WO2020256476A1 - Radical-based adhesive composition, polarizing plate protective film comprising same, polarizing plate comprising same protective film, and image display device comprising same polarizing plate - Google Patents

Abstract

The present specification relates to a radical-based adhesive composition, a polarizing plate protective film comprising same, a polarizing plate comprising same protective film, and an image display device comprising same polarizing plate.

Description

Radical adhesive composition, protective film for polarizing plate including same, polarizing plate including same, and image display device including same

This application claims the benefit of the filing date of Korean Patent Application No. 10-2019-0073558 filed with the Korean Intellectual Property Office on June 20, 2019, the entire contents of which are incorporated herein.

The present specification relates to a radical-based adhesive composition, a protective film for a polarizing plate including the same, a polarizing plate including the same, and an image display device including the same.

Polarizing plates have been generally used in a structure in which a protective film is laminated on one or both sides of a polarizer made of polyvinyl alcohol (hereinafter referred to as PVA)-based resin dyed with dichroic dye or iodine using an adhesive. Conventionally, a triacetyl cellulose (hereinafter referred to as TAC)-based film has been mainly used as a polarizing plate protective film, but this TAC film has a problem that it is easily deformed in a high temperature and high humidity environment. Therefore, in recent years, protective films of various materials that can replace the TAC film have been developed, for example, polyethylene terephthalate (PET), cycloolefin polymer (hereinafter referred to as COP), acrylic film, etc. A method of using alone or in combination has been proposed.

At this time, as an adhesive used to attach the polarizer and the protective film, a water-based adhesive mainly composed of an aqueous solution of a polyvinyl alcohol-based resin is used. However, in the case of the water-based adhesive, when an acrylic film or a COP film other than TAC is used as a protective film, there is a problem that the use thereof is limited depending on the film material because the adhesive strength is weak. In addition, in the case of the water-based adhesive, in addition to the problem of poor adhesion depending on the material, when the material of the protective film applied to both sides of the PVA device is different, the problem of the occurrence of curl of the polarizing plate due to the drying process of the water-based adhesive and the initial optical Problems such as deterioration of physical properties occur. Moreover, when the water-based adhesive is used, a drying process is indispensable, and there is a problem in that a defect rate is increased due to differences in moisture permeability and thermal expansion in the drying process. As an alternative to solve the above problems, a method of using a non-aqueous adhesive instead of a water-based adhesive has been proposed.

Therefore, measures to improve the reliability and yield of a polarizing plate by using a cationic polymerizable ultraviolet curable adhesive instead of a water-based adhesive have been proposed.

Cationic polymerizable UV-curable adhesives have high curing density and high reliability by using epoxy as a main component. However, such cationic polymerization proceeds to the ring-opening reaction of the epoxy ring through a dark reaction (post-polymerization) after UV irradiation. At this time, there is a problem that it is easily affected by humidity during curing, and variations in cured state are likely to occur. Therefore, in order to express a uniform cured state, it is necessary to strictly control the moisture content of the PVA-based polarizer as well as the environmental humidity.

Radical polymerizable ultraviolet-curable adhesives are excellent in that there are relatively few problems of adhesion unevenness caused by such moisture. Since there is no inhibition of the curing reaction by moisture, the polarizer can react stably with light energy without being inhibited by the moisture in the polarizer.

In addition, from the viewpoint of thinning and durability of the polarizing plate, the thinner the thickness of the adhesive layer is, the more advantageous the adhesive has a low viscosity.

However, in the case of a radical compound, monofunctional is mainly used to maintain a low viscosity. As a result, hardening density and adhesion are low, and it is difficult to expect a good margin in the subsequent process and reliability.

In addition, when considering the reliability of the polarizing plate at high temperature and high humidity, the higher the rigidity of the adhesive layer after curing, the lower the degree of dimensional change at high temperature and high humidity, which is advantageous in reducing the defect rate of the polarizer.

In order to satisfy the characteristics of the adhesive, a method of applying a polyfunctional monomer or a monomer having a high glass transition temperature of a homopolymer may be considered, but even in this case, there is a problem in that the adhesive strength is low due to low curing density.

Thus, as a result of conducting a series of experiments to achieve the low viscosity properties of the adhesive and high stiffness after curing, it was possible to complete a highly reliable adhesive composition by appropriately controlling the curing density of the radical compound.

[Prior technical literature]

[Patent Literature]

(Patent Document 1) Japanese Patent Laid-Open 2015-011094 A (Publication date: 2015.01.19)

The present specification relates to a radical-based adhesive composition, a protective film for a polarizing plate including the same, a polarizing plate including the same, and an image display device including the same.

The present specification is a polyester-based urethane acrylate oligomer (A) having an acid value of 90 mgKOH/g to 180 mgKOH/g; A polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150°C or higher of the homopolymer; (Meth)acrylate monomer (C) having a hydrophilic functional group; And it provides a radical-based adhesive composition comprising a silane coupling agent (D).

In addition, the present specification is a protective film; And it provides a protective film for a polarizing plate provided with an adhesive layer including the above-described radical-based adhesive composition on one or both sides of the protective film.

In addition, the present specification is a polarizer; And it provides a polarizing plate including the protective film for the polarizing plate described above on one or both sides of the polarizer.

In addition, the present specification provides a display panel; And an image display device in which the polarizing plate described above is provided on one or both surfaces of the display panel.

The present specification provides a radical-based adhesive composition having excellent advantages in adhesion to a substrate without a separate treatment such as corona treatment. In addition, the radical-based adhesive composition according to the exemplary embodiment of the present specification may realize excellent heat resistance by having a high glass transition ion degree and a high storage modulus at high temperature after curing.

1 and 2 illustrate exemplary stacked structures of a polarizing plate according to an exemplary embodiment of the present specification.

3 shows the experimental method of Experimental Example 1.

4 shows the experimental method of Experimental Example 5.

[Explanation of code]

101, 105: protective film

102, 104: adhesive layer

103: polarizer

Hereinafter, the present specification will be described in detail.

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In the present specification, when a member is said to be located "on" another member, this includes not only the case where the member is in contact with the other member, but also the case where another member exists between the two members.

In the present specification, the "radical adhesive composition" does not contain a polymerizable compound other than a radical polymerizable compound, or contains a small amount, such as less than 10 parts by weight, or less than 1 part by weight based on 100 weight of the total composition It means an adhesive composition. In the present specification, a urethane acrylate oligomer, a polyfunctional (meth)acrylate monomer, and a (meth)acrylate monomer having a hydrophilic functional group are all radically polymerizable compounds.

An exemplary embodiment of the present specification is a polyester-based urethane acrylate oligomer (A) having an acid value of 90 mgKOH/g to 180 mgKOH/g; A polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150°C or higher of the homopolymer; (Meth)acrylate monomer (C) having a hydrophilic functional group; And it provides a radical-based adhesive composition comprising a silane coupling agent (D).

The radical adhesive composition, including the polyester-based urethane acrylate oligomer (A), has excellent heat resistance and water resistance by providing relaxation by a polyester group even when the total glass transition temperature (Tg) of the composition is lowered. . In addition, the radical-based adhesive composition has an advantage of excellent adhesion to the protective film without a separate treatment such as corona treatment. In particular, the polyester-based urethane acrylate oligomer (A) has an excellent effect of adhesion to the unpretreated protective film compared to other oligomers such as epoxy-based urethane acrylate oligomers. When the radical-based adhesive composition is applied to the protective film, the bonding surface of the protective film with the adhesive is eroded by an ester group having an acid value, so that the adhesive composition has a physical structure capable of permeating the protective film surface well. That is, it is possible to increase the adhesion to the protective film by implementing both the physical and chemical effects of the ester group.

By controlling the acid value of the polyester-based urethane acrylate oligomer, it is possible to improve adhesion of the adhesive composition to the protective film. Specifically, the polyester-based urethane acrylate oligomer has an acid value of 90 mgKOH/g to 180 mgKOH/g, preferably an acid value of 95 mgKOH/g to 175 mgKOH/g, more preferably an acid value of 100 mgKOH/g 170 mgKOH/g. When the above range is satisfied, excellent adhesion to the protective film may be secured by the adhesive composition effectively etching the protective film. In addition, if the degree of etching the protective film is less than the above range, the degree of etching the protective film is low, so that adhesion is deteriorated. If the amount exceeds the above range, there is a problem of excessive etching of the protective film, so the range of the acid value was adjusted to the above range.

The acid value is a measurement of the equivalent of KOH required to neutralize the acidic content of the polyacid or its ester (carboxyl group of the polyvalent acid) contained in the sample. It means the corresponding amount. The acid value can be determined by the following method.

First, a 0.1N potassium hydroxide solution to be used for titration is prepared in order to measure the acid value of the synthesized acrylate oligomer. Add 5.9 g of 95wt% reagent grade potassium hydroxide to a 1L flask, then add a small amount of water to completely dissolve. Methanol is added thereto and mixed so that the total volume becomes 1L to prepare a titration solution.

To calculate the correction factor of the prepared titration solution, 10 mL of a 35wt% HCl solution is added to a beaker, and 2-3 drops of a phenolphthalein indicator are added. Here, the 0.1 N potassium hydroxide titration solution prepared above is added until it turns pale red, and the used volume is calculated. Of the values obtained by repeating this experiment three times, the average value A (mL) is calculated by averaging the remaining three values excluding the maximum and minimum values, and then the correction factor f is calculated using the following equation.

f = 5.611 / A

After taking about 1 g of a sample and accurately measuring the mass (M), it is dissolved in 42.8 g (50 mL) of toluene. Add 2-3 drops of 1 wt% phenolphthalein indicator and titrate with 0.1 N potassium hydroxide solution while stirring, measure the consumed amount (B) in mL, and calculate the acid value using the following formula.

Acid Value = 5.611 x N x f x B / M

Where N: the concentration of the potassium hydroxide standard solution,

f: correction of potassium hydroxide solution

factor, B: consumption of potassium hydroxide solution (mL),

M: mass of the sample (g)

The method of obtaining the acid value is an example of an acid/base titration method in which the carboxyl group of a polyacid or its ester is titrated with KOH as a base, and known methods for analyzing unreacted acidic components or ester components thereof may be used. For example, in the case of an ester component of a polyhydric acid, the acid value may be obtained by analyzing the unreacted ester component in 1 kg of a sample using gas chromatography analysis, etc., and then calculating the amount of KOH corresponding thereto.

The polyester-based urethane acrylate oligomer is a component that controls the physical properties (eg, hardness, adhesion, flexibility, etc.) of the cured resin by forming a crosslinked structure with a photoreactive monomer, a polyfunctional (meth)acrylate-based reactive monomer, When applied to a radical-based adhesive composition, it is possible to further improve molding processability, elasticity and adhesion.

The urethane acrylate oligomer has a chemical structure having acrylate groups at both ends of the structure of the oligomer. Specifically, the urethane acrylate oligomer is a polyester-based polyol compound; Isocyanate compounds; And it may be formed from a composition comprising an acrylate-based compound.

The polyester-based urethane acrylate oligomer may be synthesized through the following synthesis process. That is, after reacting a polyester-based polyol compound (P) having an ester group (R ₁ ) with a diisocyanate-based compound (I) to have an isocyanate group at the terminal, primary synthesis is performed, and then an acrylate compound having a hydroxy group ( A) can be reacted with an isocyanate group to prepare a final polyester-based urethane acrylate oligomer. In addition, although it may be a polymer synthesized by the following reaction equation, it may be a simple mixture of raw materials.

By the polyester-based polyol compound, the oligomer contains a polyester chemical structure in the main chain, and as a result, when it has the same degree of curing, it has better absorption of steps compared to an oligomer not containing a polyester chemical structure It can be advantageous for securing reliability due to its high efficiency.

The diisocyanate-based compound is specifically, a group consisting of 1,6-hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), and combinations thereof It may include one selected from. Specifically, the diisocyanate-based compound may include isophorone diisocyanate (IPDI), and in this case, the oligomer includes a chemical structure of a cycloalkylene structure in the main chain, and as a result, includes such a chemical structure. Compared to the case of not doing so, it is possible to obtain an advantage in securing high temperature and high humidity reliability.

The acrylate-based compound is a compound for imparting an acrylate group to both ends of the oligomer, and may include an acrylate compound having a hydroxy group. Specifically, the acrylate-based compound may include one selected from the group consisting of hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), hydroxybutyl acrylate (HBA), and combinations thereof. .

In an exemplary embodiment of the present specification, the number average molecular weight of the polyester-based urethane acrylate oligomer may be 1,000 to 50,000, preferably 1,000 to 35,000, and more preferably 1,000 to 20,000. When the number average molecular weight of the urethane acrylate oligomer is less than 1,000, abrasion resistance, adhesion, and chemical resistance of the cured adhesive layer may be deteriorated. In addition, when the number average molecular weight of the urethane acrylate oligomer exceeds 50,000, pencil hardness, abrasion resistance, adhesion, and chemical resistance of the cured adhesive layer may be deteriorated.

In an exemplary embodiment of the present specification, the number of functional groups of the polyester-based urethane acrylate oligomer may be 1 to 10. In consideration of the photocuring speed and water resistance, the polyester-based urethane acrylate oligomer may have 1 to 8 functional groups, preferably 2 to 6 functional groups. In this case, the urethane acrylate oligomer having a specific number of functional groups may be a concept including another urethane acrylate oligomer that substantially serves as a urethane acrylate oligomer having the specific number of functional groups. For example, in a urethane acrylate oligomer having a 10-functional group, when one functional group of the functional groups is substantially inactive, the urethane acrylate oligomer having such a 10-functional group may be included in the urethane acrylate oligomer having a 9 functional group. .

In an exemplary embodiment of the present specification, the viscosity of the polyester-based urethane acrylate oligomer at 25° C. is 1,000 cPs or more and 50,000 cPs or less, preferably 2,000 cPs or more and 50,000 cPs or less, more preferably 2,500 cPs or more 50,000 cPs It can be below. In the above-described viscosity and molecular weight range, when preparing a cured product, it has excellent molding processability, and excellent elasticity and adhesion.

In one embodiment of the present specification, the radical-based adhesive composition comprises 1 to 20 parts by weight of the polyester-based urethane acrylate oligomer, preferably 1 to 15 parts by weight, more preferably, based on 100 parts by weight of the total composition. It is included in 1 to 10 parts by weight. When the content of the urethane acrylate oligomer is less than 1 part by weight, adhesion and durability of the cured adhesive layer may be deteriorated. When the content of the urethane acrylate oligomer exceeds 20 parts by weight, the cured adhesive layer becomes excessively flexible and thus the pencil hardness and abrasion resistance decrease, as well as the viscosity of the radical-based adhesive composition increases, which may reduce workability. .

In one embodiment of the present specification, the radical-based adhesive composition further includes a polyfunctional (meth)acrylate monomer (B2) having a glass transition temperature (Tg) of less than 150°C of the homopolymer.

In one embodiment of the present specification, the radical-based adhesive composition may contain two or more types of polyfunctional (meth)acrylate monomers. When two or more types of polyfunctional (meth)acrylate monomers are contained, a more appropriate curing density is achieved than that of a radical polymerizable compound containing one type of polyfunctional (meth)acrylate monomer, and good adhesion can be imparted. Therefore, when the adhesive composition is applied to a polarizing plate, it is possible to prevent the occurrence of cracks in the polarizer due to thermal shock.

In the exemplary embodiment of the present specification, the radical-based adhesive composition may include two types of multifunctional acrylate compounds. For example, a polyfunctional acrylate compound having a glass transition temperature of 100° C. or more and less than 150° C. and a polyfunctional acrylate compound having a glass transition temperature of 150° C. or more may be combined, or a polyfunctional acrylate compound having a chain structure and a ring. Structured polyfunctional acrylate compounds can be combined.

In the exemplary embodiment of the present specification, the total content of the polyfunctional (meth)acrylate monomer (when a polyfunctional (meth)acrylate monomer of less than 150°C is further included, the polyfunctional (meth)acrylate monomer of less than 150°C The total amount of the total amount) is preferably about 55 parts by weight to 70 parts by weight, or about 55 parts by weight to 65 parts by weight, based on the total 100 parts by weight of the radical-based adhesive composition. When the total content of the polyfunctional acrylate compound satisfies the above range, it is possible to secure a high storage modulus after curing while maintaining good adhesion.

In the exemplary embodiment of the present specification, the radical adhesive composition may further include a monofunctional acrylate compound. The monofunctional acrylate-based compound is preferably about 0.01 to 25 parts by weight, or 1 to 25 parts by weight, based on 100 parts by weight of the total of the radical-based adhesive composition. Examples of the monofunctional acrylate-based compound include phenoxyethyl acrylate, benzyl acrylate, isobornyl acrylate, tetrahydrofuranyl acrylate, isodecyl acrylate, lauryl acrylate, etc., but are limited thereto. It does not become.

In the exemplary embodiment of the present specification, the radical-based adhesive composition includes a (meth)acrylate monomer (C) having a hydrophilic functional group. The (meth)acrylate monomer (C) may be one having at least one hydrophilic functional group in the molecule. The (meth)acrylate monomer (C) having a hydrophilic functional group exhibits an effect of enhancing compatibility with the substrate and improving compatibility between the substrate surface and the adhesive. Particularly, when used for a polarizer, excellent adhesion of the adhesive composition between the substrate and the polarizer can be provided.

In addition, the (meth)acrylate monomer (C) having a hydrophilic functional group may be used without particular limitation as long as radical polymerization is possible due to the presence of an unsaturated double bond between carbons in the molecule. At this time, the hydrophilic functional group is not particularly limited as long as hydrogen bonding is possible, such as a hydroxy group, a carboxyl group, a urethane group, an amine group, and an amide group, but among them, a hydroxy group is more preferable for realization of excellent adhesion. For example, the (meth)acrylate monomer having a hydrophilic functional group may be a (meth)acrylate having an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, having one or more hydroxy groups. For example, monofunctional (meth)acrylate having a hydroxy group is 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2- It may be one or more of hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate, and these may be used alone or in combination of two or more Can be used.

The content of the (meth)acrylate monomer (C) having a hydrophilic functional group is preferably 10 parts by weight to 20 parts by weight, or 15 parts by weight to 20 parts by weight, based on 100 parts by weight of the radical-based adhesive composition.

In the exemplary embodiment of the present specification, the radical-based adhesive composition may include two or more types of polyfunctional (meth)acrylate monomers and a (meth)acrylate monomer having one type of hydrophilic functional group.

In the exemplary embodiment of the specification, the radical-based adhesive composition includes a polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150°C or higher of the homopolymer. Preferably, when a polyfunctional (meth)acrylate monomer having a glass transition temperature of 180°C or higher is included, it has a higher glass transition temperature from the Tan delta (Tan Delta) peak, and the storage modulus at high temperature is higher. The glass transition temperature of the homopolymer of the polyfunctional (meth)acrylate monomer may be, for example, 400°C or less or 300°C or less.

In this specification, Tan delta (Tan Delta) means the ratio of the storage modulus and the loss modulus. Specifically, the Tan δ (Tan Delta) may be represented by the following equation.

Tanδ(Tan Delta) = storage modulus / loss modulus

In the present specification, the "glass transition temperature" means a temperature at which a polymer material is converted from a hard solid state such as glass to a rubber state having elasticity. The glass transition temperature is determined according to the structural properties of the monomer, and thus the polymer has its own glass transition temperature depending on the type of the polymerized monomer. The lower the glass transition temperature, the higher the flexibility of the material, and the higher the glass transition temperature, the stronger the material. Since the monomer itself cannot measure the glass transition temperature, the glass transition temperature is generally measured by polymerizing a homopolymer of the monomer. However, in this specification, the glass transition temperature is determined from a Tan Delta (Tan) value. A temperature corresponding to Tanδmax, which has the largest value (peak) in Tanδ (Tan Delta) value according to temperature, may be defined as a glass transition degree.

The multifunctional (meth)acrylate monomer is generated when using a low molecular weight acrylic copolymer by forming a second crosslinked structure through curing by radiation irradiation and making the adhesive more hard during curing. A desired storage modulus (G') can be secured while improving the durability deterioration problem. In addition, it is a component that makes coating easier by diluting the adhesive composition and adjusting the viscosity. That is, the multifunctional (meth)acrylate monomer serves to improve the workability of the adhesive composition by controlling the viscosity while maintaining viscoelasticity while imparting durability to the cured adhesive layer.

As a polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150°C or higher of the homopolymer, for example, dimethyloltricyclodecane diacrylate (Tg: 214°C), (trishydroxy Ethylisocyanurate)triacrylate (Tg: 225°C), [2-[1,1-dimethyl-2[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxane- 5 days] methyl acrylate (Tg: 180°C), 9,9-bis[4-(2-acrylooxyethoxy) phenylflorene (Tg: 179°C) and (trishydroxyethylisocyanurate) Triacrylate (Tg: 275°C) may be exemplified, but is not limited thereto.

The content of the polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150° C. or higher of the homopolymer is 5 parts by weight to 40 parts by weight, or 10 parts by weight based on 100 parts by weight of the radical adhesive composition. It is preferable that it is about 15 to 30 parts by weight or 35 to 35 parts by weight. If the content is less than 5 parts by weight, durability may be deteriorated or it may be difficult to suppress light leakage under a high temperature or high temperature/humidity environment, and even if the content is more than 40 parts by weight, durability may be reduced.

The glass transition temperature after curing of the radical-based adhesive composition may be 80°C or more and 150°C or less. When the glass transition temperature is less than, the cured product of the radical-based adhesive composition deteriorates heat resistance and durability.

The peak value of Tanδ after curing of the radical-based adhesive composition may be 0.2 or higher, and the glass transition temperature at the peak value of Tanδ may be 90°C or higher. If it is less than the above range, the adhesion of the cured product of the radical-based adhesive composition, moist heat resistance, and durability deteriorate. When the glass transition temperature due to the Tan delta (Tan Delta) peak is in the above range, there is little thermal deformation of the adhesive layer in the temperature range for evaluating reliability, so that high reliability can be secured.

In order to measure the Tan delta (Tan Delta), a radical-based adhesive composition is first coated on a release film and photocured by irradiating a light amount of 1,000 mJ/cm ² at a temperature of 23° C. and a relative humidity of 55% to prepare a cured film. In this case, the thickness of the cured film is 30 μm to 50 μm, and may be, for example, 30 μm. After removing the release film, a specimen prepared in the size of width x length x thickness (5.3mm x 5mm x 30㎛) was subjected to a temperature sweep test (Strain 0.04%, Preload force 0.05N, Force) using DMA Q800 (TA instrument). Track 125%, Frequency 1Hz) from 0℃ to 150℃ at 5℃/min and measure the storage modulus. After that, the Y-axis on the graph obtained using the analysis tool is set as the numerical change of Tanδ (Tan Delta), and the temperature at Tanδmax, which has the largest value, is defined as the glass transition temperature.

The storage modulus at 80° C. after curing of the radical-based adhesive composition may be 800 Mpa or more and 2,000 Mpa or less, preferably 900 Mpa or more and 2,000 Mpa or less, and more preferably 1,000 MPa or more and 2,000 MPa or less. The range of the storage modulus is a storage modulus at 80°C, and the storage modulus at a temperature other than 80°C may have different values. When the storage modulus at 80° C. is within the above range, the polarizer protection performance of the adhesive layer provided between the polarizer and the protective film may be effectively performed. Specifically, it is possible to effectively suppress the occurrence of cracks in the polarizer in a harsh environment such as thermal shock.

When the storage modulus at 80° C. after curing of the radical-based adhesive composition is less than 800 MPa, it is difficult to suppress contraction and expansion of the polarizer due to temperature during the thermal shock evaluation process, resulting in cracks of the polarizer, and the storage modulus at 80° C. is 2,000. If the Mpa is exceeded, the polarizing plate may be warped depending on the polarizer and the laminated substrate.

In the present specification, the crack may mean a long broken portion in the MD (machine direction) direction. For example, the length of the crack may be 0.01 mm or more.

In order to measure the storage modulus, a radical-based adhesive composition is first coated on a release film and photocured by irradiating a light amount of 1,000 mJ/cm ² at a temperature of 23° C. and 55% relative humidity to prepare a cured film. In this case, the thickness of the cured film may be 30 μm to 50 μm, for example 30 μm. After removing the release film, a specimen prepared in the size of width x length x thickness (5.3mm x 5mm x 30㎛) was subjected to a temperature sweep test (strain 0.04%, preload force: 0.05N) using a DMA Q800 (TA instrument). The storage modulus was measured while increasing the temperature at 5℃/min from 0℃ to 150℃ with Force Track: 125%, Frequency: 1Hz).

The radical adhesive composition may not have an ether bond peak (1,080cm ^-1 ) in the IR spectrum after curing. The compound having an epoxy functional group is a cationic polymerizable material that is not radically polymerizable, and the amount is small even when used as an additive for imparting functions other than polymerization properties.As a result, after curing, the ether bond peak (1,080 cm ^-1 ).

In the exemplary embodiment of the present specification, the radical-based adhesive composition does not contain an epoxy compound as a polymerizable compound, but may contain a small amount as an additive. The content of the epoxy compound is 0.1 parts by weight to 5 parts by weight, preferably, 0.1 parts by weight to 3 parts by weight, more preferably 0.1 parts by weight to 1 part by weight, based on the total 100 parts by weight of the radical-based adhesive composition. I can.

Whether the radical-based adhesive composition contains an epoxy compound can be confirmed by measuring an IR spectrum. The epoxy adhesive composition containing the epoxy compound has an ether bond peak (1,080 cm ^-1 ) in the IR spectrum due to the ether bond generated by the ring opening of the epoxy ring, whereas the radical adhesive composition containing the acrylate compound has an ether bond. It has no binding peak. In addition, in the vicinity of 1,200cm ^-1 to 1,000cm ^-1 , three peaks can be found in the epoxy-based adhesive composition, but only one peak is found in the radical-based adhesive composition.

In an exemplary embodiment of the present invention, the radical-based adhesive composition may include a photoacid generator (E) or a photoinitiator (F), or may include a photoacid generator (E) and a photoinitiator (F).

As the photoacid generator (E), a conventionally known photoacid generator can be used without particular limitation. Specifically, examples thereof include an aromatic diazonium salt, an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt, and an iron-allene complex. These may be used alone or in combination of two or more.

Examples of the aromatic diazonium salt include benzene diazonium hexafluoroantimonate, benzene diazonium hexafluorophosphate, and benzene diazonium hexafluoroborate.

Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4 -Nonylphenyl)iodonium hexafluorophosphate, etc. are mentioned.

As the aromatic sulfonium salt, for example, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl[4-(phenyl Thio)phenyl]sulfoniumhexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, 4,4'-bis[diphenylsulfonio]diphenylsulfide bishexafluoro Lophosphate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluoroantimonate, 4,4'-bis[di(β-hydroxyethoxy) )Phenylsulfonio]diphenylsulfide bishexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7-[di(p -Toluyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4 -(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4-(p-tert-butylphenylcarbonyl)-4'-di(p -Toluyl)sulfonio-diphenylsulfide tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium phosphate, etc. are mentioned.

Examples of the iron-allene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, and xylene-cyclopentadie. Nial iron (II)-tris (trifluoromethylsulfonyl) metanide, etc. are mentioned.

The photoacid generator may be commercially available, for example, CPI-100P, 101A, 200K, 210S (above, San Apro Co., Ltd. product), Kayarard (registered trademark) PCI-220, PCI-620 ( The above, manufactured by Nihon Kayaku Co., Ltd.), UVI-6990 (above, manufactured by Union Carbide), Adekaoptomer (registered trademark) SP-150, SP-170 (above, manufactured by ADEKA Corporation) ), CI-5102, CIT-1370, 1682, CIP-1866S, 2048S, 2064S (above, manufactured by Nihon Soda Corporation), DPI-101, 102, 103, 105, MPI-103, 105, BBI- 101, 102, 103, 105, TPS-101, 102, 103, 105, MDS-103,105, DTS-102, 103 (above, manufactured by Midori Chemical Co., Ltd.), PI-2074 (Rodia Japan (Ro- Diapan) Co., Ltd.), and the like.

The content of the photoacid generator is preferably 0.5 parts by weight or more and 7 parts by weight or less, and more preferably It is 1 part by weight or more and 4 parts by weight or less. By setting the amount of the photoacid generator to be 0.5 parts by weight or more, the curability of the adhesive after ultraviolet irradiation becomes good. On the other hand, by setting the amount to be 7 parts by weight or less, it is possible to suppress a decrease in adhesiveness and durability due to bleed out. When calculating the content of the photoacid generator, the total weight of the radical-based adhesive composition means the total of the remaining components excluding the photoacid generator.

The kind of the photoinitiator is not particularly limited, and a conventionally known photoinitiator may be preferably used. Photoinitiators may be used alone or in combination of two or more.

The photoinitiator is specifically an inorganic peroxide such as hydrogen peroxide, potassium persulfate or ammonium persulfate, t-butyl hydroperoxide, t-dibutyl peroxide, cumene hydroperoxide, acetyl peroxide, benzoyl peroxide, and lauroyl peroxide. Peroxide, azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, and azobiscyanovaler Azo compounds such as acids, acetophenones, benzoin, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, 2,3-dialkyldione compounds, disulfide compounds, fluorine Roamine compounds, aromatic sulfoniums, lopyne dimers, onium salts, borate salts, active esters, active halogens, inorganic complexes, coumarins, and the like. More specifically, acetophenone, 3-methylacetophenone, benzyldimethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[4 Acetophenones such as -(methylthio)phenyl]-2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; Benzophenones, including benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; Benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; Thioxanthones such as 4-isopropyl thioxanthone; 1-hydroxycyclohexylphenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, and the like.

The photoinitiator may be a commercial product, for example, IRGACURE (registered trademark) 184, 819, 907, 651, 1700, 1800, 819, 369, 261, DAROCUR (registered trademark) TPO , Darocure (registered trademark) 1173 (above, BASF Japan Co., Ltd. product), Esacure (registered trademark) KIP150, TZT (above, DKSH Japan Co., Ltd. product), KAYACURE (registered trademark) BMS, DMBI (Above, Nihon Kayaku Co., Ltd. product), etc.

In addition, the photoinitiators are amines such as ethyl amine, triethanolamine and dimethylaniline, polyamines, divalent iron salt compounds, ammonia, triethylaluminum, triethylboron, and organometallic compounds such as diethylzinc, sodium sulfite, hydrogen sulfite You may use together suitable reducing agents, such as sodium, cobalt naphthenate, sulfinic acid, and mercaptan.

The radical-based adhesive composition may include a photosensitizer. The type of the photosensitizer is not particularly limited, and a conventionally known photosensitizer can be preferably used. Photosensitizers may be used alone or in combination of two or more.

Specific examples of the photosensitizer include, for example, pyrene; Benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α-dimethoxy-α phenylacetophenone; Benzophenones such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, and 4,4'-bis(diethylamino)benzophenone derivative; Thioxanthone derivatives such as 2-chloro thioxanthone, 2-isopropyl thioxanthone, and 2,4-diethyl thioxanthone; Anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; Acridone derivatives such as N-methylacridone and N-butylacridone; In addition, α-diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compounds, halogen compounds, and the like can be mentioned.

The photosensitizer may be a synthetic product or a commercial product. Examples of commercially available products include, for example, Kayaku (registered trademark) DMBI, BDMK, BP-100, BMBI, DETX-S, EPA (above, Nihon Kayaku Co., Ltd. product), Anthracure (registered trademark) UVS-1331, UVS -1221 (above, manufactured by Kawasaki Kasei Co., Ltd.), Yubecryl P102, 103, 104, 105 (above, manufactured by UCB), and the like.

The amount of at least one of the photoinitiator and the photosensitizer (the total amount used in the case of using a photoinitiator and a photosensitizer in combination) is preferably based on the total weight of the remaining components excluding the photoinitiator and photosensitizer in the radical adhesive composition. Preferably, they are 0.1 parts by weight or more and 7 parts by weight or less, more preferably 0.2 parts by weight or more and 3.5 parts by weight, and 0.2 parts by weight or more and 2.5 parts by weight or less. In the above range, since the curing efficiency is excellent by irradiation with ultraviolet rays, it is possible to suppress a decrease in adhesion and durability due to bleed-out.

In the exemplary embodiment of the present specification, the type of the silane coupling agent (D) is not particularly limited, and for example, vinylchlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclo Hexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethoxysilane, 3-glycidoxypropyltriethoxysilane , p-styryltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyl Diethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3 -Dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane , Bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, etc. are mentioned. These can be used alone or in combination of two or more.

The radical-based adhesive composition may contain additives in addition to the above components as necessary to a degree that does not significantly reduce the effect of the present invention.

The additives include, for example, other polymerizable components other than the above, ultraviolet absorbers, antioxidants, heat stabilizers, inorganic fillers, softeners, antioxidants, anti-aging agents, stabilizers, tackifier resins, modifying resins (polyol resin, phenol resin, acrylic Resin, polyester resin, polyolefin resin, etc.), leveling agents, defoaming agents, plasticizers, dyes, pigments (colored pigments, extender pigments, etc.), treatment agents, sunscreen agents, fluorescent whitening agents, dispersants, light stabilizers, antistatic agents, lubricants, etc. Can be lifted.

The content of the additive is preferably 0.01 parts by weight or more and 20 parts by weight or less, more preferably 0.02 parts by weight or more and 10 parts by weight or less, more preferably 0.05 parts by weight or more and 5 parts by weight or less, based on the total 100 parts by weight of the adhesive composition. Do. By setting the content of the additive in the above range, the effect of the adhesive of the present invention can be sufficiently exhibited. The total weight of the adhesive composition may mean the total of the remaining components excluding the additive.

The adhesive strength of the cured product of the radical-based adhesive composition to the non-pretreated polyethylene terephthalate film may be 150 gf/20mm, preferably 170 gf/20mm, more preferably 200 gf/20mm or more. Satisfying the above range means that the radical-based adhesive composition has excellent adhesion to the polyethylene terephthalate film. When the above numerical range is satisfied, there is an advantage in that there is no need for pretreatment in order to increase the adhesion of the protective film. Since the pretreatment is to increase the adhesion of the film, there is a corona treatment or the like. Whether or not the polyethylene terephthalate film is pretreated can be confirmed through a contact angle, the contact angle of the non-pretreated polyethylene terephthalate film may be 50 degrees to 70 degrees, and the contact angle of the pretreated polyethylene terephthalate film may be less than 50 degrees. The contact angle may be measured by a method generally used in the field to which this technology belongs. For example, after dropping a liquid drop onto a film, an angle formed between a stationary liquid drop and a film surface may be measured. At this time, as the type of liquid, water (DI water) or an organic solvent may be used. An example of a contact angle tester used to measure the contact angle is Phonenix 300.

The viscosity at 25° C. of the radical-based adhesive composition may be 10 cPs or more and 100 cPs or less, preferably 10 cPs or more and 80 cPs or less, and more preferably 10 cPs or more and 65 cPs or less. When the viscosity is within this range, the processability of the composition is improved and air bubbles can be prevented in the adhesive layer formed from the adhesive composition.

The method for producing the radical adhesive composition is not particularly limited, and can be obtained by mixing the components. You may use an organic solvent suitably for viscosity adjustment. The mixing method is also not particularly limited, and the mixture may be sufficiently stirred and mixed at room temperature (20° C. or more and 25° C. or less) until the inside of the liquid becomes uniform in a room shielded from UV light so that curing does not proceed.

The radical adhesive composition is a polarizing plate (polarizing film), a retardation film, an elliptically polarizing film, an antireflection film, a luminance enhancing film, an indium oxide/tin sputtering transparent conductive film (ITO film), various electronic film members or protective films, etc. It can be used suitably. Especially, it is preferable to be used for a polarizing plate (polarizing film).

The present specification is a protective film; And it provides a protective film for a polarizing plate provided with an adhesive layer including the above-described radical-based adhesive composition on one or both sides of the protective film.

In the exemplary embodiment of the present specification, the thickness of the adhesive layer is preferably greater than 0㎛ 20㎛ or less, more than 0㎛ 10㎛, preferably 0.1㎛ to 10㎛ or 0.1㎛ to 5㎛ degree. This is because if the thickness of the adhesive layer is too thin, the uniformity and adhesion of the adhesive layer may be deteriorated, and if the thickness of the adhesive layer is too thick, the appearance of the polarizing plate may be wrinkled.

The present specification is a polarizer; And it provides a polarizing plate including the protective film for the polarizing plate described above on one or both sides of the polarizer. Referring to FIGS. 1 and 2, the polarizing plate includes protective films 101 and 105 on one or both sides of the polarizer 103 via adhesive layers 102 and 104.

In the present specification, the polarizer may be a polarizer well known in the art, for example, a film made of polyvinyl alcohol (PVA) containing iodine or a dichroic dye. The polarizer may be manufactured by dyeing iodine or a dichroic dye to a polyvinyl alcohol-based film, but the method of manufacturing the polarizer is not particularly limited. In the present specification, the polarizer refers to a state in which the protective layer (or protective film) is not included, and the polarizing plate refers to a state including the polarizer and the protective layer (or protective film).

The polarizer is a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing a polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, a polyvinyl alcohol-based resin film adsorbed with a dichroic dye It is manufactured through a process of treating with a boric acid aqueous solution, a process of washing with water after treatment with an aqueous boric acid solution, and bonding a protective layer to a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. .

The uniaxial stretching may be performed before dyeing with a dichroic dye, simultaneously with dyeing with a dichroic dye, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Further, it is also possible to uniaxially stretch in a plurality of these steps. In order to perform uniaxial stretching, it may be uniaxially stretched between rolls having different circumferential speeds, or uniaxially stretched using a heat roll. Further, it may be dry stretching performed in the air, or wet stretching performed in a state swollen by a solvent. The draw ratio is not particularly limited, but is usually 4 to 8 times.

Meanwhile, the polarizer preferably has a thickness of 5 μm to 40 μm, and more preferably 5 μm to 25 μm. If the thickness of the polarizer is thinner than the above numerical range, optical properties may deteriorate, and if the thickness of the polarizer is thicker than the above numerical range, the amount of shrinkage of the polarizer at a low temperature (eg -30°C) increases, thereby reducing the overall durability of the polarizing plate in relation to heat. .

In addition, when the polarizer is a polyvinyl alcohol-based film, the polyvinyl alcohol-based film may be used without particular limitation as long as it includes a polyvinyl alcohol resin or a derivative thereof. In this case, the derivatives of the polyvinyl alcohol resin include polyvinyl formal resin and polyvinyl acetal resin, but are not limited thereto. In addition, commercially available polyvinyl alcohol-based films such as P30, PE30, PE60 from Guraray, M2000, M3000, M6000, etc. from Japan Synthetic Company may be used, but the present invention is not limited thereto.

The polyvinyl alcohol-based film preferably has a degree of polymerization of 1,000 to 10,000, and more preferably 1,500 to 5,000. When the degree of polymerization satisfies the above numerical range, the movement of molecules is free and may be flexibly mixed with iodine or a dichroic dye.

As the material for the protective film, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and isotropy is preferable. For example, cellulose resins such as cellulose diacetate and cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate (PMMA), polystyrene, acrylonitrile and styrene Polystyrene resin such as ene copolymer (AS resin), polycarbonate resin, polyethylene, polypropylene, ethylene/propylene copolymer, polyolefin resin such as cycloolefin polymer, polyvinyl chloride resin, polyamide resin such as nylon or aromatic polyamide , Polyimide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyphenylene sulfide resin, polyvinyl alcohol resin, polyvinylidene chloride resin, polyvinyl butyral resin, polyarylate resin, polyoxy And a methylene resin, an epoxy resin, or a blend of these resins.

Preferably, the protective film may be the above-described cellulose-based film.

Specifically, a cellulose resin, a cycloolefin polymer (COP), polyethylene terephthalate (PET), or an acrylic resin, which is an ester of cellulose and fatty acids, is preferable. Examples of the cellulose resin include cellulose stripe acetate (TAC), cellulose diacetate, cellulose stripe propionate, and cellulose dipropionate. Among these, cellulose triacetate, cycloolefin polymer, polyethylene terephthalate, or acrylic resin is preferred from the viewpoint of availability and cost, and cycloolefin polymer, polyethylene terephthalate, or acrylic resin is considered from the viewpoint of availability and moisture permeability. Is more preferable. If the moisture permeability of the protective film is high, moisture can penetrate the protective film and easily enter the polarizer side, which may deteriorate the quality of the polarizer. However, if you use a cycloolefin polymer, polyethylene terephthalate, or acrylic resin, it should be noted that Can be suppressed.

In addition, the cellulose triacetate can be saponified, but the unsaponified one is more preferable.

The protective film surface may be modified by corona discharge treatment. There is no restriction|limiting in particular as a corona discharge treatment method, It can process using a general corona discharge treatment apparatus (for example, Kasuga Electric Co., Ltd. product). By corona discharge treatment, active groups, such as a hydroxyl group, are formed on the surface of a protective film, for example, and it is thought that this contributes to the improvement of adhesion more. In the case of using saponified cellulose triacetate as a protective film, an effect of improving adhesion such as corona discharge treatment can be expected, so that corona discharge treatment is not necessarily required. However, since the saponification treatment is complicated in the process and becomes expensive, it is preferable in the manufacturing process to use unsaponified cellulose triacetate after corona discharge treatment.

As the discharge amount of the corona discharge treatment particularly limited and is not, 30W and min / m ² or more 300W and min / m ² or less range is preferably, 50W and min / m ² or more 250W and min / m ² within the following range of More preferable. In such a range, the adhesion between the protective film and the adhesive can be improved without deteriorating the protective film itself, which is preferable. Here, the amount of discharge is the amount of work to the object by corona discharge determined by the following equation, and the corona discharge power is determined based on this.

The manufacturing method of the polarizing plate is not particularly limited, and can be manufactured by bonding the polarizer and the protective film using the aforementioned radical adhesive composition by a conventionally known method. The applied adhesive expresses adhesiveness by irradiation with ultraviolet rays to constitute an adhesive layer.

When applying the said radical adhesive composition, you may apply to either a protective film or a polarizer, and you may apply to both. The radical-based adhesive composition is preferably applied so that the thickness of the adhesive layer after drying is more than 0 and 20 μm or less. The thickness of the adhesive layer can be adjusted by the solid content concentration in the adhesive solution or by the adhesive application device. In addition, the thickness of the adhesive layer can be confirmed by observing the cross section with a scanning electron microscope (SEM). The method of applying the adhesive is also not particularly limited, and various means such as a method of directly dropping the adhesive, a roll coating method, a spray method, and an immersion method can be employed.

After applying the adhesive, the polarizer and the protective film are bonded together by a roll laminator or the like.

After the bonding, the polarizing plate is irradiated with ultraviolet rays for curing the adhesive. The light source of ultraviolet rays is not particularly limited, but low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps, chemical lamps, black light lamps, microwave excitation mercury lamps, metal halide lamps, etc. can be used. . Although the ultraviolet irradiation amount (accumulated light amount) is not particularly limited, it is preferable that the ultraviolet irradiation amount in the wavelength region effective for activation of the polymerization initiator is 100 mJ/cm ² or more and 2,000 mJ/cm ² or less. If it is within this range, the reaction time is appropriate, and it is possible to prevent deterioration of the adhesive itself or the polarizing film due to heat radiated from the lamp and heat generated during polymerization.

The polarizing plate may be stored at room temperature (20° C. or more and 25° C. or less, specifically 25° C.) for 16 hours or more and 30 hours or less immediately after UV irradiation. Upon completion of the curing, the polarizing plate is completed.

The present specification is a display panel; And an image display device in which the polarizing plate described above is provided on one or both surfaces of the display panel.

The present specification is a display panel; And an image display device in which the polarizing plate is provided on a viewing side of the display panel or on a surface opposite to the viewing side of the display panel.

The display panel may be a liquid crystal panel, a plasma panel, and an organic light emitting panel. Accordingly, the image display device may be a liquid crystal display device (LCD), a plasma display device (PDP), and an organic light emitting display device (OLED). More specifically, the image display device may be a liquid crystal display device including a liquid crystal panel and polarizing plates respectively provided on both sides of the liquid crystal panel, and at this time, at least one of the polarizing plates according to an exemplary embodiment of the present specification described above It may be a polarizing plate including a polarizer.

In this case, the type of the liquid crystal panel included in the liquid crystal display device is not particularly limited. For example, the panel is not limited to the type and has a passive matrix type such as a twisted nematic (TN) type, a super twisted nematic (STN) type, a ferroelectic (F) type, or a polymer dispersed (PD) type; An active matrix type panel such as a two terminal type or a three terminal type; Known panels, such as an IPS (In Plane Switching) panel and a vertical alignment (VA) panel, may all be applied. In addition, other configurations constituting the liquid crystal display device, for example, the types of upper and lower substrates (eg, color filter substrates or array substrates) are not particularly limited, and configurations known in the art are not limited. Can be employed.

Hereinafter, in order to describe the present specification in detail, it will be described in detail with reference to examples. However, the embodiments according to the present specification may be modified in various forms, and the scope of the present specification is not construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely describe the present specification to those of ordinary skill in the art.

<Preparation of radical adhesive composition>

A radical-based adhesive composition having a composition according to Table 1 was prepared.

<Experimental Example 1: Protective film adhesion test>

The prepared radical-based adhesive composition was applied to both surfaces of a polarizer prepared in advance (manufactured by LG CHEM), and a protective film (PET film) for peeling was laminated. Thereafter, the radical-based adhesive composition was cured by irradiating UV rays with a wavelength of 365 nm so that the irradiation amount (accumulated amount of light) was 2,000 mJ/cm ² , so that the polarizer and the protective film for peeling were bonded to each other, and the width of 2 cm * length of 15 cm It was cut to size to prepare a polarizing plate sample. At this time, for each radical-based adhesive composition, the pretreatment conditions of the peeling protective film were changed, and in the case of the pre-treatment protective film, a solution of 10% KOH concentration in the portion where the radical-based adhesive composition is provided is coronavirus at a temperature of 45 degrees. Processed.

As shown in FIG. 3, any one of the protective films for peeling was peeled off at least 3 cm at a peel angle of 90 degrees and a peel rate of 0.5 cm/sec, and the peel force at this time was measured three times to calculate an average value. When measuring the peel force, an XT Plus Texture Analyzer (manufactured by TA) was used.

T/T in Table 1 means that the analyzer and the protective film for peeling are peeled off, TAC/Ad means that the adhesive layer and the protective film for peeling are peeled off, and PVA/Ad means that between the polarizer and the adhesive layer It means peeling. The adhesive can be classified as having excellent performance only when the analyzer and the protective film for peeling are separated.

<Experimental Example 2: Measurement of glass transition temperature and storage modulus after curing>

The prepared radical-based adhesive composition was applied to both surfaces of a polarizer (manufacturer) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the radical-based adhesive composition was cured by irradiating UV rays with a wavelength of 365 nm so that the irradiation amount (accumulated light amount) was 2000 mJ/cm ² . This was cut into a size of 5.3 mm in width * 4.5 cm in length, and the protective film for peeling was peeled to obtain a cured product (cured film) of a radical-based adhesive composition. Using a viscoelastic measuring device (Dynamic mechanical analyzer: manufactured by DMA Q800 TA instrument), the cured film was installed so that its long side was in the tensile direction, and the frequency was set to 1 Hz, the measurement start temperature -30°C, and the heating rate 5°C/min. Then, the viscoelasticity was measured. The glass transition temperature (Tg) was taken as the temperature at which Tanδ became the maximum value, and the peak value of Tanδ was taken as the maximum value.

In addition, the temperature sweep test (strain 0.04%, Preload force: 0.05N, Force Track: 125%, Frequency: 1Hz) using DMA Q800 (TA instrument) is used to store the temperature from 0℃ to 150℃ at 5℃/min. The modulus of elasticity was measured and the value measured at 80°C was read.

<Experimental Example 3: Water resistance evaluation>

The prepared radical-based adhesive composition was applied to both surfaces of a polarizer (manufacturer) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the radical-based adhesive composition was cured by irradiating UV rays with a wavelength of 365 nm so that the irradiation amount (accumulated light amount) was 2000 mJ/cm ² . This was cut to have a length of 150 mm, respectively, with respect to the direction of the absorption axis of the polarizer and the direction perpendicular thereto. Thereafter, a pressure-sensitive adhesive was applied to one surface of the peeling protective film, and the glass was laminated to a glass substrate, and left at 25° C. for 24 hours. After that, the glass plate was left in a water bath at 60° C. for 24 hours and taken out. The appearance of this sample was visually checked to confirm whether the polarizer color disappeared and whether the film was peeled off. It was described as OK that there was no color loss or the film was not peeled off, and the case where there was color loss or the film was peeled off was described as NO.

<Experimental Example 4: Thermal shock evaluation>

The prepared radical-based adhesive composition was applied to both surfaces of a polarizer (manufacturer) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the radical-based adhesive composition was cured by irradiating UV rays with a wavelength of 365 nm so that the irradiation amount (accumulated light amount) was 2000 mJ/cm ² . This was cut to have a length of 150 mm, respectively, with respect to the direction of the absorption axis of the polarizer and the direction perpendicular thereto. Thereafter, a pressure-sensitive adhesive was applied to one surface of the peeling protective film, and the glass was laminated to a glass substrate, and left at 25° C. for 24 hours.

Thereafter, the glass substrate was allowed to stand at -40°C for 30 minutes and 85°C for 30 minutes as one cycle, but this was repeated 100 cycles. After applying thermal shock, it was observed whether or not a polarizer crack existed from the end of the polarizing plate in the stretching direction of the polarizer (arrow direction), and when a polarizer crack was observed, the length of the crack was measured. When a plurality of cracks were observed, evaluation was made using the average value. A case where no crack occurred or the length of the crack was less than 1 mm was marked as pass, and a case where the length of crack was 1 mm or more was marked as rejected.

<Experimental Example 5: Evaluation of stiffness>

The prepared radical-based adhesive composition was applied to both surfaces of a polarizer (manufacturer) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the radical-based adhesive composition was cured by irradiating ultraviolet rays with a wavelength of 365 nm so that the irradiation amount (accumulated light amount) was 2,000 mJ/cm ² . This was cut into a size of 3 cm in width * 7 cm in length, and the protective film for peeling was peeled to obtain a cured product (cured film) of a radical-based adhesive composition.

As shown in Figure 4, when the cured film is folded in a loop shape and fixed to a viscoelasticity measuring device (Dynamic Mechanical Analyzer: manufactured by DMA Q800 TA instrument), pressed with a force of 1 g and 30 m/min on the bent surface, and a 20 mm distance is pressed. The force of was recorded as the stiffness of the cured film.

<Experimental Example 6: Evaluation of the viscosity of the entire composition>

The viscosity of each composition was evaluated.

Assessment Methods:

-Measuring device: BROOKFIELD VISCOMETER DV-Ⅱ+PRO

-Speed: 90 RPM

-Spindle: No. 18

<Experimental Example 7: Evaluation of viscosity of urethane acrylate oligomer>

The viscosity of each urethane oligomer at 25°C was evaluated.

-Measuring device: BROOKFIELD VISCOMETER DV-Ⅱ+PRO

-Speed: 0.01 rpm

-Spindle: No. 18

<Experimental Example 8: Measurement of acid value of urethane acrylate oligomer>

The acid value of the urethane acrylate was measured in the manner described above.

A description of the identification codes in Tables 1 and 2 is as follows.

A: urethane acrylate oligomer

(a): polyester urethane acrylate oligomer

B1: Polyfunctional (meth)acrylate monomer having a glass transition temperature (Tg) of 150°C or higher of the homopolymer

B2: Polyfunctional (meth)acrylate monomer having a glass transition temperature (Tg) of less than 150°C of the homopolymer

C: (meth)acrylate monomer having a hydrophilic functional group;

D: silane coupling agent;

E: photoacid generator; And

F: photoinitiator

DPGDA: Dipropylene glycol diacrylate (Tg: 102°C)

M370: tris (2-hydroxyethyl) isocyanurate triacrylate (Tg: 225°C)

4-HBA: 4-hydroxybutyl acrylate (Tg: -56°C)

R-604: [2-[1,1-dimethyl-2[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5yl] methyl acrylate (Tg: 180°C)

KBM403: (3-glycidoxypropyl) trimethoxysilane

I250: (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluoro phosphate

TPO: diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide

DETX: 2,4-diethyl thioxanthone

The parts by weight of A, B(B1, B2), C, and D refer to parts by weight of each material based on the total weight of A to D.

The parts by weight of E and F mean parts by weight of each material based on the total weight of 100 in which all of the A to D are summed.

From the above results, it was confirmed that the radical-based adhesive compositions according to Examples 1 and 2 had excellent adhesion to PET films that were not subjected to corona treatment. This is because, as the radical-based adhesive composition contains a polyester-based urethane acrylate oligomer whose acid value is adjusted, the adhesive strength of the adhesive layer to the protective film is excellently secured.

In addition, when the radical-based adhesive composition according to Examples 1 and 2 was applied to a polarizing plate, it was confirmed that heat resistance and water resistance were improved, and stiffness was increased.

Claims (16)

1. Polyester-based urethane acrylate oligomer (A) having an acid value of 90 mgKOH/g to 180 mgKOH/g;

   A polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150°C or higher of the homopolymer;

   (Meth)acrylate monomer (C) having a hydrophilic functional group; And

   Radical adhesive composition containing a silane coupling agent (D).
2. The method according to claim 1, wherein the polyester-based urethane acrylate oligomer (A) is a polyester-based polyol compound; Isocyanate compounds; And a radical-based adhesive composition formed from a composition comprising an acrylate-based compound.
3. The radical-based adhesive composition according to claim 1, wherein the polyester-based urethane acrylate oligomer (A) has a viscosity of 1,000 cPs or more and 50,000 cPs or less at 25°C.
4. The radical adhesive composition according to claim 1, wherein the polyester-based urethane acrylate oligomer (A) is included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the total composition.
5. The radical-based adhesive composition according to claim 1, further comprising a polyfunctional (meth)acrylate monomer (B2) having a glass transition temperature (Tg) of less than 150°C of the homopolymer.
6. The radical-based adhesive composition according to claim 1, wherein the radical-based adhesive composition has a glass transition temperature of 80°C or more and 150°C or less after curing.
7. The radical-based adhesive composition according to claim 1, wherein the peak value of Tanδ after curing of the radical-based adhesive composition is 0.2 or more, and the glass transition temperature at the peak value of Tanδ is 90°C or more.
8. The radical-based adhesive composition according to claim 1, wherein the radical-based adhesive composition has a storage modulus of 800 Mpa or more and 2,000 Mpa or less at 80° C. after curing.
9. The radical-based adhesive composition according to claim 1, which does not have an ether bond peak (1,080cm ^-1 ) in the IR spectrum after curing.
10. The radical-based adhesive composition according to claim 1, wherein the adhesive strength of the cured product of the radical-based adhesive composition to an unpretreated polyethylene terephthalate film is 150 gf/20mm or more.
11. The radical adhesive composition according to claim 1, wherein the viscosity at 25°C is 10 cPs or more and 100 cPs or less.
12. Protective film; And

    A protective film for a polarizing plate provided with an adhesive layer comprising a cured product of the radical-based adhesive composition according to any one of claims 1 to 11 on one or both sides of the protective film.
13. The protective film of claim 12, wherein the adhesive layer has a thickness of more than 0 µm and 20 µm or less.
14. The protective film according to claim 12, wherein the protective film is a cellulose-based film.
15. Polarizer; And

    A polarizing plate comprising a protective film for a polarizing plate according to claim 12 provided on one or both sides of the polarizer.
16. Display panel; And

    An image display device comprising the polarizing plate according to claim 15 provided on one or both surfaces of the display panel.

Images