Adhesive films, optical films, and organic EL display devices

Abstract

To provide an adhesive film which is more excellent in low moisture permeability, ultraviolet absorbability, heat and humidity resistance and light resistance and to provide an adhesive film excellent in transparency, adhesiveness and step absorbing property (shape followability) when the adhesive film is used for an optical device with a step shape such as an organic EL display device.SOLUTION: There is provided an adhesive film which contains (A) a hydrogenated block copolymer, (B) an ultraviolet absorber and (C) an antioxidant, wherein the hydrogenated block copolymer (A) contains (a1) a polymer block containing an aromatic vinyl monomer unit and (a2) a polymer block containing a hydrogenated conjugated diene monomer unit and the ultraviolet absorber (B) has a Fedors SP value of 11.0 to 12.0 (cal / cm3)1 / 2 at 25°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to adhesive films, optical films, and organic EL display devices. [Background technology]

[0002] Organic electroluminescent (hereinafter sometimes abbreviated as organic EL) display devices are widely used in various applications, including smartphones. The organic EL elements contained in organic EL display devices are known to be susceptible to moisture and degrade due to moisture in the atmosphere. For this reason, the display panel of organic EL display devices is equipped with an optical film that has a barrier function, and the adhesive used to laminate the optical film is also required to be impermeable to moisture in the atmosphere (low moisture permeability).

[0003] Patent Document 1 discloses that an adhesive film using a sealing resin comprising a copolymer of a diene and an olefin compound containing one carbon-carbon double bond, and an adhesive composition comprising a specific polyfunctional active energy ray polymerizable compound, can effectively block moisture or oxygen from flowing into an organic electronic device from the outside, and possesses not only reliability under harsh conditions such as high temperature and high humidity, but also excellent optical properties.

[0004] Patent Document 2 discloses that a sealing film using an adhesive composition containing a polymer derived from butylene, having a Mooney viscosity (η*) of 5000 to 107 Pa·s measured by shear stress using an 8 mm diameter flat panel jig at a 5% strain, a frequency of 1 Hz, and a temperature in the range of 30°C to 150°C, can form a structure that effectively blocks moisture or oxygen from flowing into an organic electronic device from the outside, and possesses excellent processability in the panel manufacturing process and excellent heat resistance retention under high temperature and high humidity conditions.

[0005] Generally, organic light-emitting diode (OLED) displays are used in mobile devices such as smartphones used outdoors. The surface of the OLED display panel uses a circular polarizer to prevent reflection of ambient light. However, the circular polarizer also absorbs light from the OLED elements, so to maintain a certain brightness, the luminescence intensity of the OLED elements needs to be increased. This results in high power consumption for OLED displays. In recent years, there has been a growing demand for reduced power consumption in OLED displays, and OLED displays that do not use circular polarizers are highly anticipated. On the other hand, circular polarizers also play a role in absorbing light such as ultraviolet rays that enter the display panel of an organic EL display device from the outside. Therefore, if the circular polarizer is removed from the organic EL display device, the organic components of the display panel and the organic EL elements will be exposed to light such as ultraviolet rays from the outside, which may accelerate light-induced degradation in the organic EL display device. For this reason, there is a need to introduce a material that absorbs light such as ultraviolet rays in place of the circular polarizer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-513155 [Patent Document 2] Japanese Patent Publication No. 2019-194348 [Overview of the project] [Problems that the invention aims to solve]

[0007] Although the adhesive composition disclosed in Patent Document 1 is disclosed as being able to effectively block the intrusion of moisture, maintain reliability under high temperature and high humidity conditions, and have excellent optical properties, its ultraviolet transmittance and light resistance have not been considered. Therefore, when the adhesive composition disclosed in Patent Document 1 is used in an organic EL display device that does not use a circular polarizer, there is a risk of causing degradation of the organic EL display device due to light such as ultraviolet rays. Furthermore, while the composition disclosed in Patent Document 2 allows for the formation of a structure that can effectively block moisture or oxygen flowing into the organic EL device from the outside, and exhibits excellent heat resistance under high temperature and high humidity conditions, the effectiveness of the adhesive composition itself in effectively blocking moisture or oxygen, and the degradation of the organic EL display device due to light such as ultraviolet rays, have not been evaluated. Therefore, if the adhesive composition disclosed in Patent Document 2 is used in an organic EL display device that does not use a circular polarizing plate, there is a risk of causing degradation of the organic EL display device due to moisture in the atmosphere or light such as ultraviolet rays.

[0008] Therefore, the object of the present invention is to provide an adhesive film with excellent low moisture permeability, ultraviolet absorption, resistance to humid heat, and light resistance. Furthermore, the object is to provide an adhesive film with excellent transparency, adhesion, and step absorption (shape conformability) when used in optical devices having stepped shapes within the display surface, such as organic EL display devices. Moreover, the object is to provide an optical film and an organic EL display device using the adhesive film of the present invention. [Means for solving the problem]

[0009] The inventors conducted diligent research and discovered that an adhesive film containing a specific block copolymer, a specific ultraviolet absorber, and an antioxidant can solve the above problems, and thus completed the disclosed technology. Specifically, the disclosed technology is as follows.

[0010] According to one aspect of the disclosed technology, the invention comprises (A) a hydrogenated block copolymer, (B) an ultraviolet absorber, and (C) an antioxidant, wherein the (A) hydrogenated block copolymer comprises (a1) a polymer block containing aromatic vinyl monomer units and (a2) a polymer block containing hydrogenated conjugated diene monomer units, and the (B) ultraviolet absorber has a Fedors SP value of 11.0 to 12.0 (cal / cm²) at 25°C. 3 ) 1 / 2 An adhesive film characterized by the above can be provided. The content of the aforementioned (B) ultraviolet absorber is preferably 5 to 70 parts by mass per 100 parts by mass of the (A) hydrogenated block copolymer. The aforementioned adhesive film has an average UV transmittance of 10.0% or less at 380-400 nm when its thickness is 50 μm, and a water vapor transmittance of 100 g / m² at 40°C and 90% RH. 2 It is preferable that it be 24 hours or less. The adhesive film preferably has a haze value of 2.0% or less when its thickness is 50 μm. The adhesive film preferably has a storage modulus of 0.05 to 0.50 MPa at 25°C when the measurement frequency is 1 Hz. Preferably, the adhesive film has an average ultraviolet transmittance of 10.0% or less at 380-400 nm when stored for 1000 hours in an environment of 85°C and 85% RH, with a thickness of 50 μm. The aforementioned (B) UV absorber is preferably in liquid form at 23°C. The hydrogenated block copolymer (A) is preferably a hydrogenated styrene-based copolymer. The aforementioned (C) antioxidant is preferably a phenol compound. According to another aspect of the disclosed technology, an optical film including the adhesive film can be provided. According to another aspect of the disclosed technology, an organic EL display device including the adhesive film can be provided. [Effects of the Invention]

[0011] According to the disclosed technology, it is possible to provide an adhesive film with excellent low moisture permeability, ultraviolet absorption, humid heat resistance, and light resistance. Furthermore, when used in optical devices having stepped shapes such as organic EL display devices, it is possible to provide an adhesive film with excellent transparency, adhesion, and step absorption (shape conformability). Moreover, it is possible to provide an optical film and an organic EL display device using the adhesive film of the present invention. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the disclosed technology will be described in detail. In this specification, the notation "a~b" in the description of a numerical range indicates a≥b unless otherwise specified.

[0013] <<<Adhesive film>>> The adhesive film of the present disclosure contains (A) a hydrogenated block copolymer, (B) an ultraviolet absorber, and (C) an antioxidant.

[0014] <<Composition of the adhesive film>> <(A) Hydrogenated block copolymer> (A) The hydrogenated block copolymer is a copolymer containing (a1) a polymer block containing an aromatic vinyl monomer unit and (a2) a polymer block containing a hydrogenated conjugated diene monomer unit. Here, hydrogenation means that hydrogen is added to the unsaturated bonds of the polymer block containing the conjugated diene monomer unit contained in the block copolymer. For (A) the hydrogenated block copolymer, it is possible to use a block copolymer in which some or all of the unsaturated bonds are hydrogenated, but a block copolymer in which all of the unsaturated bonds are hydrogenated is preferably used. (A) The hydrogenated block copolymer can make the low moisture permeability and light resistance of the adhesive film of the present disclosure more excellent.

[0015] (A) The hydrogenated block copolymer contains (a1) a polymer block containing an aromatic vinyl monomer unit. The polymer block containing (a1) an aromatic vinyl monomer unit is not particularly limited, and examples thereof include those containing monomer units derived from styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc.

[0016] (A) The hydrogenated block copolymer contains a polymer block containing (a2) hydrogenated conjugated diene monomer units. The polymer block containing (a2) hydrogenated conjugated diene monomer units is not particularly limited, and examples thereof include those containing monomer units obtained by hydrogenating 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc.

[0017] (A) The hydrogenated block copolymer can be obtained, for example, by synthesizing a block copolymer containing (a1) a polymer block containing aromatic vinyl monomer units and a polymer block containing conjugated diene monomer units, and then hydrogenating the polymer block containing conjugated diene monomer units.

[0018] The method for synthesizing a block copolymer containing (a1) a polymer block containing aromatic vinyl monomer units and a polymer block containing conjugated diene monomer units is not particularly limited, and known methods can be used. Examples thereof include solution polymerization method, gas phase polymerization method, bulk polymerization method, etc.

[0019] The method for hydrogenating a block copolymer containing (a1) a polymer block containing aromatic vinyl monomer units and a polymer block containing conjugated diene monomer units is not particularly limited, and known methods can be used. Examples thereof include a method of reacting the block copolymer with hydrogen under hydrogen pressure of 20 to 150 °C and 0.1 to 10.0 MPa in the presence of a hydrogenation catalyst.

[0020] As the hydrogenation catalyst, for example, compounds containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, Pt atoms, etc. can be used. More specifically, metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, Re, etc.; Supported heterogeneous catalysts in which metals such as Pd, Ni, Pt, Rh, Ru, etc. are supported on carriers such as carbon, silica, alumina, diatomaceous earth, etc.; A homogeneous Ziegler-type catalyst combining an organic salt or acetylacetone salt of a metal element such as Ni or Co, with a reducing agent such as organoaluminum; Organometallic compounds or complexes such as Ru and Rh; Examples include fullerenes and carbon nanotubes that have absorbed hydrogen. These can be used individually or in combination in any ratio.

[0021] (A) As the hydrogenated block copolymer, hydrogenated styrene-based copolymers are preferred, and hydrogenated versions of triblock copolymers such as polystyrene-polybutadiene-polystyrene (SBS) block copolymer, polystyrene-polybutadiene-polystyrene-polybutadiene-polystyrene (SBSBS) copolymer, polystyrene-polyisoprene-polystyrene (SIS) copolymer, polystyrene-polyisoprene-polystyrene-polyisoprene-polystyrene (SISIS) copolymer, and block copolymers such as polystyrene-polyisoprene-polystyrene-polybutadiene-polystyrene (SISBS) copolymer, multiblock copolymer, tapered block copolymer, and star block copolymer can be used. Note that (A) the hydrogenated block copolymer may be linear or branched.

[0022] Furthermore, commercially available hydrogenated block copolymers (A) can also be used. Examples of commercially available hydrogenated block copolymers (A) include ToughTec® manufactured by Asahi Kasei Chemicals, Kraton® manufactured by Kraton, Septon® manufactured by Kuraray, and Dynalon manufactured by JSR.

[0023] (A) The weight-average molecular weight of the hydrogenated block copolymer can be 10,000 to 500,000, preferably 20,000 to 400,000, and more preferably 30,000 to 300,000. (A) When the weight-average molecular weight of the hydrogenated block copolymer is within this range, an adhesive film with excellent low moisture permeability, resistance to wet heat, and light resistance can be obtained, and an adhesive film with excellent adhesion and step absorption (shape conformability) can also be obtained.

[0024] (A) The weight-average molecular weight of the hydrogenated block copolymer is calculated based on the molecular weight in polystyrene terms, measured using gel permeation chromatography (GPC).

[0025] <(B) UV absorber> (B) The UV absorber has a Fedors SP value (solubility parameter) of 11.0-12.0 (cal / cm³) at 25°C. 3 ) 1 / 2 (B) When the Fedors SP value of the UV absorber at 25°C falls within the specified range, an adhesive film with superior transparency, low moisture permeability, UV absorption, and light resistance can be obtained.

[0026] (B) As the UV absorber, salicylic acid-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, triazine-based UV absorbers, cyanoacrylate-based UV absorbers, nickel-based UV absorbers, etc., can be used. These can be used individually or in combination in any ratio. Of these, benzotriazole-based UV absorbers and triazine-based UV absorbers are preferred in terms of transparency, low moisture permeability, UV absorption, and light resistance. Furthermore, (B) the UV absorber is preferably liquid at 23°C. By using such a (B) UV absorber, an adhesive film with superior transparency, low moisture permeability, UV absorption, and light resistance can be obtained.

[0027] <(C) Antioxidant> (C) Antioxidants that can be used include phenol compounds, sulfur compounds, phosphorus compounds, quinone compounds, and amine compounds. These can be used individually or in combination in any ratio. Examples of phenolic compounds include p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, Irganox 1010, Irganox 1330, Irganox 3114, Irganox 1035 (all manufactured by BASF Japan), Sumilizer MDP-S, and Sumilizer GA-80 (both manufactured by Sumitomo Chemical Co., Ltd.). Examples of sulfur compounds include 3,3'-thiodipropionate distearyl, Sumilizer TPL-R, Sumilizer TPM, Sumilizer TPS, Sumilizer MB, and Sumilizer TP-D (all manufactured by Sumitomo Chemical Co., Ltd.). Examples of phosphorus compounds include tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, poly(dipropylene glycol)phenyl phosphite, diphenylisodecyl phosphite, 2-ethylhexyl diphenyl phosphite, triphenyl phosphite, Irgafos168, Irgafos38 (all manufactured by BASF Japan), and Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.). Examples of quinone compounds include p-benzoquinone and 2-tert-butyl-1,4-benzoquinone. Examples of amine compounds include dimethylaniline and phenothiazine. Among these antioxidants, phenol compounds are preferred because they allow for the creation of adhesive films with excellent properties such as low moisture permeability, resistance to moist heat, light resistance, adhesion, and step absorption (shape conformability).

[0028] <Other ingredients> The adhesive film may contain other components besides those described above, as long as they do not impair the effects of the disclosed technology. Examples of other components include tackifiers, plasticizers, heat stabilizers, light stabilizers, crystal nucleating agents, impact modifiers, pigments, lubricants, antistatic agents, flame retardants, flame retardant aids, compatibilizers, coupling agents, crosslinking agents, and solvents. These can be used individually or in combination in any ratio. Of these, it is preferable to include tackifiers and plasticizers, and more preferable to use tackifiers and plasticizers in combination, as this allows for the creation of an adhesive film with excellent adhesion and step absorption (shape conformability).

[0029] Known tackifiers can be used, such as rosin compounds including natural rosin, modified rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, hydrogenated rosin, and pentaerythritol ester of hydrogenated rosin; Terpene compounds such as copolymers of natural terpenes, three-dimensional polymers of natural terpenes, aromatically modified terpene resins, hydrogenated derivatives of aromatically modified terpene resins, terpene phenol resins, hydrogenated derivatives of terpene phenol resins, terpene resins (monoterpenes, diterpenes, triterpenes, polypertenes, etc.), hydrogenated terpene resins, etc. Examples of petroleum hydrocarbon compounds include aliphatic petroleum hydrocarbon resins, hydrogenated derivatives of aliphatic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins, hydrogenated derivatives of aromatic petroleum hydrocarbon resins, dicyclopentadiene resins, hydrogenated derivatives of dicyclopentadiene resins, C5 / C9 copolymer resins, hydrogenated derivatives of C5 / C9 copolymer resins, cyclic aliphatic petroleum hydrocarbon resins, and hydrogenated derivatives of cyclic aliphatic petroleum hydrocarbon resins. These can be used individually or in combination in any ratio. Of these, petroleum hydrocarbon compounds are preferred, and aromatic petroleum hydrocarbon resins, hydrogenated derivatives of aromatic petroleum hydrocarbon resins, cyclic aliphatic petroleum hydrocarbon resins, and hydrogenated derivatives of cyclic aliphatic petroleum hydrocarbon resins are more preferred.

[0030] The softening point of the tackifier is not particularly limited, but for example, it can be 70 to 190°C, preferably 80 to 160°C, and more preferably 90 to 135°C. When the softening point of the tackifier is within this range, an adhesive film with excellent adhesion and step absorption (shape conformability) can be obtained. The softening point of the tackifier is measured based on the softening point test method (ring-ball method) specified in JIS K5902:1969 "Rosin".

[0031] The plasticizer can be any known material, such as thermoplastic resins like polyolefins, polyesters, and epoxy; softeners like paraffin oil, naphthenic process oils, and aromatic process oils; oligomers; oils like animal oils and vegetable oils; and petroleum fractions like kerosene, heavy oil, light oil, and naphtha. These can be used individually or in any combination in any ratio. Of these, thermoplastic resins are preferred because they are less likely to cause bleed-out, polyolefins are more preferred in terms of compatibility with (A) hydrogenated block copolymers, and liquid polyisobutylene and liquid polybutene are even more preferred. The weight-average molecular weight of the thermoplastic resin is not particularly limited, but for example, it can be 500 to 100,000, preferably 500 to 80,000, and more preferably 500 to 60,000.

[0032] <<Physical properties of adhesive film>> <Average UV transmittance in the 380-400nm range> When the thickness of the adhesive film is 50 μm, the average ultraviolet transmittance (hereinafter sometimes abbreviated as average ultraviolet transmittance) at 380-400 nm is preferably 10.0% or less, more preferably 9.0% or less, and even more preferably 8.5% or less. When the average ultraviolet transmittance of the adhesive film is within this range, the adhesive film absorbs ultraviolet light sufficiently, and when the adhesive film is used in an organic EL display device, it is possible to prevent degradation of the organic EL display device due to ultraviolet light.

[0033] The method for measuring the average ultraviolet transmittance of an adhesive film involves using a spectroscopic analyzer to measure the transmittance of light with a wavelength of 380-400 nm at 1 nm intervals, assuming the adhesive film has a thickness of 50 μm, and then calculating the average value of these measurements.

[0034] <Water vapor transmission rate at 40°C and 90%RH> The water vapor transmission rate of the adhesive film at 40°C and 90% RH (hereinafter sometimes abbreviated as water vapor transmission rate) is 100 g / m². 2 / 24 hours or less is preferable, 90g / m 2 / 24 hours or less is more preferable, 70g / m 2 / 24 hours or less is even more preferable. When the water vapor permeability of the adhesive film is within this range, the adhesive film has excellent low moisture permeability, and therefore, when the adhesive film is used in an organic EL display device, it is possible to prevent deterioration of the organic EL display device due to moisture in the atmosphere.

[0035] The water vapor permeability of the adhesive film is measured using a moisture vapor permeability meter in accordance with JIS Z0208:1976, under conditions of 40°C and 90% RH (Condition B). The adhesive film thickness is assumed to be 50 μm for measurement.

[0036] <Haze value> When the thickness of the adhesive film is 50 μm, the haze value (hereinafter sometimes abbreviated as haze value) is preferably 2.0% or less, and more preferably 1.5% or less. When the haze value of the adhesive film is within this range, the adhesive film has excellent transparency, and when the adhesive film is used in an organic EL display device, it is possible to make the display of the organic EL display device clearer.

[0037] The haze value of the adhesive film is measured using a haze meter with a thickness of 50 μm, in accordance with the method specified in JIS K7136:2000.

[0038] <Storage modulus> When the measurement frequency of the adhesive film is 1 Hz, the storage modulus at 25°C is preferably 0.05 to 0.50 MPa, and more preferably 0.05 to 0.30 MPa. When the storage modulus of the adhesive film is within this range, the adhesive film has excellent flexibility. Therefore, when the adhesive film is used in an organic EL display device, it absorbs the irregularities (step shapes) present in the organic EL display device and prevents irregularities from occurring on the display surface of the organic EL display device (in other words, it has step-following properties). Furthermore, since the adhesive film has excellent adhesion to various substrates such as optical films, when the adhesive film is used in an organic EL display device, it is possible to achieve excellent adhesion to components such as optical films, making it less likely for the optical film to lift or peel off.

[0039] The storage modulus of adhesive film is measured using a dynamic viscoelasticity measuring device, with a measurement frequency of 1 Hz and a measurement temperature of 25°C.

[0040] <Average UV transmittance after moist heat treatment> When the adhesive film is stored for 1000 hours at 85°C and 85%RH, the average ultraviolet transmittance at 380-400 nm (hereinafter sometimes abbreviated as the average ultraviolet transmittance after moist heat treatment), assuming a thickness of 50 μm, is preferably 10.0% or less, more preferably 9.0% or less, and even more preferably 8.5% or less. When the average ultraviolet transmittance of the adhesive film after moist heat treatment falls within this range, the adhesive film has superior moist heat resistance. Therefore, when the adhesive film is used in an organic EL display device, even when used in high-temperature, high-humidity environments such as outdoors, the adhesive film can sufficiently absorb ultraviolet rays, preventing degradation of the organic EL display device due to ultraviolet rays.

[0041] The method for measuring the average ultraviolet transmittance of an adhesive film after moist heat treatment involves storing the adhesive film, with a thickness of 50 μm, in an environment of 85°C and 85% RH for 1000 hours. Then, using a spectroscopic analyzer, the transmittance of light with wavelengths of 380-400 nm is measured at 1 nm intervals, and the average value is calculated.

[0042] <<Method for manufacturing adhesive film>> A predetermined amount of (A) hydrogenated block copolymer, (B) ultraviolet absorber, and (C) antioxidant is weighed and then stirred and mixed to prepare an adhesive film composition. At this time, if necessary, a predetermined amount of other components such as tackifiers and plasticizers are also mixed in the same manner. The mixing of each component can be carried out by dissolving in a solvent or under heating, if necessary.

[0043] The content of (A) hydrogenated block copolymer in the adhesive film composition is preferably 20 to 99% by mass, and more preferably 25 to 70% by mass, when the total solid content mass of the adhesive film composition is taken as 100% by mass. In this specification, the total solid content mass of the adhesive film composition means the mass when the adhesive film composition is completely dried (solvent removed).

[0044] The content of (B) ultraviolet absorber in the adhesive film composition is preferably 1 to 30.0% by mass, more preferably 3 to 25.0% by mass, and even more preferably 4.5 to 20.0% by mass, when the total solid content mass of the adhesive film composition is 100% by mass. Furthermore, when the content of (A) hydrogenated block copolymer is 100 parts by mass, the content of (B) ultraviolet absorber is preferably 5 to 70 parts by mass, and more preferably 10 to 60 parts by mass.

[0045] The content of (C) antioxidant in the adhesive film composition is preferably 0.01 to 3.0% by mass, more preferably 0.05 to 0.5% by mass, and even more preferably 0.08 to 0.3% by mass, when the total solid content mass of the adhesive film composition is 100% by mass. Furthermore, when the content of (A) hydrogenated block copolymer is 100 parts by mass, the content of (C) antioxidant is preferably 0.1 to 1.0 parts by mass, and more preferably 0.2 to 0.5 parts by mass.

[0046] When a tackifier is added to the adhesive film composition, the content of the tackifier is preferably 5 to 40.0% by mass, and more preferably 10 to 35.0% by mass, based on the total solid content mass of the adhesive film composition being 100% by mass. Furthermore, when the content of (A) hydrogenated block copolymer is 100 parts by mass, the content of the tackifier is preferably 10 to 120 parts by mass, and more preferably 20 to 100 parts by mass.

[0047] When a plasticizer is added to the adhesive film composition, the plasticizer content is preferably 5 to 40.0% by mass, and more preferably 10 to 35.0% by mass, based on the total solid content mass of the adhesive film composition being 100% by mass. Furthermore, when the content of (A) hydrogenated block copolymer is 100 parts by mass, the content of plasticizer is preferably 10 to 120 parts by mass, and more preferably 20 to 100 parts by mass.

[0048] Adhesive films can be manufactured, for example, by coating an adhesive film composition onto a release substrate, drying it as needed, and then laminating a protective film onto it.

[0049] The substrate is not particularly limited, but examples include polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyethylene film, polytetrafluoroethylene film, polypropylene film, paper, etc. Furthermore, by using optical films such as polarizing films, phase difference films, brightness enhancement films, color filters, light diffusion films, and viewing angle compensation films as the substrate, it can be used in liquid crystal displays and organic EL displays.

[0050] The protective film protects the surface of the adhesive film opposite to the substrate and is not particularly limited, but can be made of polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyethylene film, polytetrafluoroethylene film, polypropylene film, paper, etc. It is preferable to select a protective film in which the adhesion strength between the protective film and the adhesive film is lower than the adhesion strength between the substrate and the adhesive film. To make the adhesion strength between the protective film and the adhesive film lower than the adhesion strength between the substrate and the adhesive film, a protective film with a release treatment applied to its surface can be used.

[0051] The thickness of the adhesive film is not particularly limited, but can be 10 to 200 μm depending on the application. The thickness of the adhesive film can be adjusted, for example, by applying the adhesive film composition to a substrate and using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, or spray coater.

[0052] <<Applications of adhesive film>> The adhesive film can be laminated onto various films depending on the application. It is particularly suitable for fixing functional films used in the display sections of liquid crystal displays and organic EL displays, such as screen protection films, shatterproof films, polarizing films, phase difference films, brightness enhancement films, color filters, light diffusion films, and viewing angle compensation films. [Examples]

[0053] The disclosed technology will be described in more detail using examples, but the disclosed technology is not limited to these examples.

[0054] <<Making Adhesive Films>> According to the formulations of each raw material shown in Table 1, each raw material was mixed and stirred to dissolve in a solvent to prepare the adhesive film compositions of Examples 1-6 and Comparative Examples 1-4. The amounts of each raw material in Table 1 are shown in parts by mass. The obtained adhesive film compositions of each example and comparative example were applied onto a release PET film using a film applicator with a film thickness adjustment function so that the adhesive film thickness after solvent removal was 50 μm. The solvent components were dried and removed to form an adhesive film. A release PET film was laminated onto the adhesive film to obtain the double-sided release PET-backed adhesive films of each example and comparative example.

[0055] <Raw materials> (Hydrogen-added block copolymer) • Hydrogenated block copolymer 1: Septon 2002 (manufactured by Kuraray Co., Ltd., styrene-ethylene-propylene-styrene structure, weight-average molecular weight 40,000) • Hydrogenated block copolymer 2: Septon 2006 (manufactured by Kuraray Co., Ltd., styrene-ethylene-propylene-styrene structure, weight-average molecular weight 280,000) • Hydrogenated block copolymer 3: Septon 1020 (manufactured by Kuraray Co., Ltd., styrene-ethylene-propylene structure, weight-average molecular weight 85,000) (UV absorber) • UV absorber 1: Tinuvin 384 (BASF, benzotriazole-based UV absorber, liquid at 23°C, SP value 10.8) • UV absorber Tinuvin 109 (manufactured by BASF, benzotriazole-based UV absorber, liquid at 23°C, SP value 11.1) • UV absorber 3: Tinuvin477 (BASF, hydroxyphenyltriazine-based UV absorber, liquid at 23°C, SP value 11.4) • UV absorber 4: Seesorb107 (manufactured by Cipro Chemical Co., Ltd., benzophenone-based UV absorber, solid at 23°C, SP value 13.0) (Antioxidant) • Antioxidant 1: Irganox 1010 (manufactured by BASF, a phenolic antioxidant) (Adhesion agent) • Tackifier 1: Alcon P125 (manufactured by Arakawa Chemical Industries, Ltd., alicyclic saturated hydrocarbon resin, softening point 125±5℃) • Tackifier 2: FTR6100 (manufactured by Mitsui Chemicals, aromatic petroleum hydrocarbon resin, softening point 95°C) (Plasticizer) • Plasticizer 1: TETRAX 4T (manufactured by ENEOS, polyisobutylene, weight-average molecular weight 59,000) • Plasticizer 2: HV-100 (manufactured by ENEOS Corporation, polyisobutylene, weight-average molecular weight 1,100)

[0056] [Table 1]

[0057] <<Measurement and Evaluation>> Table 2 shows the measurement and evaluation results of each physical property of the adhesive films in each example and comparative example. <Average UV transmittance in the 380-400nm range> The average ultraviolet transmittance of the adhesive film was measured by the following method. For each example and comparative example, the double-sided release PET adhesive film was peeled off, and a 100 μm thick PET film (Toyobo Co., Ltd., A4360) was laminated to one main surface side of the adhesive film, and a 1.8 mm thick soda glass was laminated to the other main surface side of the adhesive film to create an adhesive film laminate. The obtained adhesive film laminate was irradiated with ultraviolet light from the main surface side of the PET film using a spectroscopic analyzer (Shimadzu Corporation, UV-2550), and the transmittance was measured at 1 nm intervals at wavelengths of 380 to 400 nm, and the average value of these values ​​was calculated.

[0058] <Water vapor transmission rate at 40°C and 90%RH> The water vapor permeability of the adhesive film was measured by the following method. For each example and comparative example, the double-sided release PET adhesive film was peeled off, leaving only the adhesive film. The water vapor permeability was measured using a moisture vapor permeability measuring device in accordance with JIS Z0208:1976 under conditions of 40°C and 90% RH (Condition B).

[0059] <Haze value> The haze value of the adhesive film was measured by the following method. For each example and comparative example of adhesive film laminates prepared for the measurement of average ultraviolet transmittance, the haze value was measured in accordance with JIS K7136:2000 by irradiating the main surface side of the PET film of the adhesive film laminate with light using a haze meter (NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0060] <Storage modulus at 25°C> The storage modulus of the adhesive film was measured by the following method. For each example and comparative example, the double-sided release PET adhesive film was peeled off, and multiple layers of the same adhesive film were stacked so that each adhesive film had a thickness of 1 mm. These layers were then punched out using an 8 mm diameter circular die to form test specimens. Using an 8 mm parallel plate, the storage modulus of the test specimens was measured using a dynamic viscoelasticity analyzer (HAAKE MARS, Thermo Fisher Scientific). The measurement conditions were a temperature of 25°C and a measurement frequency of 1 Hz.

[0061] <Average UV transmittance after moist heat treatment> The average ultraviolet transmittance of the adhesive film was measured by the following method. The adhesive film laminates of each example and comparative example prepared for the measurement of average ultraviolet transmittance were stored for 1000 hours in a constant temperature and humidity chamber set to 85°C and 85%RH, and then left at room temperature (25°C environment) for 24 hours. After that, ultraviolet light was irradiated from the main surface of the PET film of the adhesive film laminate using a spectroscopic analyzer, and the transmittance was measured at 1 nm intervals at wavelengths of 380 to 400 nm, and the average value of these values ​​was calculated.

[0062] <Exterior> The appearance of the adhesive film was assessed by the following method. For each example and comparative example prepared using the measurement of average ultraviolet transmittance, the appearance of the adhesive film laminate was visually inspected. The evaluation was conducted according to the following criteria. ○: No lifting, peeling, discoloration, and / or foaming are observed. ×: Lifting, peeling, discoloration, and / or foaming may be observed in part or in whole.

[0063] <Lightfastness Test> The light resistance test of the adhesive film was conducted by the following method. For the adhesive film with double-sided peelable PET in each example and each comparative example, the double-sided peelable PET films were peeled off. After laminating a PET film with a thickness of 100 μm (manufactured by Toyobo Co., Ltd., A4360) on one main surface side of the adhesive film, the other main surface side of the adhesive film was laminated on the entire display screen surface of a 7-inch organic EL display (manufactured by Midas Co., Ltd., MCT070PC12W800480LML) to obtain an organic EL display for evaluation. Subsequently, half of the display screen surface was covered with aluminum foil to create a light-shielding portion (the remaining half of the display screen surface other than the light-shielding portion was used as the irradiation portion). The organic EL display for evaluation having the light-shielding portion and the irradiation portion was placed in a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., ultraviolet fade meter U48, light source: carbon arc lamp), and ultraviolet rays (illuminance: 500 W / m 2 , BP temperature 63°C ± 3°C) were irradiated from the PET film side for 40 hours. After peeling off the aluminum foil of the light-shielding portion after the test, the organic EL display was white-displayed at the maximum luminance, and then the lighting state was visually confirmed. The evaluation was based on the following criteria. ○: No luminance difference or color difference can be confirmed between the irradiation portion and the light-shielding portion. ×: A luminance difference or color difference can be confirmed between the irradiation portion and the light-shielding portion.

[0064]

Table 2

[0065] From the above, the adhesive film of the embodiment of the present invention is excellent in low moisture permeability, ultraviolet absorption, heat and humidity resistance, and light resistance. Further, when used in an optical device having a step shape such as an organic EL display device, it can be made into an adhesive film excellent in transparency, adhesion, and step absorption (shape followability).

Claims

1. (A) A hydrogenated block copolymer, (B) an ultraviolet absorber, and (C) an antioxidant, The (A) hydrogenated block copolymer is a hydrogenated styrene-based copolymer and comprises (a1) a polymer block containing aromatic vinyl monomer units and (a2) a polymer block containing hydrogenated conjugated diene monomer units. The weight-average molecular weight of the hydrogenated block copolymer (A) is 30,000 to 300,000. The aforementioned (B) UV absorber has a Fedors SP value of 11.0 to 12.0 (cal / cm²) at 25°C. ３ ) １／２ And, The content of the ultraviolet absorber (B) is 5 to 70 parts by mass per 100 parts by mass of the hydrogenated block copolymer (A), The adhesive film is characterized in that the antioxidant (C) is a phenol compound.

2. The adhesive film according to claim 1, characterized in that the content of the antioxidant (C) is 0.1 to 1.0 parts by mass per 100 parts by mass of the hydrogenated block copolymer (A).

3. When the thickness is 50 μm, the average UV transmittance in the 380-400 nm range is 10.0% or less. The water vapor transmission rate at 40°C and 90% RH is 100 g / m³. ２ The adhesive film according to claim 1 or 2, characterized in that it is 24 hours or less.

4. An adhesive film according to any one of claims 1 to 3, characterized in that the haze value is 2.0% or less when the thickness is 50 μm.

5. The adhesive film according to any one of claims 1 to 4, characterized in that the storage modulus at 25°C when the measurement frequency is 1 Hz is 0.05 to 0.50 MPa.

6. An adhesive film according to any one of claims 1 to 5, characterized in that, after storage for 1000 hours at 85°C and 85% RH, the average ultraviolet transmittance at 380-400 nm is 10.0% or less when the thickness is 50 μm.

7. The adhesive film according to any one of claims 1 to 6, characterized in that the (B) ultraviolet absorber is liquid at 23°C.

8. An optical film comprising the adhesive film described in any one of claims 1 to 7.

9. An organic EL display device comprising an adhesive film according to any one of claims 1 to 7.

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