Adhesive composition, adhesive film containing the same, polarizing film containing the same, and display device containing the polarizing film.

Abstract

The present application relates to an adhesive composition, an adhesive film containing the same, a polarizing film containing the same, and a display device containing the polarizing film.

Description

[Technical Field]

[0001] This application claims the benefit as of the filing date of Korean Patent Application No. 10-2022-0010599, filed with the Korean Intellectual Property Office on January 25, 2022, and all its contents are incorporated herein by reference. This application relates to an adhesive composition, an adhesive film containing the same, a polarizing film containing the same, and a display device including the polarizing film. [Background technology]

[0002] In recent years, leveraging advancements in optical technology, various display devices utilizing different methods, such as plasma display panels (PDPs), liquid crystal displays (LCDs), and organic light-emitting diodes (OLEDs), have been proposed and commercialized as replacements for conventional cathode ray tubes. Recently, the characteristics required of such display devices have become increasingly sophisticated, and consequently, the characteristics required of peripheral components such as optical films and polarizing films applied to these display devices are also becoming more sophisticated.

[0003] Liquid crystal display (LCD) displays are used in various display devices such as TVs, mobile phones, car navigation systems, portable game consoles, and other portable terminals, taking advantage of their characteristics such as low power consumption, low voltage operation, light weight, and thinness. Examples of these LCD displays include VA (Vertical Alignment) mode, IPS (In-Plane Switching) mode, FFS (Fringe Field Switching) mode, and OCB (Optical Compensated Bend) mode. These LCD displays generally consist of a backlight, a liquid crystal cell containing liquid crystal molecules sandwiched between two electrodes, and two polarizing plates provided on both sides of the liquid crystal cell. When voltage is applied, the transmitted light is controlled by the change in the optical refractive index of the liquid crystal molecules, and an image can be displayed. In these modes, the light absorption axes of the two polarizing films are arranged at a 90° angle to each other so that no light is transmitted when no voltage is applied to the liquid crystal cell (voltage unapplied). LCD displays that display black when no voltage is applied and white when voltage is applied are called normally black type.

[0004] Recently, efforts have been made in the polarizing film market to minimize defects and increase product productivity. Conventionally, as a protective substrate for polarizing films, moisture-permeable substrates (WVRT > 200g / m²) have been used. 2 We have been manufacturing polarizing plates with water-based adhesives using TAC (Triacetyl cellulos) (which is a type of adhesive used in some products), but currently we are using non-permeable substrates such as PET, acrylic, or COP film (WVRT < 200g / m²). 2 (day) is also primarily used. Furthermore, while the substrates for polarizing plates are becoming more diverse, poorly adhesive substrates are also being used.

[0005] In conventional applications, when using either a moisture-permeable or non-moisture-permeable protective substrate alone, it was possible to attach the upper / lower protective substrates of the polarizing plate with a single type of adhesive, depending on the type of protective substrate. However, in recent applications, where moisture-permeable and non-moisture-permeable substrates are used simultaneously, or where poorly adhering substrates are used, it has become difficult to achieve sufficient adhesive strength with a single water-based adhesive.

[0006] In other words, adhesive compositions that exhibit good adhesion to moisture-permeable protective substrates are unsuitable for non-moisture-permeable substrates, and adhesive compositions that exhibit good adhesion to non-moisture-permeable protective substrates are unsuitable for moisture-permeable substrates. Furthermore, poorly adhering substrates have also been developed. Currently, as the characteristics of substrates are applied in a wide variety of ways, adhesives must also differ depending on the substrate. Research is needed to improve the adhesive margin of adhesives so that they can be applied to moisture-permeable, non-moisture-permeable, and poorly adhering substrates.

[0007] Currently, to solve these problems, it has become common practice to use separate adhesives on the top and bottom surfaces of polarizing plates, tailored to the moisture-permeable and moisture-impermeable substrates. However, while using separate adhesives for moisture-permeable and moisture-impermeable substrates has the advantage of improving adhesive strength, it necessitates changing the adhesive each time depending on the product group, leading to increased costs due to adhesive replacement and decreased product productivity.

[0008] When the adhesive applied to a polarizing film is replaced, a floating period of approximately 3-6 hours is generally observed, followed by additional time for path changes due to wet / dry switching, adhesive discharge / refilling, mesh roll replacement, and pipe cleaning / washing.

[0009] Therefore, it is necessary to develop an adhesive layer that can be applied to polarizing plates regardless of the type of protective substrate (moisture-permeable substrate, non-moisture-permeable substrate, or poorly adhering substrate) attached to the polarizing plate, in accordance with the currently applied product group. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Registered Patent Publication No. 6536022 [Overview of the project] [Problems that the invention aims to solve]

[0011] This application relates to an adhesive composition, an adhesive film containing the same, a polarizing film containing the same, and a display device including the polarizing film. [Means for solving the problem]

[0012] One embodiment of this specification provides an adhesive composition for polarizers comprising: a monofunctional cationic polymerizable monomer having a glass transition temperature (Tg) of 0°C or less; a difunctional cationic polymerizable monomer including a cationic polymerizable monomer containing an alicyclic ring and a cationic polymerizable monomer containing an aromatic ring; a polyfunctional radical polymerizable monomer; a cationic photoinitiator; and a photosensitizer. In another embodiment, an adhesive film is provided that includes the adhesive composition or cured product thereof according to this application.

[0013] In another embodiment, a polarizing film is provided, comprising: a polarizer; a first adhesive layer and a second adhesive layer provided on both sides of the polarizer; a first transparent protective film provided on the side of the first adhesive layer opposite to the side in contact with the polarizer; and a second transparent protective film provided on the side of the second adhesive layer opposite to the side in contact with the polarizer, wherein the first adhesive layer and the second adhesive layer are the adhesive film according to this application. Finally, the present invention provides a display device including a polarizing film. [Effects of the Invention]

[0014] An adhesive composition according to an embodiment of the present invention comprises: a monofunctional cationic polymerizable monomer having a glass transition temperature (Tg) of 0°C or lower; a bifunctional cationic polymerizable monomer containing a cationic polymerizable monomer containing an alicyclic ring and a cationic polymerizable monomer containing an aromatic ring; a polyfunctional radical polymerizable monomer; a cationic photoinitiator; and a photosensitizer.

[0015] As described above, the adhesive composition according to the present application necessarily includes five components, and has the characteristic of exhibiting excellent adhesive strength regardless of whether the substrate to be adhered is a moisture-permeable or non-moisture-permeable substrate. In particular, by including specific components, in addition to moisture-permeable or non-moisture-permeable substrates, the adhesive strength with a difficult-to-adhere substrate is also excellent. In the subsequent production of polarizing plates, the adhesive composition according to the present application can be used regardless of the type of protective substrate, which has the advantageous characteristics of improving the yield and productivity.

[0016] Furthermore, the adhesive layer containing the adhesive composition according to the present application reduces the surface energy, does not induce bubbles during the process, has excellent wetting properties on the polarizing plate or the substrate, and has the characteristic that the apparent quality of the polarizing film containing this is excellent.

Brief Description of the Drawings

[0017]

Figure 1

Modes for Carrying Out the Invention

[0018] Before describing the present invention, first, some terms are defined. In this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components, but may further include other components. In this specification, "p~q" means the range of "p or more and q or less". In this specification, acrylate means that it includes all acrylates and (meth)acrylates.

[0019] In this specification, when a polymer contains a certain monomer as a monomer unit, it means that the monomer participates in the polymerization reaction and is included as a repeating unit in the polymer. In this specification, when it is said that a polymer contains a monomer, this is interpreted in the same way as that the polymer contains the monomer as a monomer unit. In this specification, the term "polymer" is understood to be used in a broad sense including copolymers unless otherwise specified as "homopolymer". In this specification, the term "monomer unit" means the state in which the compound is polymerized and bonded in the polymer.

[0020] In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are the molecular weights in terms of polystyrene measured by gel permeation chromatography (GPC) using monodisperse polystyrene polymers (standard samples) with various degrees of polymerization commercially available for molecular weight measurement as standard substances. In this specification, the molecular weight means the weight average molecular weight unless otherwise specified.

[0021] Hereinafter, for those with ordinary knowledge in the technical field to which the present invention belongs to easily implement the present invention, a detailed description will be given with reference to the drawings. However, the present invention can be embodied in various different forms and is not limited to the following description.

[0022] One embodiment of the present application provides an adhesive composition for a polarizing plate, which includes a monofunctional cationic polymerizable monomer having a glass transition temperature (Tg) of 0 °C or lower; a bifunctional cationic polymerizable monomer including a cationic polymerizable monomer containing an alicyclic ring and a cationic polymerizable monomer containing an aromatic ring; a polyfunctional radical polymerizable monomer; a cationic photoinitiator; and a photosensitizer.

[0023] The adhesive composition according to this application always contains the five compositions described above and is characterized by exhibiting excellent adhesive strength regardless of whether the substrate to be bonded is moisture-permeable or moisture-impermeable. In particular, by including specific compositions, it exhibits excellent adhesive strength not only to moisture-permeable or moisture-impermeable substrates but also to poorly adhering substrates. This means that the adhesive composition according to this application can be used in the production of subsequent polarizing plates regardless of the type of protective substrate, which is advantageous for improving yield and productivity.

[0024] The characteristics of each adhesive composition included in this application are described below. In one embodiment of this application, the adhesive composition comprises a monofunctional cationic polymerizable monomer having a glass transition temperature (Tg) of 0°C or lower. The fact that the cationic polymerizable monomer is monofunctional may mean that it contains one functional group, in which case the functional group may mean a functional group that plays a specific role in the monomer.

[0025] In one embodiment of this application, the monofunctional cationic polymerizable monomer having a glass transition temperature (Tg) of 0°C or lower may contain an epoxy group or an oxetane group as a functional group.

[0026] In another embodiment, the adhesive composition may have a glass transition temperature (Tg) of 0°C or lower, preferably -5°C or lower, more preferably -10°C or lower, and may satisfy a range of -100°C or higher, preferably -80°C or higher, more preferably -50°C or higher.

[0027] In this specification, the glass transition temperature is a value measured using a time-difference scanning calorimeter (DSC, Mettler Inc.) by sealing approximately 10 mg of a sample in a dedicated pan and heating it in a constant temperature-elevating environment, plotting the endothermic and exothermic amounts of the substance associated with the phase transition as a function of temperature.

[0028] Specifically, the glass transition temperature is the nominal value listed in literature, catalogs, etc., or the value calculated based on the following general formula (1) (Fox formula). [General formula (1)] 1 / Tg=W1 / Tg1+W2 / Tg2++Wn / Tgn In the general formula (1) above, Tg is the glass transition temperature of polymer A (unit: K), Tgi(i=1, 2, ...n) is the glass transition temperature when monomer i forms a homopolymer (unit: K), and Wi(i=1, 2, ...n) is the mass fraction of monomer i in the total monomer component.

[0029] The general formula (1) above represents the calculation formula when polymer A contains n types of monomer components: monomer 1, monomer 2, ..., monomer n.

[0030] In one embodiment of this application, based on 100 parts by weight of the adhesive composition, the monofunctional cationic polymerizable monomer may be 20 parts by weight or more, preferably 23 parts by weight or more, and 40 parts by weight or less, preferably 30 parts by weight or less.

[0031] The adhesive composition contains a monofunctional cationic polymerizable monomer that satisfies the glass transition temperature range and content, and is characterized by having excellent adhesion to commonly applied moisture-permeable substrates, and furthermore, by ensuring adhesion to difficult-to-adhere substrates.

[0032] In one embodiment of this application, the present invention provides an adhesive composition for polarizing plates, wherein the monofunctional cationic polymerizable monomer comprises a monofunctional epoxy monomer having 8 to 20 carbon atoms; or a monofunctional oxetane monomer having 5 to 15 carbon atoms.

[0033] In one embodiment of this application, the monofunctional cationic polymerizable monomer may consist of a monofunctional epoxy monomer having 8 to 20 carbon atoms. In one embodiment of this application, the monofunctional epoxy monomer having 8 to 20 carbon atoms may be represented by the following formula 1.

[0034] [ka]

[0035] In the above formula 1, m is an integer between 6 and 15 (inclusive). In one embodiment of this application, m is an integer between 6 and 15, preferably between 8 and 13, and more preferably between 10 and 13.

[0036] In one embodiment of this application, the monofunctional oxetane monomer having 5 to 15 carbon atoms may be represented by the following formula 2.

[0037] [ka]

[0038] In the above formula 2, Ar1 and Ar2 may be substituted or unsubstituted C1-C60 linear or branched alkyl groups.

[0039] In one embodiment of this application, Ar1 and Ar2 may be substituted or unsubstituted C1-C60 linear or branched alkyl groups. In another embodiment, Ar1 and Ar2 may be substituted or unsubstituted C1-C40 linear or branched alkyl groups. In another embodiment, Ar1 and Ar2 may be substituted or unsubstituted C1-C20 linear alkyl groups. In another embodiment, Ar1 and Ar2 may be linear alkyl groups of C1 to C20. In another embodiment, Ar1 and Ar2 may be a methyl group, an ethyl group, a propyl group, a butyl group, or an octyl group.

[0040] In one embodiment of this application, the term "substitution" means that a hydrogen atom bonded to a carbon atom of a compound is replaced by another substituent, and the position of substitution is not limited as long as it is a position where a hydrogen atom can be substituted, i.e., a position where a substituent can be substituted, and if two or more substituents are substituted, the two or more substituents may be the same or different from one another.

[0041] In this specification, “substituted or unsubstituted” means substituted or unsubstituted with one or more substituents selected from the group consisting of deuterium; halogens; cyano groups; linear or branched alkyls of C1-C60; linear or branched alkenyls of C2-C60; linear or branched alkynyls of C2-C60; monocyclic or polycyclic cycloalkyls of C3-C60; monocyclic or polycyclic heterocycloalkyls of C2-C60; monocyclic or polycyclic aryls of C6-C60; monocyclic or polycyclic heteroaryls of C2-C60; -SiRR'R''; -P(=O)RR'; alkylamines of C1-C20; monocyclic or polycyclic arylamines of C6-C60; and monocyclic or polycyclic heteroarylamines of C2-C60, or substituted or unsubstituted with substituents in which two or more substituents selected from the exemplified substituents are linked.

[0042] R, R', and R'' may be the same or different from each other, and each may independently be a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0043] In one embodiment of this application, the adhesive composition may include a difunctional cationic polymerizable monomer comprising a cationic polymerizable monomer containing an alicyclic ring and a cationic polymerizable monomer containing an aromatic ring.

[0044] As described above, the adhesive composition of this application contains a difunctional cationic polymerizable monomer, and in particular, it always contains a cationic polymerizable monomer containing an alicyclic ring and a cationic polymerizable monomer containing an aromatic ring. As described above, the difunctional cationic polymerizable monomer satisfies the above composition, and the adhesive composition has the characteristic of having an excellent curing speed and ensuring adhesion to poorly adhering substrates.

[0045] In one embodiment of this application, the cationic polymerizable monomer containing the alicyclic ring is a first epoxy monomer having two or more epoxy groups in its molecule, at least one of which is an alicyclic epoxy group, and the cationic polymerizable monomer containing the aromatic ring may be a second epoxy monomer having two or more epoxy groups in its molecule, the epoxy groups being non-alicyclic epoxy groups.

[0046] In one embodiment of this application, the cationic polymerizable monomer containing the alicyclic ring is a first epoxy monomer having two or more epoxy groups in its molecule, at least one of which is an alicyclic epoxy group.

[0047] In another embodiment, the cationic polymerizable monomer containing the alicyclic ring is a first epoxy monomer having two or more epoxy groups in its molecule, wherein the two epoxy groups are alicyclic epoxy groups.

[0048] In one embodiment of this application, the cationic polymerizable monomer containing the alicyclic ring includes the alicyclic ring, and the alicyclic ring may also contain an alicyclic epoxy group.

[0049] In one embodiment of this application, the cationic polymerizable monomer containing the aromatic ring has two or more epoxy groups in its molecule, and the epoxy groups are secondary epoxy monomers which are non-alicyclic epoxy groups.

[0050] In another embodiment, the cationic polymerizable monomer containing the aromatic ring is a secondary epoxy monomer having two or more epoxy groups in its molecule, wherein the two epoxy groups are non-alicyclic epoxy groups.

[0051] In one embodiment of this application, based on 100 parts by weight of the adhesive composition, the amount of the bifunctional cationic polymerizable monomer may be 40 parts by weight or more, preferably 45 parts by weight or more, and may be 65 parts by weight or less, more preferably 60 parts by weight or less.

[0052] In one embodiment of this application, an adhesive composition is provided in which, based on 100 parts by weight of the difunctional cationic polymerizable monomer, the cationic polymerizable monomer containing the alicyclic ring is 30 parts by weight or more and 60 parts by weight or less; and the cationic polymerizable monomer containing the aromatic ring is 40 parts by weight or more and 70 parts by weight or less.

[0053] In another embodiment, based on 100 parts by weight of the bifunctional cationic polymerizable monomer, the cationic polymerizable monomer containing the alicyclic ring may be 30 parts by weight or more and 60 parts by weight or less; preferably 35 parts by weight or more and 60 parts by weight or less, more preferably 55 parts by weight or more and 60 parts by weight or less.

[0054] In another embodiment, based on 100 parts by weight of the bifunctional cationic polymerizable monomer, the cationic polymerizable monomer containing the aromatic ring may be 40 parts by weight or more and 70 parts by weight or less; preferably 40 parts by weight or more and 65 parts by weight or less, more preferably 40 parts by weight or more and 55 parts by weight or less.

[0055] In one embodiment of this application, the adhesive composition contains a difunctional cationic polymerizable monomer that satisfies the above composition and content, and is characterized by having an excellent curing speed and being able to ensure adhesive strength to poorly adhering substrates. In one embodiment of this application, the polyfunctional radical polymerizable monomer may include an acrylate monomer or a methacrylate monomer. In this case, the functional group may include a (meth)acrylate group.

[0056] In one embodiment of this application, an adhesive composition is provided in which the polyfunctional radical polymerizable monomer comprises one or more selected from the group consisting of acrylates containing two functional groups and acrylates containing three or more functional groups.

[0057] In one embodiment of this application, the polyfunctional radical polymerizable monomer means an acrylate having two or more functional groups in its molecule, and the functional groups may be acrylate groups.

[0058] In one embodiment of this application, the number of functional groups of the polyfunctional radical polymerizable monomer may be 2 to 10, preferably 2 to 6, and more preferably 2 to 5.

[0059] The polyfunctional radical polymerizable monomer may be expressed differently depending on whether it has two functional groups (e.g., a bifunctional acrylate) or three functional groups (e.g., a trifunctional acrylate).

[0060] In one embodiment of this application, typical examples of difunctional acrylates include alkylene glycol di(meth)acrylates, polyoxyalkylene glycol di(meth)acrylates, halogen-substituted alkylene glycol di(meth)acrylates, aliphatic polyol di(meth)acrylates, hydrogenated dicyclopentadiene or tricyclodecanedialkanol di(meth)acrylates, dioxane glycol or dioxanedialkanol di(meth)acrylates, di(meth)acrylates of alkylene oxide adducts of bisphenol A or bisphenol F, and epoxy di(meth)acrylates of bisphenol A or bisphenol F.

[0061] In one embodiment of this application, more specific examples of difunctional acrylates include ethylene glycol di(meth)acrylate, 1,3-butanediol (meth)acrylate, 1,4-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate, ditrimethylolpropane di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate. Relate, di(meth)acrylate of neopentyl glycol hydroxypivalate, 2,2-bis[4-{2-(2-(meth)acryloyloxyethoxy)ethoxy}phenyl]propane, 2,2-bis[4-{2-(2-(meth)acryloyloxyethoxy)ethoxy}cyclohexyl]propane, hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, 1,3-di Examples include xane-2,5-diyldi(meth)acrylate (also known as dioxane glycol di(meth)acrylate), di(meth)acrylate of the acetal compound of hydroxypivalinaldehyde and trimethylolpropane (chemical name: 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane), and di(meth)acrylate of 1,3,5-tris(2-hydroxyethyl)isocyanurate.

[0062] In one embodiment of this application, a typical example of a polyfunctional acrylate with three or more functions is a poly(meth)acrylate of aliphatic polyols with three or more functions. Specific examples include glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin ethylene oxide-modified tri(meth)acrylate, and ethylene oxide-modified trimethylolpropane tri(meth)acrylate.

[0063] On the other hand, acrylate oligomers include urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and epoxy (meth)acrylate oligomers.

[0064] In one embodiment of this application, the polyfunctional acrylate may be neopentyl glycol hydroxypivalate diacrylate or tris(2-hydroxyethyl)isocyanurate triacrylate.

[0065] In one embodiment of this application, one polyfunctional radical polymerizable monomer may be used. In one embodiment of this application, two types of polyfunctional radical polymerizable monomers may be used.

[0066] In one embodiment of this application, the polyfunctional radical polymerizable monomer may be present in an amount of 100 parts by weight or more, preferably 13 parts by weight or more, and 30 parts by weight or less, preferably 25 parts by weight or less, based on 100 parts by weight of the adhesive composition.

[0067] As described above, by including the polyfunctional cationic polymerizable monomer in the above composition and content range in the adhesive composition, the adhesive strength does not decrease even when a moisture-permeable substrate or a moisture-impermeable substrate is laminated on both sides of the polarizing plate, and excellent adhesive strength is achieved. Furthermore, the moisture-permeable adhesive composition has the characteristic of having excellent wettability of the substrate.

[0068] In one embodiment of this application, an adhesive composition is provided in which, based on 100 parts by weight of the adhesive composition, the monofunctional cationic polymerizable monomer is 20 parts by weight or more; the difunctional cationic polymerizable monomer is 40 parts by weight or more; and the polyfunctional radical polymerizable monomer is 10 parts by weight or more.

[0069] In one embodiment of this application, the adhesive composition may include a cationic photoinitiator and a photosensitizer.

[0070] In this application, the cationic photoinitiator can be any one that can initiate polymerization of each composition by irradiation with ultraviolet light, and conventional known ones may be used.

[0071] In one embodiment of this application, the cationic photoinitiator refers to a compound that acts on a cationic polymerizable group, such as an epoxy group, to initiate a cationic polymerization reaction, thereby producing cationic species and Lewis acids upon irradiation with active energy rays such as ultraviolet light.

[0072] The aforementioned cationic photoinitiator refers to a compound that generates acid (H+) by active energy rays, and specifically, it may be a cationic photoinitiator containing, for example, an iodonium salt or a sulfonium salt.

[0073] More specifically, cationic photoinitiators containing the iodonium salt include (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis(pentafluorophenyl)borate, bis(dodecylphenyl)iodonium hexafluorophosphate, and bis(dodecylphenyl)iodonium hexafluoro Examples include, but are not limited to, antimonates, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluoroantimonate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate, and 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate.

[0074] In one embodiment of this application, the cationic photoinitiator is for promoting polymerization and improving the curing rate, and any cationic initiator commonly used in the art may be used as the photoinitiator without limitation.

[0075] Furthermore, in one embodiment of this application, the reactivity of radical polymerization is improved by incorporating the photosensitizer, thereby improving the mechanical strength and adhesion of the adhesive layer. The photosensitizer can be any compound having maximum absorption at wavelengths longer than 380 nm, and examples include carbonyl compounds, organosulfur compounds, persulfur compounds, redox compounds, azo and diazo compounds, halogen compounds, anthracene compounds, and photoreducible dyes.

[0076] In one embodiment of this application, an adhesive composition is provided in which, based on 100 parts by weight of the adhesive composition, the photoinitiator is contained in an amount of 0.1 parts by weight or more and 5 parts by weight or less, and the photosensitizer is contained in an amount of 0.1 parts by weight or more and 5 parts by weight or less.

[0077] In another embodiment, the adhesive composition may contain 0.1 parts by weight or more and 5 parts by weight or less of the photoinitiator, preferably 1 part by weight or more and 4 parts by weight or less, and more preferably 1.5 parts by weight or more and 3.5 parts by weight or less, based on 100 parts by weight of the adhesive composition.

[0078] In another embodiment, the adhesive composition may contain 0.1 parts by weight to 5 parts by weight, preferably 1 part by weight to 3 parts by weight, and more preferably 1.5 parts by weight to 2.5 parts by weight, based on 100 parts by weight of the adhesive composition.

[0079] In one embodiment of this application, the adhesive composition may further comprise at least one selected from the group consisting of a solvent, a dispersant, a thermal initiator, a crosslinking agent, and a tackifier.

[0080] According to one embodiment of this specification, the crosslinking agent is hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate having 2 to 14 ethylene groups, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, or 2-trisacryloyloxymethyl Polyhydric alcohols such as ethylphthalic acid, propylene glycol di(meth)acrylate with 2 to 14 propylene groups, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and mixtures of acidic derivatives of dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate (trade names: TO-2348, TO-2349 from Nippon Toagosei Co., Ltd.) are converted with α,β-unsaturated carboxylic acids. Compounds obtained by sterling; compounds obtained by adding (meth)acrylic acid to compounds containing a glycidyl group, such as trimethylolpropane triglycidyl ether acrylic acid adduct and bisphenol A diglycidyl ether acrylic acid adduct; ester compounds of compounds having a hydroxyl group or an ethylenically unsaturated bond, such as phthalate diesters of β-hydroxyethyl (meth)acrylate and toluene diisocyanate adduct of β-hydroxyethyl (meth)acrylate, with polyvalent carboxylic acids, or adducts with polyisocyanates; alkyl esters of (meth)acrylate, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; and 9,9'-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene may be included, but are not limited to, and general compounds known in the art may be used. Furthermore, the dispersant and thermal initiator may be those known in the industry.

[0081] Toluene may be used as the solvent, but the solvent is not limited to toluene, and any general organic solvent containing toluene may be used as long as it can dissolve the specific substance.

[0082] In one embodiment of this application, an adhesive film is provided that includes the adhesive composition or cured product thereof according to this application. The adhesive film may be laminated onto the base film during manufacturing. In one embodiment of this application, the adhesive film may contain the adhesive composition according to one embodiment of this application as is.

[0083] In one embodiment of this application, the adhesive sheet may include a cured product of an adhesive composition according to one embodiment of this application.

[0084] In one embodiment of this application, the base film may be selected from the group consisting of polyethylene terephthalate (PET), polyester, polycarbonate (PC), polyimide (PI), polyethylene terephthalate (PEN), polyether ether ketone (PEEK), polyarylate (PAR), polycycloolefin (PCO), polynorbornene, polyethersulfone (PES), and cycloolefin polymer (COP).

[0085] In another embodiment, the base film may be polyethylene terephthalate (PET).

[0086] In one embodiment of this application, the thickness of the base film may be 10 μm or more and 200 μm or less, preferably 15 μm or more and 100 μm or less, and more preferably 20 μm or more and 75 μm or less.

[0087] Furthermore, the base film is preferably transparent. Here, "transparent" means that the light transmittance of the base film is 80% or higher in the visible light spectrum (400-700 nm).

[0088] In one embodiment of this application, an adhesive film is provided which further includes an irregularly shaped film on one or both sides of the adhesive film.

[0089] The aforementioned release film may be a hydrophobic film, and refers to a transparent layer that adheres to one surface of the adhesive film as a protective layer for a very thin adhesive film. A film with excellent mechanical strength, thermal stability, moisture shielding properties, isotropy, etc. may be used. For example, acetate-based films such as triacetylcellulose (TAC), polyester-based films, polyethersulfone-based films, polycarbonate-based films, polyamide-based films, polyimide-based films, polyolefin-based films, cycloolefin-based films, polyurethane-based films, and acrylic resin films may be used, but the film is not limited to these as long as it is a commercially available silicone-treated release film.

[0090] In one embodiment of this application, the adhesive film is provided having a thickness of 0.1 μm or more and 300 μm or less. In another embodiment, the thickness of the adhesive film may be 3 μm or more and 100 μm or less, preferably 5 μm or more and 80 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0091] When the thickness of the adhesive film is within the aforementioned range, it exhibits excellent rework properties in the event of misapplication, and in particular, it has the characteristic of leaving no foreign matter behind when the adhesive film is removed.

[0092] In one embodiment of this application, the adhesive film may have a surface energy of 35 mN / m or less. In one embodiment of this application, the adhesive film may have a surface water contact angle of 70° or more.

[0093] In one embodiment of this application, the adhesive film may have a surface energy of 35 mN / m or less, 30 N / m or less, or 25 mN / m or less, and may also satisfy the range of a surface energy of 5 mN / m or more. In one embodiment of this application, the adhesive film may have a surface water contact angle of 70° or more, 100° or more, or 110° or more, and may satisfy the range of a surface water contact angle of 180° or less.

[0094] An adhesive film according to one embodiment of this application satisfies the aforementioned surface water contact angle and surface energy, and by including a UV-curing adhesive composition containing monofunctional and polyfunctional acrylates of a specific composition and content, it satisfies the aforementioned range and has the characteristic of having excellent wettability with a substrate.

[0095] In one embodiment of this application, a polarizing film is provided, comprising: a polarizer; a first adhesive layer and a second adhesive layer provided on both sides of the polarizer; a first transparent protective film provided on the side of the first adhesive layer opposite to the side in contact with the polarizer; and a second transparent protective film provided on the side of the second adhesive layer opposite to the side in contact with the polarizer, wherein the first adhesive layer and the second adhesive layer are adhesive films according to this application.

[0096] In this case, the polarizer is not particularly limited, and polarizers well known in the art, such as a film made of polyvinyl alcohol (PVA) containing iodine or a dichroic dye, are used.

[0097] A polarizer exhibits the property of being able to extract only light vibrating in one direction from incident light while vibrating in multiple directions. Such properties can be achieved by stretching iodine-absorbing PVA (polyvinyl alcohol) under high tension. For example, more specifically, a polarizer can be formed by a swelling step of immersing a PVA film in an aqueous solution to swell it, a dyeing step of the swollen PVA film with a dichroic substance that imparts polarizing properties, a stretching step of stretching the dyed PVA film to align the dichroic dye substance parallel to the stretching direction, and a complementary color step of correcting the color of the PVA film after the stretching step. However, the polarizing plate of the present invention is not limited to this.

[0098] One embodiment of this application provides a polarizing film in which the adhesive strength of the surface of the first adhesive layer in contact with the first transparent protective film and the adhesive strength of the surface of the second adhesive layer in contact with the second transparent protective film are 120 gf / inch or more.

[0099] In another embodiment, the adhesive strength of the surface of the first adhesive layer in contact with the first transparent protective film and the surface of the second adhesive layer in contact with the second transparent protective film may be 120 gf / inch or more, preferably 150 gf / inch or more, and may satisfy a range of 2,000 gf / inch or less, but the upper limit is not limited.

[0100] In other words, the first adhesive layer and the second adhesive layer containing the adhesive composition according to this application satisfy the aforementioned adhesive strength with the first transparent protective substrate and the second transparent protective substrate, and satisfy an adhesive strength above a certain range regardless of the type of transparent protective substrate, and have the characteristic that the adhesive film of this application can be used with polarizing films having various types of transparent protective substrates.

[0101] In one embodiment of this application, the first transparent protective film and the second transparent protective film have a moisture permeability of 150 g / m². 2 Transparent protective film with a moisture permeability of 150g / m² or less (less than 24h).2 It may include a transparent protective film with a 24-hour or longer lifespan; or a non-adherent transparent protective film.

[0102] In one embodiment of this application, the moisture permeability is 150 g / m². 2 Transparent protective films with a moisture permeability of 24 hours or less can be used without restriction as long as they meet the above-mentioned moisture permeability range, and may specifically include polyethylene terephthalate (PET) film, cycloolefin polymer (COP) film, or acrylic film.

[0103] In one embodiment of this application, the moisture permeability is 150 g / m². 2 Transparent protective films with a moisture permeability of 24 hours or more can be used without restriction as long as they meet the aforementioned moisture permeability range, and specifically, they may include triacetylcellulose (TAC) film.

[0104] In one embodiment of this application, the non-adherent transparent protective film may contain a monomer comprising an aliphatic ring containing a hydrophilic polar functional group. Specifically, the hydrophilic polar functional group may be a carboxyl group (-COOH).

[0105] In other words, the polarizing film according to this application uses a first protective film on the upper part of the polarizer and a second protective film on the lower part of the polarizer. Regardless of whether a poorly adhesive substrate, a moisture-permeable substrate, or a non-moisture-permeable substrate is used for the upper and lower parts, the adhesive composition according to this application has a predetermined composition and content, thereby having the characteristic of excellent adhesive strength as described above.

[0106] Figure 1 shows a laminated structure of a polarizing film according to one embodiment of the present application. Specifically, it can be seen that a first adhesive layer 4 and a second adhesive layer 2 are provided on both sides of the polarizer 3, and a first transparent protective film 5 and a second transparent protective film 1 are included on top of each. Figure 1 is merely one example, and the types of protective substrates that can be placed above and below the polarizer are not limited thereto.

[0107] In one embodiment of this application, a polarizing film is provided in which the first adhesive layer and the second adhesive layer are identical.

[0108] In other words, unlike conventional methods that use multiple types of adhesives even when using moisture-permeable, moisture-impermeable, and poorly adhesive substrates simultaneously in the polarizer, this method uses the same type of adhesive layer, resulting in superior productivity of the polarizing film and preventing increased costs due to adhesive replacement. Finally, the present invention provides a display device including the polarizing film relating to this application. [Examples]

[0109] The present application will be described in more detail below using examples relating to this application and comparative examples not relating to this application, but the scope of this application is not limited by the examples presented below.

[0110] <Example of experiment> Adhesive compositions having the composition and content shown in Table 1 below were prepared. Subsequently, the adhesive composition is applied to both sides of the polarizer (manufactured by Nippon Gosei Co., Ltd.), and a non-adherent film (Konica Corporation, Sanuqui Film) is used as the first transparent protective film, and Toyobo's PET film (moisture permeability <50g / m²) is used as the first transparent protective film. 2 After laminating the film (day) as a second transparent protective film, it was bonded by roll lamination.

[0111] Subsequently, ultraviolet light was irradiated onto the polarizing plate to cure the adhesive composition. The ultraviolet light source is not particularly limited, but low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc., which have an emission distribution of wavelengths of 400 nm or less were used.

[0112] The irradiation dose (cumulative light dose) is 2000 mJ / cm². 2To achieve this, the polarizer and the protective release film were bonded together by curing the polarizer adhesive composition by irradiating it with ultraviolet light at a wavelength of 365 nm. A polarizer sample was then manufactured by cutting it to a size of 2 cm wide x 15 cm long. In this process, the protective release film for each polarizer adhesive composition was pre-treated with KOH.

[0113] The polarizing film was stored at room temperature (20°C to 25°C, specifically 25°C) for 16 to 30 hours immediately after UV irradiation. The polarizing film was obtained upon completion of curing.

[0114] [Table 1]

[0115] In Table 1, the content may refer to the total content of the adhesive composition (the five types in Table 1). Specifically, in Table 1, the content of monofunctional cationic polymerizable monomers, difunctional cationic polymerizable monomers, and polyfunctional radical polymerizable monomers is shown based on 100 parts by weight of monomer, while the content of cationic photoinitiators and photosensitizers is shown based on 100 parts by weight of the total adhesive composition.

[0116] In Table 1 above, LD-111 (Hajin Chemtech) used as a monofunctional cationic polymerizable monomer is an aliphatic glycidyl ether (total number of carbon atoms 15-17), OXT212 (Toagosei Co., Ltd.) is 3-ethyl-3-[[(2-ethylhexyl)oxy]methyl]oxetane (total number of carbon atoms 13), LD221 (Hajin Chemtech) is 1,4-butanediol diglycidyl ether (Tg greater than 0°C), and OXT101 (Toagosei Co., Ltd.) is a monofunctional cationic polymerizable monomer with a Tg greater than 0°C.

[0117] In Table 1 above, Celloxide 2021P (Daicel Corporation), used as a difunctional cationic polymerizable monomer, is (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexyl carboxylate, and YDF-170 (National Highway Chemical Company) is a reaction product of formaldehyde and oligomer (with 1-chloro-2,3-epoxypropane and phenol).

[0118] In Table 1 above, M262 (Yonehara Shoji Co., Ltd.), used as a polyfunctional radical polymerizable monomer, is tricyclodecanedimethanol diacrylate; M222 (Yonehara Shoji Co., Ltd.) is dipropylene glycol diacrylate; M200 (Yonehara Shoji Co., Ltd.) is 1,6-hexanediol diacrylate; and M3130 (Yonehara Shoji Co., Ltd.) is trimethylolpropane ethoxylate triacrylate. In Table 1 above, IBOA (Yonehara Shoji Co., Ltd.) is isoboronyl acrylate, which is a monofunctional radical polymerizable monomer.

[0119] Omnicat 250 (IGM), used as an initiator in Table 1 above, is (4-methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate (1-)impropylene carbonate (in propylene carbonate).

[0120] In Table 1 above, DETX (LAMSON), used as a photosensitizer, is 2,4-diethylthioxanthone. In this case, the monomer may further contain other additives, and the amount of additives is not included in Table 1 above.

[0121] The adhesive films containing the adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated in Experimental Examples 1 and 2 below, and the results are shown in Table 2.

[0122] [Table 2]

[0123] <Experimental Example 1: Adhesive Force Experiment of Protective Film> The protective substrate for peeling was peeled at a peeling speed of 0.5 cm / sec for 3 cm or more, and the peeling force at this time was measured three times to calculate the average value. When measuring the peeling force, an XT Plus Texture Analyzer (manufactured by TA Co., Ltd.) was used. At this time, the peeling force ( gf / 25mm ) is 200 gf / 25mm or more is rated as ◎, 120 gf / 25mm or more and less than 200 gf / 25mm is rated as ○, 100 gf / 25mm or more and less than 120 gf / 25mm is rated as △, 100 gf / 25mm less than is rated as ×, and each was evaluated.

[0124] <Experimental Example 2: Curing Rate> The polarizing plate adhesive composition was cured by irradiating ultraviolet light with a wavelength of 365 nm so that the irradiation dose (integrated light amount) became 2000 mJ / cm 2 . Immediately after peeling the protective film, the cured coating film was rubbed by hand to check the presence or absence of the coating film being pushed.

[0125] When the curing rate was 10 seconds or less, it was rated as ◎, when it was more than 10 seconds and 20 seconds or less, it was rated as ○, when it was more than 20 seconds and 50 seconds or less, it was rated as △, and when it was more than 50 seconds, it was rated as ×, and each was evaluated.

[0126] As can be confirmed in Tables 1 and 2 above, the adhesive compositions according to Examples 1 to 4 necessarily contain five compositions and exhibit excellent adhesive force regardless of the moisture-permeable, non-moisture-permeable, and difficult-to-adhere substrates to be adhered. In particular, by including a specific composition, in addition to moisture-permeable or non-moisture-permeable substrates, the adhesive force with difficult-to-adhere substrates is extremely excellent. In the subsequent production of polarizing plates, it was confirmed that the adhesive composition according to the present application can be used regardless of the type of protective substrate, and has an advantageous feature for improving the yield and productivity.

[0127] In Comparative Examples 1 and 5, it was confirmed that when a monofunctional cationic polymerizable monomer with a glass transition temperature exceeding 0°C was used, the adhesion to the moisture-permeable protective substrate, which is a TAC substrate, was excellent, but the adhesion to the poorly adhering protective substrate was not ensured.

[0128] In the case of Comparative Example 2, the case does not include a cationic polymerizable monomer containing an aromatic ring, and in the case of Comparative Example 3, the case does not use a cationic polymerizable monomer containing an alicyclic ring. As can be seen in Table 2, in the case of Comparative Example 2 and Comparative Example 3, the adhesive strength to moisture-permeable and moisture-impermeable protective substrates was reduced, and in particular, it was confirmed that adhesive strength to poorly adhering protective substrates could not be ensured.

[0129] In the case of Comparative Example 4, it was confirmed that when a monofunctional radical polymerizable monomer was used instead of a polyfunctional radical polymerizable monomer, similar adhesion to the poorly adhering protective substrate was not ensured, and the curing speed also decreased.

[0130] In other words, the experiment confirmed that the adhesive film containing the adhesive composition according to the present invention can be used to bond polarizing plate protective films, and that it exhibits excellent adhesive strength regardless of the type of polarizing plate protective film, thereby simplifying the process and facilitating mass production. [Explanation of Symbols]

[0131] 1. Second transparent protective film 2 ···Second adhesive layer 3. Polarizer 4 ···First adhesive layer 5 ···First transparent protective film

Claims

1. Monofunctional cationic polymerizable monomers with a glass transition temperature (Tg) of 0°C or lower; A difunctional cationic polymerizable monomer consisting only of cationic polymerizable monomers containing alicyclic rings and cationic polymerizable monomers containing aromatic rings; Polyfunctional radical polymerizable monomers; Cationic photoinitiators; and Photosensitizer; A polarizing plate adhesive composition comprising: The cationic polymerizable monomer containing the alicyclic ring is a first epoxy monomer having two epoxy groups in its molecule, at least one of which is an alicyclic epoxy group. The aforementioned cationic polymerizable monomer containing the aromatic ring is a secondary epoxy monomer having two epoxy groups in its molecule, wherein the epoxy groups are non-alicyclic epoxy groups. The monofunctional cationic polymerizable monomer is included in an amount of 20 to 40 parts by weight, based on 100 parts by weight of the polarizing plate adhesive composition. The aforementioned bifunctional cationic polymerizable monomer is included in an amount of 40 parts by weight or more and 60 parts by weight or less, based on 100 parts by weight of the polarizing plate adhesive composition. The polyfunctional radical polymerizable monomer is included in an amount of 10 to 30 parts by weight, based on 100 parts by weight of the polarizing plate adhesive composition. The aforementioned polarizing plate adhesive composition comprises, based on 100 parts by weight of the polarizing plate adhesive composition, 0.1 parts by weight to 5 parts by weight of a cationic photoinitiator and 0.1 parts by weight to 5 parts by weight of a photosensitizer. The aforementioned polarizing plate adhesive composition contains 55 to 60 parts by weight of a cationic polymerizable monomer containing an alicyclic ring, based on 100 parts by weight of the aforementioned difunctional cationic polymerizable monomer. Adhesive composition for polarizing plates.

2. The adhesive composition for polarizing plates according to claim 1, wherein the monofunctional cationic polymerizable monomer comprises a monofunctional epoxy monomer having 8 to 20 carbon atoms; or a monofunctional oxetane monomer having 5 to 15 carbon atoms.

3. The adhesive composition for polarizing plates according to claim 1, wherein the polyfunctional radical polymerizable monomer comprises one or more selected from the group consisting of acrylates containing two functional groups and acrylates containing three or more functional groups.

4. An adhesive film comprising the polarizing plate adhesive composition according to any one of claims 1 to 3, or a cured product thereof.

5. The adhesive film according to claim 4, wherein the thickness of the adhesive film is 0.1 μm or more and 300 μm or less.

6. Polarizer; A first adhesive layer and a second adhesive layer provided on both sides of the polarizer; A first transparent protective film provided on the surface of the first adhesive layer opposite to the surface in contact with the polarizer; and A second transparent protective film provided on the side of the second adhesive layer opposite to the side in contact with the polarizer; A polarizing film containing, A polarizing film wherein the first adhesive layer and the second adhesive layer are adhesive films according to claim 4.

7. The polarizing film according to claim 6, wherein the first adhesive layer and the second adhesive layer are the same.

8. A display device comprising the polarizing film described in claim 6.

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