CN109207103B

CN109207103B - Adhesive film and adhesive composition for polarizing plate, polarizing plate including the same, and optical display including the same

Info

Publication number: CN109207103B
Application number: CN201810728650.6A
Authority: CN
Inventors: 伊里纳·纳玛; 韩仁天; 金大润; 崔柱烈
Original assignee: Samsung SDI Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 2017-07-04
Filing date: 2018-07-04
Publication date: 2021-11-26
Anticipated expiration: 2038-07-04
Also published as: CN109207103A

Abstract

Disclosed are an adhesive film and an adhesive composition for a polarizing plate, a polarizing plate including the adhesive film, and an optical display including the polarizing plate. The adhesive film for a polarizing plate includes: comprises having C₄‑C₈Alkyl (meth) acrylate, (meth) acrylate having hydroxyl group, and (meth) acrylate having C₁‑C₃A (meth) acrylic copolymer of a monomer mixture of at least one of a (meth) acrylic acid ester of an alkyl group and a (meth) acrylic monomer having an amide group, and satisfying the following formulas 1 and 2:<formula 1>0.20≤tanδ2≤0.40<Formula 2>tan delta 2-tan delta 1 ≦ 0.04 where tan delta 1 is a tan delta value of the adhesive film for a polarizing plate at 23 ℃ and tan delta 2 is a tan delta value of the adhesive film for a polarizing plate at 80 ℃.

Description

Adhesive film and adhesive composition for polarizing plate, polarizing plate including the same, and optical display including the same

Citations to related applications

This application claims the benefit of having korean patent application No. 10-2017-.

Technical Field

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

Background

The liquid crystal display includes a liquid crystal panel and polarizing plates attached to both surfaces of the liquid crystal panel. The polarizing plate includes a polarizer and a protective film attached to one or both surfaces of the polarizer to protect the polarizer. The polarizing plate is attached to the liquid crystal panel via an adhesive film for polarizing plate.

The adhesive film for a polarizing plate is prepared by depositing the adhesive composition on a release film in a predetermined thickness and then drying. The adhesive film for a polarizing plate is provided in the form of a laminate of a release film, an adhesive film for a polarizing plate, and a release film for packaging, storage, and/or delivery. The peeling film prevents the adhesive film from being contaminated by foreign substances. However, the adhesive film for a polarizing plate may come into contact with external solid particles during packaging, storage or delivery and may be pressed thereby. Such indentations in the adhesive film are referred to as depressions.

Although the release film is formed on the adhesive film, it is difficult to prevent such a dent from being generated in the adhesive film. The polarizing plate including such an adhesive film having depressions may result in poor screen quality. On the other hand, the adhesive film for a polarizing plate is attached to the polarizing plate and cut before processing. During this process, the adhesive film can be collapsed by the solid particles. Therefore, there is a need for an adhesive film that can prevent the generation of depressions by solid particles or can be quickly recovered even when the adhesive film is collapsed by the solid particles.

As a method for reducing the dishing in the adhesive film, the content of the curing agent or the glass transition temperature of the (meth) acrylic copolymer in the adhesive film is increased. However, the increase in the content of the curing agent causes the polarizing plate to warp at high temperature. In addition, an increase in the glass transition temperature of the (meth) acrylic copolymer causes the polarizing plate to warp at high temperature.

The background art of the present invention is disclosed in Japanese unexamined patent publication No. 2015-010192.

Disclosure of Invention

An aspect of the present invention is to provide an adhesive film for a polarizing plate capable of suppressing and/or rapidly recovering depressions in the adhesive film, for example, due to solid particles, during processing, cutting, packaging, and/or storage of the adhesive film.

Another aspect of the present invention is to provide an adhesive film for a polarizing plate capable of suppressing warpage due to shrinkage of the polarizing plate (polarizer) at high temperature.

It is still another aspect of the present invention to provide an adhesive film for a polarizing plate capable of realizing an excellent light leakage inhibiting effect by alleviating shrinkage of a polarizer at high temperature.

It is still another aspect of the present invention to provide an adhesive film for a polarizing plate, which exhibits good durability at high temperature or under high temperature/high humidity conditions, and has good properties in inhibiting corrosion and reworkability when attached to a metal adherend including an Indium Tin Oxide (ITO) film.

According to one aspect of the present invention, an adhesive film for a polarizing plate includes: comprises having C₄-C₈Alkyl (meth) acrylate, (meth) acrylate having hydroxyl group, and (meth) acrylate having C₁-C₃A (meth) acrylic copolymer of a monomer mixture of at least one of a (meth) acrylic acid ester of an alkyl group and a (meth) acrylic monomer having an amide group, and satisfying the following formulae 1 and 2:

< formula 1>

0.20≤tanδ2≤0.40

< formula 2>

tanδ2–tanδ1≤0.04

(wherein tan. delta.1 is the tan. delta. value of the adhesive film for polarizing plate at 23 ℃ and tan. delta.2 is the tan. delta. value of the adhesive film for polarizing plate at 80 ℃).

According to another aspect of the present invention, an adhesive for a polarizing plateA composition of a composition comprising: comprises having C₄-C₈Alkyl (meth) acrylate, (meth) acrylate having hydroxyl group, and (meth) acrylate having C₁-C₃A (meth) acrylic copolymer of a monomer mixture of at least one of an alkyl (meth) acrylate and an amide group-containing (meth) acrylic monomer; wherein the adhesive film for a polarizing plate formed from the adhesive composition for a polarizing plate satisfies the following formulae 1 and 2:

< formula 1>

0.20≤tanδ2≤0.40

< formula 2>

tanδ2–tanδ1≤0.04

According to still another aspect of the present invention, a polarizing plate includes the adhesive film for a polarizing plate according to the present invention.

According to still another aspect of the present invention, an optical display includes the adhesive film for a polarizing plate according to the present invention or the polarizing plate according to the present invention.

Drawings

FIG. 1 is a schematic diagram for measuring creep.

Fig. 2 is a schematic diagram for measuring light leakage.

Detailed Description

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings to provide those skilled in the art with a full understanding of the invention. It is to be understood that the present invention may be embodied in various forms and is not limited to the following embodiments.

Herein, the terms "adhesive film for polarizing plate" (or "adhesive film for polarizing plate") and "adhesive composition for polarizing plate" can be simply represented by the terms "adhesive film" and "adhesive composition", respectively.

Herein, the term "(meth) acryl" refers to acryl and/or methacryl.

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

The adhesive film for a polarizing plate according to one embodiment of the present invention includes: comprises having C₄-C₈Alkyl (meth) acrylate, (meth) acrylate having hydroxyl group, and (meth) acrylate having C₁-C₃A (meth) acrylic copolymer of a monomer mixture of at least one of a (meth) acrylic acid ester of an alkyl group and a (meth) acrylic monomer having an amide group, and satisfying the following formulae 1 and 2:

< formula 1>

0.20≤tanδ2≤0.40

< formula 2>

tanδ2–tanδ1≤0.04

When the adhesive film for a polarizing plate satisfies formula 1 and formula 2 and includes the (meth) acrylic copolymer, the adhesive film can suppress and/or rapidly recover during processing, cutting, packaging, and/or storage of the adhesive film, for example, a dent due to solid particles in the adhesive film, and can suppress a warp due to shrinkage of the polarizing plate (polarizer) at high temperature. The adhesive film satisfying the formula 1 but not satisfying the formula 2 does not have an effect of suppressing warpage due to shrinkage of the polarizing plate at high temperature, nor an effect of suppressing or rapidly restoring depressions in the adhesive film, thereby suffering from a decrease in processability. In one embodiment, the adhesive film satisfies formulas 1 and 2 and has a sag of about 18 μm or less, for example, about 9 μm or less, or about 8 μm or less. Within this range, the adhesive film does not suffer from dishing or slight dishing, and thus can be used for a polarizing plate. Herein, the term "depressions" refers to the depth or depression of the depressions in the adhesive film.

Preferably, the adhesive film has a tan delta 2 value of from about 0.21 to about 0.38, more preferably from about 0.23 to about 0.35. Preferably, the adhesive film has a difference of (tan delta 2-tan delta 1) of about-0.20 to about 0.02. The adhesive films have tan delta 1 values of from about 0.10 to about 0.50, preferably from about 0.15 to about 0.45, and more preferably from about 0.18 to about 0.45. Within this range, the adhesive film can satisfy the formulas 1 and 2.

In one embodiment, the adhesive film may satisfy formula 3:

< formula 3>

tanδ2/tanδ1<1.1

When the adhesive film satisfies formula 3, the adhesive film can suppress warpage due to shrinkage of the polarizing plate at high temperature even if the adhesive film does not contain a carboxylic acid group, and can suppress or quickly recover depressions in the adhesive film. Preferably, the adhesive film has a ratio of tan delta 2 to tan delta 1 (tan delta 2/tan delta 1) of from about 0.50 to about 1.05.

The adhesive film may be formed of an adhesive composition for a polarizing plate, the adhesive composition including: containing a compound having C₄-C₈Alkyl (meth) acrylate, (meth) acrylate having hydroxyl group, and (meth) acrylate having C₁-C₃A (meth) acrylic copolymer of a monomer mixture of at least one of an alkyl (meth) acrylate and an amide group-containing (meth) acrylic monomer; and a curing agent.

Said has C₄-C₈The alkyl (meth) acrylate forms a matrix of the adhesive film to improve mechanical strength of the adhesive film while allowing other components to be included in the monomer mixture in appropriate amounts such that the adhesive film satisfies formulas 1 and 2. For example, said has C₄-C₈The (meth) acrylate of the alkyl group is a non-hydroxyl group-containing monomer having no hydroxyl group, and may include, but is not limited to, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, and isooctyl (meth) acrylate. These may be used alone or as a mixture thereof.

In one embodiment, the compound has C₄-C₈The (meth) acrylate of the alkyl group may include a (meth) acrylate having a glass transition temperature of-45 ℃ or less, preferably-70 to-45 ℃ in the homopolymer phase. Within this range, the compound has C₄-C₈The alkyl (meth) acrylate allows the adhesive film to satisfy formulas 1 and 2 together with other components in the monomer mixture. For example, said has C₄-C₈The (meth) acrylate of the alkyl group may include at least one of n-butyl acrylate, 2-ethylhexyl acrylate, and n-hexyl acrylate, but is not limited thereto.

Said has C₄-C₈The alkyl (meth) acrylate may be present in the monomer mixture in an amount of about 40 mol% to about 78 mol%, for example, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, or 78 mol%, preferably about 43 mol% to about 78 mol%. Within this range, the adhesive film can maintain mechanical strength while satisfying formulas 1 and 2.

The (meth) acrylate having a hydroxyl group can improve the adhesive strength of the adhesive film by reacting with the curing agent. The (meth) acrylate having a hydroxyl group may include a monomer having C having at least one hydroxyl group₁-C₂₀Alkyl (meth) acrylates. For example, the (meth) acrylate having a hydroxyl group may include at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 1-chloro-2-hydroxypropyl (meth) acrylate, and combinations thereof.

The (meth) acrylate having a hydroxyl group may be present in the monomer mixture in an amount of about 0.1 mol% to about 20 mol%, for example, 0.1 mol%, 0.5 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, or 20 mol%, about 0.1 mol% to about 15 mol%, preferably about 1 mol% to about 10 mol%, more preferably about 1 mol% to about 5 mol%. Within this range, the adhesive film can maintain mechanical strength while satisfying formulas 1 and 2.

The monomer mixture may include about 10 mol% to about 40 mol% of the monomer mixture having C₁-C₃At least one of a (meth) acrylate of an alkyl group and the (meth) acrylic monomer having an amide group. Accordingly, the adhesive film can satisfy formulas 1 and 2.

In some embodiments, the monomer mixture may include the monomer having C₁-C₃An alkyl group, and may be free of the (meth) acrylic monomer having an amide group. In other embodiments, the monomer mixture may include the (meth) acrylic monomer having an amide group, and may not include the monomer having C₁-C₃Alkyl (meth) acrylates. In other embodiments, the monomer mixture may include both the monomer having C₁-C₃An alkyl group (meth) acrylate and the (meth) acrylic monomer having an amide group.

Preferably said monomer mixture has said formula C₁-C₃At least one of the (meth) acrylate of the alkyl group and the (meth) acrylic monomer having the amide group has a glass transition temperature of about 5 to about 150 ℃ in a homopolymer phase. Within this range, the monomer mixture allows the adhesive film to satisfy formulas 1 and 2 while improving durability thereof.

Said has C₁-C₃The (meth) acrylate of the alkyl group may include at least one of methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate, but is not limited thereto. Preferably said has C₁-C₃The alkyl (meth) acrylate has a glass transition temperature of 5 to 50 ℃ in the homopolymer phase. Within this range, the adhesive film may satisfy formulas 1 and 2 while improving durability thereof.

Said has C₁-C₃The alkyl (meth) acrylate may be present in the monomer mixture in an amount of 0 mol% to about 40 mol%, for example, 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, or 40 mol%, about 1 mol% to about 40 mol%, or about 5 mol% to about 40 mol%. Within this range, the monomer mixture allows the adhesive film to satisfy the formulas 1 and 2 while improving durability thereof.

The (meth) acrylic monomer having an amide group may include a (meth) acrylic monomer containing a morpholine group, such as at least one of (meth) acryloylmorpholine and (meth) acrylamide, but is not limited thereto. Preferably, the (meth) acrylic monomer having an amide group has a glass transition temperature of about 100 to about 200 ℃ in a homopolymer phase. The (meth) acrylic monomer having an amide group preferably includes a (meth) acrylic monomer containing a morpholino group, such as (meth) acryloylmorpholine. Within this range, the monomer mixture allows the adhesive film to satisfy the formulas 1 and 2 while improving durability thereof.

The (meth) acrylic monomer having an amide group may be present in an amount of 0 mol% to about 40 mol%, for example, 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol% or 40 mol%, about 1 mol% to about 20 mol%, for example, from about 1 mol% to about 15 mol%, for example, from about 5 mol% to about 15 mol%, is present in the monomer mixture. Within this range, the monomer mixture allows the adhesive film to satisfy formulas 1 and 2 while improving durability thereof.

The monomer mixture may further comprise a (meth) acrylic monomer having a tertiary amine group. The (meth) acrylic monomer having a tertiary amine group can improve the polymerization rate of the (meth) acrylic copolymer and the aging rate of the adhesive film.

The (meth) acrylic monomer having a tertiary amine group may include C having a tertiary amine-containing group₁-C₅Alkyl (meth) acrylates. For example, the (meth) acrylic monomer having a tertiary amine group may include a dialkylaminoalkyl (meth) acrylate, and may include at least one of dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dimethylaminobutyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, diethylaminobutyl (meth) acrylate, and dibutylaminoethyl (meth) acrylate.

The (meth) acrylic monomer having a tertiary amine group can be present in the monomer mixture in an amount of 0 mol% to about 15 mol%, for example, 0 mol%, 0.01 mol%, 0.02 mol%, 0.03 mol%, 0.04 mol%, 0.05 mol%, 0.06 mol%, 0.07 mol%, 0.08 mol%, 0.09 mol%, 0.1 mol%, 0.2 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, about 0.001 mol% to about 15 mol%, specifically about 0.01 mol% to about 10 mol%, more specifically about 0.01 mol% to about 1 mol%. Within this range, the monomer mixture may increase the aging rate of the adhesive composition for a polarizing plate or a dried product thereof at room temperature while improving the curing reaction thereof.

The monomer mixture may further include at least one of a (meth) acrylate having an alicyclic group and a (meth) acrylate having an aromatic group. The (meth) acrylate having an alicyclic group and the (meth) acrylate having an aromatic group can improve light leakage characteristics of the adhesive film.

At least one of the (meth) acrylate having an alicyclic group and the (meth) acrylate having an aromatic group may be present in the monomer mixture in an amount of 0 mol% to about 20 mol%, for example, 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, or 20 mol%, about 0.001 mol% to about 20 mol%, for example, about 5 mol% to about 20 mol%, for example, about 10 mol% to about 15 mol%. Within this range, the monomer mixture can improve light leakage characteristics of the adhesive film.

The (meth) acrylate having an alicyclic group is a compound having C₅-C₂₀And may include at least one of cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, methylcyclohexyl (meth) acrylate, and dicyclopentenyl (meth) acrylate. These may be used alone or as a mixture thereof. Preferably, the (meth) acrylate having an alicyclic group includes at least one of cyclohexyl (meth) acrylate and isobornyl (meth) acrylate.

The (meth) acrylate having an aromatic group may include a monomer having C₆-C₂₀Aryl or C₇-C₂₀(meth) acrylate of aralkyl. Specifically, the (meth) acrylate having an aromatic group may include benzyl (meth) acrylate, but is not limited thereto.

The monomer mixture is free of (meth) acrylic monomers having carboxylic acid groups. The adhesive film includes a carboxylic acid group-free (meth) acrylic polymer to inhibit corrosion of the metal adherend. The (meth) acrylic copolymer can have an acid number of about 5mg KOH/g or less, particularly about 1mg KOH/g or less. Within this range, the (meth) acrylic copolymer is capable of directly or indirectly achieving corrosion inhibition with respect to the adherend.

The monomer mixture may be free of (meth) acrylates having long chain alkyl groups. When the monomer mixture contains a (meth) acrylate having a long-chain alkyl group, the (meth) acrylic copolymer cannot obtain the advantageous effects of the present invention. The "(meth) acrylate having a long chain alkyl group" can mean having C₁₀-C₂₅Alkyl (meth) acrylates.

The (meth) acrylic copolymer has a glass transition temperature of from about-30 ℃ to about-10 ℃, preferably from about-25 ℃ to about-10 ℃, more preferably from about-22 ℃ to about-13 ℃. Within this range, the adhesive film can suppress sagging and warping.

The (meth) acrylic copolymer may have a weight average molecular weight of about 500,000g/mol to about 1,500,000g/mol, preferably about 500,000g/mol to about 1,000,000g/mol, more preferably about 700,000g/mol to about 1,000,000 g/mol. Within this range, the adhesive film can suppress sagging and warping.

The (meth) acrylic copolymer can be prepared by a typical polymerization method. The polymerization method may include typical methods known to those skilled in the art. For example, the (meth) acrylic copolymer may be prepared by a typical copolymer polymerization method, e.g., suspension polymerization, emulsion polymerization, solution polymerization, etc., after adding an initiator to the monomer mixture. The polymerization may be carried out at a temperature of about 65 ℃ to about 70 ℃ for about 6 hours to about 8 hours. The initiator may be a typical initiator including an azo-type polymerization initiator and/or a peroxide polymerization initiator such as benzoyl peroxide or acetyl peroxide.

The curing agent is capable of providing adhesive strength by reacting with the (meth) acrylic copolymer. The curing agent may include a thermal curing agent and a light curing agent. The curing agent may be present in an amount of about 0.001 to about 5 parts by weight, for example, 0.001, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 parts by weight, preferably about 0.001 to about 3 parts by weight, more preferably about 0.05 to about 3 parts by weight, about 0.3 to about 3 parts by weight, or about 0.1 to about 2.5 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the curing agent can provide an adhesive effect to the adhesive composition through crosslinking of the adhesive composition while preventing deterioration of transparency due to excessive use.

The thermal curing agent may include at least one of an isocyanate curing agent, for example, at least one of a polyalkylene glycol-unmodified isocyanate curing agent and a polyalkylene glycol-modified isocyanate curing agent; a metal chelate curing agent; an epoxy curing agent; an aziridine curing agent; an amine curing agent; and a thermal polymerization initiator. The thermal curing agent preferably includes at least one of an isocyanate curing agent and a metal chelate curing agent. These may be used alone or in combination thereof.

The isocyanate curing agent may be a bifunctional or polyfunctional isocyanate curing agent, preferably a bifunctional to hexafunctional isocyanate curing agent, but is not limited thereto.

In one embodiment, the isocyanate curing agent may include at least one of the polyalkylene glycol unmodified isocyanate curing agent and the polyalkylene glycol modified isocyanate curing agent.

The polyalkylene glycol unmodified isocyanate curing agent may include an isocyanate curing agent that does not contain polyalkylene glycol units. For example, the polyalkylene glycol unmodified isocyanate curing agent may include at least one of Xylene Diisocyanate (XDI) including m-xylene diisocyanate and the like, methylene bis (phenyl isocyanate) (MDI) including 4,4' -methylene bis (phenyl isocyanate) and the like, naphthalene diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

The polyalkylene glycol-modified isocyanate curing agent may include a curing agent in which one or more isocyanate groups in a bifunctional or polyfunctional polyalkylene glycol-unmodified isocyanate curing agent are modified with a polyalkylene glycol. The polyalkylene glycol-modified isocyanate curing agent can reduce dishing if not used in excess, and can suppress light leakage and warpage of a polarizing plate at high temperatures by reducing creep generation at high temperatures. In particular, the adhesive film formed from the adhesive composition can be quickly restored to an original state even when the adhesive film is pressed by solid particles, thereby improving workability.

The polyalkylene glycol-modified isocyanate curing agent may be prepared by mixing a polyalkylene glycol with a di-or polyfunctional isocyanate curing agent in a predetermined molar ratio and then reacting at a predetermined temperature. One or more isocyanate groups in the isocyanate curing agent are modified by reaction with a polyalkylene glycol. The polyalkylene glycol-modified isocyanate curing agent may be prepared by mixing the polyalkylene glycol with a di-or polyfunctional isocyanate curing agent in a molar ratio of about 1:2 to about 1:6, followed by reaction at about 40 to about 70 ℃. Herein, in order to improve the reaction yield, a reaction catalyst such as DBTDL (dibutyltin dilaurate) may be used.

Preferably, the polyalkylene glycol-modified isocyanate curing agent is a difunctional isocyanate curing agent. With the curing agent, the (meth) acrylic copolymer can be sufficiently cured and allow quick recovery of the adhesive film even in the case where the adhesive film has dents (depressions).

The polyalkylene glycol may have a number average molecular weight (Mn) of from about 300g/mol to about 5000g/mol, preferably from about 400g/mol to about 3000 g/mol. Within this range, the polyalkylene glycol can suppress warpage of the polarizing plate at high temperatures, allow effective curing of the (meth) acrylic copolymer by preventing an excessive increase in the number average molecular weight of the curing agent, and improve the sag-inhibiting effect.

The polyalkylene glycol includes a plurality of alkylene glycol repeating units having primary or secondary alcohol carbons, for example, polypropylene glycol (PPG), polyethylene glycol (PEG), and the like. The isocyanate curing agent modified with a polyol having a tertiary alcohol carbon (e.g., trimethylolpropane) increases in rigidity at high temperatures, thereby deteriorating the warpage or dent inhibiting effect.

The di-or higher-functional isocyanate curing agent means a di-to hexa-functional isocyanate curing agent, and may include at least one of Xylene Diisocyanate (XDI) including m-xylene diisocyanate and the like, methylene bis (phenyl isocyanate) (MDI) including 4,4' -methylene bis (phenyl isocyanate) and the like, naphthalene diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Isocyanate curing agents preferably having aromatic groups, for example, Xylene Diisocyanate (XDI) including m-xylene diisocyanate, methylene bis (phenyl isocyanate) (MDI) including 4,4' -methylene bis (phenyl isocyanate), and the like can be used. The bifunctional or higher isocyanate curing agent is capable of reducing a difference in refractive index together with the (meth) acrylic monomer having an aromatic group, thereby further improving transparency of the adhesive film.

The polyalkylene glycol-modified isocyanate curing agent may have a weight average molecular weight of from about 350g/mol to about 5000g/mol, preferably from about 450g/mol to about 4000 g/mol. Within this range, the polyalkylene glycol-modified isocyanate curing agent can ensure the curing effect of the (meth) acrylic copolymer and the warpage-suppressing effect at high temperatures.

In one embodiment, an adhesive film comprising the polyalkylene glycol-modified isocyanate curative may have a creep at 85 ℃ of about 200 μm or greater, for example, about 250 μm or greater, for example, from about 250 μm to about 800 μm. Within this range, the adhesive film can suppress light leakage and warpage of the polarizing plate.

The metal chelate curing agent may include a polyvalent metal coordinately bound coordination compound such as aluminum. For example, the metal chelate curing agent may include an aluminum-based chelating compound such as aluminum tris (ethylacetoacetate), aluminum diisopropylacetoacetate, and aluminum tris (acetylacetonate).

The thermal polymerization initiator may include at least one of an azo-based compound, a peroxide compound, and a redox compound. Examples of the peroxide compound may include: inorganic peroxides such as potassium perchlorate, ammonium persulfate, and hydrogen peroxide; and organic peroxides, such as diacyl peroxide, peroxydicarbonate, peroxyester, tetramethylbutyl peroxyneodecanoate, bis (4-butylcyclohexyl) peroxydicarbonate, bis (2-ethylhexyl) peroxycarbonate, butyl peroxyneodecanoate, dipropyl peroxydicarbonate, diisopropyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, diethoxyhexyl peroxydicarbonate, hexyl peroxydicarbonate, dimethoxybutyl peroxydicarbonate, bis (3-methoxy-3-methoxybutyl) peroxydicarbonate, dibutyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1,3, 3-tetramethylbutyl peroxypivalate, hexyl peroxypivalate, butyl peroxypivalate, trimethylhexanoyl peroxide, Dimethyl hydroxybutyl peroxyneodecanoate, amyl peroxyneodecanoate, butyl peroxyneodecanoate, tert-butyl peroxyneoheptanoate, amyl peroxypivalate, tert-butyl peroxypivalate, tert-amyl peroxy-2-ethylhexanoate, lauroyl peroxide, dilauroyl peroxide, didecanoyl peroxide, benzoyl peroxide, and dibenzoyl peroxide.

Preferably, the thermal curing agent is present in an amount of about 0.001 to about 5 parts by weight, for example, 0.001, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 parts by weight, preferably about 0.001 to about 3 parts by weight, more preferably about 0.05 to about 3 parts by weight, about 0.3 to about 3 parts by weight, or about 0.1 to about 2.5 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the heat-curing agent can provide an adhesive effect to the adhesive composition through crosslinking of the adhesive composition while preventing deterioration of transparency due to excessive use.

The photo-curing agent may include at least one of difunctional to hexafunctional (meth) acrylates and a photoinitiator.

The di-to hexa-functional (meth) acrylate includes one of difunctional acrylates, such as 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, dicyclopentyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified di (meth) acrylate, di (meth) acryloyloxyethyl isocyanurate, allylated cyclohexyl di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, dimethylol dicyclopentane di (meth) acrylate, ethylene oxide-modified hexahydrophthalic acid di (meth) acrylate, and mixtures thereof, Tricyclodecane dimethanol (meth) acrylate, neopentyl glycol modified trimethylpropane di (meth) acrylate, adamantane di (meth) acrylate and 9, 9-bis [4- (2-acryloyloxyethoxy) phenyl ] fluorene; trifunctional acrylates, such as trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, trifunctional urethane (meth) acrylate, and tri (meth) acryloyloxyethyl isocyanurate; tetrafunctional acrylates, such as diglycerin tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; pentafunctional acrylates, such as dipentaerythritol penta (meth) acrylate; and hexafunctional acrylates such as dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, and urethane (meth) acrylate (e.g., a reaction product of an isocyanate monomer and trimethylolpropane tri (meth) acrylate).

The di-to hexafunctional (meth) acrylate may be present in an amount of about 0.1 to about 5.0 parts by weight, for example, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 parts by weight, preferably about 0.1 to about 1.0 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the photo-curing agent can provide an adhesive effect to the adhesive composition by crosslinking of the adhesive composition, while preventing deterioration of transparency due to excessive use.

The photoinitiator may be any initiator as long as the initiator is capable of generating radicals by irradiation of light to cause photopolymerization of the adhesive composition. For example, the photoinitiator may include benzoin, hydroxyketones, aminoketones, phosphine oxide initiators, and the like.

The photoinitiator may be present in an amount of about 0.1 to about 5.0 parts by weight, for example, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 parts by weight, preferably about 0.1 to about 2.0 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the photoinitiator can provide an adhesive effect to the adhesive composition through crosslinking of the adhesive composition while preventing deterioration of transparency due to excessive use.

The adhesive composition may comprise a solvent. The solvent may improve coatability of the adhesive composition while preventing self-curing of the adhesive composition. The solvent may be a typical solvent known to those skilled in the art. For example, the solvent may include at least one of methyl ethyl ketone, ethyl acetate, and toluene.

The adhesive composition may further include at least one of a silane coupling agent, a reworking agent, a curing catalyst, an antistatic agent, and a curing accelerator.

The silane coupling agent enables to realize an adhesive film exhibiting high adhesion to an adherend such as glass. The silane coupling agent may include any typical silane coupling agent known to those skilled in the art. For example, the silane coupling agent may include a silane coupling agent selected from the group consisting of silicon compounds having an epoxy structure, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane and (meth) acryloyloxypropyltrimethoxysilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; and 3-chloropropyltrimethoxysilane, but is not limited thereto.

The silane coupling agent may be present in an amount of about 0.001 parts by weight to about 5 parts by weight, particularly about 0.001 parts by weight to about 3 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the adhesive film can exhibit good durability and undergo little change in composition and physical properties over time.

The reworking agent may improve reworkability of the adhesive film and may include a polysiloxane oligomer or a mixture comprising the same. The rework agent may be present in an amount of about 0.001 parts by weight to about 5 parts by weight, particularly about 0.005 parts by weight to about 1 part by weight, with respect to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the reworking agent can improve reworkability without affecting the performance of the adhesive film for a polarizing plate.

The antistatic agent is used to suppress generation of static electricity during rework of the adhesive film, and may include a typical antistatic agent. The antistatic agent may be present in an amount of about 0.001 parts by weight to about 5 parts by weight, particularly about 0.1 parts by weight to about 3 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the antistatic agent may provide an antistatic function without affecting the performance of the adhesive film for a polarizing plate.

The curing catalyst may comprise a compound selected from boron compounds, for example, complexes of boron trifluoride, in particular, ether complexes of boron trifluoride, tetrahydrofuran complexes of boron trifluoride (BF)₃-THF), aniline complex of boron trifluoride (BF)₃Anilines), in particular BF₃·O(CH₃)₂(boron trifluoride dimethyl Ether Compound), BF₃·O(C₂H₅)₂(boron trifluoride diEthyl etherate), and the like; phosphine compounds such as triphenylphosphine, tributylphosphine, tris (p-methylphenyl) phosphine, tris (nonylphenyl) phosphine, triphenylphosphine/triphenylboronate, tetraphenylborate, etc.; secondary or tertiary amine compounds, for example, triethylamine, α -tertiary amine compounds (e.g., KH-30, Kukdo), such as benzyldiethylamine or benzyldimethylamine, and the like; imidazole compounds such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, etc.; the sulfonic acid compound is, for example, at least one member of the group consisting of p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid, methanesulfonic acid, methanedisulfonic acid, phenolsulfonic acid, and the like. The curing catalyst may be present in an amount of about 0.01 to about 5 parts by weight, particularly about 0.05 to about 2 parts by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the curing catalyst can reduce the curing rate.

The adhesive composition may further comprise typical additives. The additives may include ultraviolet absorbers, antioxidants, adhesion-imparting resins, plasticizers, and the like. The additive may be present in an amount of about 0.001 parts by weight to about 5 parts by weight, specifically about 0.01 parts by weight to about 1 part by weight, relative to 100 parts by weight of the (meth) acrylic copolymer. Within this range, the additive may achieve its inherent effects without affecting the performance of the adhesive film for polarizing plates.

The adhesive composition may have a viscosity of about 1,000cP to about 4,000cP at about 25 ℃. Within this range, the adhesive composition can facilitate thickness adjustment of the adhesive film, form the adhesive film without generating spots, and provide a uniform coating surface.

The adhesive film is optically clear for application to optical displays. In particular, the adhesive film may have a light transmittance of about 85% or more, more particularly about 85% to about 95%, at a wavelength of 380nm to 780 nm.

The adhesive film may have a thickness of about 100 μm or less, particularly about 5 μm to about 50 μm. Within this range, the adhesive film is suitable for use in optical displays.

A sample comprising the adhesive film on the glass substrate may have a warpage of less than about 15mm at 85 ℃. Within this range, the adhesive film can suppress the warpage of the polarizing plate at high temperature, thereby ensuring good screen visibility at high temperature.

The adhesive film may be made by coating the adhesive composition to a predetermined thickness, and then drying and aging under constant temperature/humidity conditions of about 25 ℃ to about 35 ℃ and about 30% to about 60% RH (relative humidity).

Next, a polarizing plate and an optical display according to an embodiment of the present invention will be described.

A polarizing plate according to an embodiment of the present invention may include the adhesive film for a polarizing plate according to the embodiment of the present invention. The polarizing plate may be manufactured by attaching the adhesive film according to the embodiment to one surface of a polarizing plate or by applying the adhesive composition according to the embodiment to one surface of a polarizing plate to a predetermined thickness, and then aging.

An optical display according to an embodiment of the present invention may include the adhesive film according to the present invention or the polarizing plate according to the present invention. The optical display may include a liquid crystal display and an organic light emitting diode display, but is not limited thereto. The optical display according to the invention may comprise a flexible display.

The polarizing plate may include a polarizer, an optical film formed on at least one surface of the polarizer, and an adhesive film formed on at least one surface of the optical film. The polarizers and optical films are the same as those known to those skilled in the art. The polarizing plate may have a thickness of about 25 μm to about 100 μm, particularly about 50 μm to about 85 μm. In this thickness range, the polarizing plate can be used for an optical display. The polarizing plate may include a polarizer, an optical film formed on at least one surface of the polarizer, and an adhesive film formed on at least one surface of the optical film. The optical film is an optically transparent film, and may include a cellulose film including a triacetyl cellulose film, a polyester film including a polyethylene terephthalate film, a polycarbonate film, an acrylic film, a cyclic olefin polymer film, and the like.

The liquid crystal display may include a liquid crystal display including IPS liquid crystal, but is not limited thereto.

Next, the present invention will be described in more detail with reference to some examples. It should be noted, however, that these examples are for illustrative purposes only and are not to be construed as limiting the present invention in any way.

Preparation example 1: preparation of (meth) acrylic copolymer

In a 1L reactor equipped with a cooler for facilitating temperature adjustment, ethyl acetate was placed while purging with nitrogen. Then, 100 parts by weight of a monomer mixture comprising 66.975 mol% of n-Butyl Acrylate (BA), 20 mol% of Methyl Acrylate (MA), 10 mol% of Acryloylmorpholine (ACMO), 3 mol% of 4-hydroxybutyl acrylate (4-HBA) and 0.025 mol% of dimethylaminoethyl acrylate (DMAEA) was added to the reactor. Additionally, a mixture of ethyl acetate and methyl ethyl ketone was added to the reactor. Then, nitrogen was introduced into the reactor for 30 minutes to remove oxygen from the monomer mixture, and then the internal temperature of the reactor was maintained at 65 ℃. After the monomer mixture was uniformly stirred, 0.06 part by weight of dimethyl 2,2' -azobis (2-methylpropionate) (V601) was added to the reactor as an initiator, followed by reaction for 4 hours. The internal temperature of the reactor was increased to 65 ℃, and the initiator was further added to the reactor. After reacting at 70 ℃ for 2 hours, the obtained mixture was cooled and methyl ethyl ketone was added to the obtained mixture, thereby preparing a 25 wt% solution of a (meth) acrylic copolymer.

Preparation examples 2 to 14: preparation of (meth) acrylic copolymer

Each (meth) acrylic copolymer was prepared in the same manner as in preparation example 1, except that the kind and content of the monomer in the monomer mixture were changed as shown in table 1. In preparation examples 11 and 12, the polymerization was carried out at different time periods.

TABLE 1

In table 1, BA: n-butyl acrylate, MA: methyl acrylate, CHA: cyclohexyl acrylate, IBXA: isobornyl acrylate, BzA: benzyl acrylate, ACMO: acryloyl morpholine, 4-HBA: 4-hydroxybutyl acrylate, AA: acrylic acid, DMAEA: acrylic acid dimethyl amino ethyl ester

In table 1, Mw: weight average molecular weight (unit: g/mol) of acrylic copolymer, Tg: glass transition temperature (unit:. degree. C.) of the acrylic copolymer.

Preparation example 15: preparation of polyalkylene glycol-modified isocyanate curing agent

In a round-bottomed flask, polypropylene glycol (PPG) having a number average molecular weight (Mn) of 400 and xylene diisocyanate (XDI, weight average molecular weight: 188g/mol, TCI Chemicals) were placed in a molar ratio (PPG: XDI)1: 2. Then, the resulting mixture was heated to 60 ℃ and DBTDL as a reaction catalyst was slowly added in an amount of 0.2 wt% per 1mol of xylene diisocyanate to prepare a reaction mixture. The reaction mixture was allowed to stand at 70 ℃ for 2 hours until the isocyanate groups were removed from the reaction mixture. When the amount of the remaining xylylene diisocyanate reaches 1% by weight or less, the reaction is completed, thereby providing a polyalkylene glycol-modified isocyanate curing agent.

Preparation examples 16 to 22: preparation of polyalkylene glycol-modified isocyanate curing agent

Each polyalkylene glycol-modified isocyanate curing agent was prepared by the same method as in preparation example 15, except that polypropylene glycol (PPG) and 4,4' -methylenebis (phenyl isocyanate) (MDI, weight average molecular weight: 250.25g/mol, TCI Chemicals) listed in Table 2 were used in a molar ratio of 1:2(PPG: MDI) in Place of Polypropylene Glycol (PPG) and Xylene Diisocyanate (XDI) having a number average molecular weight (Mn) of 400 and the amount of DBTDL was changed.

TABLE 2

In table 2, PPG-400: polypropylene glycol having a number average molecular weight of 400 (PPG-400D, Kumho Petrochemicals), PPG-1000: polypropylene glycol having a number average molecular weight of 1,000 (PPG-1000D, Kumho Petrochemicals), PPG-2000: polypropylene glycol having a number average molecular weight of 2,000 (PPG-2000D, Kumho Petrochemicals), PPG-3000: polypropylene glycol having a number average molecular weight of 3,000 (PPG-3000D, Kumho Petrochemicals).

The details of the components used in the examples and comparative examples are as follows.

(A) (meth) acrylic copolymer: (meth) acrylic copolymers prepared in production examples of Table 1

(B) Curing agent:

(B1) isocyanate curing agent: trimethylol propane xylene diisocyanate adduct (TD-75, Soken, solids content 75 wt%)

(B2) Metal chelate curing agent: m-12AT, solids content 10% by weight

(B3) TMPTA: trimethylolpropane triacrylate

(B4) PETA: pentaerythritol tetraacrylate

(B5) IRGACURE-184: 1-hydroxycyclohexyl phenyl ketones

(B6) TPO: 2, 4-trimethylbenzoyldiphenylphosphine oxide

(B11) (B18): polyalkylene glycol-modified isocyanate curing agent of Table 2

(C) Curing catalyst: s accelerator (Soken)

(D) Silane coupling agent: a-50(Soken)

(E) Antistatic agent: FC-4400(3M, USA)

(F) A reworking agent: MAC-2101(Soken)

Example 1

17 parts by weight of the (meth) acrylic copolymer (A1) was mixed with 0.025 parts by weight of the isocyanate curing agent (B1). In addition, 0.01 parts by weight of the curing catalyst (S accelerator, Soken) (C), 0.05 parts by weight of the silane coupling agent (a-50, Soken) (D), 0.75 parts by weight of the antistatic agent (FC-4400,3M, USA) (E), and 0.05 parts by weight of the reworking agent (MAC-2101, Soken) (F) were mixed, and methyl ethyl ketone was added to the mixture in an amount of 4 times the weight of the (meth) acrylic copolymer, thereby preparing an adhesive composition for a polarizing plate. Herein, the content of each component is defined as the solid content excluding the solvent.

Examples 2 to 12

Each adhesive composition for a polarizing plate was prepared by the same method as in example 1, except that the kind and/or amount of the (meth) acrylic copolymer and the kind and/or amount (unit: parts by weight) of the curing agent were changed as shown in table 3.

Examples 13 to 20

Each adhesive composition for a polarizing plate was prepared by the same method as in example 1, except that the kind and/or amount of the (meth) acrylic copolymer and the kind and/or amount (unit: parts by weight) of the curing agent were changed as shown in table 4.

Comparative examples 1 to 4

The components of the adhesive compositions prepared in examples and comparative examples are shown in tables 3 and 4.

TABLE 3

TABLE 4

The adhesive compositions for polarizing plates of examples and comparative examples were evaluated for the following characteristics. The evaluation results are shown in tables 5 and 6.

(1) Durability: a polyvinyl alcohol film was stretched to three times its original length at 60 ℃, stained with iodine, and further stretched to 2.5 times in a boric acid solution at 40 ℃, thereby preparing a polarizer (thickness: 23 μm). Then, polarizing plates were produced by adhering 80 μm thick triacetyl cellulose films and 42 μm thick triacetyl cellulose films, respectively, to the opposite surfaces of the polarizer. Each of the adhesive compositions prepared in examples and comparative examples was coated on the release film and dried at 90 ℃ for 4 minutes to remove the solvent, and then the release film was removed, thereby preparing an adhesive sheet. The prepared adhesive sheet was attached to the surface of a triacetyl cellulose film having a thickness of 42 μm of the polarizing plate, and left to stand under constant temperature and humidity conditions of 23 ℃ and 55% RH for 24 hours, thereby preparing a polarizing plate including an adhesive film.

The polarizing plate was cut into a rectangle having a size of 100mm × 80mm (length × width) (MD × TD of the polarizing plate). The cut polarizing plate was attached to an alkali-free glass plate (110mm × 90mm, length × width) via the adhesive sheet, thereby preparing a sample for durability measurement. Then, the sample was autoclaved at 50 ℃ for 1000 seconds, thereby producing a sample in which the polarizing plate was stacked on the glass plate. The samples were left at 85 ℃ for 500 hours or at 60 ℃ and 95% RH for 500 hours. The durability of the test piece was evaluated by the following criteria.

O: without falling off, dragging, or generating bubbles

Δ: micro-shedding, micro-dragging, or micro-bubble generation, and bubble size less than 100 μm

X: severe shedding, severe dragging and severe bubble generation with bubble size of 100 μm or more

(2) Warping: each of the adhesive compositions prepared in examples and comparative examples was coated on a polyethylene terephthalate release film and dried at 90 ℃ for 4 minutes. The obtained adhesive film had a thickness of 25 μm. A polarizing plate having a triacetyl cellulose film adhered to the opposite surface of the polarizer was produced by the same method as in (1), and the adhesive film was laminated on the surface of a 42 μm thick triacetyl cellulose film of the polarizing plate and left at 23 ℃ and 55% RH for 24 hours. The polarizing plate having the adhesive film thereon was cut into a rectangle having a size of 210mm × 25mm (length × width) (MD × TD of the polarizer). The cut polarizing plate was attached to an alkali-free glass plate (210mm × 25mm × 0.5mm, length × width × thickness) via the adhesive film and autoclaved at 50 ℃ for 1000 seconds, thereby preparing a sample for evaluating warpage.

The sample was placed in an oven at 85 ℃ for 72 hours and then placed in the atmosphere at room temperature for 2 hours. Then, the sample is placed on a flat surface with one end of the sample fixed to the flat surface, and then the distance from the flat surface to the other end of the sample is repeatedly measured. The average value of the warpage obtained by measuring the distance 5 times was recorded as the warpage of the test piece.

(3) Indentation: each of the adhesive compositions prepared in examples and comparative examples was coated on a 38 μm-thick polyethylene terephthalate release film and dried at 90 ℃ for 4 minutes, thereby preparing an adhesive film having a thickness of 25 μm. A polarizing plate having a triacetyl cellulose film adhered to the opposite surface of the polarizer was produced by the same method as in (1), and the adhesive film was laminated on the surface of a 42 μm thick triacetyl cellulose film of the polarizing plate and left at 23 ℃ and 55% RH for 24 hours. The polarizing plate having the adhesive film thereon was cut into a size of 50mm × 10mm (length × width). The polarizing film was prepared as a sample by placing the cut polarizing plate on a soda-lime glass plate (thickness: 1mm) with the release film face upward, and then fixing the polarizing film on the glass plate with a tape.

The indentation was measured at 25 ℃ using a TA instrument (TEXTURE ANALYZER TA. XT Plus, load cell: 5kg, EKO Instruments). A spherical stainless steel tip (diameter: 1mm) of a TA instrument was placed at a height of 1mm above the sample peeling film. The peeling film was pressed by a spherical stainless steel tip for 15 seconds under a load of 50gf, and the spherical stainless steel tip was removed from the peeling film. Thereafter, the sample was left for 5 minutes. Then, the release film was taken out from the test specimen, and the dent formed on the adhesive film was observed by a 3D optical profiler, and then the maximum depth of the pressing mark was recorded.

(4) tan δ: tan δ was measured on the adhesive film by temperature sweep testing using Anton Paar Physica MCR 300. The measurement was performed while heating from 0 ℃ to 120 ℃ at a heating rate of 10 ℃/min. The adhesive film has a thickness of 600 μm to 1,000 μm.

TABLE 5

In table 5, tan δ 1 is the tan δ value of the adhesive film at 23 ℃ and tan δ 2 is the tan δ value of the adhesive film at 80 ℃.

(1) Durability: the durability was evaluated by the same method as the durability evaluation of table 5.

(2) Warping: the warpage was evaluated by the same method as the warpage evaluation of table 5.

(3) Indentation: dents were evaluated by the same method as the dent evaluation of table 5 except that the test piece was placed for the period of time listed in table 6 after removing the spherical stainless steel tip from the peeling film.

(4) Creep deformation: referring to fig. 1, creep of the adhesive film was evaluated using a texture analyzer ta.xt PLUS (load cell 5kg, EKO Instruments). Each of the adhesive compositions prepared in examples and comparative examples was coated on a polyethylene terephthalate release film and dried at 90 ℃ for 4 minutes. A polarizing plate having a triacetyl cellulose film adhered to the opposite surface of the polarizer was produced by the same method as in (1), and the adhesive film was laminated on the surface of the 42 μm thick triacetyl cellulose film of the polarizing plate and left at 23 ℃ and 55% RH for 24 hours, thereby producing a sample 23 having an adhesive film 21 (thickness: 25 μm) attached to one surface of the polarizing plate 22. The sample was cut into a rectangle having dimensions of 100mm × 15mm (length × width) (MD × TD of the polarizing plate). Then, as shown in fig. 1, the sample was attached to a soda lime glass plate 20 with the MD of the polarizer perpendicular to one surface of the glass plate 20, and the adhesive film was attached to the glass plate in an adhesive area (a × b) of 15mm × 15 mm. Then, the sample attached to the glass plate was autoclaved at 50 ℃ for 1000 seconds and left at room temperature for 24 hours. Creep was evaluated based on the pushing distance of the specimen 23 from the soda-lime glass plate 20 when the specimen was pulled by the weight W for 1000 seconds. Creep was measured at a temperature of 85 ℃ and the weight W of the creep was 1,500 g.

(5) Light leakage: a polarizing plate including an adhesive film was produced by the same method as in (1). The produced polarizing plate was cut into polarizing plates having an upper plate size of 150mm × 90mm (MD × TD of the polarizer) and a lower plate size of 90mm × 150mm (MD × TD of the polarizer). An upper polarizing plate was attached to the upper surface of an alkali-free glass plate having dimensions of 160mm × 100mm (length × width), and a lower polarizing plate was attached to the lower surface of the alkali-free glass plate. Herein, the upper and lower polarizing plates are disposed such that the MD of the upper polarizing plate is orthogonal to the MD of the lower polarizing plate. The laminate of the polarizing plate was autoclaved at 50 ℃ for 1000 seconds, thereby preparing a sample for measuring light leakage. The samples were placed in an oven at 85 ℃ for 500 hours and then at room temperature for 2 hours. Then, light leakage was measured. After the PLS mode LCD was operated using the sample, the brightness of the front surface of the display panel was measured from a height of 1m using a brightness tester (RISA, hilled co., Ltd.). In particular, measuring saidBrightness of central area of panel

And the brightness of each corner of the panel where light leakage occurs

And

as shown in fig. 2, the radius of the brightness measurement circle at each corner is 0.5 cm. In the context of figure 2 of the drawings,

and

indicating the luminance measurement point. The light leakage (Δ L) is quantified according to the following equation 4. A lower Δ L value indicates better light leakage characteristics. Light leakage was evaluated according to the following criteria.

< formula 4>

ΔL＝|[(a+b+d+e)/4]/c-1|

Wherein a, b, d and e represent luminance measurement points in FIG. 2

And

the brightness value measured at (high brightness region), and c is the central region in FIG. 2

(low luminance region).

O: no light leakage, and delta L is more than or equal to 0 and less than or equal to 0.1.

Δ: light leakage, 0.1< Δ L < 0.3.

X: severe light leakage, 0.3 ≤ Δ L

(6) tan δ: tan δ was evaluated by the same method as tan δ evaluation of table 5.

TABLE 6

In table 6, tan δ 1 is the tan δ value of the adhesive film at 23 ℃, and tan δ 2 is the tan δ value of the adhesive film at 80 ℃.

As can be seen in table 5, the adhesive film for a polarizing plate according to the present invention can suppress warpage of a polarizing plate and has a low depth of depression, thereby achieving suppression of depression in the adhesive film and/or rapid recovery of depression in the adhesive film due to solid particles during processing, cutting, packaging, and storage of the adhesive film.

In contrast, the adhesive films of comparative examples 1 to 4 did not satisfy formulas 1 and 2 and had high dent depths.

As can be seen in table 6, the adhesive film for a polarizing plate according to the present invention can suppress light leakage and warpage of the polarizing plate and has a low depth of depression, thereby making it possible to suppress depression in the adhesive film and/or rapidly recover depression in the adhesive film due to solid particles during processing, cutting, packaging and storage of the adhesive film.

Accordingly, the present invention provides an adhesive film for a polarizing plate, which is capable of suppressing and/or rapidly restoring depressions in the adhesive film due to solid particles during processing, cutting, packaging, and/or storage of the adhesive film.

The invention provides an adhesive film for a polarizing plate, which can ensure that light leakage is basically inhibited by alleviating the shrinkage of the polarizing plate at high temperature.

The present invention provides an adhesive film for a polarizing plate, which exhibits good durability under high temperature or high temperature/high humidity conditions and has good performance in terms of corrosion inhibition and reworkability when adhered to a metal adherend including an Indium Tin Oxide (ITO) film.

It is to be understood that various modifications, alterations, adaptations, and equivalent embodiments may occur to one skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. An adhesive film for a polarizing plate, comprising: containing a compound having C₄-C₈Alkyl (meth) acrylates; a (meth) acrylate having a hydroxyl group; and has C₁-C₃A (meth) acrylic copolymer of a monomer mixture of (meth) acrylic acid esters of alkyl groups, the adhesive film satisfying formula 1 and formula 2:

< formula 1>

0.20≤tanδ2≤0.40

< formula 2>

-0.02≤tanδ2–tanδ1≤0.02

Wherein tan delta 1 is a tan delta value of the adhesive film for a polarizing plate at 23 ℃ and tan delta 2 is a tan delta value of the adhesive film for a polarizing plate at 80 ℃,

wherein the (meth) acrylic copolymer has a glass transition temperature of-30 to-10 ℃ and a weight average molecular weight of 500,000 to 1,500,000g/mol,

wherein the monomer mixture further comprises a (meth) acrylic monomer having an amide group.

2. The adhesive film for a polarizing plate according to claim 1, wherein tan δ 2-tan δ 1 is in the range of-0.20 to 0.02.

3. The adhesive film for a polarizing plate according to claim 1, wherein the adhesive film satisfies formula 3:

< formula 3>

tanδ2/tanδ1<1.1

Wherein tan δ 1 is a tan δ value of the adhesive film for a polarizing plate at 23 ℃, and tan δ 2 is a tan δ value of the adhesive film for a polarizing plate at 80 ℃.

4. The adhesive for polarizing plate according to claim 1A membrane, wherein the membrane has C₄-C₈The alkyl (meth) acrylate is present in the monomer mixture in an amount of 40 mol% to 78 mol%.

5. The adhesive film for polarizing plate of claim 1, wherein the adhesive film has C₁-C₃At least one of the (meth) acrylate of the alkyl group and the (meth) acrylic monomer having the amide group is present in the monomer mixture in an amount of 10 mol% to 40 mol%.

6. The adhesive film for polarizing plate of claim 1, wherein the adhesive film has C₁-C₃Both the alkyl (meth) acrylate and the (meth) acrylic monomer having an amide group are present in the monomer mixture in an amount of 10 to 40 mol%.

7. The adhesive film for a polarizing plate according to claim 1, wherein the (meth) acrylic monomer having an amide group comprises a (meth) acrylic monomer containing a morpholino group.

8. The adhesive film for a polarizing plate according to claim 1, wherein the monomer mixture does not contain a (meth) acrylate having a long chain alkyl group.

9. The adhesive film for polarizing plates according to claim 1, wherein the monomer mixture further comprises at least one of a (meth) acrylate having an alicyclic group and a (meth) acrylate having an aromatic group.

10. The adhesive film for a polarizing plate according to claim 1, wherein the monomer mixture further comprises a (meth) acrylic monomer having a tertiary amine group.

11. The adhesive film for a polarizing plate of claim 1, wherein the adhesive film is formed of an adhesive composition comprising the (meth) acrylic copolymer and a curing agent comprising at least one of an isocyanate curing agent and a metal chelate curing agent.

12. The adhesive film for a polarizing plate of claim 11, wherein the isocyanate curing agent comprises at least one of a polyalkylene glycol-unmodified isocyanate curing agent and a polyalkylene glycol-modified isocyanate curing agent.

13. The adhesive film for a polarizing plate of claim 12, wherein the polyalkylene glycol-modified isocyanate curing agent comprises at least one of polypropylene glycol and polyethylene glycol having a number average molecular weight of 300g/mol to 5,000 g/mol.

14. The adhesive film for a polarizing plate of claim 1, wherein the adhesive film is formed of an adhesive composition comprising the (meth) acrylic copolymer and a curing agent comprising a photoinitiator and at least one of di-to hexafunctional (meth) acrylates.

15. The adhesive film for a polarizing plate according to claim 1, wherein the adhesive film has depressions of 18 μm or less.

16. An adhesive composition for a polarizing plate, comprising: containing a compound having C₄-C₈Alkyl (meth) acrylates; a (meth) acrylate having a hydroxyl group; and has C₁-C₃(meth) acrylic copolymers of a monomer mixture of alkyl (meth) acrylates; and a curing agent, wherein the curing agent,

wherein an adhesive film for a polarizing plate formed from the adhesive composition satisfies the following formulae 1 and 2:

< formula 1>

0.20≤tanδ2≤0.40

< formula 2>

-0.02≤tanδ2-tanδ1≤0.02

17. The adhesive composition for a polarizing plate according to claim 16, wherein the curing agent comprises at least one of an isocyanate curing agent and a metal chelate curing agent.

18. The adhesive composition for a polarizing plate according to claim 17, wherein the isocyanate curing agent comprises at least one of a polyalkylene glycol-unmodified isocyanate curing agent and a polyalkylene glycol-modified isocyanate curing agent.

19. The adhesive composition for a polarizing plate according to claim 18, wherein the polyalkylene glycol-modified isocyanate curing agent comprises at least one of polypropylene glycol and polyethylene glycol having a number average molecular weight of 300g/mol to 5,000 g/mol.

20. The adhesive composition for a polarizing plate according to claim 16, wherein the curing agent comprises a photoinitiator and at least one of di-to hexafunctional (meth) acrylates.

21. A polarizing plate comprising the adhesive film for a polarizing plate according to any one of claims 1 to 15.

22. An optical display comprising the polarizing plate according to claim 21.