CN113906114A

CN113906114A - Radical adhesive composition, protective film for polarizing plate comprising the radical adhesive composition, polarizing plate comprising the same, and image display device comprising the polarizing plate

Info

Publication number: CN113906114A
Application number: CN202080038287.0A
Authority: CN
Inventors: 金东旭; 金熹正; 权润京
Original assignee: Shanjin Optoelectronics Suzhou Co Ltd
Current assignee: Shanjin Photoelectric Guangzhou Co ltd
Priority date: 2019-06-20
Filing date: 2020-06-19
Publication date: 2022-01-07
Anticipated expiration: 2040-06-19
Also published as: WO2020256476A1; JP2022536080A; KR20200145760A; TWI788677B; TW202106827A; CN113906114B; KR102294150B1; JP7395096B2

Abstract

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

Description

Radical adhesive composition, protective film for polarizing plate comprising the radical adhesive composition, polarizing plate comprising the same, and image display device comprising the polarizing plate

Technical Field

The present application claims the benefit of the application date of korean patent application No. 10-2019-0073558, which was filed in korean patent office at 20.6.2019, the entire contents of which are incorporated herein by reference.

Background

The polarizing plate generally has the following structure: a protective film is laminated on one surface or both surfaces of a polarizing plate including a polyvinyl alcohol (hereinafter referred to as PVA) resin dyed with a dichroic dye or iodine by an adhesive. Conventionally, triacetyl cellulose (hereinafter, referred to as TAC) based films have been mainly used as polarizing plate protective films, but such TAC films have a problem of being easily deformed in a high-temperature and high-humidity environment. Therefore, protective films of various materials have been developed recently as alternatives to TAC films, and for example, methods of using polyethylene terephthalate (PET), cycloolefin polymer (hereinafter, referred to as COP), acrylic films, and the like alone or in combination thereof have been proposed.

In this case, as an adhesive for attaching the polarizer and the protective film, an aqueous adhesive mainly containing an aqueous solution of a polyvinyl alcohol resin is used. However, when an acrylic film or COP film other than TAC is used as the protective film, the aqueous adhesive has a weak adhesion force, and thus the use of the aqueous adhesive is limited by the material of the film. In addition, the aqueous adhesive has problems such as poor adhesion due to the raw material, curling (curl) of the polarizing plate due to the drying process of the aqueous adhesive, and deterioration of initial optical properties when the raw materials of the protective films applied to both surfaces of the PVA element are different from each other. In addition, when the aqueous adhesive is used, there are problems as follows: a drying step is required, and in such a drying step, differences in moisture permeability, thermal expansion, and the like occur, and the defect rate increases. As a countermeasure for solving the above-described problems, a nonaqueous adhesive is proposed to be used instead of the aqueous adhesive.

Therefore, it has been proposed to improve the reliability and yield of a polarizing plate by using a cationically polymerizable ultraviolet curable adhesive instead of an aqueous adhesive.

The cationically polymerizable ultraviolet-curable adhesive contains an epoxy resin as a main component, and has the advantages of high curing density and high reliability. However, this cationic polymerization is a ring-opening reaction of epoxy rings by a dark reaction (post-polymerization) after irradiation with ultraviolet rays, and in this case, there is a problem that the cationic polymerization is easily affected by humidity during curing and variation in the cured state is easily caused. Therefore, in order to obtain a uniform cured state, it is necessary to strictly control not only the environmental humidity but also the water content of the PVA-based polarizing material.

The radical polymerizable ultraviolet curable adhesive is excellent because the problem of uneven adhesion force due to moisture as described above is small. Since there is no inhibition of the curing reaction by moisture, the reaction can be stably performed by the light energy in the polarizer without being inhibited by the reaction by moisture.

In addition, in view of the thinning and durability of the polarizing plate, the thinner the adhesive layer is, the more advantageous the thinner the adhesive layer is, and therefore, in order to satisfy such a requirement, the lower the viscosity of the adhesive is, the more advantageous the adhesive layer is.

However, since the radical compound mainly uses a monofunctional group in order to maintain a low viscosity, the curing density and adhesion are low, and it is difficult to have a good margin in terms of subsequent processes and reliability.

In consideration of the reliability of the polarizing plate under high temperature and high humidity, the higher the rigidity of the adhesive layer after curing, the lower the degree of dimensional change under high temperature and high humidity, and therefore, it is advantageous to reduce the fraction defective of the polarizing plate.

In order to satisfy the characteristics of such an adhesive, a monomer having a high glass transition temperature, which is a polyfunctional monomer or a homopolymer, may be used, but in this case, there is also a problem that the curing density is low and the adhesive strength is reduced.

Therefore, a series of experiments for achieving low viscosity characteristics of the adhesive and high rigidity after curing have been conducted, and as a result, it is possible to realize an adhesive with high reliability by appropriately adjusting the curing density of the radical compound.

[ Prior art documents ]

[ patent document ]

(patent document 1) Japanese laid-open patent 2015-011094A (published: 2015.01.19)

Disclosure of Invention

[ problems to be solved by the invention ]

[ means for solving problems ]

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

Further, the present specification provides a protective film for a polarizing plate, comprising: a protective film; and an adhesive layer comprising the radical adhesive composition as described above on one or both sides of the protective film.

In addition, the present specification provides a polarizing plate comprising: a polarizing member; and a protective film for a polarizing plate as described above, which is provided on one or both surfaces of the polarizing element.

In addition, the present specification provides an image display device including: a display panel; and a polarizing plate as described above, provided on one or both surfaces of the display panel.

[ Effect of the invention ]

The present specification provides a radical adhesive composition having an advantage of excellent adhesion to a substrate without additionally performing a treatment such as corona treatment. In addition, the radical adhesive composition according to one embodiment of the present specification has a high glass transition temperature after curing and a high storage modulus amount at a high temperature, and thus can realize excellent heat resistance.

Drawings

Fig. 1 and 2 are diagrams showing an exemplary lamination structure of a polarizing plate according to an embodiment of the present disclosure.

FIG. 3 is a diagram showing the experimental method of Experimental example 1.

FIG. 4 is a diagram showing the experimental method of Experimental example 5.

Detailed Description

The present specification will be described in detail below.

In the present specification, when a certain component is described as being "included" in a certain part, unless otherwise specified, it means that other components may be included without excluding other components.

In the present specification, when a component is referred to as being "on" another component, the component includes not only a case where the component is adjacent to the other component but also a case where another component is present between the two components.

In the present specification, the term "radical adhesive composition" refers to an adhesive composition that does not include other polymerizable compounds than radical polymerizable compounds, or includes a small amount (for example, less than 10 parts by weight or less than 1 part by weight based on 100 parts by weight of the entire composition) of other polymerizable compounds. 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 radical polymerizable compounds.

One embodiment of the present description provides a free radical adhesive composition comprising: a polyester-based urethane acrylate oligomer (A) having an acid value of 90mgKOH/g to 180 mgKOH/g; a polyfunctional (meth) acrylate monomer (B) having a homopolymer glass transition temperature (Tg) of 150 ℃ or higher; a (meth) acrylate monomer (C) having a hydrophilic functional group; and a silane coupling agent (D).

The radical adhesive composition includes the polyester-based urethane acrylate oligomer (a), and thus, when the glass transition temperature (Tg) of the entire composition is decreased, Relaxation (Relaxation) due to the polyester group is also imparted, and thus, the radical adhesive composition has an advantage of being excellent in heat resistance and water resistance. In addition, the radical adhesive composition has the following advantages: the protective film has excellent adhesion to the protective film without additional treatment such as corona treatment. In particular, the polyester-based urethane acrylate oligomer (a) has the following effects: the adhesion to the non-pretreated protective film is superior to other oligomers such as epoxy urethane acrylate oligomers. When the radical adhesive composition is coated on a protective film, the composition has the following physical structure: the bonding surface between the protective film and the adhesive is corroded by the ester group having an acid value, so that the adhesive composition easily penetrates the surface of the protective film. That is, the physical effect and the chemical effect by the ester group can be simultaneously achieved to increase the adhesion force to the protective film.

The acid value of the polyester urethane acrylate oligomer can be adjusted to improve the adhesion of the adhesive composition to the protective film. Specifically, the acid value of the polyester urethane acrylate oligomer may be 90mgKOH/g to 180mgKOH/g, preferably 95mgKOH/g to 175mgKOH/g, and more preferably 100mgKOH/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. If the acid value is less than the above range, the adhesion is decreased because the protective film is etched to a small extent, and if the acid value exceeds the above range, the protective film is excessively etched, so that the acid value is adjusted to the above range.

The acid value is an equivalent of KOH to be measured for neutralizing the acid component (carboxyl group of the polybasic acid) of the polybasic acid or the ester thereof included in the sample, and means an amount corresponding to the same amount of KOH milliequivalents as the acid component in the sample. The acid value can be determined by the following method.

First, in order to measure the acid value of the synthesized acrylate oligomer, a 0.1N potassium hydroxide solution for titration was prepared. After 5.9g of 95 wt% reagent grade potassium hydroxide was placed in a 1L volume flask, a small amount of water was added to complete dissolution. Methanol was added thereto and mixed to make the total volume to 1L to prepare a titration solution.

To determine the calibration factor (factor) of the prepared titration solution, 10mL of 35 wt% HCl solution was placed in a beaker and 2-3 drops of phenolphthalein indicator were added. Here, the 0.1N potassium hydroxide titration solution prepared above was added until it became light red, and the amount used was calculated. Of the values obtained by repeating the above-described experiment 3 times, the remaining 3 values excluding the maximum value and the minimum value were averaged to obtain an average value a (ml), and then the correction factor f was calculated using the following formula.

f＝5.611/A

About 1g of a sample was sampled and the mass (M) was accurately measured, and then the sample was dissolved in 42.8g (50mL) of toluene. After 2 to 3 drops of 1 wt% phenolphthalein indicator were added, the amount (B) consumed was measured in mL by titration with 0.1N potassium hydroxide solution under stirring, and the acid value was calculated by the following formula.

Acid Value (Acid Value) 5.611 XNXfB/M

Wherein, N: concentration of potassium hydroxide standard solution

f: correction factor for potassium hydroxide solution

B: consumption of Potassium hydroxide solution (mL)

M: quality (g) of sample

The method of determining the acid value is an example of an acid group/base titration method in which a carboxyl group of a polybasic acid or an ester thereof is titrated with KOH as a base, and a known method of analyzing an unreacted acid component or an ester component thereof may be used. For example, the acid value may be determined by analyzing the unreacted ester component in a 1kg sample by gas chromatography or the like and then calculating the amount of KOH corresponding to the analyzed unreacted ester component.

The polyester urethane acrylate oligomer is a component that forms a cross-linked structure with a polyfunctional (meth) acrylate reactive monomer as a photoreactive monomer to control physical properties (e.g., hardness, adhesive force, flexibility, etc.) of a cured resin, and can further improve molding processability, elasticity, and adhesion when applied to a radical adhesive composition.

The urethane acrylate oligomer has a chemical structure having acrylate groups at both ends of the oligomer structure. Specifically, the urethane acrylate oligomer may be formed of a composition including a polyester polyol compound, an isocyanate compound, and an acrylate compound.

The polyester urethane acrylate oligomer can be synthesized by the following synthesis method. That is, the polyester-based urethane acrylate oligomer can be finally prepared by the following method: so as to have an ester group (R)₁) The polyester-based polyol compound (P) of (2) is reacted with the diisocyanate-based compound (I) to have an isocyanate group at the end, and then the acrylate-based compound (A) having a hydroxyl group is reacted with the isocyanate group. The polymer (co-polymer) may be synthesized by the following reaction formula, or may be in the form of a mixture (mixture) obtained by simply mixing the raw materials.

According to the polyester-based polyol compound, the oligomer includes a polyester chemical structure in the main chain, and as a result, when having the same degree of curing, the level difference water absorption and the curing reaction efficiency are superior to those of the oligomer not including a polyester chemical structure, and thus it is advantageous for securing reliability.

Specifically, the diisocyanate-based compound may include one selected from the group consisting of 1, 6-Hexamethylene Diisocyanate (HDI), Toluene Diisocyanate (TDI), isophorone diisocyanate (IPDI), Xylene Diisocyanate (XDI), and a combination thereof. Specifically, the diisocyanate-based compound may include isophorone diisocyanate (IPDI), in which case the oligomer includes a chemical structure of a cycloalkylene structure in a main chain, and as a result, may be advantageous in ensuring reliability under high temperature and high humidity, as compared to a case where such a chemical structure is not included.

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

In one embodiment of the present specification, the number average molecular weight of the polyester urethane acrylate oligomer may be 1,000 to 50,000, preferably 1,000 to 35,000, and more preferably 1,000 to 20,000. In the case where the number average molecular weight of the urethane acrylate oligomer is less than 1,000, the abrasion resistance, adhesion, and chemical resistance of the cured adhesive layer may be reduced. In addition, in the case where the number average molecular weight of the urethane acrylate oligomer exceeds 50,000, the pencil hardness, abrasion resistance, adhesion, and chemical resistance of the cured adhesive layer may be reduced.

In one embodiment of the present specification, the number of functional groups of the polyester urethane acrylate oligomer may be 1 to 10. The polyester-based urethane acrylate oligomer may have 1 to 8 functional groups, preferably 2 to 6 functional groups, in consideration of photocuring speed, water resistance, and the like. At this time, the urethane acrylate oligomer having the specific number of functional groups may be substantially a concept including other urethane acrylate oligomers performing the function of the urethane acrylate oligomer having the specific number of functional groups. For example, in the case where one of the functional groups of the urethane acrylate oligomer having 10 functional groups is substantially inactive, such a urethane acrylate oligomer having 10 functional groups may be included in the urethane acrylate oligomer having 9 functional groups.

In one embodiment of the present specification, the polyester urethane acrylate oligomer may have a viscosity of 1,000cPs or more and 50,000cPs or less, preferably 2,000cPs or more and 50,000cPs or less, and more preferably 2,500cPs or more and 50,000cPs or less at 25 ℃. When a cured product is prepared within the viscosity and molecular weight ranges as described above, excellent moldability is exhibited, and excellent elasticity and adhesiveness are exhibited.

In one embodiment of the present specification, the polyester-based urethane acrylate oligomer in the radical adhesive composition is 1 to 20 parts by weight, preferably 1 to 15 parts by weight, and more preferably 1 to 10 parts by weight, based on 100 parts by weight of the total composition. In the case where the content of the urethane acrylate oligomer is less than 1 part by weight, the adhesion and durability of the cured adhesive layer may be reduced. In the case where the content of the urethane acrylate oligomer exceeds 20 parts by weight, the cured adhesive layer becomes too soft, so that not only pencil hardness and abrasion resistance are reduced, but also viscosity of the radical adhesive composition is increased, thereby reducing workability.

In one embodiment of the present description, the free radical adhesive composition further includes a multifunctional (meth) acrylate monomer (B2) having a homopolymer glass transition temperature (Tg) of less than 150 ℃.

In one embodiment of the present specification, the radical adhesive composition may contain two or more kinds of polyfunctional (meth) acrylate monomers. When two or more kinds of polyfunctional (meth) acrylate monomers are contained, a more suitable curing density can be obtained than in the case of a radical polymerizable compound containing one kind of polyfunctional (meth) acrylate monomer, and a good adhesive force can be imparted. Therefore, in the case where the adhesive composition is applied to a polarizing plate, the polarizing plate can be prevented from being cracked due to thermal shock.

In one embodiment of the present description, the free radical adhesive composition may include two multifunctional acrylate compounds. For example, a multifunctional acrylate compound having a glass transition temperature of 100 ℃ or more and less than 150 ℃ may be combined with a multifunctional acrylate compound having a glass transition temperature of 150 ℃ or more, or a multifunctional acrylate compound having a chain structure may be combined with a multifunctional acrylate compound having a ring-containing structure.

In one embodiment of the present specification, the total content of the polyfunctional (meth) acrylate monomers (in the case where the polyfunctional (meth) acrylate monomers having a temperature of less than 150 ℃ are included, the total content of the polyfunctional (meth) acrylate monomers having a temperature of less than 150 ℃ is preferably about 55 to 70 parts by weight or about 55 to 65 parts by weight based on 100 parts by weight of the radical adhesive composition as a whole. In the case where the entire content of the multifunctional acrylate compound satisfies the above range, good adhesion can be maintained and a high storage modulus can be secured after curing.

In one embodiment of the present description, the radical adhesive composition may further include a monofunctional acrylate compound. The monofunctional acrylate compound is preferably present in an amount of about 0.01 to 25 parts by weight, or about 1 to 25 parts by weight, based on 100 parts by weight of the entire radical adhesive composition. Examples of the monofunctional acrylate compound include, but are not limited to, phenoxyethyl acrylate, benzyl acrylate, isobornyl acrylate, tetrahydropyranyl acrylate, isodecyl acrylate, and lauryl acrylate.

In one embodiment of the present description, the radical adhesive composition includes a (meth) acrylate monomer (C) having a hydrophilic functional group. The (meth) acrylate monomer (C) may have at least one hydrophilic functional group in the molecule. The (meth) acrylate monomer (C) having a hydrophilic functional group exhibits an effect of improving compatibility with a substrate to improve compatibility between the surface of the substrate and an adhesive. In particular, when used in a polarizer, the adhesive composition can provide excellent adhesion between a substrate and the polarizer.

Further, the (meth) acrylate monomer (C) having a hydrophilic functional group is not particularly limited as long as it has an unsaturated double bond between carbons in the molecule and can be used if it can be subjected to radical polymerization. In this case, the hydrophilic functional group is not particularly limited if it is a group capable of hydrogen bonding such as a hydroxyl group, a carboxyl group, a carbamate group, an amine group, and an amide group, and among them, a hydroxyl group is more preferable in order to achieve excellent adhesion. For example, the (meth) acrylate monomer having a hydrophilic functional group may be a (meth) acrylate having one or more hydroxyl groups and having an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. For example, the monofunctional (meth) acrylate having a hydroxyl group may be one or more of 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-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.

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

In one embodiment of the present disclosure, the radical adhesive composition may include two or more kinds of polyfunctional (meth) acrylate monomers and one kind of (meth) acrylate monomer having a hydrophilic functional group.

In one embodiment of the specification, the radical adhesive composition includes a polyfunctional (meth) acrylate monomer (B) having a homopolymer glass transition temperature (Tg) of 150 ℃ or higher. Preferably, when the multifunctional (meth) acrylate monomer having a glass transition temperature of 180 ℃ or higher is included, the glass transition temperature is higher 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 ℃ or lower or 300 ℃ or lower.

In the present specification, Tan δ (Tan Delta) refers to the ratio of storage modulus to loss modulus. Specifically, Tan δ (Tan Delta) can be expressed by the following formula.

Tan Delta (Tan Delta) ═ storage modulus/loss modulus

In the present specification, the "glass transition temperature" refers to a temperature at which a high molecular substance is transformed from a solid state as hard as glass to a rubber state having elasticity. Since the glass transition temperature is determined by the structural properties of the monomer, the polymer has a glass transition temperature specific to the kind of monomer to be polymerized. The lower the glass transition temperature, the more flexible the material, and the higher the glass transition temperature, the stronger the material. The glass transition temperature cannot be measured by the monomer itself, and therefore, is generally measured by polymerizing a homopolymer of the monomer. However, in the present specification, the glass transition temperature is determined in accordance with the Tan δ (Tan Delta) value. The temperature corresponding to Tan δ max having the largest value (peak) among Tan δ (Tan Delta) values corresponding to temperatures may be defined as the glass transition temperature.

The polyfunctional (meth) acrylate monomer forms a second crosslinked structure by curing upon irradiation with radiation, and the adhesive is made harder (hard) during curing, thereby making it possible to ensure a desired storage modulus (G') while improving the problem of reduced durability that occurs when using a low-molecular-weight acrylic copolymer. The polyfunctional (meth) acrylate monomer is a component that can be easily applied by adjusting the viscosity by diluting the adhesive composition. That is, the polyfunctional (meth) acrylate monomer functions as follows: the cured adhesive layer is provided with durability while maintaining viscoelasticity, and the workability of the adhesive composition is improved by adjusting the viscosity.

Examples of the polyfunctional (meth) acrylate monomer (B) having a glass transition temperature (Tg) of 150 ℃ or higher in the homopolymer include, but are not limited to, dimethylol tricyclodecane diacrylate (Tg: 214 ℃), (triethoxyethyl isocyanurate) triacrylate (Tg: 225 ℃), [2- [1, 1-dimethyl-2 [ (1-oxoallyl) oxy ] ethyl ] -5-ethyl-1, 3-dioxan-5-yl ] methacrylate (Tg: 180 ℃), 9-bis [4- (2-acryloyloxyethoxy) phenylfluorene (Tg: 179 ℃) and (triethoxyethyl isocyanurate) triacrylate (Tg: 275 ℃).

The content of the polyfunctional (meth) acrylate monomer (B) having a glass transition temperature (Tg) of the homopolymer of 150 ℃ or higher is preferably about 5 to 40 parts by weight, 10 to 35 parts by weight, or 15 to 30 parts by weight with respect to 100 parts by weight of the entire radical adhesive composition. When the content is less than 5 parts by weight, the durability under high temperature or high temperature and high humidity environment is reduced or the light leakage is difficult to be suppressed, and when it exceeds 40 parts by weight, the durability is also reduced.

The glass transition temperature of the radical adhesive composition after curing can be 80 ℃ to 150 ℃. If the glass transition temperature is not reached, the moist heat resistance and durability of the cured product of the radical adhesive composition are deteriorated.

The peak value of Tan δ after curing of the radical adhesive composition may be 0.2 or more, and the glass transition temperature at the peak value of Tan δ may be 90 ℃ or more. If the content is less than the above range, the cured product of the radical adhesive composition may have poor adhesion, moist heat resistance and durability. When the glass transition temperature corresponding to the Tan δ (Tan Delta) peak is in the above range, there is almost no thermal deformation of the adhesive layer in the temperature range in which reliability is evaluated, so that high reliability can be ensured.

To determine the Tan Delta (Tan Delta), a free radical adhesive composition was first applied to a release film and irradiated at a temperature of 23 ℃ and a relative humidity of 55% at 1,000mJ/cm²To make it photo-cured, thereby preparing a cured film.At this time, the thickness of the cured film is 30 μm to 50 μm, and may be 30 μm, for example. After removing the release film, the storage modulus was measured by a Temperature sweep test (Temperature sweep test) (tension (Strain) 0.04%, pre-load Force (Preload) 0.05N, Force Track (Force Track) 125%, Frequency (Frequency)1Hz) using a Dynamic thermo-mechanical analyzer (DMA) Q800 (Thermal Analysis, TA) instrument (instrument)) by raising the Temperature of a test piece manufactured in a size of horizontal x vertical x thickness (5.3mm x 5mm x 30 μm) from 0 ℃ to 150 ℃ at 5 ℃/min. Thereafter, the Y-axis on the graph obtained with the analysis tool is set to the numerical variation of Tan δ (Tan Delta), and the temperature at Tan δ max having the maximum value is defined as the glass transition temperature.

The storage modulus at 80 ℃ after curing of the radical adhesive composition may be 800Mpa to 2,000Mpa, preferably 900Mpa to 2,000Mpa, and more preferably 1,000Mpa to 2,000 Mpa. The storage modulus ranges as a storage modulus at 80 ℃, and storage moduli at temperatures other than 80 ℃ may have different values. In the case where the storage modulus at 80 ℃ is in the above range, the provision of the adhesive layer between the polarizer and the protective film can effectively perform the performance of protecting the polarizer. Specifically, the occurrence of cracks in the polarizer can be effectively suppressed under severe environments such as thermal shock.

In the case where the storage modulus at 80 ℃ after curing of the radical adhesive composition is less than 800Mpa, it is difficult to suppress shrinkage and expansion of the polarizer due to temperature during thermal shock evaluation, and thus cracks are generated in the polarizer, and in the case where the storage modulus at 80 ℃ exceeds 2,000Mpa, a warpage phenomenon of the polarizer occurs depending on a substrate laminated with the polarizer.

In the present specification, the crack may refer to a portion where the polarizing plate is elongated in a Mechanical Direction (MD) to be broken. For example, the length of the crack may be 0.01mm or more.

To determine the storage modulus, a free radical adhesive composition was first applied to a release film and irradiated at a temperature of 23 ℃ and a relative humidity of 55% at 1,000mJ/cm²Amount of light ofTo be photo-cured, thereby producing a cured film. At this time, the thickness of the cured film is 30 μm to 50 μm, and may be 30 μm, for example. After removing the release film, the storage modulus was measured by a temperature sweep test (tension 0.04%, pretightening force: 0.05N, force orbit: 125%, frequency: 1Hz) using DMAQ800(TA Instrument) by raising the temperature of a test piece manufactured in the dimensions of horizontal X longitudinal X thickness (5.3mm X5 mm X30 μm) from 0 ℃ to 150 ℃ at 5 ℃/min.

The free radical adhesive composition may be free of ether linkage peaks in the Infrared (IR) spectrum after curing (1,080 cm)^-1) The composition of (1). The compound having an epoxy functional group is used as a non-radical polymerizable cationic polymerizable material, and when it is used as an additive for imparting a function other than a polymerization property, it is used in a small amount, and therefore, it does not have an ether bond peak (1,080 cm) in an IR spectrum after curing^-1)。

In one embodiment of the present description, the radical adhesive composition may include an epoxy compound in a small amount as an additive instead of as a polymerizable compound. The content of the epoxy compound may be 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, and more preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the radical adhesive composition as a whole.

Whether the radical adhesive composition includes an epoxy compound can be confirmed by measuring an IR spectrum. The epoxy adhesive composition comprising an epoxy compound has an ether bond peak (1,080 cm) in the IR spectrum by generating an ether bond through ring opening of a ring^-1) In contrast, the radical adhesive composition including the acrylate compound has no peak of ether bond. In addition, the epoxy adhesive composition may be in the range of 1,200cm^-1To 1,000cm^-1In the vicinity of the peak, 3 peaks were observed, but only one peak was observed in the radical adhesive composition.

In one embodiment of the present invention, the radical adhesive composition may include the photoacid generator (E) or the photoinitiator (F), or both the photoacid generator (E) and the photoinitiator (F).

As the photoacid generator (E), conventionally known photoacid generators can be used without particular limitation. Specific examples thereof include onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, iron-arene complexes, and the like. These may be used alone or in combination of two or more.

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

Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and bis (4-nonylphenyl) iodonium hexafluorophosphate.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl ] sulfonium hexafluoroantimonate, diphenyl [4- (phenylthio) phenyl ] sulfonium hexafluorophosphate, 4' -bis [ diphenylsulfonium ] diphenylsulfide bis hexafluorophosphate, 4' -bis [ bis (β -hydroxyethoxy) phenylthio ] diphenylsulfide bis hexafluoroantimonate, 4' -bis [ bis (β -hydroxyethoxy) phenylthio ] diphenylsulfide bis hexafluorophosphate, 7- [ bis (p-toluoyl) thio ] -2-isopropylthioxanthone hexafluoroantimonate, 7- [ bis (p-toluoyl) thio ] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, and the like, 4-phenylcarbonyl-4 ' -diphenylthio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4' -diphenylthio-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4' -di (p-toluoyl) thio-diphenylsulfide tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl ] sulfonium phosphate, and the like.

Examples of the iron-arene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumyl-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris (trifluoromethylsulfonyl) methanate, and the like.

The photoacid generators may be commercially available ones, and examples thereof include CPI-100P, 101A, 200K, 210S (see San-Apro (サンアプロ) Co., Ltd.), Kayarad (registered trademark) PCI-220, PCI-620 (see Japan chemical Co., Ltd.), UVI-6990 (see Union Carbide (ユニオンカーバイド) Co., Ltd.), Adekaoptomer (registered trademark) SP-150, SP-170 (see ADEKA Co., Ltd.), CI-5102, CIT-1370, 1682, CIP-1866S, 2048S, 2064S (see Nippon Soda (Japan)) DPI-101, 102, 103, 105, MPI-103, 105, BBI-101, 102, 103, 105, TPS-101, 102, 103, 105, MDS-101, 102, 105, 103, 105, and so-do, 105. DTS-102, 103 (Midori Kagaku (みどり - ) Co., Ltd.), PI-2074(Rhodia Japan (ローディアジャパン) 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 1 part by weight or more and 4 parts by weight or less, based on the entire weight of the radical adhesive composition or 100 parts by weight of the composition excluding the photoacid generator in the radical adhesive composition. By setting the amount of the photoacid generator to 0.5 parts by weight or more, the adhesive can be favorably cured after irradiation with ultraviolet rays. On the other hand, by setting the amount to 7 parts by weight or less, it is possible to suppress the decrease in adhesion or durability due to bleeding (bleeding out). In calculating the content of the photoacid generator, the total weight of the radical adhesive composition refers to the sum of the remaining components excluding the photoacid generator.

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

Specifically, examples of the photoinitiator include inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate, organic peroxides such as t-butyl hydroperoxide, t-dibutyl peroxide, cumyl hydroperoxide, acetyl peroxide, benzoyl peroxide, and lauroyl peroxide, azo compounds such as azobisisobutyronitrile, azobis-2, 4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisoamidine hydrochloride, and azobiscyanovaleric acid, acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, 2, 3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfonium compounds, rofen dimers, onium salts, borate salts, active esters, active halides, inorganic complexes, and mixtures thereof, Coumarins and the like. More specifically, there may be mentioned acetophenone compounds such as acetophenone, 3-methylacetophenone, benzildimethylketal, 1- (4-cumyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenones including benzophenone, 4-chlorobenzophenone, 4' -diaminobenzophenone; benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; 1-hydroxycyclohexyl phenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, etc.

Examples of the photoinitiator include IRGACURE (registered trademark) 184, 819, 907, 651, 1700, 1800, 819, 369, 261, DAROCUR (registered trademark) TPO, DAROCUR (registered trademark) 1173 (hereinafter, referred to as BASF Japan ltd), Esacure (registered trademark) KIP150, TZT (hereinafter, referred to as DKSH Japan ltd), KAYACURE (registered trademark) BMS, and DMBI (hereinafter, referred to as Japan ltd).

Further, the photoinitiator may be used in combination with an appropriate reducing agent such as an amine such as ethylamine, triethanolamine or dimethylaniline, polyamine, a 2-valent iron salt compound, an organic metal compound such as ammonia, triethylaluminum, triethylboron or diethylzinc, sodium sulfite, sodium hydrogen sulfite, cobalt naphthenate, sulfinic acid or mercaptan.

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

Specific examples of the photosensitizer include pyrene; benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α -dimethoxy- α -phenylacetophenone; benzophenone derivatives such as benzophenone, 2, 4-dichlorobenzophenone, methyl benzoylbenzoate, 4 '-bis (dimethylamino) benzophenone, and 4,4' -bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone and 2, 4-diethylthioxanthone; anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone; further, α -diethoxyacetophenone, benzil, fluorenone, xanthone, uranyl compound, halogen compound and the like are exemplified.

The photosensitizer may be a synthetic product or a commercially available product. Examples of commercially available products include Kayacure (registered trademark) DMBI, BDMK, BP-100, BMBI, DETX-S, EPA (described above as a product of Nippon chemical Co., Ltd.), Anthracure (registered trademark) UVS-1331, UVS-1221 (described above as a product of Kawasaki Kasei Chemicals (Kawasaki chemical Co., Ltd., )), Uvecryl P102, 103, 104, and 105 (described above as a product of UCB Co., Ltd.).

The amount of at least one of the photoinitiator and the photosensitizer (in the case of using both the photoinitiator and the photosensitizer, the total amount thereof) is preferably 0.1 to 7 parts by weight, more preferably 0.2 to 3.5 parts by weight, and 0.2 to 2.5 parts by weight, based on the total weight of the components excluding the photoinitiator and the photosensitizer in the radical adhesive composition. Within the above range, the curing efficiency is excellent by irradiation with ultraviolet rays, and thus the deterioration of the adhesion and durability due to bleeding can be suppressed.

In one embodiment of the present specification, the type of the silane coupling agent (D) is not particularly limited, and examples thereof include vinylchlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-vinyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and the like, 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, N-phenyltrimethoxysilane, N-propyltrimethoxysilane, N-phenyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, N-phenyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2-aminopropyl-3-aminopropyl-trimethoxysilane, N-propyltrimethoxysilane, N-ethyltrimethoxysilane, N-isopropyltrimethoxysilane, N-ethyltrimethoxysilane, N-2-aminopropyl-ethylmethyldimethoxysilane, N-isopropyltrimethoxysilane, N-isopropyltrimethoxysilane, N-2-isopropyltrimethoxysilane, N-3-N-isopropyltrimethoxysilane, N-isopropyltrimethoxysilane, N-3-N-represents a-N-one, N-one, or one, or one, or one or, 3-isocyanatopropyltriethoxysilane, and the like. These may be used alone or in combination of two or more.

The radical adhesive composition may optionally include additives in addition to the above components to the extent that the effect of the present invention is not significantly reduced.

Examples of the additives include polymerizable components other than the above-mentioned components, ultraviolet absorbers, antioxidants, heat stabilizers, inorganic fillers, softeners, antioxidants, aging inhibitors, stabilizers, adhesion-imparting resins, modified resins (polyol resins, phenol resins, acrylic resins, polyester resins, polyolefin resins, and the like), leveling agents, antifoaming agents, plasticizers, dyes, pigments (coloring pigments, extending pigments, and the like), treatment agents, ultraviolet blocking agents, fluorescent whitening agents, dispersants, light stabilizers, antistatic agents, lubricants, and the like.

The content of the additive is preferably 0.01 to 20 parts by weight, more preferably 0.02 to 10 parts by weight, and still more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the entire adhesive composition. By setting the content of the additive within the above range, the effects of the adhesive of the present invention can be sufficiently exhibited. The overall weight of the adhesive composition may refer to the sum of the remaining ingredients excluding the additives.

The adhesion force of the cured product of the radical adhesive composition to the non-pretreated polyethylene terephthalate film may be 150gf/20mm, preferably 170gf/20mm, more preferably 200gf/20mm or more. Satisfying the above range means that the radical adhesive composition is excellent in adhesion to a polyethylene terephthalate film. When the above numerical value range is satisfied, there is an advantage that pretreatment for improving the adhesion of the protective film is not required. The pretreatment is a treatment for improving the adhesion of the film, and thus there are corona treatment and the like. Whether the polyethylene terephthalate film is pretreated or not may be confirmed according to a contact angle, a contact angle of the non-pretreated polyethylene terephthalate film may be 50 to 70 degrees, and a contact angle of the pretreated polyethylene terephthalate film may be less than 50 degrees. The contact angle can be determined by methods commonly used in the art, for example, the angle that a stationary droplet makes with the surface of a film can be determined after the droplet is dropped on the film. At this time, as the kind of the liquid, water (Deionized (DI) water) or an organic solvent may be used. Examples of a contact angle tester used for measuring the contact angle include Phonenix 300.

The viscosity of the radical adhesive composition at 25 ℃ may be 10cPs to 100cPs, preferably 10cPs to 80cPs, and more preferably 10cPs to 65 cPs. When the viscosity is in the above range, the processability of the composition can be improved and the generation of bubbles in the adhesive layer formed from the adhesive composition can be prevented.

The method for preparing the radical adhesive composition is not particularly limited, and can be obtained by mixing the components. For adjusting the viscosity, an organic solvent may also be suitably used. The mixing method is not particularly limited, and the mixture may be sufficiently stirred and mixed at room temperature (20 ℃ to 25 ℃) in a room shielded from Ultraviolet (UV) light until the inside of the liquid becomes uniform, so as not to be cured.

The radical adhesive composition can be suitably used for a polarizing plate (polarizing film), a retardation film, an elliptically polarizing film, an antireflection film, a brightness enhancement film, an Indium Tin Oxide sputtered transparent conductive film (ITO film), various electronic-related film members, a protective film, and the like. Among them, it is preferably used in a polarizing plate (polarizing film).

The present specification provides a protective film for a polarizing plate, comprising: a protective film; and an adhesive layer comprising the radical adhesive composition as described above on one or both sides of the protective film.

In one embodiment of the present specification, the thickness of the adhesive layer is preferably more than 0 μm and 20 μm or less, and more preferably 0.1 μm to 10 μm or 0.1 μm to 5 μm or so. The reason for this is that: if the thickness of the adhesive layer is too thin, the uniformity and adhesion of the adhesive layer may be reduced, and if the thickness of the adhesive layer is too thick, the appearance of the polarizing plate may be wrinkled.

The present specification provides a polarizing plate, comprising: a polarizing member; and a protective film for a polarizing plate as described above, which is provided on one or both surfaces of the polarizing element. Referring to fig. 1 and 2, the polarizing plate includes

protective films

101 and 105 on one or both surfaces of a polarizer 103 with

adhesive layers

102 and 104 as a medium.

In the present specification, as the polarizing member, a polarizing member known in the art, for example, a film composed of polyvinyl alcohol (PVA) including iodine or dichroic dye may be used. The polarizer can be produced by dyeing a polyvinyl alcohol film with iodine or a dichroic dye, but the production method thereof is not particularly limited. In this specification, the polarizer refers to a state not including a protective layer (or a protective film), and the polarizing plate refers to a state including the polarizer and the protective layer (or the protective film).

The polarizing plate is manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; a step of washing the treated product with water after the treatment with an aqueous boric acid solution; and a step of bonding the protective layer to the uniaxially stretched polyvinyl alcohol resin film on which the dichroic dye is adsorbed and aligned by performing the above steps.

The uniaxial stretching may be performed before dyeing with the dichroic dye, may be performed simultaneously with dyeing with the dichroic dye, or may be performed after dyeing with the dichroic dye. In the case where uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before boric acid treatment or may be performed while boric acid treatment is performed. In addition, uniaxial stretching may be performed in the above-described plural steps. For the uniaxial stretching, the stretching may be performed uniaxially between rolls having different peripheral speeds, or uniaxially by using a heat roll. Further, the stretching may be performed in a dry stretching mode in which stretching is performed in the air, or in a wet stretching mode in which stretching is performed in a state of being swollen by a solvent. The stretch ratio is not particularly limited, and is usually 4 to 8 times.

On the other hand, the thickness of the polarizer is preferably 5 μm to 40 μm, and more preferably 5 μm to 25 μm. If the thickness of the polarizer is smaller than the above numerical range, the optical characteristics are deteriorated, and if the thickness is larger than the above numerical range, the shrinkage of the polarizer at a low temperature (e.g., -30 ℃) is increased to deteriorate the durability of the entire polarizing plate with respect to heat.

In addition, in the case where the polarizer is a polyvinyl alcohol film, the polyvinyl alcohol film may be used without particular limitation as long as the polyvinyl alcohol film includes 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. Further, commercially available polyvinyl alcohol films such as P30, PE30, and PE60 from Curare, and M2000, M3000, and M6000 from japan synthesis may be used, but the present invention is not limited thereto.

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

The protective film material is preferably excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, and the like. Examples thereof include 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 resins such AS polystyrene and acrylonitrile-styrene copolymer (AS resin), polyolefin resins such AS polycarbonate resins, polyethylene, polypropylene, ethylene-propylene copolymers and cycloolefin polymers, polyvinyl chloride resins, polyamide resins such AS nylon and aromatic polyamides, polyimide resins, polysulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene sulfide resins, polyvinyl alcohol resins, polyvinylidene chloride resins, polyvinyl butyral resins, polyarylate resins, polyoxymethylene resins, epoxy resins, and mixtures of these resins.

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

Specifically, the cellulose resin as an ester of cellulose and a fatty acid is preferably cycloolefin polymer (COP), polyethylene terephthalate (PET), or acrylic resin. Examples of the cellulose resin include cellulose Triacetate (TAC), cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among them, cellulose triacetate, cycloolefin polymer, polyethylene terephthalate, or acrylic resin is preferable from the viewpoint of acquisition easiness or cost, and cycloolefin polymer, polyethylene terephthalate, or acrylic resin is more preferable from the viewpoint of acquisition easiness or water permeability. If the protective film has high water permeability, moisture permeates through the protective film and easily enters the polarizer side, so that there is a concern that the quality of the polarizer may be degraded, but if a cycloolefin polymer, polyethylene terephthalate, or acrylic resin is used, the above problem can be significantly suppressed.

In addition, saponified triacetylcellulose may also be used, but unsaponified triacetylcellulose is more preferably used.

The protective film surface may be a protective film surface modified by corona discharge treatment. The corona discharge treatment method is not particularly limited, and a normal corona discharge treatment apparatus (for example, an inhibitor manufactured by Kasuga motor) can be used for the treatment. By performing the corona discharge treatment, active groups such as hydroxyl groups are formed on the surface of the protective film, which is considered to contribute more to the improvement of the adhesion. In the case of using saponified cellulose triacetate as the protective film, the effect of improving the adhesion can be expected like the corona discharge treatment, and therefore, the corona discharge treatment is not necessarily performed. However, since the saponification treatment is complicated and expensive, it is preferable to use unsaponifiable triacetylcellulose by performing a corona discharge treatment in the production process.

The discharge amount of the corona discharge treatment is not particularly limited, but is preferably 30 W.min/m²Above 300 W.min/m²The range below is more preferably 50 W.min/m²Above 250 W.min/m²The following ranges. Within such a range, the adhesiveness between the protective film and the adhesive can be improved without heating the protective film itself, which is preferable. Here, the discharge amount is an amount of work of corona discharge to the object, which is obtained by the following equation, and the corona discharge power is determined based on this amount.

The method for manufacturing the polarizing plate is not particularly limited, and may be manufactured as follows: the polarizer and the protective film are bonded by a conventionally known method using the radical adhesive composition described above. The applied adhesive exhibits adhesiveness by irradiation with ultraviolet rays, thereby constituting an adhesive layer.

When the radical adhesive composition is applied, the composition may be applied to either a protective film or a polarizer, or may be applied to both. The radical adhesive composition is preferably applied so that the thickness of the adhesive layer after drying is more than 0 μm and 20 μm or less. The thickness of the adhesive layer can be adjusted by the concentration of the solid component in the solution of the adhesive or the coating device of the adhesive. The thickness of the adhesive layer can be confirmed by observing the cross section with a Scanning Electron Microscope (SEM). The method for applying the adhesive is also not particularly limited, and various methods such as a method of directly dropping the adhesive, a roll coating method, a spraying method, and a dipping method can be employed.

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

After the above-described joining, the polarizing plate is irradiated with ultraviolet rays in order to cure the adhesive. The light source of the ultraviolet ray 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 excitation mercury lamp, a metal halide lamp, or the like having a light emission distribution at a wavelength of 400nm or less can be used. The ultraviolet irradiation amount (cumulative light amount) is not particularly limited, but it is preferable that the ultraviolet irradiation amount in the wavelength region effective for activation of the polymerization initiator is 100mJ/cm²Above 2,000mJ/cm²The following. When the amount is within the above range, the reaction time is appropriate, and the adhesive itself or the polarizing film can be prevented from being heated by the heat of lamp radiation or heat generated during polymerization.

The polarizing plate may be a polarizing plate that is stored at room temperature (20 ℃ to 25 ℃, specifically 25 ℃) for 16 hours to 30 hours immediately after irradiation with ultraviolet rays. And finishing the polarizing plate after the curing is finished.

The present specification provides an image display device including: a display panel; and a polarizing plate as described above, provided on one or both surfaces of the display panel.

The present specification provides an image display device including: a display panel; and a polarizing plate as described above, which is provided on the visible side of the display panel or on the opposite side of the visible 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 include 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 a polarizing plate including the polarizer according to one embodiment of the present specification.

In this case, the type of the liquid crystal panel included in the liquid crystal display device is not particularly limited. For example, the type thereof is not limited, and a passive matrix panel such as a Twisted Nematic (TN) type, a Super Twisted Nematic (STN) type, a ferroelectric (F) type, or a Polymer Dispersed (PD) type; active matrix panels such as two-terminal (two-terminal) or three-terminal (three-terminal); known panels such as In-Plane Switching (IPS) panels and Vertical Alignment (VA) panels. Further, the types of other components constituting the liquid crystal display device, for example, the upper substrate and the lower substrate (for example, a color filter substrate or an array substrate) are not particularly limited, and any component known in the art can be used without limitation.

Hereinafter, the present specification will be described in detail with reference to examples in order to specifically describe the present specification. However, the embodiments described herein may be modified into various forms, and the scope of the present description is not limited to the embodiments described below. The embodiments of the present description are provided to more fully describe the present description to those of ordinary skill in the art.

< preparation of radical adhesive composition >

A free radical adhesive composition having the composition of table 1 below was prepared.

< Experimental example 1: test of adhesion force of protective film

The prepared radical adhesive composition was coated on both sides of a polarizer (manufactured by LG CHEM) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the irradiation dose (cumulative light amount) was adjusted to 2,000mJ/cm²The radical adhesive composition was cured by irradiating uv light having a wavelength of 365nm, and a polarizing plate sample was produced by adhering the polarizing plate and the protective film for peeling to each other and cutting the polarizing plate sample in a size of 2cm in width by 15cm in length. In this case, the pretreatment conditions of the release protective film were changed for each radical adhesive composition, and in the case of pretreating the protective film, the portion having the radical adhesive composition was subjected to corona treatment using a solution having a KOH concentration of 10% under a temperature condition of 45 ℃.

As shown in fig. 3, any of the protective films for peeling was peeled at a peeling angle of 90 degrees and a peeling speed of 0.5cm/sec by 3cm or more, and the peeling force at that time was measured 3 times to calculate an average value. For measuring the peel force, XT Plus Texture Analyzer (manufactured by TA) was used.

T/T in Table 1 means peeling between the analyzer and the peeling protective film, TAC/Ad means peeling between the adhesive layer and the peeling protective film, and PVA/Ad means peeling between the polarizer and the adhesive layer. Only when the analyzer and the release protective film were peeled off from each other, the adhesive was considered to have excellent performance.

< Experimental example 2: measurement of glass transition temperature and storage modulus after curing >

The prepared radical adhesive composition was applied to both sides of a polarizer (manufacturing company) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the irradiation dose (integrated light amount) was 2000mJ/cm²Curing the radical adhesive composition by irradiating ultraviolet rays having a wavelength of 365 nm. The resultant was cut into a size of 5.3mm in width and 4.5cm in length, and the protective film for peeling was peeled off to obtain a cured product (cured film) of the radical adhesive composition. The cured film was set with the long side in the stretching direction using a viscoelasticity measuring apparatus (Dynamic mechanical analyzer) (DMA Q800, TA Instrument Co., Ltd.) and viscoelasticity was measured at a frequency of 1Hz, a measurement start temperature of-30 ℃ and a temperature rise rate of 5 ℃/min. The glass transition temperature (Tg) is a temperature at which Tan δ becomes a maximum value, and the peak of Tan δ becomes the maximum value.

In addition, the storage modulus was measured by a temperature sweep test (tension 0.04%, pretightening force: 0.05N, force orbit: 125%, frequency: 1Hz) at a rate of 5 ℃/min from 0 ℃ to 150 ℃ using DMA Q800(TA Instrument), and the value measured at 80 ℃ was read.

< Experimental example 3: evaluation of Water resistance >

The prepared radical adhesive composition was coated on both sides of a polarizer (manufacturing company) prepared in advance, and a protective film for peeling was laminated and a protective film for peeling (PET film) was laminated. ThereafterThe irradiation dose (cumulative light dose) was 2000mJ/cm²Curing the radical adhesive composition by irradiating ultraviolet rays having a wavelength of 365 nm. The polarizer was cut to a length of 150mm in the direction of the absorption axis of the polarizer and in the direction perpendicular thereto. Thereafter, an adhesive was applied to one surface of the protective film for peeling, and the protective film was laminated (glass plating) on a glass substrate, and then left at 25 ℃ for 24 hours. Thereafter, the glass plate was placed in a water bath at 60 ℃ for 24 hours and then taken out. Whether the polarizer was discolored or not and whether the film was peeled or not were confirmed by visually confirming the appearance of the sample. The case where NO discoloration or film peeling occurred was referred to as OK, and the case where discoloration or film peeling occurred was referred to as NO.

< Experimental example 4: thermal shock assessment

The prepared radical adhesive composition was applied to both sides of a polarizer (manufacturing company) prepared in advance, and a protective film (PET film) for peeling was laminated. Thereafter, the irradiation dose (integrated light amount) was 2000mJ/cm²Curing the radical adhesive composition by irradiating ultraviolet rays having a wavelength of 365 nm. The polarizer was cut so that the length thereof was 150mm in each of the direction of the absorption axis of the polarizer and the direction perpendicular thereto. Thereafter, an adhesive was applied to one surface of the protective film for peeling, and the protective film was laminated (glass plating) on a glass substrate, and then left at 25 ℃ for 24 hours.

Thereafter, the glass substrate was left at-40 ℃ for 30 minutes and at 85 ℃ for 30 minutes as one cycle, and 100 cycles were repeated. After the thermal shock was applied, the polarizer was observed from the end of the polarizer along the extending direction (arrow direction) of the polarizer for the presence of cracks, and if cracks were observed, the length of the cracks was measured. In the case where a plurality of cracks were observed, the evaluation was performed using the average value thereof. The test piece was marked as pass when no crack was generated or the length of the crack was less than 1mm, and as fail when the length of the crack was 1mm or more.

< Experimental example 5: stiffness evaluation

Prepared by coating both sides of a polarizer (manufacturing company)The radical adhesive composition was prepared, and a protective film for peeling (PET film) was laminated. Thereafter, the irradiation dose (cumulative light amount) was adjusted to 2,000mJ/cm²Curing the radical adhesive composition by irradiating ultraviolet rays having a wavelength of 365 nm. The resultant was cut into a size of 3cm in width and 7cm in length, and the protective film for peeling was peeled off to obtain a cured product (cured film) of the radical adhesive composition.

As shown in FIG. 4, the cured film was fixed to a viscoelasticity measuring apparatus (Dynamic mechanical analyzer: DMA Q800TA instrument Co., Ltd.) by folding the cured film into a ring shape, the curved surface was pressed with a force of 1g and 30m/min, and the force at the time of pressing for a distance of 20mm was recorded as the rigidity of the cured film.

< Experimental example 6: evaluation of viscosity of composition as a whole >

The viscosity of each composition was evaluated.

The evaluation method comprises the following steps:

-an assay device: brookfield VISCOMETER (BROOKFIELD VISCOMETER) DV-II + PRO

Speed: 90RPM

Spindle: number 18

< Experimental example 7: evaluation of viscosity of urethane acrylate oligomer >

The viscosity at 25 ℃ of each urethane oligomer was evaluated.

-an assay device: brookfield viscometer DV-II + PRO

-speed: 0.01rpm

-a main shaft: number 18

< Experimental example 8: acid value measurement of urethane acrylate oligomer

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

[ Table 1]

[ Table 2]

The reference symbols in tables 1 and 2 are described below.

A: urethane acrylate oligomer

(a) The method comprises the following steps Polyester urethane acrylate oligomer

B1: a polyfunctional (meth) acrylate monomer having a homopolymer glass transition temperature (Tg) of 150 ℃ or higher

B2: polyfunctional (meth) acrylate monomers having a homopolymer glass transition temperature (Tg) of less than 150 ℃

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

d: a silane coupling agent;

e: a 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-5 yl ] methacrylate (Tg: 180 ℃ C.)

KBM 403: (3-glycidoxypropyl) trimethoxysilane

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

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

DETX: 2, 4-diethylthioxanthone

The parts by weight of A, B (B1, B2), C and D are parts by weight relative to 100 parts by weight of the total of A to D.

The parts by weight of E and F are parts by weight of each substance relative to 100 parts by weight of the total weight of all of A to D.

From the above results, it is understood that the radical adhesive compositions of examples 1 and 2 are excellent in adhesion to the PET film without corona treatment. The reason for this is that: the radical adhesive composition includes a polyester-based urethane acrylate oligomer with an adjusted acid value, and thus the adhesive layer is excellent in adhesion to a protective film.

In addition, it was confirmed that when the radical adhesive compositions of examples 1 and 2 were applied to a polarizing plate, heat resistance and water resistance were improved and rigidity was improved.

[ description of symbols ]

101. 105 protective film

102. 104 adhesive layer

103 polarizer

Claims

1. A free radical adhesive composition comprising:

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

a polyfunctional (meth) acrylate monomer (B) having a homopolymer glass transition temperature (Tg) of 150 ℃ or higher;

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

a silane coupling agent (D).

2. The radical adhesive composition according to claim 1, wherein the polyester urethane acrylate oligomer (a) is formed of a composition comprising a polyester polyol compound, an isocyanate compound, and an acrylate compound.

3. The radical adhesive composition according to claim 1, wherein the polyester-based urethane acrylate oligomer (a) has a viscosity of 1,000cPs or more and 50,000cPs or less at 25 ℃.

4. The radical adhesive composition according to claim 1, wherein the polyester urethane acrylate oligomer (a) is 1 to 20 parts by weight with respect to 100 parts by weight of the composition as a whole.

5. The free radical adhesive composition of claim 1, further comprising a multifunctional (meth) acrylate monomer (B2) having a homopolymer glass transition temperature (Tg) of less than 150 ℃.

6. The radical adhesive composition according to claim 1, wherein the glass transition temperature after curing is 80 ℃ to 150 ℃.

7. The radical adhesive composition according to claim 1, wherein a peak value of Tan δ after curing is 0.2 or more, and a glass transition temperature at the peak value of Tan δ is 90 ℃ or more.

8. The radical adhesive composition according to claim 1, wherein the storage modulus at 80 ℃ after curing is 800MPa or more and 2,000MPa or less.

9. The free radical adhesive composition of claim 1, wherein after curing, there are no ether linkage peaks (1,080 cm) in the IR spectrum^-1)。

10. The radical adhesive composition according to claim 1, wherein the adhesion force of a cured product thereof to a non-pretreated polyethylene terephthalate film is 150gf/20mm or more.

11. The radical adhesive composition according to claim 1, wherein the viscosity at 25 ℃ is from 10cPs to 100 cPs.

12. A protective film for a polarizing plate, comprising:

a protective film; and

an adhesive layer having a cured product of the radical adhesive composition according to any one of claims 1 to 11 on one or both surfaces of the protective film.

13. The protective film for a polarizing plate according to claim 12, wherein the adhesive layer has a thickness of 0 μm to 20 μm.

14. The protective film for a polarizing plate according to claim 12, which is a cellulose-based film.

15. A polarizing plate, comprising:

a polarizing member; and

the protective film for a polarizing plate according to claim 12, which is provided on one or both surfaces of the polarizing element.

16. An image display device, comprising:

a display panel; and

the polarizing plate of claim 15, which is disposed on one or both sides of the display panel.