KR20210085209A - Curable adhesive composition, protective film for plarizing plate, polarizing plate and image display apparatus comprising same - Google Patents

Abstract

The present specification relates to an adhesive composition, a protective film for a polarizing plate including the same, the polarizing plate including the same, and an image display device including the same. The adhesive composition of the present specification has an effect of increasing curing reliability in various environments by similarly adjusting a curing rate in a condition in which a wavelength band of light is long and a condition in which a wavelength band of light is short.

Description

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

The present specification relates to an 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.

A polarizing plate has been used in a structure in which a protective film is laminated using an adhesive on one or both sides of a polarizer made of a polyvinyl alcohol (hereinafter referred to as PVA)-based resin dyed with a dichroic dye or iodine. Conventionally, a triacetyl cellulose (hereinafter referred to as TAC)-based film has been mainly used as a polarizing plate protective film, but there is a problem in that such a TAC film 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, polyethylene terephthalate), a cycloolefin polymer (hereinafter referred to as COP), an acrylic film, etc. A method of using it alone or in combination has been proposed.

In this case, 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 the protective film, there is a problem in that the use 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 according to the material, when the material of the protective film applied to both sides of the PVA device is different, the problem of curling of the polarizing plate due to the drying process of the water-based adhesive and the initial optics Problems such as deterioration of physical properties occur. Moreover, when using the water-based adhesive, a drying process is absolutely necessary, and there is a problem in that a difference in moisture permeability, thermal expansion, etc. occurs in the drying process, thereby increasing the defect rate. As an alternative to solving the above problems, a method of using a non-aqueous adhesive instead of an aqueous adhesive has been proposed.

Therefore, methods for improving the reliability and yield of a polarizing plate by using a cationically polymerizable UV-curable adhesive instead of a water-based adhesive have been proposed.

When irradiating an energy ray to one surface of the laminate to cure the adhesive, the amount of energy ray reaching the adhesive composition provided on the opposite side of the irradiated direction is reduced because the irradiated energy ray is absorbed by the polarizer. Accordingly, there is a difference in the curing speed of the adhesive layer. This may cause curls in the polarizer.

In order to solve this, by using a photoinitiator with high sensitivity to light in the long wavelength region, the curing speed of the adhesive provided on the side and the opposite side to which the light is irradiated is controlled so that the curing speed is similar to prevent curling in the polarizing plate.

Japanese Patent Application Laid-Open No. 2015-011094 A (published on: January 19, 2015)

The present specification relates to an 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 includes a long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm, and ^{irradiating light with a wavelength of 381 nm to 420 nm and an intensity of 100 W/cm 2} under isothermal conditions of 25° C. and a light differential scanning calorimeter (Photo-DSC) ) when the curing behavior is analyzed using, the curing time (t1) at which the maximum exothermic peak appears is 100 seconds or less to provide an adhesive composition.

In addition, the present specification is a protective film; and a protective film for a polarizing plate provided with an adhesive layer including the adhesive composition described above on one surface of the protective film.

In addition, the present specification is a polarizer; And it provides a polarizing plate comprising the above-described protective film for the polarizing plate 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 above-described polarizing plate is provided on one or both surfaces of the display panel.

The present specification provides an adhesive composition having an improved curing rate.

In addition, the adhesive composition of the present specification has the effect of increasing curing reliability in various environments by similarly controlling the curing rate in a condition in which the wavelength band of light is long and a condition in which the wavelength band of light is short.

In addition, the adhesive composition of the present specification has the effect of increasing curing reliability in various environments by similarly adjusting the curing rate in an environment with a small amount of light and an environment with a large amount of light.

In addition, since the adhesive composition of the present specification has high curing reliability, it has the advantage of minimizing the problem of curling in the polarizing plate during curing.

1 and 2 show an exemplary laminated structure of a polarizing plate according to an exemplary embodiment of the present specification.
3 shows the absorption wavelength of the polymerization initiator.
4 shows the experimental method of Experimental Example 2.

Hereinafter, the present specification will be described in detail.

In the specification, when a part "includes" a certain component, this 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 a case in which a member is in contact with another member but also a case in which another member exists between the two members.

The present specification includes a long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm, and ^{irradiating light with a wavelength of 381 nm to 420 nm and an intensity of 100 W/cm 2} under isothermal conditions of 25° C. and a light differential scanning calorimeter (Photo-DSC) ) when the curing behavior is analyzed using, the curing time (t1) at which the maximum exothermic peak appears is 100 seconds or less to provide an adhesive composition.

In general, the polarizing plate is manufactured by manufacturing a polarizing plate laminate laminated through an adhesive layer formed from an adhesive composition, and then curing the adhesive layer by irradiating ultraviolet rays to the polarizing plate laminate.

However, when the polarizing plate laminate includes a substrate having low transmittance for ultraviolet rays such as a liquid crystal material (for example, a film having a light transmittance of 20% or less for light having a wavelength of 340 nm), ultraviolet rays do not pass through the substrate well. There is a problem in that it does not easily reach the adhesive layer provided on the opposite side. When the adhesive layer provided on the opposite surface is not sufficiently cured, curling may occur in each component of the laminate during the polarizing plate manufacturing process.

In order to solve this, when the amount of ultraviolet light is increased, there is a problem in that the polarization characteristics of the polarizer included in the polarizing plate laminate are impaired.

Conversely, when the wavelength of the light source emitting active energy ray is long, the active energy ray can easily pass through the member provided between the light source and the adhesive layer, and thus there is an advantage in reaching the adhesive layer well. At this time, it is necessary to improve the sensitivity of the active energy ray reaching the adhesive layer and the adhesive layer.

The present invention improves the sensitivity to active energy rays by including a long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm in the adhesive composition. In this case, by improving the curing speed of the adhesive layer not only when the adhesive composition is provided on the light source side, but also when the adhesive composition is provided on the far side from the light source, the above-described curl phenomenon was prevented.

The present specification includes a long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm, and ^{irradiating light with a wavelength of 381 nm to 420 nm and an intensity of 100 W/cm 2} under isothermal conditions of 25° C. and a light differential scanning calorimeter (Photo-DSC) ) when the curing behavior is analyzed using, the curing time (t1) at which the maximum exothermic peak appears is 100 seconds or less to provide an adhesive composition. The maximum exothermic peak at this time is defined as a first maximum exothermic peak.

The absorption wavelength of the long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm can be confirmed from the UV-VIS spectrum measurement results under the condition of 0.001% Acetonitrile. Examples of the long-wavelength polymerization initiator include TPO. Referring to FIG. 3 , since TPO has an absorption wavelength of 340 nm to 400 nm, it can be confirmed that it is advantageous in absorbing light of a longer wavelength compared to other polymerization initiators.

The curing behavior through the optical differential scanning calorimeter is shown by measuring and calculating the change in calorific value during the curing reaction. In this case, as the measuring device, a measuring device generally used in the field to which this technology belongs may be used, for example, TA Instruments DSC Q2000 may be used. For the measurement, after performing zero heart flow at room temperature (25° C.) to set the heat flow to a zero point, light can be irradiated, and omnicure s2000 products can be used as irradiation accessories for irradiating light.

At this time, the light may be exposed at a wavelength of 381 nm to 420 nm and ^{an intensity of 100 W/cm 2} under isothermal conditions of 25° C., and the curing behavior according to time may be observed and recorded.

The wavelength of the light may be selected within the absorption wavelength band range of the long-wavelength polymerization initiator included in the adhesive composition. For example, when the absorption wavelength of the long-wavelength polymerization initiator is 340 nm to 400 nm, the wavelength of the light to be exposed may be 390 nm.

In addition, when the curing behavior was analyzed using a differential scanning calorimeter (Photo-DSC) under the conditions of exposure at a wavelength of 340 nm to 380 nm and ^{an intensity of 100 W/cm 2 at an isothermal condition of 25° C., the maximum exothermic peak appears} The second curing time t2 may be 100 seconds or less. For example, the wavelength may be selected within the absorption wavelength band range of the long-wavelength polymerization initiator included in the adhesive composition. For example, when the absorption wavelength of the long-wavelength polymerization initiator is 340 nm to 400 nm, the wavelength of the light to be exposed may be 365 nm. The maximum exothermic peak at this time is defined as a second maximum exothermic peak.

The first curing time and the second curing time refer to a time point at which curing of the adhesive composition is completed. When the curing time is small, the curing rate is fast, and when the curing time is large, the curing rate is slow. The curing time means the value of the x-axis when the x-axis is time and the Y-axis is the maximum value of the Photo-DSC curve expressed as a graph composed of heat flow (W/g). At this time, the value of the x-axis is defined as "curing time", and the value of the y-axis is defined as the "maximum exothermic peak".

The first curing time and the second curing time may be 100 seconds or less, 70 seconds or less, and most preferably 40 seconds or less, respectively. The small curing time means that the curing rate is fast.

In the curing behavior analysis, the light irradiated to the adhesive composition may be light transmitted through a film having a light transmittance of 20% or less with respect to light having a wavelength of 340 nm. That is, the adhesive composition of the present invention has an advantage of excellent sensitivity to light passing through a film having low transmittance to ultraviolet rays.

The adhesive composition of the present invention may have a value calculated by the following formula of 0.01 or less.

[Equation 1]

In Equation 1 above,

t1 is the maximum when the adhesive composition is irradiated with light at a wavelength of 381 nm to 420 nm and ^{an intensity of 100 W/cm 2} under isothermal conditions of 25° C. and the curing behavior is analyzed using a differential scanning calorimeter (Photo-DSC). is the curing time (t1) at which the exothermic peak appears,

t2 is the maximum when the curing behavior of the adhesive composition is analyzed using a differential scanning calorimeter (Photo-DSC) under the conditions of exposure to ^{a wavelength of 340 nm to 380 nm and an intensity of 100 W/cm 2} at an isothermal condition of 25° C. of the adhesive composition. The second curing time (t2) at which the exothermic peak appears.

When the above range is satisfied, the sensitivity to light having a wavelength of 381 nm to 420 nm is excellent, and sensitivity to a wavelength of 340 nm to 380 nm is all excellent, so that the curing rate is excellent even in a wide wavelength band.

The content of the long-wavelength polymerization initiator may be adjusted to a specific range in order to increase the sensitivity to the long-wavelength. For example, the long-wavelength polymerization initiator may be included in an amount of 1 to 2 parts by weight, 1.2 to 1.9 parts by weight, preferably 1.3 to 1.8 parts by weight, based on 100 parts by weight of the total adhesive composition.

The adhesive composition may include a radically polymerizable compound or a cationically polymerizable compound.

The cationically polymerizable compound may include an epoxy compound or an oxetane compound.

The radically polymerizable compound refers to a compound in which polymerization occurs by a radical initiation reaction. In the present specification, the urethane acrylate oligomer, the polyfunctional (meth)acrylate monomer, and the (meth)acrylate monomer having a hydrophilic functional group are all radically polymerizable compounds.

The adhesive composition of the present invention comprises 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 a silane coupling agent (D).

The adhesive composition contains the polyester-based urethane acrylate oligomer (A), and even when the total glass transition temperature (Tg) of the composition falls, it provides retardation by the polyester group, thereby providing excellent heat resistance and water resistance. has In addition, the adhesive composition has excellent adhesion to the film, and has the advantage of excellent adhesion to the film without a separate treatment such as corona treatment. In particular, the polyester-based urethane acrylate oligomer has an excellent adhesion to the non-pretreated protective film compared to other oligomers such as epoxy-based urethane acrylate oligomer. When the above-described adhesive composition is applied to the protective film, the bonding surface of the protective film with the adhesive is eroded by the ester group having an acid value, so that the adhesive has a physical structure that can easily penetrate the protective film surface. That is, it is possible to increase the adhesion by simultaneously implementing the physical and chemical effects of the ester group.

By adjusting the acid value of the polyester-based urethane acrylate oligomer, the adhesive strength of the adhesive composition to the protective film may be improved. 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 to 170 mgKOH/g. When the above range is satisfied, the adhesive composition effectively etches the protective film, thereby ensuring excellent adhesion to the protective film. In addition, when the range is less than the above range, the degree of etching the protective film is small, so the adhesive strength is lowered, and when it exceeds the 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 to measure the equivalent of KOH required to neutralize the acid component (carboxyl group of the polyhydric acid) of the polyhydric acid or its ester contained in 1 kg of the sample, and the same amount of KOH as the acid content in 1 kg of the sample is measured. It means the amount corresponding to the equivalent weight. The said acid value can be calculated|required by the following method.

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

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

f = 5.611 / A

Take about 1 g of the sample, measure the mass (M) accurately, and then dissolve it 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. At this time, measure the consumed amount (B) in mL, and then calculate the acid value using the following formula.

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

where N: concentration of potassium hydroxide standard solution,

f: Calibration of potassium hydroxide solution

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

M : mass of sample (g)

The method for obtaining the acid value is an example of an acid/base titration method in which a carboxyl group of a polyhydric acid or an ester thereof is titrated with KOH as a base, and known methods for analyzing an unreacted acid component or an ester component thereof may also 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 the sample using gas chromatography analysis, etc., and then calculating the amount of KOH corresponding thereto.

The polyester-based urethane acrylate oligomer forms a cross-linked structure with a photoreactive monomer, a polyfunctional (meth)acrylate-based reactive monomer, to control the physical properties (e.g., hardness, adhesion, flexibility, etc.) of the cured resin, When applied to an adhesive composition, moldability, elasticity and adhesion can be improved.

The urethane acrylate oligomer has a chemical structure having acrylate groups at both ends in the structure of the oligomer. Specifically, the urethane acrylate oligomer is a polyester-based polyol compound; isocyanate-based 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, a polyester-based polyol compound (P) having an ester group (R1) is reacted with a diisocyanate-based compound (I) to first synthesize an isocyanate group at the terminal, and then an acrylate-based compound having a hydroxyl group (A) ) can be reacted with isocyanate to prepare a final polyester-based urethane acrylate oligomer. Alternatively, it may be a polymer (co-polymer) synthesized by the following reaction scheme, but may be in the form of a simple mixed mixture.

Due to the polyester-based polyol compound, the oligomer includes a polyester chemical structure in the main chain, and as a result, when it has the same degree of curing, it has better step absorption compared to an oligomer that does not contain a polyester chemical structure, and the curing reaction It may be advantageous for securing reliability due to high efficiency.

The isocyanate compound is specifically selected from the group consisting of 1,6-hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI) and combinations thereof may contain one. Specifically, the isocyanate compound may include isophorone diisocyanate (IPDI), and in this case, the oligomer contains a chemical structure of a cycloalkylene structure in the main chain, and as a result, does not contain this chemical structure An advantage can be obtained in securing the reliability of high temperature and high humidity compared to the case.

The acrylate-based compound is a compound for providing acrylate groups to both ends of the oligomer, and may include an acrylate compound having a hydroxyl 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. .

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 1000, abrasion resistance, adhesion, and chemical resistance of the cured adhesive layer may be reduced. 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 reduced.

The number of functional groups of the polyester-based urethane acrylate oligomer may be 1 to 10. Considering the photocuring rate and water resistance, the urethane acrylate 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 other urethane acrylate oligomers substantially performing the role of the 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 among the functional groups has substantially no activity, the urethane acrylate oligomer having a 10-functional group may be included in the urethane acrylate oligomer having a 9 functional group. .

The polyester-based urethane acrylate oligomer may have a viscosity at 25° C. of 1,000 cPs or more and 50,000 cPs or less, preferably 2,000 cPs or more and 50,000 cPs or less, and more preferably 2,500 cPs or more and 50,000 cPs or less. In the above-mentioned viscosity and molecular weight range, when the cured product is manufactured, the molding processability is excellent, and the elasticity and adhesiveness are excellent.

The adhesive composition contains 1 to 20 parts by weight of the urethane acrylate oligomer based on 100 parts by weight of the total composition, preferably 1 to 15 parts by weight, and more preferably 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 reduced. When the content of the urethane acrylate oligomer exceeds 20 parts by weight, the cured adhesive layer becomes excessively flexible to reduce pencil hardness and abrasion resistance, as well as increase the viscosity of the adhesive composition, thereby reducing workability.

The adhesive composition further includes a polyfunctional (meth)acrylate monomer (B2) having a glass transition temperature (Tg) of less than 150° C. of the homopolymer.

The adhesive composition may contain two or more polyfunctional (meth)acrylate monomers. When two or more kinds of polyfunctional (meth)acrylate monomers are contained, it is possible to achieve a more appropriate curing density than a radically polymerizable compound containing one kind of polyfunctional (meth)acrylate monomer to provide good adhesion. Therefore, when applied to a polarizer, it is possible to prevent the occurrence of cracks in the polarizer due to thermal shock.

The adhesive composition may include two types of polyfunctional acrylate compounds. For example, a polyfunctional acrylate compound having a glass transition temperature of 100°C or higher and less than 150°C and a polyfunctional acrylate compound having a glass transition temperature of 150°C or higher may be combined, or a polyfunctional acrylate compound having a chain structure and a ring Polyfunctional acrylate compounds of the structure may be combined.

The total content of the polyfunctional (meth) acrylate monomer (when the polyfunctional (meth) acrylate monomer of less than 150 ° C. is further included, the total content of the polyfunctional (meth) acrylate monomer that is less than 150 ° C. The total content) is the adhesive Based on 100 parts by weight of the total composition, it is preferably about 55 parts by weight to 70 parts by weight, or 55 parts by weight to 65 parts by weight. 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.

The adhesive composition may further include a monofunctional acrylate-based compound. The monofunctional acrylate-based compound is preferably in an amount of 0.01 parts by weight to 25 parts by weight, or about 1 part by weight to 25 parts by weight, based on 100 parts by weight of the total amount of the adhesive composition. The monofunctional acrylate-based compound may include, for example, phenoxyethyl acrylate, benzyl acrylate, isobornyl acrylate, tetrahydrofuranyl acrylate, isodecyl acrylate, and lauryl acrylate, but is limited thereto. it's not going to be

The adhesive composition includes a (meth)acrylate monomer (C) having a hydrophilic functional group having at least one hydrophilic functional group in a molecule. The (meth)acrylate monomer (C) having the hydrophilic functional group exhibits an effect of enhancing compatibility between the substrate surface and the adhesive by increasing compatibility with the substrate. In particular, when used for a polarizer, it is possible to provide excellent adhesion of the adhesive between the substrate and the polarizer.

In addition, as the (meth)acrylate monomer (C) having a hydrophilic functional group, as long as radical polymerization is possible due to the presence of an unsaturated double bond between carbons in the molecule, it can be used without any particular limitation. At this time, the hydrophilic functional group is not particularly limited as long as hydrogen bonding is possible, such as a hydroxyl group, a carboxyl group, a urethane group, an amine group, an amide group, etc., but among them, a hydroxyl group is more preferable for the implementation 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 having 1 to 5 carbon atoms, having one or more hydroxyl groups. For example, monofunctional (meth)acrylate having a hydroxyl 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 for

The (meth) acrylate monomer having a hydroxyl group is not limited as long as it is clearly known in the art, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol Hydroxyalkylene (C2-4) glycol (meth)acrylate, such as (meth)acrylate, etc. exist, but is not limited to this. These may be used alone or in combination of two or more.

The (meth)acrylate monomer (C) having a hydrophilic functional group is preferably included in an amount of 10 to 20 parts by weight, or 15 to 20 parts by weight, based on 100 parts by weight of the total adhesive composition.

The adhesive composition may include two or more polyfunctional (meth)acrylate monomers and a (meth)acrylate monomer having one hydrophilic functional group.

In an exemplary embodiment of the specification, the adhesive composition includes a polyfunctional (meth)acrylate monomer (B) having a glass transition temperature (Tg) of 150° C. or higher of a 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 δ (Tan Delta) peak, and a higher storage modulus at high temperature. 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 δ (Tan Delta) refers to the ratio of the storage modulus to the loss modulus. Specifically, the Tan δ (Tan Delta) may be expressed by the following formula.

Tan δ (Tan Delta) = Storage Elasticity / Loss Elasticity

As used herein, the "glass transition temperature" refers to 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 therefore, the polymer has an intrinsic glass transition temperature according to 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, in general, the glass transition temperature is measured by polymerizing a homopolymer of the monomer. However, in the present specification, the glass transition temperature is determined from the value of Tan δ (Tan Delta). The temperature corresponding to Tan δmax having the largest value (peak) in Tan δ (Tan Delta) values according to temperature is the glass transition temperature.

The polyfunctional (meth)acrylate monomer forms a second cross-linked structure through curing by irradiation with radiation and makes the adhesive more hard during curing, which occurs when using a low molecular weight acrylic copolymer. The desired storage modulus (G') can be secured while improving the durability degradation problem. In addition, it is a component to facilitate coating by diluting the adhesive composition to adjust the viscosity. That is, the polyfunctional (meth)acrylate monomer serves to improve the workability of the adhesive composition by controlling the viscosity and maintaining viscoelasticity while imparting durability to the cured adhesive layer.

As the 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 yl]methyl acrylate (Tg: 180°C), 9,9-bis[4-(2-acrylooxyethoxy)phenylfluorene (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 to 40 parts by weight, or 10 parts by weight, based on 100 parts by weight of the total adhesive composition. to 35 parts by weight, or preferably 15 to 30 parts by weight. If the content is less than 5 parts by weight, durability may be reduced or it may be difficult to suppress light leakage under a high temperature or high temperature/humid environment, and even if it is more than 40 parts by weight, durability may be reduced.

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

The peak value of tanδ after curing of the adhesive composition may be 0.2 or more, and the glass transition temperature at the peak value of tanδ may be 90°C or more. If it is less than the above range, the adhesiveness of the cured product of the adhesive composition, heat and moisture resistance and durability may be deteriorated. When the glass transition temperature due to the Tan δ (Tan Delta) peak is within the above range, there is almost no thermal deformation of the adhesive layer in the temperature range for evaluating reliability, so high reliability can be secured.

In order to measure the Tan δ (Tan Delta), an adhesive composition is first coated on a release film and photocured by irradiating an amount of light of ^{1,000mJ/cm 2 at a temperature of 23° C. and a relative humidity of 55% to prepare a cured film.} At this time, the thickness of the cured film is 30㎛ to 50㎛, for example, may be 30㎛. 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). The storage modulus is measured while raising the temperature from 0°C to 150°C at 5°C/min with Track 125%, Frequency 1Hz). Thereafter, the Y-axis on the graph obtained using the analysis tool is set as the numerical change of Tan δ (Tan Delta), and the temperature at Tan δmax having the largest value is defined as the glass transition temperature.

The storage elastic modulus at 80° C. after curing of the 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 a different value. When the storage elastic 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 elastic modulus at 80° C. after curing of the adhesive composition is less than 800 Mpa, it is difficult to suppress the shrinkage and expansion of the polarizer due to temperature in the thermal shock evaluation process, and cracks of the polarizer occur, and the storage elastic modulus at 80° C. exceeds 2,000 Mpa In this case, it may lead to bending of the polarizer depending on the polarizer and the substrate to be laminated.

In the present specification, the crack may refer to a long broken portion of the polarizing plate 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 elastic modulus, an adhesive composition is first coated on a release film and photocured by irradiating an amount of light of ^{1,000mJ/cm 2 at a temperature of 23° C. and a relative humidity of 55% to prepare a cured film.} At this time, 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 DMA Q800 (TA instrument). The storage modulus was measured while raising the temperature from 0°C to 150°C at 5°C/min using Force Track: 125%, Frequency: 1Hz).

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

The adhesive composition does not include an epoxy compound as a polymerizable compound, and may include 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 100 parts by weight of the total amount of the adhesive composition.

Whether the adhesive composition contains an epoxy compound can be confirmed by measuring an IR spectrum. The epoxy-based 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 ring opening of the epoxy ring, whereas the adhesive composition containing the acrylate compound has an ether bond peak do not have In addition, in the ^{vicinity of 1,200cm -1} to 1,000cm ^-1 , the epoxy-based adhesive composition can confirm three peaks, but only one peak is found in the adhesive composition.

The viscosity at 25° C. of the 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 can be improved and bubbles can be prevented from occurring in the adhesive layer formed from the adhesive composition.

The manufacturing method in particular of the said adhesive composition is not restrict|limited, It is possible to obtain by mixing the said component. You may use an organic solvent suitably for viscosity adjustment. There is no particular limitation on the mixing method, and in a room protected from UV light so that curing does not proceed, sufficient stirring and mixing may be performed at room temperature (20° C. or more and 25° C. or less) until the liquid becomes uniform.

The adhesive composition is suitable for a polarizing plate (polarizing film), retardation film, elliptically polarizing film, antireflection film, brightness enhancement film, indium tin oxide sputtering transparent conductive film (ITO film), various electronic related film members or protective films, etc. can be used Especially, it is preferable to use for a polarizing plate (polarizing film).

The present specification is a protective film; and a protective film for a polarizing plate provided with an adhesive layer including the adhesive composition described above on one surface of the protective film.

The thickness of the adhesive layer may be greater than 0 µm and less than or equal to 20 µm, greater than or equal to 0 µm and less than or equal to 10 µm, preferably 0.1 µm to 10 µm or 0.1 µm to 5 µm. This is because, when the thickness of the adhesive layer is too thin, the uniformity and adhesion of the adhesive layer may be reduced, and when the thickness of the adhesive layer is too thick, a problem in which the appearance of the polarizing plate is wrinkled may occur.

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

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 a polyvinyl alcohol-based film with iodine or a dichroic dye, but the manufacturing method thereof is not particularly limited. In the present specification, a polarizer means a state not including a protective layer (or protective film), and a polarizing plate means a state including a polarizer and a protective layer (or protective film).

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

Said uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, and may be performed after dyeing with a dichroic dye. When performing uniaxial stretching after dyeing|staining with a dichroic dye, this uniaxial stretching may be performed before a boric-acid process, and may be performed during a boric-acid process. Moreover, it is also possible to perform uniaxial stretching in these several steps. In order to perform uniaxial stretching, uniaxial stretching may be performed between rolls having different peripheral speeds, or uniaxial stretching may be performed using a hot roll. Moreover, the dry-type extending|stretching which extends|stretches in air|atmosphere may be sufficient, and wet extending|stretching which extends|stretches in the state swollen with the solvent may be sufficient. 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, more preferably 5 μm to 25 μm. If the thickness of the polarizer is thinner than the numerical range, optical properties may be deteriorated, and if it is thicker than the numerical range, the shrinkage of the polarizer at low temperature (for example, -30°C) may increase, thereby weakening the heat-related durability of the overall polarizing plate. .

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 contains a polyvinyl alcohol resin or a derivative thereof. In this case, the derivative of the polyvinyl alcohol resin includes, but is not limited to, a polyvinyl formal resin, a polyvinyl acetal resin, and the like. In addition, commercially available polyvinyl alcohol-based films such as P30, PE30, PE60 manufactured by Kuraray, M2000, M3000, M6000, and the like manufactured by Nippon Synthetic Company may be used, but the present invention is not limited thereto.

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

The material for the protective film is preferably a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. 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 and acrylonitrile styrene Polystyrene resins such as renal copolymers (AS resins), polycarbonate resins, polyethylene, polypropylene, ethylene/propylene copolymers, polyolefin resins such as cycloolefin polymers, polyvinyl chloride resins, polyamide resins such as nylon and aromatic polyamides , polyimide resin, polysulfone resin, polyether sulfone resin, polyether ether ketone 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.

Specifically, a cellulose resin, a cycloolefin polymer (COP), a polyethylene terephthalate (PET) or an acrylic resin which is an ester of cellulose and a fatty acid is preferable. Examples of the cellulose resin include cellulose triacetate (TAC), cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate, a cycloolefin polymer, a polyethylene terephthalate, or an acrylic resin is preferable from a viewpoint of availability and cost, and a cycloolefin polymer, a polyethylene terephthalate, or an acrylic resin when the viewpoint of availability and water permeability are taken into consideration. is more preferable. If the moisture permeability of the protective film is high, moisture may penetrate the protective film and easily enter the polarizer side, and there is a risk that the quality of the polarizer may deteriorate. However, if cycloolefin polymer, polyethylene terephthalate, or acrylic resin is used, this should be taken into account. can be suppressed

Moreover, although a saponified thing can be used for cellulose triacetate, an unsaponified thing is more preferable.

The surface of the protective film 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 in the protective film surface, for example, and it is thought that this contributes to the improvement of adhesiveness more. When using saponified cellulose triacetate as a protective film, since the effect of adhesive improvement like corona discharge treatment can be anticipated, corona discharge treatment is not necessarily required. However, since the process of saponification treatment is complicated and it becomes high cost, it is more preferable from the viewpoint of a manufacturing process that unsaponified cellulose triacetate is corona-discharge-treated and used.

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 preferably. If it is such a range, the adhesiveness of a protective film and an adhesive agent can be improved without deteriorating protective film itself, and it is preferable. Here, the discharge amount is the amount of work to the target object by the corona discharge calculated by the following formula, and the corona discharge power is determined based on this.

There is no restriction|limiting in particular in the manufacturing method of the said polarizing plate, It can manufacture by bonding a polarizer and a protective film using the adhesive composition mentioned above by a conventionally well-known method.

When apply|coating the said adhesive composition, you may apply|coat to any one of a protective film and a polarizer, and you may apply|coat to both. It is preferable to apply an adhesive agent so that the thickness of the adhesive bond layer after drying may become more than 0 and 20 micrometers or less. The thickness of the adhesive layer is more preferably 500 nm or more and 3 µm or less in order to obtain a uniform in-plane thickness and to obtain sufficient adhesive strength. The thickness of the adhesive layer can be adjusted by the concentration of the solid content in the solution of the adhesive or the application device of the adhesive. In addition, the thickness of an adhesive bond layer can be confirmed by observing a cross section with a scanning electron microscope (SEM). There is no restriction|limiting in particular also in the method of apply|coating an adhesive agent, Various means, such as the method of dripping the adhesive agent directly, the roll coating method, the spraying method, the immersion method, are employable.

After the adhesive is applied, the polarizer and the protective film are bonded using a roll laminator or the like.

After the bonding, light is irradiated to the polarizing plate for curing the adhesive. The light source is not particularly limited, but a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, etc. can be used. Although the amount of accumulated light is not specifically limited, It is preferable that the irradiation amount of the wavelength range effective for activation of a polymerization initiator is 100 mJ/cm ² or more and 2,000 mJ/cm ^{2 or less.} If it is this range, reaction time is suitable, and it can prevent that deterioration of adhesive agent itself or a polarizer arises by the heat radiating from a lamp|ramp and heat_generation|fever at the time of 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 light irradiation. A polarizing plate is completed by completion of hardening.

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

The present specification includes a display panel; and an image display device in which the above-described polarizing plate is provided on the 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 provided on both surfaces of the liquid crystal panel, and in this case, at least one of the polarizing plates may be the aforementioned polarizing plate.

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

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

<Preparation of adhesive composition>

An adhesive composition having a composition according to Table 1 was prepared.

<Experimental Example 1: Measurement of curing time>

The curing behavior of the prepared adhesive composition was analyzed using a differential scanning calorimeter (Photo-DSC). Specifically, the prepared adhesive composition sample was put into an optical differential scanning calorimeter, and the calorific value over time was measured and recorded.

^{At this time, when DSC analysis was performed under the first condition of exposure to a wavelength of 390 nm and an intensity of 100 W/cm 2} at an isothermal condition of 25° C., the time at which the first maximum exothermic peak (P1) appeared was the first curing time (t1) , and the peak area (Q1) at this time was calculated, and when DSC analysis was performed under the second condition of exposure to a ^{wavelength of 365 nm and an intensity of 100 W/cm 2 at an isothermal condition of 25° C., the second maximum exothermic peak (P1)} ) was referred to as the second curing time (t2), and the peak area (Q2) at this time was calculated.

<Experimental Example 2: Measurement of Peel Force>

A polarizing plate laminate was prepared by coating the prepared adhesive composition on both sides of a previously prepared polarizer (manufactured by LG CHEM), and laminating a peeling protective film (PET film). Then, after placing a light source on the side of any one of the protective films, the adhesive composition is cured by irradiating light with a wavelength of 365 nm so that ^{the irradiation amount (accumulated light amount) of the light source is 2,000 mJ/cm 2 ,} The polarizer and the protective film for peeling were adhered to each other, and cut to a size of 2 cm wide * 15 cm long to prepare a polarizer sample. Thereafter, the polarizing plate was prepared by stabilizing by standing for 24 hours.

At this time, as shown in FIG. 4 , any one of the protective films for peeling was peeled off at a peeling rate of 0.5 cm/sec or more by 3 cm, and the peel force at this time was measured three times to calculate an average value. When measuring the peel force, XT Plus Texture Analyzer (manufactured by TA) was used.

T/T means peeling between the analyzer and the protective film for peeling, T/A means peeling between the adhesive layer and the protective film for peeling, and P/A means peeling between the polarizer and the adhesive layer it means. The adhesive can be classified as having excellent performance when there is a separation between the analyzer and the peeling protective film (T/T).

<Experimental Example 3: Existence of appearance curls>

The appearance of the polarizing plate laminate prepared in Experimental Example 2 before and after lamination was visually observed. A case in which a large number of appearance curls occurred was classified as C, a case in which some appearance curled was classified as B, and a case in which external curl did not occur was classified as A.

type or unit Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 composition A (a) 5 5 7 5 5 5 B1 M370 21 21 27 21 21 21 B2 DPGDA 34 34 44 34 34 34 C 4-HBA 15 15 21 15 15 15 D KBM 403 25 25 0 25 25 25 E I250 1.5 1.5 0 1.5 0 1.5 TPO 1.7 1.7 1.7 1.7 1.7 0 F DETX 1.2 0 1.2 0 1.2 1.2 ITX 0 1.2 0 0 0 0 evaluation Experimental Example 1 t1(sec) 33.6 43.8 44.4 46.2 49.8 uncured t2(sec) 33 40.8 39.6 41.4 41.4 uncured Q1 (J/g) 266.6 254.9 277 260.8 349.1 uncured Q2 (J/g) 379.4 297.7 280.1 250.5 300.8 uncured Experimental Example 2 Illuminated surface (gf/20mm) 370 (T/T) 260 (T/T) 40 (P/A) 210 (P/A) 230 (T/A) uncured Non-irradiated surface (gf/20mm) 420 (T/T) 340 (T/T) 80 (T/A) 270 (T/A) 290 (T/A) uncured Experimental Example 3 Exterior curls A B C C C uncured A: Urethane acrylate oligomer
(a): Polyester-based urethane acrylate oligomer (viscosity: 24000cps)
B1: A polyfunctional (meth)acrylate monomer having a glass transition temperature (Tg) of 150° C. or higher of the homopolymer
B2: a 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: photoinitiator; and
F: photosensitizer
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 hexafluorophosphate
TPO: 2,4-diethylthioxanthone, diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide
DETX: 2,4-diethylthioxanthone

The parts by weight of A, B (B1, B2), C and D mean parts by weight of each material based on the total weight of 100 including all of A to D.
The parts by weight of E and F refer to parts by weight of each material based on the total weight of 100 including all of A to D.

From the above results, it was confirmed that Comparative Example 1 not containing TPO as a long-wavelength photoinitiator was not cured.

On the other hand, in the case of Examples 1 to 5 containing TPO, it was confirmed that the curing speed was as short as 100 seconds or less.

101, 105: protective film
102, 104: adhesive layer
103: polarizer

Claims (17)

It contains a long-wavelength polymerization initiator having an absorption wavelength of 340 nm to 400 nm,
When the curing behavior was analyzed using a differential scanning calorimeter (Photo-DSC) after irradiating light with a wavelength of 381 nm to 420 nm and ^{an intensity of 100 W/cm 2 under an isothermal condition of 25° C.,}
The adhesive composition that the curing time (t1) at which the maximum exothermic peak appears is 100 seconds or less. The method according to claim 1,
When the curing behavior was analyzed using a differential scanning calorimeter (Photo-DSC) under the conditions of exposure at a wavelength of 340 nm to 380 nm and ^{an intensity of 100 W/cm 2 at an isothermal condition of 25° C.,}
The second curing time (t2) at which the maximum exothermic peak appears is 100 seconds or less. The method according to claim 1,
An adhesive composition having a value calculated by the following formula of 0.01 or less.
[Equation 1]

In Equation 1 above,
t1 is the maximum when the adhesive composition is irradiated with light at a wavelength of 381 nm to 420 nm and ^{an intensity of 100 W/cm 2} under isothermal conditions of 25° C. and the curing behavior is analyzed using a differential scanning calorimeter (Photo-DSC). is the curing time (t1) at which the exothermic peak appears,
t2 is the maximum when the curing behavior of the adhesive composition is analyzed using a differential scanning calorimeter (Photo-DSC) under the conditions of exposure to ^{a wavelength of 340 nm to 380 nm and an intensity of 100 W/cm 2} at an isothermal condition of 25° C. of the adhesive composition. The second curing time (t2) at which the exothermic peak appears. The method according to claim 1,
An adhesive composition comprising 1 to 2 parts by weight of the long-wavelength polymerization initiator based on 100 parts by weight of the total adhesive composition. The method according to claim 1,
An adhesive composition comprising a radically polymerizable compound or a cationically polymerizable compound. The method according to claim 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
An adhesive composition comprising a silane coupling agent (D). 7. The method of claim 6,
The polyester-based urethane acrylate oligomer (A) is a polyester-based polyol compound; isocyanate-based compounds; And an adhesive composition formed from a composition comprising an acrylate-based compound. 7. The method of claim 6,
The polyester-based urethane acrylate oligomer (A) has a viscosity at 25° C. of 1,000 cPs or more and 50,000 cPs or less. 7. The method of claim 6,
An adhesive composition comprising 1 to 20 parts by weight of the polyester-based urethane acrylate oligomer (A) based on 100 parts by weight of the total adhesive composition. The method according to claim 1,
An adhesive composition further comprising a polyfunctional (meth)acrylate monomer (B2) having a glass transition temperature (Tg) of less than 150° C. of the homopolymer. The method according to claim 1,
An adhesive composition having a glass transition temperature of 80° C. or more and 150° C. or less after curing. The adhesive composition of claim 1, wherein the viscosity at 25°C is 10 cPs or more and 100 cPs or less. protective film; and
A protective film for a polarizing plate provided with an adhesive layer comprising a cured product of the adhesive composition according to any one of claims 1 to 12 on one surface of the protective film. The protective film for a polarizing plate according to claim 13, wherein the thickness of the adhesive layer is greater than 0 µm and less than or equal to 20 µm. The protective film for a polarizing plate according to claim 13, wherein the protective film is a cellulose-based film. polarizer; and
A polarizing plate comprising a protective film for the polarizing plate according to claim 13 provided on one or both sides of the polarizer. display panel; and
An image display device comprising the polarizing plate according to claim 16 provided on one or both surfaces of the display panel.

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