG. 2 , an adhesive layer or an adhesive layer is formed on the lower surface of the first liquid crystal retardation layer 200 so that the polarizing plate can be adhered to a panel for an optical display device, or the like. The adhesive layer or the adhesive layer may be formed of a (meth)acrylic composition known to those skilled in the art, but is not limited thereto.

first adhesive layer

The first adhesive layer 300 is formed between the polarizer 100 and the first liquid crystal retardation layer 200 , and may adhere the polarizer 100 and the first liquid crystal retardation layer 200 to each other.

In one embodiment, the first adhesive layer 300 may be directly formed on the polarizer and the first liquid crystal retardation layer, respectively. The "directly formed" means that an adhesive layer, an adhesive layer, or an adhesive layer other than the first adhesive layer 300 is not formed between the polarizer 100 and the first liquid crystal retardation layer 200 .

The first adhesive layer 300 may have a thickness of 10 nm to 500 nm, for example, 50 nm to 200 nm. In the above range, it is possible to obtain a thinning effect of the polarizing plate.

The first adhesive layer 300 is formed of the above-described adhesive composition for a polarizing plate.

third protective layer

The third protective layer 400 may be formed on the upper surface of the polarizer 100 to protect the polarizer 100 or provide an additional function to the polarizer.

The third protective layer 400 may include a conventional optically transparent protective film or protective coating layer known to those skilled in the art. For example, the protective film includes a cellulose ester-based resin containing triacetyl cellulose (TAC), etc., a cyclic polyolefin-based resin containing an amorphous cyclic polyolefin, etc., a polycarbonate-based resin, polyethylene terephthalate (PET), etc. Polyacrylate-based resins including polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, acyclic-polyolefin-based resins, polymethylmethacrylate resins, and the like; It may include at least one of a polyvinyl alcohol-based resin, a polyvinyl chloride-based resin, and a polyvinylidene chloride-based resin.

The third protective layer 400 has a thickness of 5 μm to 200 μm, specifically, 30 μm to 120 μm, may be 10 μm to 100 μm in the case of a protective film type, and 1 μm to 50 μm in the case of a protective coating layer type It can be μm. It can be used for a polarizing plate in the above range.

Although not shown in FIG. 2 , a functional coating layer such as a hard coating layer, an anti-fingerprint layer, and an anti-reflection layer may be additionally formed on the upper surface of the third protective layer 400 to provide an additional function to the polarizing plate.

Also, although not shown in FIG. 2 , the third protective layer 400 may be adhered to the polarizer 100 by an adhesive layer. In this case, the adhesive layer may be formed of the above-described adhesive composition for a polarizing plate of the present invention, or may be formed of a water-based adhesive or a photocurable adhesive known to those skilled in the art.

Hereinafter, a polarizing plate of another embodiment of the present invention will be described with reference to FIG. 3 .

3, the polarizing plate is a third protective layer 400, a polarizer 100, a first adhesive layer 300, a first liquid crystal retardation layer 200, a second adhesive layer 600, a second liquid crystal retardation layer ( 500) is included. A third protective layer 400 is laminated on the upper surface of the polarizer 100 , and the first adhesive layer 300 , the first liquid crystal retardation layer 200 , and the second from the polarizer 100 on the lower surface of the polarizer 100 . The adhesive layer 600 and the second liquid crystal retardation layer 500 are sequentially stacked. It is substantially the same as the polarizing plate of FIG. 2 , except that the second adhesive layer 600 and the second liquid crystal retardation layer 500 are further formed on the lower surface of the first liquid crystal retardation layer 200 .

second liquid crystal retardation layer

The second liquid crystal retardation layer 500 may prevent reflection of external light by circularly polarizing linearly polarized light emitted after external light passes through the polarizer 100 to improve screen quality.

In one embodiment, the second liquid crystal retardation layer 500 may have an in-plane retardation (Re) of 225 nm to 350 nm, specifically 225 nm to 300 nm, for example, λ/2 retardation at a wavelength of 550 nm. In the above range, it is possible to obtain an effect of improving screen quality by lowering the reflectance for external light.

In another embodiment, the second liquid crystal retardation layer 500 may have an in-plane retardation (Re) of 100 nm to 220 nm, specifically 100 nm to 180 nm, for example, λ/4 retardation at a wavelength of 550 nm. In the above range, it is possible to obtain an effect of improving screen quality by lowering the reflectance for external light.

The second liquid crystal retardation layer 500 may have a thickness of 0.1 μm to 30 μm, for example, 1 μm to 10 μm. Within the above range, the polarizing plate may be thinned and a target retardation may be realized.

The second liquid crystal retardation layer 500 has low adhesiveness. The low adhesion may be due to the second liquid crystal retardation layer being formed of a liquid crystal composition and having nx and ny in an appropriate range to implement the above-described in-plane retardation.

In one embodiment, the second liquid crystal retardation layer 500 may contain a hydrophobic aromatic ring-containing liquid crystal compound. For example, the second liquid crystal retardation layer 500 may be formed of the composition described in the above-described first liquid crystal retardation layer 200 .

second adhesive layer

The second adhesive layer 600 is formed between the first liquid crystal retardation layer 200 and the second liquid crystal retardation layer 500, and the first liquid crystal retardation layer 200 and the second liquid crystal retardation layer 500 are adhered to each other. can

In one embodiment, the second adhesive layer 600 may be directly formed on the first liquid crystal retardation layer 200 and the second liquid crystal retardation layer 500 , respectively. The "directly formed" means that an adhesive layer, an adhesive layer, or an adhesive layer other than the second adhesive layer 600 is not formed between the first liquid crystal retardation layer 200 and the second liquid crystal retardation layer 500 .

In one embodiment, the second adhesive layer 600 may be formed of the adhesive composition for a polarizing plate of the present invention described above in the first adhesive layer 300 .

In this case, the second adhesive layer 600 may have a thickness of 10 nm to 500 nm, for example, 50 nm to 100 nm. In the above range, it is possible to obtain a thinning effect of the polarizing plate.

In another embodiment, the second adhesive layer 600 may be formed of a conventional photocurable adhesive known to those skilled in the art. The photocurable adhesive may include an epoxy-based compound or a (meth)acrylic-based compound, and a photoinitiator. The epoxy-based compound or (meth)acrylic compound, and the photoinitiator may be selected from common types known to those skilled in the art.

In this case, the second adhesive layer 600 may have a thickness of 0.1 μm to 10 μm, for example, 1 μm to 5 μm. Within the above range, the adhesive force between the first liquid crystal retardation layer and the second liquid crystal retardation layer may be secured and the thickness of the polarizing plate may be reduced.

Although not shown in FIG. 3 , since an adhesive layer or an adhesive layer is also formed on the lower surface of the second liquid crystal retardation layer 600 , the polarizing plate may be adhered to a panel for an optical display device or the like. The adhesive layer or the adhesive layer may be formed of a (meth)acrylic composition known to those skilled in the art, but is not limited thereto.

Hereinafter, the manufacturing method of the polarizing plate of this invention is demonstrated.

The method for manufacturing a polarizing plate is to form a coating layer by applying the adhesive composition for a polarizing plate of the present invention to the surface or rear surface of the liquid crystal retardation layer, laminating the coating layer and a polarizer, and curing the adhesive composition for a polarizing plate to form a polarizer and a liquid crystal retardation layer Adhering may be included.

The method for producing a polarizing plate is to form a coating layer by applying the adhesive composition for a polarizing plate of the present invention to the surface or back surface of the liquid crystal retardation layer, laminating the coating layer and the liquid crystal retardation layer, and curing the adhesive composition for the polarizing plate to form a liquid crystal retardation layer and Adhering the liquid crystal retardation layer may be included. Before applying the adhesive composition for a polarizing plate to the surface or the back surface of the liquid crystal retardation layer, the adhesive force may be increased by corona-treating the surface or the back surface of the liquid crystal retardation layer, respectively.

The application may be performed by a conventional method known to those skilled in the art. For example, it may include, but is not limited to, a die coater, a bar coater, and the like. The curing may include thermal curing the coating layer. Thermal curing is not particularly limited and may be performed, for example, at 40° C. to 100° C. for 1 minute to 60 minutes or more.

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

For example, the optical display device may include, but is not limited to, a light emitting display device including an organic light emitting display device, a liquid crystal display device, and the like. For example, the optical display device may include a flexible optical display device.

Hereinafter, the configuration and operation of the present invention will be described in more detail through embodiments of the present invention. However, the following examples are provided to help the understanding of the present invention, and the scope of the present invention is not limited to the following examples.

A. Third protective layer: COP film (G+, Zeon, hard coating layer is formed on the upper surface, thickness: 28㎛)

B. First liquid crystal retardation film: a liquid crystal retardation film (Fujifilm, QLAA218, TAC) formed with a liquid crystal retardation layer (having a λ/2 retardation at a wavelength of 550 nm) on the lower surface of the base film (TAC film, thickness: 80 μm) The absorption axis is oriented at an angle of 17.5° to the MD of the film)

C. First liquid crystal retardation film: a liquid crystal retardation film (Fuji Film, QLAA338, TAC) formed with a liquid crystal retardation layer (having a λ/2 retardation at a wavelength of 550 nm) on the lower surface of the base film (TAC film, thickness: 80 μm) The absorption axis is oriented at an angle of -17.5° to the MD of the film)

D. Second liquid crystal retardation film: liquid crystal retardation film (FUJIFILM, QLAB, TAC) in which a liquid crystal retardation layer (having a λ/4 retardation at a wavelength of 550 nm) is formed on the upper surface of the base film (TAC film, thickness: 80 μm) The absorption axis is oriented at an angle of 77.5° to the MD of the film)

E.Corona treatment: Corona irradiation at 10mpm speed and 1000W output using a corona treatment device (AFS).

Example 1

<Third protective layer treatment>

The lower surface of the third protective layer was corona-treated.

<Manufacture of polarizer>

A polyvinyl alcohol-based film (Mitsubishi Chemical, polymerization degree: 2800, thickness: 20 μm) was immersed in 0.3% iodine aqueous solution and dyed. The film was stretched at a draw ratio of 5.0 times in MD uniaxial direction. The stretched polyvinyl alcohol-based film was immersed in 3% boric acid aqueous solution and 2% potassium iodide aqueous solution for color correction. A polarizer (thickness: 7 μm) was prepared by drying at 50° C. for 4 minutes.

<Manufacture of photocurable adhesive for polarizer>

Epoxy compound 2021P (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, Daicel) 80 parts by weight, Epoxy compound EX141 (phenyl glycidyl ether, Nagase Chemtech) 20 parts by weight, A photocurable adhesive for a polarizing plate was prepared by mixing 5 parts by weight of a cationic polymerization initiator CPI100P (SanApro).

<Production of water-based adhesive composition for polarizing plate>

3 parts by weight of acetoacetylated polyvinyl alcohol-based resin was dissolved in 100 parts by weight of water at 95° C. while stirring for 60 minutes. After cooling the obtained solution completely at room temperature, 0.1 parts by weight of a poly(ethyleneimine)-based crosslinking agent and 0.15 parts by weight of tannic acid were sequentially added, mixed with each other, and stirred with a magnetic stirrer to prepare an aqueous adhesive composition for a polarizing plate.

Table 1 below shows the content (unit: parts by weight) of the poly(ethyleneimine)-based crosslinking agent and tannic acid based on the solid content based on 3 parts by weight of the polyvinyl alcohol-based resin. In Table 1 below, "-" indicates that the component is not included.

<Manufacture of polarizing plate>

The above-mentioned corona treatment was performed on the surface of the first liquid crystal retardation film B.

Polyvinyl alcohol-based resin (Mitsubishi Chemical, Z200, acetoacetylated polyvinyl alcohol resin, average degree of polymerization: 1200, degree of saponification: 99 mol%, degree of acetoacetylation modification: 5 mol%) 3 parts by weight of water at 95°C It was put into 100 parts by weight and dissolved while stirring for 60 minutes. After the obtained solution is completely cooled at room temperature, 0.1 parts by weight of a poly(ethyleneimine)-based crosslinking agent (Nippon Catalyst, SP018) and 0.5 parts by weight of a zirconium compound (Zircosol-ZN, solvent is water, Jeilhee Element Chemicals) are sequentially added. After mixing with each other, the mixture was stirred with a magnetic stirrer to prepare an adhesive for a polarizing plate.

The prepared adhesive for a polarizing plate was coated on the upper surface of the prepared polarizer to a predetermined thickness, and the lower surface of the third protective layer was laminated on the obtained coating layer. Then, the prepared water-based adhesive composition for a polarizing plate was coated on the lower surface of the polarizer to a predetermined thickness, and the surface side of the first liquid crystal retardation film B was laminated on the obtained coating layer. At this time, the MD of the polarizer and the MD of the TAC film among the first liquid crystal retardation film B were matched with each other. Then, left in an oven at 50 ° C for 1 minute and oven at 85 ° C for 3 minutes, the third protective layer / adhesive layer / polarizer / adhesive layer / first liquid crystal retardation film (liquid crystal retardation layer / TAC film) laminated in the order was prepared.

The TAC film of the first liquid crystal retardation film was peeled off from the laminate to expose the back surface of the liquid crystal retardation layer. The above-mentioned corona treatment was carried out on the back side.

The surface side of the second liquid crystal retardation film was laminated on the coating layer obtained by applying the prepared photocurable adhesive for a polarizing plate to the rear surface of the liquid crystal retardation layer to a predetermined thickness. At this time, the MD of the polarizer and the MD of the TAC film among the second liquid crystal retardation film were matched with each other. Then, from the side of the second liquid crystal retardation film, UV was irradiated with a metal halide lamp at 100 mJ/cm ² and left at room temperature for 1 day, and then the TAC film of the second liquid crystal retardation film was peeled off. Through this, the third protective layer / adhesive layer (thickness: 100nm) / polarizer / adhesive layer (thickness: 100nm) / liquid crystal retardation layer (λ/2 retardation) / adhesive layer (thickness: 3㎛) / liquid crystal retardation layer (λ/4 retardation) ) to prepare a laminated polarizing plate in the order of.

Examples 2 and 3

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the type and/or content of each component in the aqueous adhesive composition for a polarizing plate was changed as shown in Table 1 (unit: parts by weight) below. .

Example 4

A third protective layer was treated in the same manner as in Example 1, and a polarizer, an adhesive for a polarizing plate, a photocurable adhesive for a polarizing plate, and a water-based adhesive composition for a polarizing plate were prepared.

<Manufacture of polarizing plate>

The corona treatment was performed on the surface of the first liquid crystal retardation film C and the surface of the second liquid crystal retardation film, respectively. The prepared photocurable adhesive for a polarizing plate was applied to the surface of the first liquid crystal retardation film C to a predetermined thickness, and the surface side of the second liquid crystal retardation film was laminated to the obtained coating layer. At this time, the MD of the TAC film of the first liquid crystal retardation film C and the MD of the TAC film of the second liquid crystal retardation film were made to coincide with each other. Then, the second liquid crystal retardation film side is irradiated with UV at 100mJ/cm ² with a metal halide lamp and left at room temperature for 1 day, the first liquid crystal retardation film (TAC film / liquid crystal retardation layer) / adhesive layer / second liquid crystal retardation film A laminate of (liquid crystal retardation layer/TAC film) was prepared.

The TAC film of the first liquid crystal retardation film was peeled off from the laminate to expose the back surface of the liquid crystal retardation layer. The above-mentioned corona treatment was performed on the exposed back surface.

In the same manner as in Example 1, the prepared adhesive for a polarizing plate was coated on the upper surface of the polarizer to a predetermined thickness, and the lower surface of the third protective layer was laminated on the obtained coating layer. The lower surface of the polarizer was coated with the prepared aqueous adhesive composition for a polarizing plate to a predetermined thickness, and the rear side of the liquid crystal retardation layer of the laminate was laminated on the obtained coating layer. Then, it was left in an oven at 50° C. for 1 minute and in an oven at 85° C. for 3 minutes, and the TAC film in the second liquid crystal retardation film was peeled off. Through this, the third protective layer / adhesive layer (thickness: 100nm) / polarizer / adhesive layer (thickness: 100nm) / liquid crystal retardation layer (λ/2 retardation) / adhesive layer (thickness: 3㎛) / liquid crystal retardation layer (λ/4 retardation) ) to prepare a laminated polarizing plate in the order of.

Examples 5 and 6

In Example 4, a polarizing plate was manufactured in the same manner as in Example 4, except that the type and/or content of each component in the aqueous adhesive composition for a polarizing plate was changed as shown in Table 1 (unit: parts by weight) below. .

Comparative Examples 1 to 3

In Example 1, the same method as in Example 1 was carried out, except that the type and/or content of each component in the water-based adhesive composition for a polarizing plate was changed as shown in Table 1 (unit: parts by weight) below, and the adhesive composition for a polarizing plate and a polarizing plate.

The composition (based on solid content) of the aqueous adhesive composition for a polarizing plate used in Examples and Comparative Examples is shown in Table 1 below. A portion of the liquid crystal retardation layer of the first liquid crystal retardation film that is adhered to the polarizer is shown in Table 1 below.

① ② ③ ④ ⑤ Part of the liquid crystal retardation film attached to the polarizer Example 1 3 - 0.1 0.15 - surface Example 2 3 - 0.1 0.3 - surface Example 3 3 - 0.1 0.9 - surface Example 4 3 - 0.1 0.15 - back Example 5 3 - 0.1 0.3 - back Example 6 3 - 0.1 0.9 - back Comparative Example 1 3 - 0.1 - - surface Comparative Example 2 3 - - 0.15 - surface Comparative Example 3 - 3 0.1 0.15 - surface

*In Table 1 above

①: polyvinyl alcohol-based resin (Mitsubishi Chemical, Z200, acetoacetylated polyvinyl alcohol resin, average degree of polymerization: 1200, degree of saponification: 99 mol%, degree of acetoacetylation modification: 5 mol%)

②: polyvinyl alcohol-based resin (polyvinyl alcohol resin without acetoacetylation, average degree of polymerization: 2500, degree of saponification: 99 mol%, Poval JC-25, Mitsubishi Chemical)

③: poly(ethyleneimine)-based crosslinking agent (Nippon Catalyst, SP018, having a primary amine group and/or a secondary amine group)

④: Tannic acid (Daejeong Hwageum, 100% solids)

⑤: Zirconium compound (Zircosol-ZN, solvent is water, Jeilhee Elemental Chemicals Co., Ltd.)

The following physical properties were evaluated for the aqueous adhesive composition for a polarizing plate of Examples and Comparative Examples, and the polarizing plate, and the results are shown in Table 2 below.

(1) Solution state: 100 g of the adhesive composition prepared in Examples and Comparative Examples was placed in a 250 ml glass container, stirred with a magnetic bar at 500 rpm for 1 hour, and then visually confirmed. If there was no visually discernable precipitate, "○" was evaluated as "X".

(2) Peeling force to the liquid crystal retardation layer (unit: gf/inch): The polarizing plate prepared in Examples and Comparative Examples was cut to a size of MD x TD 100mm x 25mm of the polarizer to prepare a sample. A specimen for measuring peel force was prepared by attaching a cellophane tape (length x width, 150mm x 25mm) to the liquid crystal retardation layer side of the above-mentioned sample so that a length of 50mm was left. A 90° sliding jig was installed on the lower grab of the peel force measuring device Texture analyzer (TA, TX C model), and the third protective layer of the above specimen was attached to the lower grab. The cellophane tape of the above-mentioned specimen was fixed to the lower grab of the peel force measuring device. When the liquid crystal retardation layer was peeled from the polarizer at a peeling temperature of 25° C., a peeling rate of 5 mm/sec, and a peeling angle of 90°, the peeling force at the time when the peeling first occurred was evaluated. The adhesive layer preferably has a peeling force with respect to the liquid crystal retardation layer of 250 gf/inch or more, specifically 250 gf/inch to 500 gf/inch. In the above range, the adhesive strength may be good and the reliability of the polarizing plate may be excellent.

(3) Whether or not peeling at ultra low temperature: The polarizing plates prepared in Examples and Comparative Examples were cut to a size of length x width (100mm x 100mm), and the polarizing plates were placed at equal intervals of 5 horizontal and vertical lines on the first liquid crystal retardation layer surface. It made a slight scratch to a level that could not be completely cut off. Then, it was placed in liquid nitrogen (-196° C.) and after 1 minute, if the first liquid crystal retardation layer was not separated from the polarizer, it was evaluated as “○”, and if the first liquid crystal retardation layer was separated from the polarizer even a little, it was evaluated as “X” .

(4) High-temperature, high-humidity durability: The polarizing plates prepared in Examples and Comparative Examples were cut in length x width (50mm x 50mm) so that the absorption axis direction of the polarizer was 45 degrees (diagonal direction), and then attached to a glass plate to prepare the specimen. prepared. The prepared specimen was left in a chamber at 60° C. and 95% relative humidity for 500 hours. As shown in FIG. 4 , the average value of the four values of the discoloration length of the polarizer measured in a 45 degree direction (edge of the polarizer) with respect to the length or width of the specimen was measured. The obtained average value was evaluated according to the following criteria.

○: less than 1mm

△: 1 mm or more and less than 3 mm

Х: more than 3mm

(5) Bending Reliability: For the polarizing plates prepared in Examples and Comparative Examples, a square specimen of length x width (50 mm x 50 mm) was prepared so that the absorption axis direction of the polarizer was 45 degrees (diagonal direction). 5, the prepared specimen 10 is folded in half so as to have a radius of curvature of 1.5R, respectively, and placed between two slits 20 having a fixed shape, and placed in a chamber of 60° C. and 95% relative humidity. After standing for 500 hours, it was taken out. It was evaluated as “○” when bubbles, wrinkles, or wavy patterns did not occur at all in the folded portion due to lifting at the interlayer interface, and “x” when any bubbles, wrinkles, or wavy patterns occurred.

solution state peel force Whether or not peeling at cryogenic temperatures durability Bend Reliability Example 1 ○ 350 ○ ○ ○ Example 2 ○ 500 ○ ○ ○ Example 3 ○ 440 ○ ○ ○ Example 4 ○ 250 ○ ○ ○ Example 5 ○ 360 ○ ○ ○ Example 6 ○ 330 ○ ○ ○ Comparative Example 1 ○ 50 X △ ○ Comparative Example 2 ○ 150 ○ X X Comparative Example 3 ○ 180 ○ X ○

As shown in Table 2, the adhesive composition for a polarizing plate of the present invention formed an adhesive layer having excellent adhesion between the surface and the rear surface of the liquid crystal retardation layer having low adhesiveness and the polarizer. In addition, the adhesive composition for a polarizing plate of the present invention formed an adhesive layer having excellent adhesion between the liquid crystal retardation layer and the polarizer with low adhesion even at room temperature and ultra low temperature. In addition, the adhesive composition for a polarizing plate of the present invention formed an adhesive layer capable of providing a polarizing plate having excellent high-temperature, high-humidity durability and bending reliability.

On the other hand, the adhesive composition for a polarizing plate of the comparative example that does not satisfy the configuration of the present invention could not obtain all of the above-described effects of the present invention.

Simple modifications or changes of the present invention can be easily carried out by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (14)

An acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH ₂ ) and/or a secondary amine group (-NH-), and a polyphenol-based compound, the adhesive composition for a polarizing plate.
The adhesive composition for a polarizing plate according to claim 1, wherein the crosslinking agent having a primary amine group or a secondary amine group includes at least one ethyleneimine-based crosslinking agent.
The adhesive composition for a polarizing plate according to claim 1, wherein the crosslinking agent: the polyphenol-based compound is included in a weight ratio of 1:1 to 1:20.
The adhesive composition for a polarizing plate according to claim 1, wherein the polyphenol-based compound comprises tannic acid.
The adhesive composition for a polarizing plate according to claim 1, wherein the acetoacetylated polyvinyl alcohol-based resin has an acetoacetyl group modification of 1 mol% to 30 mol%.
According to claim 1, wherein the composition is
100 parts by weight of the polyvinyl alcohol-based resin, 0.1 parts by weight to 50 parts by weight of a crosslinking agent having a primary amine group or a secondary amine group, and 1 part by weight to 100 parts by weight of the polyphenol-based compound. composition.
polarizer; a first liquid crystal retardation layer laminated on the lower surface of the polarizer; and a first adhesive layer for adhering the polarizer and the first liquid crystal retardation layer,
The first adhesive layer is formed of the adhesive composition for a polarizing plate according to any one of claims 1 to 6, a polarizing plate.
The polarizing plate of claim 7 , wherein the first liquid crystal retardation layer includes an aromatic-containing liquid crystal compound.
The polarizing plate of claim 7 , wherein a second adhesive layer and a second liquid crystal retardation layer are further laminated on a lower surface of the first liquid crystal retardation layer.
The polarizing plate of claim 9 , wherein the second liquid crystal retardation layer includes an aromatic-containing liquid crystal compound.
10. The method of claim 9, wherein the second adhesive layer is an acetoacetylated polyvinyl alcohol-based resin, a crosslinking agent having a primary amine group (-NH ₂ ) and/or a secondary amine group (-NH-) and a polyphenol-based compound Which is formed of an adhesive composition for a polarizing plate comprising a polarizing plate.
The polarizing plate according to claim 11, wherein the crosslinking agent having a primary amine group or a secondary amine group includes at least one ethyleneimine-based crosslinking agent.
The polarizing plate of claim 12 , wherein the polyphenol-based compound includes tannic acid.
The optical display device comprising the polarizing plate of claim 7.

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