Adhesive optical film

Abstract

Provided is an adhesive optical film including a light-transmissive member, and an adhesive layer laminated on the light-transmissive member. The adhesive optical film has an adhesive surface composed of the adhesive layer. The adhesive layer has a refractive index higher than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

Description

Technical Field

[0001] This invention relates to adhesive optical films, and more specifically, to adhesive optical films comprising a light-transmitting member and an adhesive layer bonded to the light-transmitting member.

[0002] This application claims priority based on Japanese Patent Application No. 2020-052408 filed on March 24, 2020, Japanese Patent Application No. 2020-166427 filed on September 30, 2020, and Japanese Patent Application No. 2021-049060 filed on March 23, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Generally, adhesives (also known as pressure-sensitive adhesives, hereinafter the same) have the property of being a soft solid (viscoelastic) in a temperature range near room temperature and easily bonding to the adherends under pressure. Utilizing this property, adhesives are widely used in various industries, from household appliances to automobiles, various machinery, electrical devices, and electronic devices, for purposes of bonding, fixing, and protection. As an example of an adhesive's use, it can be cited for bonding polarizing films, retardation films, cover window components, and various other light-transmitting components to other components in display devices such as liquid crystal displays and organic EL displays. Patent documents 1 and 2 are cited as examples of technical documents relating to adhesives for optical components.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-169382

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-128732 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Patent documents 1 and 2 disclose adhesive compositions with (meth)acrylate polymers as the main component, and adhesives formed by crosslinking such adhesive compositions. The (meth)acrylate polymers contain monomers with multiple aromatic rings as monomer units, but no specific adhesives with a refractive index higher than 1.570 are disclosed. On the other hand, techniques are known to increase the refractive index by incorporating particles formed from high-refractive-index inorganic materials (e.g., zirconium oxide particles, titanium oxide particles, etc.) into a resin. However, adhesives incorporating inorganic particles have a trade-off between refractive index and adhesive properties (e.g., peel strength, flexibility), making them difficult to apply in the adhesive field. Especially for adhesives intended for optical applications, the influence on optical properties (e.g., total transmittance, haze, etc.) must be considered when incorporating inorganic particles. Therefore, it is difficult to achieve adhesive-type optical films that possess both a refractive index higher than 1.570 and good optical properties (transparency) on translucent components (e.g., optical films) and exhibit practical adhesive performance.

[0010] The present invention was made in view of the above-mentioned situation, and its object is to provide an adhesive optical film having an adhesive layer that has both high refractive index and good optical properties. Another object of the present invention is to provide an adhesive optical film with a release liner comprising the above-mentioned adhesive optical film.

[0011] Solution for solving the problem

[0012] According to the specification, an adhesive optical film is provided, comprising a light-transmitting member and an adhesive layer laminated on the light-transmitting member. The adhesive optical film has an adhesive surface formed by the adhesive layer. The adhesive layer has a refractive index higher than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less. In such an adhesive optical film, the light-transmitting member and the adhesive layer are integrated; therefore, by using this adhesive optical film, a structure formed by laminating the light-transmitting member and the substrate using the adhesive layer can be created efficiently and with good precision.

[0013] In some embodiments, the thickness of the adhesive layer is 5 μm or more. With an adhesive layer of this thickness, good adhesive properties are readily obtained. Furthermore, an adhesive layer of this thickness readily absorbs any unevenness that may exist on the surface of the adherend, thus achieving a good seal with the adherend. Therefore, it is possible to appropriately apply a high-refractive-index adhesive layer to the adherend.

[0014] In some embodiments, the peel strength (adhesive force) of the aforementioned adhesive optical film to the glass plate is 3 N / 25 mm or more. From the viewpoint of reliable bonding with the adhered object, such adhesive force is preferred.

[0015] In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is 100 nm or less. From the viewpoint of optical homogeneity, such a highly smooth adhesive surface is preferred. For example, in applications where light is extracted through the adhesive surface (such as in a light-emitting device where the adhesive layer is positioned closer to the viewpoint than the self-emitting element), uneven brightness caused by the surface condition of the adhesive layer can be suppressed.

[0016] In some embodiments, the water absorption rate of the adhesive layer is 1.0% or less. With an adhesive layer having a low water absorption rate, dimensional changes in the adhesive layer caused by variations in the amount of moisture in the adhesive layer can be suppressed. Therefore, warping of the adhesive optical film or the laminate containing the adhesive optical film can be suppressed.

[0017] In some embodiments, the aforementioned adhesive optical film is constructed as a laminate comprising the aforementioned adhesive layer and a resin film serving as the aforementioned light-transmitting member. By attaching this type of adhesive optical film to a substrate, a structure can be easily formed in which the substrate and the aforementioned light-transmitting member are laminated using a high-refractive-index adhesive layer.

[0018] Furthermore, according to this specification, an adhesive optical film with a release liner is provided, comprising any of the adhesive optical films disclosed herein, and a release liner disposed on the adhesive surface of the aforementioned adhesive optical film. The adhesive optical films disclosed herein can preferably be used in such a manner that they are manufactured, stored, distributed, processed, etc., as such an adhesive optical film with a release liner disposed on the adhesive surface, and the release liner is peeled off from the adhesive surface before the adhered object is bonded.

[0019] It should be noted that a technical solution formed by appropriately combining the various elements described in this specification may also be included within the scope of protection claimed in this patent application. Attached Figure Description

[0020] Figure 1 A cross-sectional view illustrating the structure of an adhesive optical film according to one embodiment is shown for illustrative purposes.

[0021] Figure 2 A cross-sectional view illustrating the structure of an optical laminate containing an adhesive optical film according to one embodiment is shown for illustrative purposes. Detailed Implementation

[0022] The following describes suitable embodiments of the present invention. For matters necessary for carrying out the present invention, other than those specifically mentioned in this specification, those skilled in the art can understand based on the teachings on carrying out the invention described in this specification and common general knowledge at the time of application. The present invention can be implemented based on the disclosures in this specification and common general knowledge in the art.

[0023] It should be noted that in the following figures, components / parts that perform the same function are sometimes given the same reference numerals for description, and repeated descriptions are sometimes omitted or simplified. Furthermore, the embodiments described in the figures are schematic for the purpose of clearly illustrating the invention and do not necessarily accurately represent the dimensions or scale of the actual product provided.

[0024] In this specification, a self-emissive element refers to a light-emitting element whose brightness can be controlled by the value of the current flowing through it. A self-emissive element can be composed of a single unit or an assembly. Specific examples of self-emissive elements include, but are not limited to, light-emitting diodes (LEDs) and organic ELs. When this specification refers to a light-emitting device, the light-emitting device may include such a self-emissive element as a constituent element. Examples of the aforementioned light-emitting devices include light source module devices (e.g., planar light-emitting modules) used for illumination, and display devices that form pixels, but are not limited to them.

[0025] <Example of the composition of adhesive optical thin films>

[0026] An example of a structure of the adhesive optical film disclosed in this specification is shown below. Figure 1 The adhesive optical film 1 is constructed in the form of a single-sided adhesive optical film (single-sided adhesive sheet), comprising: an adhesive layer 10 with a first surface 10A serving as the bonding surface (adhesive surface) to the adhered object, and a light-transmitting member 20 laminated on a second surface 10B of the adhesive layer 10. The second surface 10B of the adhesive layer 10 is bonded to the first surface (non-peelable surface) 20A of the light-transmitting member 20. The light-transmitting member 20 may be, for example, an optical resin film. The light-transmitting member 20 may be an optical film such as a polarizing plate. The adhesive optical film 1 before use (before bonding to the adhered object) may be, for example, as shown in the image. Figure 1 As shown, the adhesive optical film 50 is in the form of a release liner 30, where the adhesive surface 10A is protected by a release liner 30 that serves as a peelable surface (peelable surface) at least on the adhesive layer side. Alternatively, it can be in the form of a second surface 20B of the light-transmitting member 20 (the surface opposite to the first surface 20A, also referred to as the back surface) serving as the peelable surface, and the adhesive surface 10A is protected by being wound or laminated with the adhesive surface 10A abutting against the second surface 20B. The adhesive layer 10 can be a single-layer structure or a laminated structure consisting of two or more different sub-adhesive layers in direct contact (i.e., not separated by a layer of non-adhesive material) and laminated together.

[0027] The adhesive optical film disclosed herein can be a component of an optical laminate in which optical elements are bonded to at least one surface of an adhesive layer. For example, Figure 1 The adhesive optical film 1 shown can be as follows: Figure 2The optical laminate 100, shown, has an optical component 70 bonded to its first surface 10A of the adhesive layer 10. The optical component can be, for example, a glass plate, a resin film, or a metal plate. Furthermore, in Figure 1 In the adhesive optical film 1 shown, when the light-transmitting member 20 is an optical member such as an optical film, the adhesive optical film 1 can be regarded as an optical laminate in which an optical member is bonded to the second surface 10B of the adhesive layer 10.

[0028] Furthermore, although not specifically illustrated, the adhesive optical film disclosed herein can also be in the form of a double-sided adhesive optical film. This double-sided adhesive optical film includes light-transmitting members with a first and a second surface that are non-peelable, a first adhesive layer fixedly laminated to the first surface, and a second adhesive layer fixedly laminated to the second surface. Examples of such a double-sided adhesive optical film (hereinafter also referred to as a double-sided adhesive optical film) can be exemplified as follows: Figure 1 In the illustrated adhesive optical film (single-sided adhesive sheet) 1, the second surface 20B of the light-transmitting member 20 is a non-peelable surface, and a second adhesive layer is provided on the second surface 20B. The second surface of the second adhesive layer is bonded to the second surface 20B of the light-transmitting member 20, and the first surface of the second adhesive layer (the surface opposite to the second surface) becomes the second adhesive surface of the double-sided adhesive optical film. The composition of the adhesive constituting the second adhesive layer can be the same as or different from the composition of the adhesive constituting the first adhesive layer. Before use, the double-sided adhesive optical film may be in the form where the first adhesive surface and the second adhesive surface are protected by a release liner.

[0029] It should be noted that the adhesive optical film disclosed herein can be in roll form or in single sheet form. Alternatively, it can be an adhesive optical film that has been further processed into various shapes.

[0030] <Properties of Adhesive Layers>

[0031] (Refractive index)

[0032] The adhesive optical film disclosed herein has an adhesive layer with a refractive index higher than 1.570. This adhesive layer can be achieved, for example, by using an adhesive with a refractive index higher than 1.570 to form at least one surface (adhesive surface) of the adhesive layer. According to the technology disclosed herein, an adhesive with a refractive index higher than 1.570, an adhesive composition capable of forming the adhesive, and an adhesive optical film comprising the aforementioned adhesive can be provided.

[0033] It should be noted that in this specification, the refractive index of the adhesive refers to the refractive index of the surface (bonding surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, the model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent can be used. As the measurement sample, an adhesive layer formed from the adhesive to be evaluated can be used. Specifically, the refractive index of the adhesive can be measured by the method described in the following examples. For example, the refractive index of the adhesive can be adjusted by its composition (such as the composition of the monomer components constituting the base polymer, additives used as required, etc.).

[0034] In some embodiments, the refractive index of the above-mentioned adhesive can preferably be 1.580 or more, more preferably 1.585 or more, and further preferably 1.590 or more (such as 1.595 or more). With an adhesive having this refractive index, the behavior of light passing through the adhesive can be effectively controlled based on the relative refractive index relationship between the adhesive and the adherend. In some embodiments of the adhesives disclosed herein, the refractive index of the adhesive can, for example, be 1.600 or more, or higher than 1.600, 1.605 or more, or higher than 1.605, or 1.610 or more, or higher than 1.610. The preferred upper limit of the refractive index of the adhesive can vary depending on the refractive index of the adherend, etc., and is therefore not limited to a specific range. In some embodiments, considering the balance with bonding properties and transparency, the refractive index of the adhesive can, for example, be 1.700 or less, can be 1.670 or less, or can be 1.650 or less.

[0035] When the adhesive optical film disclosed herein is in the form of a double-sided adhesive optical film with one surface being the first bonding surface and the other surface being the second bonding surface, at least the first bonding surface needs to satisfy any of the above refractive indices, and the refractive index of the second bonding surface is not particularly limited.

[0036] In some embodiments, the refractive index n2 of the second bonding surface can be approximately the same as the refractive index n1 of the first bonding surface. More specifically, the absolute value of the difference in refractive indices between the two bonding surfaces, that is, |n1 - n2|, can, for example, be less than 0.05, or less than 0.03, or less than 0.01. The lower limit of |n1 - n2| can be 0.00, or can be greater than 0.00. The relative relationship between the refractive indices of the two bonding surfaces can be n1 > n2, can be n1 < n2, or can be n1 = n2.

[0037] In other methods, the difference between the refractive index n1 of the first adhesive surface and the refractive index n2 of the second adhesive surface of the double-sided adhesive optical film, i.e., n1-n2, can be greater than 0.00, greater than 0.01, greater than 0.03, greater than 0.05, greater than 0.10, greater than 0.15, greater than 0.20, or greater than 0.25. The relationship between n1 and n2 can also be reversed. For example, a double-sided adhesive optical film with different refractive indices on the first and second adhesive surfaces can be achieved by laminating first and second adhesive layers with different refractive indices on the first and second surfaces of a light-transmitting component.

[0038] (Total light transmittance)

[0039] The adhesive optical film disclosed herein includes an adhesive layer having the aforementioned high refractive index and a total transmittance of 86% or more. In some embodiments, the total transmittance of the adhesive layer is preferably 88% or more, more preferably 90% or more (e.g., higher than 90.0%), and can be 90.5% or more, 93% or more, or 95% or more. The upper limit of the total transmittance is theoretically the value obtained by subtracting the light loss (Fresnel loss) caused by reflection at the air interface from 100%, and practically it can be about 98% or less, about 96% or less, or about 95% or less. In some embodiments, considering the refractive index and adhesive properties, the total transmittance of the adhesive layer can be about 94% or less, about 93% or less, or about 92% or less. The total transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. As a transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used. More specifically, the total light transmittance of the adhesive layer can be measured, for example, according to the embodiments described later. The total light transmittance of the adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the adhesive layer.

[0040] When the adhesive optical film disclosed herein is a double-sided adhesive optical film in which a first adhesive layer and a second adhesive layer are fixedly laminated on the first and second surfaces of a light-transmitting member, at least the first adhesive layer needs to satisfy any of the aforementioned total transmittance, and the total transmittance of the second adhesive layer is not particularly limited. In the usage mode where light passes through the thickness direction of the adhesive optical film, it is preferable that the total transmittance of the second adhesive layer satisfies any of the aforementioned total transmittance of the first adhesive layer. The relative relationship of the total transmittance of the two adhesive layers can be that the first adhesive layer > the second adhesive layer, the first adhesive layer < the second adhesive layer, or the first adhesive layer = the second adhesive layer.

[0041] (Haze value)

[0042] The adhesive optical film disclosed herein includes an adhesive layer having the aforementioned high refractive index and a haze value of 3.0% or less. In some embodiments, the haze value of the adhesive layer is preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.9% or less, and can be 0.8% or less, 0.5% or less, or 0.3% or less. There is no particular limitation on the lower limit of the haze value of the adhesive layer; from the viewpoint of improving transparency, a lower haze value is more preferred. On the other hand, in some embodiments, considering the refractive index and adhesive properties, the haze value can be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more.

[0043] Here, "haze value" refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the object being measured. It is also called turbidity. The haze value can be expressed by the following formula.

[0044] Th(%)=Td / Tt×100

[0045] In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total transmittance. The haze value can be measured according to the method described in the examples below. The haze value of the adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the adhesive layer.

[0046] When the adhesive optical film disclosed herein is a double-sided adhesive optical film in which a first adhesive layer and a second adhesive layer are fixedly laminated on the first and second surfaces of a light-transmitting member, at least the first adhesive layer needs to satisfy any of the aforementioned haze values, while the haze value of the second adhesive layer is not particularly limited. In the application mode where light passes through the thickness direction of the adhesive optical film, it is preferable that the haze value of the second adhesive layer satisfies any of the aforementioned haze values ​​of the first adhesive layer. The relative relationship between the haze values ​​of the two adhesive layers can be that the first adhesive layer > the second adhesive layer, the first adhesive layer < the second adhesive layer, or the first adhesive layer = the second adhesive layer.

[0047] (Surface smoothness of the adhesive surface)

[0048] In some of the adhesive optical films disclosed herein, the adhesive surface of the adhesive optical film preferably has high surface smoothness.

[0049] For example, the arithmetic mean roughness Ra of the aforementioned adhesive surface is preferably limited to a predetermined value or less. A configuration with an adhesive surface designed to have a low arithmetic mean roughness Ra is preferred from the viewpoint of optical homogeneity. By limiting the arithmetic mean roughness Ra, for example in applications where light is extracted through the adhesive surface (e.g., in a light-emitting device where the adhesive layer is positioned closer to the viewpoint than the self-emitting element), it is possible to suppress brightness unevenness caused by the surface condition of the adhesive layer. A low arithmetic mean roughness Ra of the adhesive surface is also advantageous for suppressing optical distortion, and the suppression of optical distortion also contributes to improving optical homogeneity. In a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, it is preferable that the arithmetic mean roughness Ra of at least the first adhesive surface is limited to a predetermined value or less, and more preferably that the arithmetic mean roughness Ra of both adhesive surfaces is limited to a predetermined value or less. By making each adhesive surface of the double-sided adhesive optical film have high surface smoothness, it is preferable to achieve adhesion with excellent optical homogeneity.

[0050] In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is preferably about 70 nm or less, more preferably about 65 nm or less, even more preferably about 55 nm or less, and may be less than 50 nm, less than 45 nm, or less than 40 nm. From the viewpoint of production efficiency, in some embodiments, the arithmetic mean roughness Ra of the adhesive surface may be, for example, about 10 nm or more, about 20 nm or more, or about 30 nm or more (e.g., about 40 nm or more). In the case where the adhesive optical film has a first adhesive surface and a second adhesive surface, the arithmetic mean roughness Ra of the first adhesive surface and the arithmetic mean roughness Ra of the second adhesive surface may be the same or different.

[0051] Furthermore, for example, the maximum height Rz of the aforementioned adhesive surface is preferably limited to a predetermined value or less. A configuration with an adhesive surface designed to have a low maximum height Rz is preferred from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example in the method of extracting light through the aforementioned adhesive surface as described above, it is possible to suppress the occurrence of brightness unevenness caused by the surface state of the adhesive layer. A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion. In a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, it is preferable that at least the maximum height Rz of the first adhesive surface is limited to a predetermined value or less, and more preferably that the maximum height Rz of both adhesive surfaces is limited to a predetermined value or less. By making each adhesive surface of the double-sided adhesive optical film have high surface smoothness, it is preferable to achieve adhesion with excellent optical homogeneity.

[0052] In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600 nm or less, more preferably about 500 nm or less, even more preferably about 450 nm or less, particularly preferably about 400 nm or less, and may be less than 350 nm, less than 300 nm, or less than 250 nm. From the viewpoint of production efficiency, in some embodiments, the maximum height Rz of the adhesive surface may be, for example, about 10 nm or more, about 50 nm or more, about 100 nm or more, or about 200 nm or more. In the form of an adhesive optical film having a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be the same or different.

[0053] The arithmetic mean roughness Ra and maximum height Rz of the bonding surface are measured using a non-contact surface roughness measuring device. As a non-contact surface roughness measuring device, an optical interferometry surface roughness measuring device can be used, for example, a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO Corporation) or its equivalent. Specific measurement operations and conditions can be set according to the measurement conditions described in the embodiments described later, or in a manner that yields results equivalent to or corresponding to those obtained under those measurement conditions.

[0054] The arithmetic mean roughness Ra and maximum height Rz of the adhesive surface can be adjusted by the composition and properties (viscosity, leveling properties, etc.) of the adhesive composition used in the formation of the adhesive layer, and the properties of the surface of the release liner protecting the adhesive surface (release surface).

[0055] (Water absorption rate)

[0056] In some embodiments of the adhesive optical film disclosed herein, the water absorption rate of the adhesive layer constituting the adhesive optical film is preferably limited to a predetermined value or less. For example, it is preferable to satisfy the aforementioned refractive index, total transmittance, and haze values, and the water absorption rate is limited to a predetermined value or less. By limiting the water absorption rate of the adhesive layer, there is a tendency to suppress dimensional changes in the adhesive layer caused by variations in the amount of moisture in the adhesive layer (e.g., absorption and release of moisture such as humidity in the environment). As a result, warping of the adhesive optical film or the optical laminate containing the adhesive optical film caused by inconsistencies in dimensional changes between the adhesive layer and adjacent layers (which may be light-transmitting components, release liner, adhered materials, etc.) can be suppressed. From the viewpoint of maintaining the flatness, transparency, refractive index, etc., of the adhesive layer at a certain level, it is also preferable to suppress variations in the amount of moisture in the adhesive layer. In addition, adhesive layers with low water absorption rates are suitable for use as adhesive optical films in components or articles containing moisture-sensitive elements, such as organic EL elements, because they do not easily absorb moisture.

[0057] In some embodiments, a water absorption rate of the adhesive layer of about 1.0% or less is suitable, preferably 0.7% or less, more preferably 0.5% or less (e.g., less than 0.5%), and can be 0.4% or less, 0.3% or less, or 0.2% or less. There is no particular limitation on the lower limit of the water absorption rate of the adhesive layer; from a practical point of view, considering both adhesive properties, it can be, for example, 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, or 0.25% or more. In the form of a double-sided adhesive optical film having a first adhesive layer and a second adhesive layer, it is preferable that at least the water absorption rate of the first adhesive layer is limited to a specified value or less. From the viewpoint of obtaining higher performance, it is more preferable that the water absorption rates of both the first and second adhesive layers are limited to specified values ​​or less.

[0058] It should be noted that the water absorption rate (also known as moisture content) of the adhesive layer is determined by the following method. The same method can also be used in the examples described later.

[0059] [Moisture content determination]

[0060] Cut a 4cm x 5cm (area: 20cm²) section from the adhesive layer of the object being evaluated, along with two release liner sheets placed on one and the other sides. 2 The adhesive layer was then sized such that the release liner on one side was removed and adhered to a pre-weighed aluminum foil. Next, the release liner on the other side of the adhesive layer was removed, and the sample was immersed in a constant temperature and humidity bath at 60°C and 90% relative humidity for 72 hours. The resulting test piece, consisting of the adhesive layer and aluminum foil, was weighed and its moisture content was determined using a moisture meter (Mitsubishi Chemical Analytech CA-200) equipped with a heating vaporization device (Mitsubishi Chemical Analytech VA-200) under the following conditions via Karl Fischer electrostatic titration.

[0061] Anode solution: AQUAMICRON AKX (manufactured by Mitsubishi Chemical)

[0062] Cathodic solution: AQUAMICRON CXU (manufactured by Mitsubishi Chemical)

[0063] Heating and vaporization temperature: 150℃

[0064] (Gel ratio)

[0065] The gelation rate of the adhesive layer is appropriately set according to the intended use and method of application, and is not limited to a specific range. For example, a gelation rate of about 99% or less, or about 97% or less, is suitable. From the viewpoint of easily and appropriately balancing high refractive index and adhesive properties, in some preferred embodiments, the gelation rate is about 95% or less, and more preferably about 92% or less (e.g., about 90% or less). From the viewpoint of appropriately accommodating the unevenness that may exist on the surface of the adhered object (e.g., uneven structures provided in a light-emitting device for the purpose of improving light extraction efficiency) and achieving good adhesion, a gelation rate that is not too high is also preferred. In some embodiments, the gelation rate may be about 88% or less, about 75% or less, or about 65% or less. Furthermore, from the viewpoint of imparting appropriate cohesion to the adhesive and appropriately exhibiting adhesive properties, a gelation rate of the adhesive layer of, for example, about 10% or more, about 20% or more, or about 30% or more, is suitable. From the viewpoint of the adhesive layer's resistance to deformation (preventing overflow due to pressure, air bubbles caused by the incorporation of foreign matter, etc.), the gelation rate is preferably about 30% or more, more preferably about 40% or more, and can be about 45% or more, about 50% or more, about 65% or more, or about 75% or more. The gelation rate can be adjusted by the molecular weight, molecular structure, concentration, and degree of crosslinking of the base polymer. The gelation rate is measured by the following method.

[0066] [Determination of gelation rate]

[0067] A specified amount of adhesive sample (weight Wg1) was wrapped in a purse-shaped pouch using a porous polytetrafluoroethylene membrane (weight Wg2) with an average pore size of 0.2 μm, and the opening was secured with kite string (weight Wg3). The porous polytetrafluoroethylene (PTFE) membrane used was the product "NITOFLON (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent product available from Nitto Denko Corporation.

[0068] The package was immersed in a sufficient amount of ethyl acetate and kept at room temperature (typically 23°C) for 7 days to allow only the sol component of the adhesive to dissolve to the outside of the membrane. The package was then removed, and the ethyl acetate adhering to its outer surface was wiped off. The package was then dried at 130°C for 2 hours, and its weight (Wg4) was measured. The gelation rate of the adhesive layer was calculated by substituting the values ​​into the following formula.

[0069] Gelation rate (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0070] In the form of a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, the aforementioned gelation rate can be applied at least to the adhesive layer constituting the first adhesive surface, and preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The gelation rates of the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface can be the same or different.

[0071] (Storage modulus G')

[0072] In the adhesive optical film disclosed herein, the storage modulus G' (hereinafter also referred to as "storage modulus G'(25)") of the adhesive constituting the adhesive layer at 25°C can be appropriately set according to the purpose of use, method of use, etc., and is not limited to a specific range. The storage modulus G'(25) of the adhesive can be, for example, about 700 kPa or less. In some embodiments, from the viewpoint of ease of adhesion to the adhered object, it is advantageous for the storage modulus G'(25) of the adhesive to be about 600 kPa or less, preferably 500 kPa or less, and more preferably 400 kPa or less (e.g., 350 kPa or less). In some embodiments, from the viewpoint of improving the flexibility of the adhesive in the room temperature region (e.g., 25°C) and making it easier to adhere to the adhered object, it is advantageous for the storage modulus G'(25) of the adhesive to be about 330 kPa or less, preferably 300 kPa or less. In some approaches that prioritize adhesion and flexibility in the room temperature range, the storage modulus G'(25) of the adhesive can be, for example, below 270 kPa or below 250 kPa, below 200 kPa is advantageous, preferably below 180 kPa, and more preferably below 160 kPa (e.g., below 140 kPa). In some approaches, the storage modulus G'(25) of the adhesive can be below 100 kPa or below 90 kPa. There is no particular limitation on the lower limit of the storage modulus G'(25) of the adhesive; from the viewpoint of processability and handling, it can be, for example, above 30 kPa, above 50 kPa, or above 70 kPa. In some approaches, considering the high refractive index, the storage modulus G'(25) can be above 100 kPa, above 150 kPa, above 200 kPa, above 250 kPa, or above 300 kPa.

[0073] In the adhesive optical films disclosed herein, the storage modulus G' (hereinafter also referred to as "storage modulus G'(50)") of the adhesive constituting the adhesive layer at 50°C is not particularly limited, and may be, for example, less than 100 kPa. In some embodiments, a storage modulus G'(50) less than 60 kPa is appropriate, preferably less than 40 kPa, and more preferably less than 38 kPa (e.g., less than 36 kPa). The adhesive with such a limited storage modulus G'(50) can be readily improved to improve the adhesion to the adhered object by appropriate heating as needed, thereby improving the bonding strength of the adhered object. There is no particular limitation on the lower limit of the storage modulus G'(50) of the adhesive. In some embodiments, from the viewpoint of the heat resistance properties of the adhesive, the storage modulus G'(50) may be, for example, more than 10 kPa, more than 15 kPa, more than 20 kPa, or more than 23 kPa.

[0074] In some of the adhesive optical films disclosed herein, the adhesive constituting the adhesive layer preferably satisfies at least one of the following conditions:

[0075] (a) The energy storage modulus G'(25) at 25°C is 350 kPa or less (preferably less than 200 kPa, for example, less than 180 kPa); and

[0076] (b) The energy storage modulus G'(50) at 50°C is less than 60 kPa (preferably less than 50 kPa, more preferably less than 40 kPa, for example less than 38 kPa).

[0077] Adhesives that at least satisfy condition (a) above are preferred from the viewpoint of adhesion to the adherend at room temperature (e.g., 25°C). Adhesives that at least satisfy condition (b) above are preferred because their adhesion to the adherend can be easily improved by heating to a temperature slightly higher than room temperature. For adhesives that do not satisfy condition (a) above but satisfy condition (b) above, they have good reworkability (re-adhesion) at the initial bonding stage at room temperature and can be used as heat-activated adhesives that can effectively improve their peel strength from the adherend by heating to a temperature slightly higher than room temperature. The aforementioned heat activation can be performed by heating the adhesive to a temperature slightly higher than room temperature when bonding the adherend. The aforementioned temperature slightly higher than room temperature is, for example, about 60°C or less, preferably about 55°C or less (e.g., about 50°C or less).

[0078] In some embodiments of the adhesive-type optical thin film disclosed herein, the ratio of the storage modulus G'(50) [kPa] of the adhesive constituting the adhesive layer to the storage modulus G'(25) [kPa], i.e., the storage modulus ratio G'(50) / G'(25), is, for example, 70% or less, or 40% or less, or 30% or less, or 20% or less. Adhesives with a small G'(50) / G'(25) ratio are suitable for use as the aforementioned heat-activated adhesives. There is no particular limitation on the lower limit of G'(50) / G'(25). For example, G'(50) / G'(25) is 5% or more, and from the viewpoint of the heat resistance properties of the adhesive, it is preferably 10% or more, or 12% or more, or 15% or more.

[0079] Storage moduli G'(25) and G'(50) can be determined by dynamic viscoelasticity measurement, and G'(50) / G'(25) can be calculated from the results. Dynamic viscoelasticity measurement can be performed using a commercially available dynamic viscoelasticity measuring device by conventional methods, such as the "Advanced Rhenometric Expansion System (ARES)" or its equivalent manufactured by TA Instruments, under the following measurement conditions. As the sample for measurement, a sample with a thickness of approximately 1.5 mm is prepared by laminating the adhesive layer of the object being evaluated as needed.

[0080] [Measurement Conditions]

[0081] Deformation mode: Torsion

[0082] Measurement frequency: 1Hz

[0083] Heating rate: 5℃ / minute

[0084] Shape: Parallel plate

[0085] The storage modulus G'(25), G'(50), and storage modulus ratio of the adhesive layer can be adjusted by selecting the composition of the monomer components of the base polymer constituting the adhesive (e.g., the type and amount of monomer (m1), whether or not a crosslinking agent is used, the type and amount used, the refractive index enhancer described later, the plasticizer, the type and amount used, etc. For example, as monomer (m1), based on using the first monomer as the main component of the first monomer (m1), by using a second monomer with a different chemical structure from the first monomer in combination with the first monomer in a smaller amount, G'(50) and G'(50) / G'(25) can be reduced based on the case where the first monomer is used alone as monomer (m1).

[0086] In the form of a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, the aforementioned storage modulus G'(25), G'(50), and storage modulus ratio are applied to at least the adhesive layer constituting the first adhesive surface, preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The storage modulus G' of the adhesive layer constituting the first adhesive surface and the storage modulus G' of the adhesive layer constituting the second adhesive surface may be the same or different.

[0087] In some embodiments of the technology disclosed herein, the peak temperature of the adhesive constituting the adhesive layer's tanδ is preferably above approximately -50°C, and more preferably below approximately 50°C. Here, the adhesive's tanδ (loss tangent) refers to the ratio of the adhesive's loss modulus G” to its storage modulus G'. That is, tanδ = G” / G'. The adhesive's tanδ can be determined as follows: A disc-shaped adhesive sample with a thickness of approximately 2 mm and a diameter of 7.9 mm is held between parallel plates. Using a viscoelastic testing apparatus, a shear strain at a frequency of 1 Hz is applied, and a temperature dispersion test of the adhesive is conducted in shear mode under conditions of a measurement temperature range of -60°C to 60°C and a heating rate of 5°C / min. Based on the storage modulus G' (Pa) and loss modulus G” (Pa) at this time, the tanδ is determined using the following formula: tanδ = G” / G'. The peak temperature of the adhesive's tanδ (hereinafter sometimes referred to as Tpeak) can be determined from the shift of tanδ within the aforementioned temperature range. As a viscoelasticity testing apparatus, ARES or its equivalent manufactured by TA Instruments can be used.

[0088] In some methods, it is advantageous for the adhesive's Tpeak to be below 45°C or 35°C, preferably below 30°C (e.g., below 25°C), and it can be below 20°C or even below 15°C. Adhesives with lower Tpeaks tend to readily achieve good initial adhesion and bonding at room temperature. On the other hand, from the viewpoint of imparting appropriate cohesion to the adhesive, it is preferable that the adhesive's Tpeak not be too low, and it is also suitable for achieving a high refractive index. From this viewpoint, in some methods, the adhesive's Tpeak is, for example, above -40°C, above -30°C, above -20°C, above -5°C, above 5°C, above 15°C, and further above 25°C. Adhesives with higher Tpeaks are preferably used in a manner where, when bonding the adherends, one or both of the adhesive and the adherends are heated to a temperature slightly above room temperature as needed. The Tpeak of an adhesive can be adjusted by selecting the composition of the adhesive (e.g., the composition of the monomer components that make up the base polymer, the refractive index enhancer, whether, type and amount of plasticizer are used).

[0089] In the form of a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, the Tpeak of the adhesive is preferably applied to at least the adhesive layer constituting the first adhesive surface, and more preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The Tpeak of the adhesive layer constituting the first adhesive surface and the Tpeak of the adhesive layer constituting the second adhesive surface may be the same or different.

[0090] <Adhesive layer>

[0091] (Basic Polymer)

[0092] In the technology disclosed herein, the type of adhesive constituting the adhesive layer is not particularly limited. The adhesive can be one or more of the following rubber-like polymers that can be used in the field of adhesives: acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluoropolymers, etc., which serve as the adhesive polymer (hereinafter also referred to as the "base polymer"), for the purpose of shaping the adhesive. From the viewpoints of adhesive performance and cost, adhesives containing acrylic polymers or rubber polymers as the base polymer are preferred. Among these, adhesives using acrylic polymers as the base polymer (acrylic adhesives) are preferred. The technology disclosed herein is preferably implemented using acrylic adhesives.

[0093] The following description focuses on adhesive optical films having an adhesive layer made of acrylic adhesive, but it is not intended to limit the adhesive layer of the adhesive optical films disclosed herein to being made of acrylic adhesive.

[0094] It should be noted that in this specification, the term "base polymer" in the adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not interpreted in any other limiting way. The aforementioned rubbery polymer refers to a polymer that exhibits rubber-like elasticity in a temperature range near room temperature. Furthermore, in this specification, "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

[0095] Furthermore, in this specification, "acrylic polymer" refers to a polymer comprising monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer." Therefore, in this specification, an acrylic polymer is defined as a polymer comprising monomer units derived from acrylic monomers. As a typical example of an acrylic polymer, polymers in which the proportion of acrylic monomers in all monomers used in the synthesis of such an acrylic polymer is greater than 50% by weight (preferably greater than 70% by weight, for example greater than 90% by weight) can be cited.

[0096] Furthermore, in this specification, "(meth)acryloyl" is a general term for both acryloyl and methacryloyl groups. Similarly, "(meth)acrylate" is a general term for both acrylates and methacrylates, and "(meth)acrylic acid" is a general term for both acrylic acid and methacrylic acid. Therefore, the concept of acrylic monomers as used herein can include both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers).

[0097] (Acrylic polymer (A))

[0098] The adhesive optical film disclosed herein can preferably be implemented as an acrylic adhesive layer comprising an acrylic adhesive layer having a refractive index higher than 1.570, a total transmittance of 86% or more, and a haze value of 3.0% or less (preferably 2.0% or less, more preferably 1.0% or less). For the acrylic polymer serving as the base polymer of the aforementioned acrylic adhesive layer, it is preferable to have a polymer containing an aromatic ring-containing monomer (m1) as a monomeric component constituting the acrylic polymer. That is, it is preferable to have an acrylic polymer containing an aromatic ring-containing monomer (m1) as a monomeric unit. Hereinafter, this acrylic polymer will also be referred to as "acrylic polymer (A)". Here, in this specification, "monomeric component constituting the acrylic polymer" refers to the monomer that constitutes a repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition, and is not limited to being included in the adhesive composition in the form of a pre-formed polymer (which may be an oligomer) or in the form of an unpolymerized monomer. That is, the monomeric component constituting the acrylic polymer can be included in the aforementioned adhesive composition in any of the forms of polymer, unpolymerized, or partially polymerized. From the viewpoint of ease of preparation of adhesive compositions, in some embodiments, adhesive compositions comprising substantially all (e.g., 95% by weight or more, preferably 99% by weight or more) of the monomer components in polymer form are preferred. Adhesive compositions comprising substantially all of the monomer components in polymer form are also preferred from the viewpoint of easily forming adhesive optical films with minimal deformation and warping.

[0099] (Single(m1))

[0100] As a monomer (m1), a compound containing at least one aromatic ring and at least one olefinic unsaturated group is used in one molecule. As a monomer (m1), one of the compounds may be used alone or in combination of two or more.

[0101] Examples of the aforementioned olefin unsaturated groups include (meth)acryloyl, vinyl, and (meth)allyl. From the viewpoint of polymerization reactivity, (meth)acryloyl is preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl is more preferred. From the viewpoint of suppressing the reduction of the adhesive's flexibility, as a monomer (m1), it is preferable to use a compound that contains one olefin unsaturated group per molecule (i.e., a monofunctional monomer).

[0102] The number of aromatic rings contained in one molecule of the compound used as a monomer (m1) can be one or more. There is no particular upper limit to the number of aromatic rings contained in the monomer (m1), for example, it can be 16 or less. In some embodiments, from the viewpoint of ease of preparation of acrylic polymer (A) and transparency of adhesive, the number of aromatic rings can be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less.

[0103] The aromatic ring of the compound used as a monomer (m1) may be, for example, a benzene ring (which may be a benzene ring that forms part of a biphenyl or fluorene structure); a fused ring of a naphthalene ring, indene ring, azulene ring, anthracene ring, or phenanthrene ring; a carbocyclic ring, for example, a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, or thiophene ring; or a heterocyclic ring. The heteroatoms included as cyclizing atoms in the above-mentioned heterocyclic rings may be, for example, one or more types selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatoms constituting the above-mentioned heterocyclic rings may be one or both of nitrogen and sulfur. The monomer (m1) may also have a structure, for example, a fused structure of one or more carbocyclic rings with one or more heterocyclic rings, such as a dinaphthothiophene structure.

[0104] The aromatic ring (preferably a carbocyclic ring) may have one or more substituents on the cyclic atom, or it may not have any substituents. When substituents are present, examples of such substituents include alkyl, alkoxy, aryloxy, hydroxyl, halogen atoms (fluorine, chlorine, bromine, etc.), hydroxyalkyl, hydroxyalkyloxy, glycidoxy, etc., but it is not limited to these. Among the substituents containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. In some embodiments, the aromatic ring may be an aromatic ring that does not have substituents on the cyclic atom, or has one or more substituents selected from the group consisting of alkyl, alkoxy, and halogen atoms (e.g., bromine atoms). It should be noted that the aromatic ring of the monomer (m1) having substituents on its cyclic atom means that the aromatic ring has substituents other than those containing olefinic unsaturated groups.

[0105] The aromatic ring and the olefinic unsaturated group can be directly bonded or bonded via a linking group. The linking group can be, for example, a group containing one or more structures selected from alkylene, oxoalkylene, poly(oxoalkylene), phenyl, alkylphenyl, alkoxyphenyl, or groups in which one or more hydrogen atoms are replaced by hydroxyl groups (e.g., hydroxyalkylene), oxy (-O-), thiooxy (-S-), etc. In some embodiments, it is preferable to use a monomer containing an aromatic ring, either directly bonded to the olefinic unsaturated group or bonded via a linking group selected from the group consisting of alkylene, oxoalkylene, and poly(oxoalkylene). The number of carbon atoms in the alkylene and oxoalkylene groups is preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. The number of repetitions of the oxoalkylene unit in the poly(oxoalkylene) group can be, for example, 2 to 3.

[0106] Examples of compounds that can be preferably used as monomers (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. One aromatic ring-containing (meth)acrylate and one aromatic ring-containing vinyl compound can be used alone or in combination of two or more. Alternatively, one or more aromatic ring-containing (meth)acrylates can be used in combination with one or more aromatic ring-containing vinyl compounds.

[0107] The content of monomer (m1) in the monomer component constituting the acrylic polymer (A) is not particularly limited and can be set in a way that achieves an adhesive layer that balances desired refractive index and adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value, etc.). In some embodiments, the content of monomer (m1) in the aforementioned monomer component can be, for example, 30% by weight or more, preferably 50% by weight or more, 60% by weight or more, or 70% by weight or more. From the viewpoint of easily obtaining a higher refractive index, in some preferred embodiments, the content of monomer (m1) can be, for example, higher than 70% by weight, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The upper limit for the content of monomer (m1) in the aforementioned monomer component is 100% by weight. From the viewpoint of achieving a good balance between high refractive index and adhesive and / or optical properties, it is advantageous to set the content of the aforementioned monomer (m1) to be less than 100% by weight, for example preferably about 99% by weight or less, more preferably 98% by weight or less, and can be 97% by weight or less, or 96% by weight or less. In some embodiments, the content of the aforementioned monomer (m1) can be 93% by weight or less, 90% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments where adhesive and / or optical properties are given greater emphasis, the content of the aforementioned monomer (m1) in the aforementioned monomer composition can be 70% by weight or less, 60% by weight or less, or 45% by weight or less.

[0108] In some embodiments of the technology disclosed herein, monomers (m1) that readily achieve high refractive index are preferably selected from the perspective of easily obtaining high refractive index effects. Examples of monomers having two or more aromatic rings per molecule (hereinafter also referred to as "monomers containing multiple aromatic rings") include: monomers having a structure in which two or more non-fused aromatic rings are bonded together by a linking group; monomers having a structure in which two or more non-fused aromatic rings are directly (i.e., without the aid of other atoms) chemically bonded together; monomers having a fused aromatic ring structure; monomers having a fluorene structure; monomers having a dinaphthothiophene structure; and monomers having a dibenzothiophene structure. Monomers containing multiple aromatic rings can be used alone or in combination of two or more.

[0109] The linking group mentioned above can be, for example, an oxygen group (-O-), a thiooxy group (-S-), or an oxoalkylene group (e.g., -O-(CH2)). n - group, where n is 1 to 3, preferably 1), thiooxyalkylene (e.g., -S-(CH2) n - group, where n is 1 to 3, preferably 1), straight-chain alkylene (i.e., -(CH2)).n - group (where n is 1 to 6, preferably 1 to 3), or groups formed by partially or completely halogenating the alkylene oxides, thioalkylene oxides, and straight-chain alkylene oxides mentioned above. From the viewpoint of adhesive flexibility, suitable examples of the above-mentioned linking groups include oxy groups, thiooxy groups, alkylene oxides, and straight-chain alkylene oxides. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded together by a linking group include (meth)acrylate phenoxybenzyl ester (e.g., (meth)acrylate m-phenoxybenzyl ester), (meth)acrylate thiophenoxybenzyl ester, (meth)acrylate benzyl benzyl ester, etc.

[0110] The monomers described above, which have structures formed by the direct chemical bonding of two or more non-fused aromatic rings, can be, for example, (meth)acrylates containing a biphenyl structure, (meth)acrylates containing a triphenyl structure, or vinyl-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate and biphenyl methyl methacrylate.

[0111] Examples of monomers with fused aromatic ring structures include (meth)acrylates containing a naphthyl ring, (meth)acrylates containing anthracene ring, vinyl-containing naphthalene, and vinyl-containing anthracene. Specific examples include 1-naphthyl methyl (meth)acrylate (also known as 1-naphthyl methyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthyl ethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0112] Specific examples of monomers with the aforementioned fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. It should be noted that monomers with the fluorene structure comprise a structural portion formed by the direct chemical bonding of two benzene rings, and are therefore included in the concept of monomers with structures formed by the direct chemical bonding of two or more non-fused aromatic rings.

[0113] Examples of monomers having the dinaphthothiophene structure include dinaphthothiophenes containing (meth)acryloyl groups, dinaphthothiophenes containing vinyl groups, and dinaphthothiophenes containing (meth)allyl groups. Specific examples include (meth)acryloyloxymethyl dinaphthothiophene (e.g., with CH2CH(R) bonded at the 5 or 6 position of the dinaphthothiophene ring). 1 Compounds with the structure )C(O)OCH2-. Here, R 1 It consists of a hydrogen atom or a methyl group. ), (meth)acryloyloxyethyl dinaphthothiophene (for example, CH2CH(R) bonded at the 5 or 6 position of the dinaphthothiophene ring). 1)C(O)OCH(CH3)- or CH2CH(R 1 Compounds with the structure )C(O)OCH2CH2-. Here, R 1 These include monomers with hydrogen atoms or methyl groups, vinyl dinaphthothiophene (e.g., compounds with a vinyl group bonded to the 5th or 6th position of the dinaphthothiophene ring), (methyl)allyloxy dinaphthothiophene, etc. It should be noted that monomers with a dinaphthothiophene structure are included in the concept of monomers with fused aromatic ring structures because they contain a naphthalene structure and also because they have a structure formed by the fusion of a thiophene ring and two naphthalene structures.

[0114] Examples of monomers having the above-mentioned dibenzothiophene structure include dibenzothiophene containing (meth)acryloyl groups and dibenzothiophene containing vinyl groups. It should be noted that monomers having the dibenzothiophene structure are included in the concept of monomers having fused aromatic ring structures because they have a structure formed by the fusion of a thiophene ring and two benzene rings.

[0115] It should be noted that neither dinaphthothiophene nor dibenzothiophene structures belong to structures formed by the direct chemical bonding of two or more non-fused aromatic rings.

[0116] As the monomer (m1) disclosed herein, a monomer having one aromatic ring (preferably a carbocyclic ring) per molecule can also be used. A monomer having one aromatic ring per molecule can, for example, contribute to improving the flexibility of the adhesive, adjusting its adhesive properties, and improving its transparency. In some embodiments, from the viewpoint of increasing the refractive index of the adhesive, a monomer having one aromatic ring per molecule is preferably used in combination with a monomer containing multiple aromatic rings.

[0117] Examples of monomers having one aromatic ring in one molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and benzyl chloro (meth)acrylate, all containing a carbon-containing aromatic ring; 2-(4,6-dibromo-2-sec-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and so on. (Meth)acrylates containing bromine-substituted aromatic rings, such as 6-(4,6-dibromo-2-sec-butylphenoxy)hexyl acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; vinyl compounds containing carbon aromatic rings, such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; compounds with vinyl substituents on heteroaromatic rings, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazolium, and N-vinyloxazole; etc.

[0118] As monomer (m1), monomers with an oxyethylidene chain sandwiched between the olefinic unsaturated group and the aromatic ring in the various aromatic ring-containing monomers described above can also be used. Such monomers with an oxyethylidene chain sandwiched between the olefinic unsaturated group and the aromatic ring can be considered as ethoxylated derivatives of the original monomer. The repeating number of the oxyethylidene unit (-CH2CH2O-) in the aforementioned oxyethylidene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, and for example, 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol di(meth)acrylate.

[0119] The content of monomers containing multiple aromatic rings in monomer (m1) is not particularly limited, and can be, for example, 5% or more by weight, 25% or more by weight, or 40% or more by weight. In some embodiments, from the viewpoint of easily achieving an adhesive with a higher refractive index, the content of monomers containing multiple aromatic rings in monomer (m1) can be, for example, 50% or more by weight, preferably 70% or more by weight, 85% or more by weight, 90% or more by weight, or 95% or more by weight. It is also possible for monomer (m1) to be substantially 100% by weight of monomers containing multiple aromatic rings. That is, as monomer (m1), only one or two or more monomers containing multiple aromatic rings can be used. In addition, in some embodiments, for example, considering the balance between high refractive index and adhesive properties and / or optical properties, the content of monomers containing multiple aromatic rings in monomer (m1) can be less than 100% by weight, and can be 98% or less by weight, 90% or less by weight, 80% or less by weight, or 65% or less by weight. In some embodiments, considering adhesive and / or optical properties, the content of monomers containing multiple aromatic rings in the monomer (m1) may be less than 70% by weight, less than 50% by weight, less than 25% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the content of monomers containing multiple aromatic rings in the monomer (m1) being less than 5% by weight. Alternatively, monomers containing multiple aromatic rings may not be used.

[0120] The content of monomers containing multiple aromatic rings in the monomer components constituting acrylic polymers is not particularly limited, and can be set in a manner that achieves an adhesive layer that balances desired refractive index and adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value, etc.). The content of monomers containing multiple aromatic rings in the aforementioned monomer components can, for example, be 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of easily achieving adhesives with higher refractive indices, the content of monomers containing multiple aromatic rings in the aforementioned monomer components can, for example, be higher than 35% by weight, preferably higher than 50% by weight, higher than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The content of monomers containing multiple aromatic rings in the above-mentioned monomer components can be 100% by weight, but from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, and can be 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, or 75% by weight or less. In some embodiments, considering adhesive properties and / or optical properties, the content of monomers containing multiple aromatic rings in the above-mentioned monomer components can be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technology disclosed herein can also be implemented with the content of monomers containing multiple aromatic rings in the above-mentioned monomer components being less than 3% by weight.

[0121] In some embodiments of the technology disclosed herein, a high-refractive-index monomer may preferably be used as at least a portion of the monomer (m1). Here, "high-refractive-index monomer" refers to a monomer with a refractive index of, for example, about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more. There is no particular upper limit to the refractive index of the high-refractive-index monomer; from the viewpoint of balancing ease of preparation of the adhesive composition with ease of achieving suitable flexibility as an adhesive, it may be, for example, 3.000 or less, 2.500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less. One high-refractive-index monomer may be used alone or in combination of two or more.

[0122] It should be noted that the refractive index of the monomer was measured using an Abbe refractometer at a measurement wavelength of 589 nm and a measurement temperature of 25°C. The Abbe refractometer can be the ATAGO "DR-M4" model or its equivalent. If the manufacturer provides a nominal value for the refractive index at 25°C, that value can be used.

[0123] As the aforementioned high refractive index monomer, a substance with a suitable refractive index can be appropriately selected from the compounds included in the concept of aromatic ring-containing monomers (m1) disclosed herein (e.g., the compounds and groups of compounds exemplified above). Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthyl methyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o-phenylphenol acrylate (repetition number of oxyethylidene unit: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6°C), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2°C), and phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35°C). g: -35℃), 6-acryloyloxymethyl dinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyl dinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyl dinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyl dinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyl dinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyl dinaphthothiophene (abbreviated as: 5VDNT, refractive index: 1.793), etc., but not limited to these.

[0124] The content of high-refractive-index monomers (i.e., aromatic ring-containing monomers with a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in monomer (m1) is not particularly limited, and can be, for example, 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of easily obtaining higher refractive indices, the content of high-refractive-index monomers in monomer (m1) can be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. It is also possible for monomer (m1) to be substantially 100% by weight of high-refractive-index monomers. In addition, in some embodiments, for example, from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, the content of high-refractive-index monomers in monomer (m1) can be less than 100% by weight, and can be 98% by weight or less, 90% by weight or less, 80% by weight or less, or 65% by weight or less. In some embodiments, considering adhesive and / or optical properties, the content of the high-refractive-index monomer in the monomer (m1) may be less than 70% by weight, less than 50% by weight, less than 25% by weight, less than 15% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the content of the high-refractive-index monomer in the monomer component (m1) being less than 5% by weight. Alternatively, the high-refractive-index monomer may not be used.

[0125] The content of high-refractive-index monomers in the monomer components constituting acrylic polymers is not particularly limited, and can be set in a way that achieves an adhesive layer that balances desired refractive index with adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value). The content of high-refractive-index monomers in the aforementioned monomer components can, for example, be 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of easily achieving adhesives with higher refractive indices, the content of high-refractive-index monomers in the aforementioned monomer components can, for example, be higher than 35% by weight, preferably higher than 50% by weight, higher than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The content of the high-refractive-index monomer in the above-mentioned monomer composition can be 100% by weight, but from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably 99% by weight or less, more preferably 98% by weight or less, and can be 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, or 75% by weight or less. In some embodiments, considering adhesive properties and / or optical properties, the content of the high-refractive-index monomer in the above-mentioned monomer composition can be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technology disclosed herein can also be implemented with the content of the high-refractive-index monomer in the above-mentioned monomer composition being less than 3% by weight.

[0126] In some preferred embodiments of the technology disclosed herein, a monomer containing aromatic rings (hereinafter sometimes referred to as "monomer L") with a Tg of less than 10°C (preferably less than 5°C or less than 0°C, more preferably less than -10°C, even more preferably less than -20°C, for example less than -25°C) is used as at least a portion of monomer (m1). If the content of the aromatic ring-containing monomer (m1) in the monomer composition is increased (particularly the aromatic ring-containing monomer (m1) equivalent to one or both of the aforementioned monomers containing multiple aromatic rings and high refractive index monomers), the storage modulus G' of the adhesive generally tends to increase. As a result, by using monomer L as part or all of the monomer (m1), the increase in storage modulus G' can be suppressed. Therefore, the flexibility suitable for use as an adhesive can be maintained better, and the refractive index can be increased. There is no particular limitation on the lower limit of the Tg of monomer L. Considering the balance with the effect of increasing the refractive index, in some embodiments, the Tg of monomer L can be, for example, greater than -70°C, greater than -55°C, or greater than -45°C. Monomer L can be used alone or in combination of two or more types.

[0127] As monomer L, a substance having a suitable Tg can be appropriately selected from the compounds included in the concept of aromatic ring-containing monomers (m1) disclosed herein (e.g., the compounds and groups of compounds exemplified above). As a suitable example of an aromatic ring-containing monomer that can be used as monomer L, m-phenoxybenzyl acrylate (Tg of homopolymer: -35°C) is listed. As another suitable example, phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C) is listed.

[0128] The content of monomer L in monomer (m1) is not particularly limited; for example, it can be 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of easily obtaining an adhesive that balances high refractive index and flexibility at a higher level, the content of monomer L in monomer (m1) can be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. It is also possible for monomer (A1) to be substantially 100% by weight of monomer L. Furthermore, in some embodiments, for example, from the viewpoint of achieving a good balance between flexibility and high refractive index suitable as an adhesive, the content of monomer L in monomer (m1) can be less than 100% by weight, less than 98% by weight, less than 90% by weight, less than 80% by weight, less than 70% by weight, less than 50% by weight, less than 25% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the monomer L content in the monomer (m1) being less than 5% by weight. Alternatively, monomer L can be omitted.

[0129] The content of monomer L in the monomer component constituting the acrylic polymer can be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of easily obtaining an adhesive that balances high refractive index and flexibility at a higher level, the content of monomer L in the monomer component can be, for example, higher than 35% by weight, preferably higher than 50% by weight, higher than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The content of monomer L in the above-mentioned monomer component can be 100% by weight, but considering the balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, 96% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments, the content of monomer L in the aforementioned monomeric components may be less than 70% by weight, less than 50% by weight, less than 25% by weight, less than 15% by weight, or less than 5% by weight. The techniques disclosed herein may also be implemented with the content of monomer L in the aforementioned monomeric components being less than 3% by weight.

[0130] In some approaches, from the viewpoint of adhesive flexibility, the glass transition temperature Tg of the monomer (m1) composition is considered. m1 It is advantageous to have a temperature below approximately 20°C, preferably below 10°C (e.g., below 5°C), more preferably below 0°C, and even more preferably below -10°C. It can be below -20°C or below -25°C. Glass transition temperature Tg m1 There is no particular lower limit. Considering the balance with the effect of increasing the refractive index, in some approaches, the glass transition temperature Tg... m1 For example, it can be above -70°C, above -55°C, or above -45°C. The technology disclosed herein can also be based on the glass transition temperature Tg. m1 It shall be implemented in a manner suitable for temperatures above -40°C, -35°C, -33°C, -30°C, or -25°C.

[0131] Here, the glass transition temperature Tg is based on the composition of the monomer (m1). m1 This refers to the glass transition temperature (Tg) calculated using the Fox equation (described later), based solely on the composition of the monomers (m1) that constitute the acrylic polymer. m1The glass transition temperature (Tg) of the homopolymer of an acrylic polymer can be calculated using only the monomer (m1) constituting the monomer composition, applying the Fox formula (described later), based on the glass transition temperature of the homopolymer of each aromatic ring-containing monomer used as monomer (m1) and the weight fraction of each aromatic ring-containing monomer in the total amount of monomer (m1). In the case where only one monomer is used as monomer (m1), the Tg of the homopolymer of that monomer is related to its glass transition temperature (Tg). m1 Consistent.

[0132] In some methods, monomer L (i.e., a monomer containing an aromatic ring with a Tg of 10°C or less, preferably 5°C or less or 0°C, more preferably -10°C or less, further preferably -20°C or less, for example -25°C or less) and monomer H with a Tg higher than 10°C can be used as the aromatic ring-containing monomer (m1). The Tg of monomer H can be, for example, higher than 10°C, higher than 15°C, or higher than 20°C. By using monomer L and monomer H in combination, for example in a composition where the content of the aromatic ring-containing monomer (m1) in the monomer composition is relatively high, it is possible to achieve a higher level of balance between the high refractive index and flexibility of the adhesive. The ratio of monomer L to monomer H can be set in a way that suitably manifests this effect and is not particularly limited. For example, it is preferable to satisfy any of the above-mentioned glass transition temperatures Tg. m1 The ratio of monomer L to monomer H is set in a certain way.

[0133] In some embodiments, the aromatic ring-containing monomer (m1) is preferably selected from compounds that do not contain a structure formed by direct chemical bonding of two or more non-fused aromatic rings (e.g., a biphenyl structure). For example, acrylic polymers composed of monomer components having a content of less than 5% by weight (more preferably less than 3% by weight, or even 0% by weight) of compounds containing a structure formed by direct chemical bonding of two or more non-fused aromatic rings are preferred. From the viewpoint of achieving a good balance between flexibility, adhesion, and high refractive index in adhesives, thus limiting the amount of compounds containing a structure formed by direct chemical bonding of two or more non-fused aromatic rings can be advantageous.

[0134] (Single (m2))

[0135] In some embodiments of the technology disclosed herein, the monomer component constituting the acrylic polymer may further contain monomer (m2) in addition to the aforementioned monomer (m1). The monomer (m2) is a monomer belonging to at least one of a hydroxyl-containing monomer (hydroxyl-containing monomer) and a carboxyl-containing monomer (carboxyl-containing monomer). The hydroxyl-containing monomer is a compound having at least one hydroxyl group and at least one olefinically unsaturated group per molecule. The carboxyl-containing monomer is a compound containing at least one carboxyl group and at least one olefinically unsaturated group per molecule. Monomer (m2) can facilitate the introduction of crosslinking points into the acrylic polymer or impart appropriate cohesiveness to the adhesive. Monomer (m2) can be used alone or in combination of two or more. Monomer (m2) is typically a monomer that does not contain an aromatic ring.

[0136] Examples of olefinic unsaturated groups present in monomer (m2) include (meth)acryloyl, vinyl, and (meth)allyl groups. From the viewpoint of polymerization reactivity, (meth)acryloyl is preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl is more preferred. From the viewpoint of suppressing the reduction of the adhesive's flexibility, it is preferable to use a compound (i.e., a monofunctional monomer) containing one olefinic unsaturated group per molecule as monomer (m2).

[0137] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, and methyl methacrylate (4-hydroxymethylcyclohexyl)methacrylate, but are not limited to these. Examples of preferred hydroxyl-containing monomers include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl methacrylate (Tg: -15°C). From the viewpoint of improved softness in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is more preferred. In a preferred embodiment, 4-hydroxybutyl acrylate may be present in 50% by weight or more (e.g., more than 50% by weight, more than 70% by weight, or more than 85% by weight) of the monomer (m2). One hydroxyl-containing monomer may be used alone or in combination of two or more.

[0138] In some methods of using hydroxyl-containing monomers as monomers (m2), the hydroxyl-containing monomers may be one or more selected from compounds without a methacryloyl group. Suitable examples of hydroxyl-containing monomers without a methacryloyl group include the various hydroxyalkyl acrylates mentioned above. For example, it is preferable that more than 50%, more than 70%, or more than 85% by weight of the hydroxyl-containing monomers used as monomers (m2) are hydroxyalkyl acrylates. By using hydroxyalkyl acrylates, hydroxyl groups that help provide crosslinking points and impart moderate cohesiveness can be introduced into acrylic polymers, and adhesives with good flexibility and adhesion in the room temperature range are readily obtained compared to the case where only the corresponding hydroxyalkyl methacrylate is used.

[0139] Examples of carboxyl-containing monomers include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylic acid, and carboxypentyl (meth)acrylic acid, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid, but are not limited to these. Examples of preferred carboxyl-containing monomers include acrylic acid and methacrylic acid. One type of carboxyl-containing monomer can be used alone, or two or more can be used in combination. Hydroxyl-containing monomers and carboxyl-containing monomers can also be used in combination.

[0140] The content of monomer (m2) in the monomer component constituting the acrylic polymer is not particularly limited and can be set according to the purpose. In some embodiments, the content of the monomer (m2) can be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. From the viewpoint of obtaining a higher performance effect, in some embodiments, the content of the monomer (A2) is preferably set to 1% by weight or more, can be set to 2% by weight or more, or can be set to 4% by weight or more. The upper limit of the content of monomer (m2) in the monomer component is set in such a way that the total content with the content of other monomers does not exceed 100% by weight. In some embodiments, it is appropriate to set the content of the monomer (m2) to 30% by weight or less or 25% by weight or less, for example. From the viewpoint of making it easier to increase the refractive index by relatively increasing the content of monomer (m1), it is preferably set to 20% by weight or less, more preferably to 15% by weight or less, and can be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

[0141] In methods using hydroxyl-containing monomers as monomers (m2), the content of hydroxyl-containing monomers in the monomer composition is not particularly limited, and can be, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.5% by weight or more). In some methods, the content of the hydroxyl-containing monomers is preferably set to 1% by weight or more of the monomer composition, and can be set to 2% by weight or more, or 4% by weight or more. The upper limit of the content of hydroxyl-containing monomers in the monomer composition is set such that the total content with the content of other monomers does not exceed 100% by weight. For example, it is appropriate to set it to 30% by weight or less or 25% by weight or less. From the viewpoint of making it easier to increase the refractive index by relatively increasing the content of monomers (m1), it is preferably set to 20% by weight or less, more preferably 15% by weight or less, and can be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

[0142] In methods using carboxyl-containing monomers as monomers (m2), the content of carboxyl-containing monomers in the monomer composition is not particularly limited, and can be, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.3% by weight or more). In some methods, the content of the carboxyl-containing monomers can be set to 1% by weight or more, 2% by weight or more, or 4% by weight or more. The upper limit of the content of carboxyl-containing monomers in the monomer composition is set such that the total amount used with other monomers does not exceed 100% by weight, for example, setting it to 30% by weight or less or 25% by weight or less is appropriate. From the viewpoint of making it easier to increase the content of monomers (m1) to achieve a high refractive index, it is preferable to set it to 20% by weight or less, more preferably 15% by weight or less, and can be less than 12% by weight or less than 10% by weight. In some methods, from the viewpoint of improving the flexibility of the adhesive, it is advantageous to set the content of the carboxyl-containing monomers to less than 7% by weight, preferably less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. The techniques disclosed herein can be preferably implemented, for example, by using only hydroxyl-containing monomers as monomers (m2), i.e., without using carboxyl-containing monomers.

[0143] The total content of monomers (m1) and (m2) in the monomer component constituting the acrylic polymer can be, for example, 31% by weight or more, preferably 51% by weight or more, 61% by weight or more, or 71% by weight or more. In some embodiments, from the viewpoint of easily and appropriately exerting the effects of these monomers, the total content of monomers (m1) and (m2) in the monomer component constituting the acrylic polymer can be, for example, 76% by weight or more, preferably 81% by weight or more, 86% by weight or more, 91% by weight or more, 96% by weight or more, 99% by weight or more, or substantially 100% by weight.

[0144] (Single m3)

[0145] The monomer components constituting acrylic polymers may, as needed, include monomers other than those described above (m1) and (m2). As an example of such an arbitrary component, alkyl (meth)acrylate (hereinafter also referred to as "monomer (m3)") can be listed. Monomer (m3) can help adjust the flexibility of the adhesive and improve its compatibility within the adhesive.

[0146] As a monomer (m3), it is preferable to use one having 1 to 20 carbon atoms at the ester terminus (i.e., C3). 1-20 Alkyl (meth)acrylates with straight or branched alkyl groups. As (meth)acrylate C 1-20 Specific examples of alkyl esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, and nonyl methacrylate. Isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, stearyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc., but not limited to these.

[0147] In some methods, it is preferable to use alkyl (meth)acrylates with a Tg of -20°C or lower (more preferably -40°C or lower, for example -50°C or lower) as at least a portion of the monomer (m3). Such low-Tg alkyl (meth)acrylates can help improve the flexibility of the adhesive. There is no particular limitation on the lower limit of the Tg of the aforementioned alkyl (meth)acrylates; for example, it can be above -85°C, above -75°C, above -65°C, or above -60°C. Specific examples of the aforementioned low-Tg alkyl (meth)acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and isononyl acrylate (iNA).

[0148] In some methods of using monomer (m3), from the viewpoint of flexibility, adhesion, etc., it is preferable that at least a portion of the monomer (m3) is an alkyl acrylate. For example, it is preferable that 50% by weight or more (more preferably 75% by weight or more, and even more preferably 90% by weight or more) of the monomer (m3) is an alkyl acrylate. It is also possible to use only one or two or more alkyl acrylates as monomer (m3) and not to use alkyl methacrylates.

[0149] In monomer components comprising alkyl (meth)acrylates, the content of alkyl (meth)acrylates in the monomer component can be set in a manner that appropriately exerts its effect. In some methods, the content of the aforementioned alkyl (meth)acrylate can be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. In some methods, the content of the aforementioned alkyl (meth)acrylate can be 15% by weight or more, 30% by weight or more, or 45% by weight or more. The upper limit of the content of monomer (m3) in the monomer component is set such that the total content with the content of other monomers does not exceed 100% by weight, for example, it can be less than 50% by weight. In some methods, the content of the aforementioned monomer (m3) can be, for example, less than 35% by weight. Generally, alkyl (meth)acrylates have a low refractive index; therefore, in order to achieve a high refractive index, it is advantageous to limit the content of monomer (m3) in the monomer component and relatively increase the content of monomer (m1). From this perspective, it is advantageous for the monomer (m3) content to be less than 24% by weight of the monomer component, preferably less than 23% by weight, more preferably less than 20% by weight, possibly less than 17% by weight, possibly less than 12% by weight, possibly less than 7% by weight, possibly less than 3% by weight, or possibly less than 1% by weight. Alternatively, monomer (m3) may be used substantially without any monomer content.

[0150] (Other monomers)

[0151] The monomer components constituting acrylic polymers may also include monomers other than those mentioned above (m1), (m2), and (m3) (hereinafter referred to as "other monomers"). These other monomers may be used for purposes such as adjusting the Tg of the acrylic polymer, adjusting its adhesive properties, and improving compatibility within the adhesive layer. One of these other monomers may be used alone, or two or more may be used in combination.

[0152] Examples of other monomers mentioned above include monomers having functional groups other than hydroxyl and carboxyl groups (monomers containing functional groups). For example, monomers containing sulfonic acid groups, phosphate groups, and cyano groups can be listed as other monomers that can improve the cohesiveness and heat resistance of adhesives. In addition, monomers that can introduce functional groups that can serve as crosslinking sites into acrylic polymers, or that can help improve peel strength and compatibility within the adhesive layer, include amide-containing monomers (e.g., (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, etc.), amino-containing monomers (e.g., (meth)acrylate aminoethyl ester, (meth)acrylate N,N-dimethylaminoethyl ester, etc.), monomers with a nitrogen-containing ring (e.g., N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide-containing monomers, epoxy-containing monomers, ketone-containing monomers, isocyanate-containing monomers, and alkoxysilyl-containing monomers, etc. It should be noted that monomers with nitrogen-containing rings, such as N-vinyl-2-pyrrolidone, also belong to the category of amide-containing monomers. The same applies to the relationship between the aforementioned monomers with nitrogen-containing rings and amino-containing monomers.

[0153] Other monomers that can be used besides the functionalized monomers mentioned above include vinyl acetate and other vinyl ester monomers; (meth)acrylates containing non-aromatic rings, such as cyclohexyl methacrylate and isobornyl methacrylate; olefin monomers such as ethylene, butadiene, and isobutene; chlorinated monomers such as vinyl chloride; alkoxy-containing monomers such as methoxyethyl methacrylate, ethoxyethyl methacrylate, and ethoxyethoxyethyl methacrylate; vinyl ether monomers such as methyl vinyl ether; etc. As a suitable example of other monomers that can be used for purposes such as improving the flexibility of adhesives, ethoxyethoxyethyl acrylate (also known as ethyl carbitol acrylate, Tg of homopolymer: -67°C) can be listed.

[0154] When using the other monomers mentioned above, there are no particular restrictions on their usage, and they can be appropriately set within a range where the total amount of monomer components does not exceed 100% by weight. In some embodiments, from the viewpoint of easily maximizing the refractive index increase effect brought about by the use of monomer (m1), the content of the other monomers mentioned above in the monomer component can be set to, for example, about 35% by weight or less, about 25% by weight or less (e.g., 0 to 25% by weight), about 20% by weight or less (e.g., 0 to 20% by weight), about 10% by weight or less, about 5% by weight or less, or for example, about 1% by weight or less. The technology disclosed herein can preferably be implemented in a manner in which the monomer component substantially does not contain the other monomers mentioned above.

[0155] In some embodiments, the monomeric components constituting acrylic polymers may be compositions in which the amount of methacrylamide monomers used is suppressed to a specified level. For example, the amount of methacrylamide monomers used in the monomeric components may be less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. From the viewpoint of achieving a well-balanced adhesive that combines flexibility, adhesion, and high refractive index, limiting the amount of methacrylamide monomers used in this way can be advantageous. The monomeric components constituting acrylic polymers may also be compositions that do not contain methacrylamide monomers (e.g., compositions containing only acryloyl monomers).

[0156] In some embodiments, for the monomer component of the base polymer (e.g., an acrylic polymer) constituting the adhesive layer, from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the adhesive, it is preferable to limit the amount of carboxyl-containing monomers used. The amount of carboxyl-containing monomers used in the monomer component may, for example, be less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. Limiting the amount of carboxyl-containing monomers in this way is also advantageous from the viewpoint of suppressing corrosion of metallic materials (e.g., metal wiring, metal films, etc., that may be present on the adhered objects) that may come into contact with or approach the adhesive disclosed herein. The techniques disclosed herein can preferably be implemented in a manner where the aforementioned monomer component does not contain carboxyl-containing monomers.

[0157] For the same reason, in some embodiments, the amount of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc., in addition to carboxyl groups) used in the monomer component constituting the adhesive layer is preferably limited. The amount of acidic functional group-containing monomers used in the monomer component of this embodiment can be determined by the preferred amount of carboxyl-containing monomers described above. The technology disclosed herein can preferably be implemented in a manner where the monomer component does not contain acidic groups (i.e., the base polymer of the adhesive layer is acid-free).

[0158] (glass transition temperature Tg of the basic polymer) T )

[0159] In some methods, the glass transition temperature (Tg) of the base polymer (e.g., an acrylic polymer) of the adhesive layer is based on the composition of the monomer components constituting the polymer. T A temperature below approximately 20°C is suitable, preferably below approximately 10°C, more preferably below 0°C, and can be below -10°C, below -20°C, below -25°C, below -28°C, or below -30°C. Glass transition temperature Tg T A lower glass transition temperature (Tg) can be advantageous from the perspective of improved adhesive flexibility. Additionally, the glass transition temperature (Tg) is also important. TFor example, the temperature can be -60°C or higher. From the viewpoint of making it easier to increase the refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, higher than -40°C, higher than -35°C, higher than -25°C, higher than -15°C, or higher than -5°C.

[0160] Here, the glass transition temperature Tg of the polymer is... T Unless otherwise specified, the glass transition temperature (Tg) is determined using the Fox formula based on the composition of the monomers constituting the polymer. The Fox formula, as shown below, is the relationship between the Tg of the copolymer and the glass transition temperature (Tgi) of the homopolymer formed by the homopolymerization of the monomers constituting the copolymer.

[0161] 1 / Tg=Σ(Wi / Tgi)

[0162] In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0163] The glass transition temperature (Tg) of homopolymers used for calculating Tg is the value recorded in known sources such as the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values ​​are recorded in the aforementioned Polymer Handbook, the highest value is used. Where the Tg of homopolymers is not recorded in known sources, the value obtained by the determination method described in Japanese Patent Application Publication No. 2007-51271 is used.

[0164] (Preparation methods of basic polymers)

[0165] In the techniques disclosed herein, the method for obtaining the base polymer of the adhesive layer (e.g., an acrylic polymer (A) composed of the monomer components described above) is not particularly limited, and known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately employed. In some embodiments, solution polymerization is preferred. The polymerization temperature during solution polymerization can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc., and can be set to approximately 20°C to 170°C (typically approximately 40°C to 140°C).

[0166] The solvent used in solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents. For example, one or a mixture of two or more solvents can be used, selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.

[0167] The initiator used in the polymerization can be appropriately selected from conventionally known polymerization initiators, depending on the type of polymerization method. For example, one or more azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) are preferred. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; etc. Further examples of polymerization initiators include redox initiators based on combinations of peroxides and reducing agents. One polymerization initiator can be used alone or in combination of two or more. The amount of polymerization initiator used is the usual amount, for example, it can be selected from a range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) relative to 100 parts by weight of monomer content.

[0168] In the above polymerization, various chain transfer agents known in the art can be used as needed. For example, thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, and α-thioglycerol can be used. Alternatively, chain transfer agents without sulfur atoms (non-sulfur chain transfer agents) can also be used. Examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenes such as α-pinene and terpinene; and styrene such as α-methylstyrene and α-methylstyrene dimer. One chain transfer agent can be used alone or in combination of two or more. The amount of chain transfer agent used relative to 100 parts by weight of the monomer raw material can be set to, for example, approximately 0.01 to 1 part by weight.

[0169] The weight-average molecular weight (Mw) of the base polymer is not particularly limited, and can be, for example, about 10 × 10⁻⁶. 4 ~500×10 4 From the viewpoint of adhesive properties, the Mw of the base polymer is preferably in the range of approximately 20 × 10⁻⁶. 4 ~400×10 4 (More preferably about 30×10) 4 ~150×10 4 For example, approximately 50×10 4 ~130×10 4) range.

[0170] Here, the Mw of the polymer can be obtained by converting polystyrene using gel permeation chromatography (GPC). Specifically, the GPC determination device, "HLC-8220GPC" (manufactured by Tosoh Corporation), can be used, and the determination can be performed under the following conditions.

[0171] [GPC Measurement Conditions]

[0172] Sample concentration: 0.2% by weight (tetrahydrofuran solution)

[0173] Sample injection volume: 10 μL

[0174] Eluent: Tetrahydrofuran (THF)

[0175] Flow rate: 0.6 mL / min

[0176] Column temperature (measurement temperature): 40℃

[0177] column:

[0178] Sample column: 1 brand name "TSKguardcolumn SuperHZ-H" + 2 pieces "TSKgel SuperHZM-H" brand name (manufactured by Tosoh Corporation)

[0179] Reference column: 1 brand name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation)

[0180] Detector: Differential refractometer (RI)

[0181] Standard sample: polystyrene

[0182] (Refractive index enhancer)

[0183] In some embodiments of the technology disclosed herein, the adhesive layer (e.g., an acrylic adhesive layer) may contain, as needed, a refractive index enhancer in addition to the base polymer. Here, in this specification, a refractive index enhancer refers to a material capable of increasing the refractive index of the adhesive layer through its use. Preferably, a material with a higher refractive index than the refractive index of the adhesive layer containing the refractive index enhancer is used as the refractive index enhancer. Furthermore, a material with a higher refractive index than the base polymer (e.g., an acrylic polymer (A)) of the adhesive layer containing the refractive index enhancer is preferred as the refractive index enhancer. By appropriately using the refractive index enhancer, a suitable balance between a higher refractive index and practical adhesive performance can be achieved. In some embodiments, the refractive index enhancer is preferably an organic material. The organic material used as the refractive index enhancer can be a polymer or a non-polymer. It may or may not have polymerizable functional groups. One refractive index enhancer may be used alone or in combination of two or more.

[0184] Refractive index enhancers (e.g., additives described later, H) RO The refractive index of the refractive index enhancer can be set to an appropriate range based on its relative relationship with the refractive index of the base polymer, and is therefore not limited to a specific range. The refractive index of the refractive index enhancer can be selected, for example, from a range higher than 1.55, higher than 1.56, or higher than 1.57, and higher than the refractive index of the base polymer. From the viewpoint of increasing the refractive index of the adhesive, in some ways, a refractive index of 1.58 or higher is advantageous, preferably 1.60 or higher, more preferably 1.63 or higher, and can be 1.65 or higher, 1.70 or higher, or 1.75 or higher. Using a refractive index enhancer with a higher refractive index allows the target refractive index to be achieved with a smaller amount of the enhancer used. This is preferred from the viewpoint of suppressing the reduction of adhesive properties and optical properties. There is no particular upper limit to the refractive index of the refractive index enhancer. From the perspective of compatibility with the adhesive, ease of achieving high refractive index and flexibility suitable for use as an adhesive, it can be, for example, 3.000 or less, 2.500 or less, 2.000 or less, 1.950 or less, 1.900 or less, or 1.850 or less.

[0185] In some methods, refractive index enhancers (e.g., additives described later, H) RO The refractive index n) b The refractive index n of the base polymer a The difference, i.e., n b -n a (hereinafter also referred to as "Δn") A The value is set to greater than 0. In some methods, Δn AFor example, it can be 0.02 or higher, 0.05 or higher, 0.07 or higher, 0.10 or higher, 0.15 or higher, or 0.20 or higher, or 0.25 or higher. Δn can be achieved by selecting the base polymer and the refractive index enhancer. A The size tends to increase, with a greater refractive index enhancement effect due to the use of refractive index improvers. Furthermore, from the perspectives of compatibility within the adhesive layer and the transparency of the adhesive layer, in some methods, Δn... A For example, it can be below 0.70, below 0.60, below 0.50, below 0.40, or below 0.35.

[0186] In some methods, refractive index enhancers (e.g., additives described later, H) RO The refractive index n) b The refractive index n of the adhesive layer containing the refractive index enhancer T The difference, i.e., n b -n T (hereinafter also referred to as "Δn") B The value is set to greater than 0. In some methods, Δn B For example, it can be 0.02 or higher, 0.05 or higher, 0.07 or higher, 0.10 or higher, 0.15 or higher, or 0.20 or higher, or 0.25 or higher. Δn can be achieved by selecting the composition of the adhesive layer and the refractive index enhancer. B The size tends to increase, with a greater refractive index enhancement effect due to the use of refractive index improvers. Furthermore, from the perspectives of compatibility within the adhesive layer and the transparency of the adhesive layer, in some methods, Δn... B For example, it can be below 0.70, below 0.60, below 0.50, below 0.40, or below 0.35.

[0187] The amount of refractive index enhancer used relative to 100 parts by weight of the base polymer (or the total amount of multiple refractive index enhancers when using multiple types) is not particularly limited and can be set according to the purpose. From the viewpoint of increasing the refractive index of the adhesive, it is advantageous, for example, to use 1 part by weight or more, 3 parts by weight or more, preferably 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. In addition, in some embodiments, the amount of refractive index enhancer used relative to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less. From the viewpoint of achieving a good balance between increasing the refractive index of the adhesive and suppressing the reduction of adhesive and optical properties, it is advantageous to use 60 parts by weight or less, preferably 45 parts by weight or less. In some approaches that place greater emphasis on adhesive and optical properties, the amount of the refractive index enhancer relative to 100 parts by weight of the base polymer can be, for example, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less. The techniques disclosed herein can also preferably be implemented with the refractive index enhancer used in an amount of less than 1 part by weight relative to 100 parts by weight of the base polymer in the adhesive layer, or with virtually no refractive index enhancer used. Here, "substantially not used" means at least not intentionally used.

[0188] (additives (H) RO ))

[0189] In some approaches, organic materials with a higher refractive index than the base polymer are preferred as refractive index enhancers. Hereinafter, such organic materials are sometimes referred to as "additives (H...)". RO )". Here, the above "H" RO "High refractive index" refers to organic materials. This is achieved by combining a base polymer (e.g., an acrylic polymer, preferably an acrylic polymer (A)) with additives (H... RO This technology enables the development of adhesives that more effectively balance refractive index with adhesive properties (peel strength, flexibility, etc.) and / or optical properties (total transmittance, haze, etc.). It is used as an additive (H... RO The organic material can be a polymer or a non-polymer. Furthermore, it may or may not have polymerizable functional groups. Additives (H) RO One type can be used alone or two or more types can be used in combination.

[0190] Additives (H) ROThe refractive index of the sample was measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25 °C, similar to that of the monomer. If the manufacturer provides a nominal value for the refractive index at 25 °C, that value can be used.

[0191] As an additive (H) RO The molecular weight of the organic materials used is not particularly limited and can be selected according to the purpose. From the viewpoint of achieving a good balance between the effect of high refractive index and other properties (such as suitability for adhesive flexibility, haze, and other optical properties), in some methods, additives (H... RO The molecular weight of the additive (H) is preferably below about 10,000, more preferably below 5,000, and even more preferably below 3,000 (e.g., below 1,000). It can be below 800, below 600, below 500, or below 400. RO The molecular weight of the additive (H) is not too large, which can be advantageous from the perspective of improving compatibility within the adhesive layer. Additionally, the additive (H) RO The molecular weight of the additive (H) can be, for example, 130 or more, or 150 or more. In some methods, the molecular weight of the additive (H) is... RO From the perspective of increasing the refractive index of ), additives (H) RO The molecular weight of the additive is preferably 170 or higher, more preferably 200 or higher, and can be 230 or higher, 250 or higher, 270 or higher, 500 or higher, 1000 or higher, or 2000 or higher. In some embodiments, polymers with a molecular weight of around 1000 to 10000 (e.g., 1000 or higher but lower than 5000) can be used as additives (H). RO ).

[0192] As an additive (H) RO The molecular weight of the additive (H) can be calculated based on its chemical structure for non-polymers or polymers with low polymerization degree (e.g., around 2-5 polymers), or determined using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS). RO When the polymer is a polymer with a higher degree of polymerization, the weight-average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. If a nominal value of the molecular weight is provided by the manufacturer, etc., that nominal value can be used.

[0193] It can be used as an additive (H) RO Examples of organic materials for the option include, but are not limited to, organic compounds having aromatic rings, organic compounds having heterocycles (which may be aromatic or non-aromatic heterocycles).

[0194] As an additive (H) ROThe aromatic ring of the above-mentioned organic compound with an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") may be selected from the same aromatic ring as that of the compound used as a monomer (m1).

[0195] The aromatic ring described above may have one or more substituents on the cyclizing atom, or it may not have any substituents. When substituents are present, examples of such substituents include alkyl, alkoxy, aryloxy, hydroxy, halogen atoms (fluorine, chlorine, bromine, etc.), hydroxyalkyl, hydroxyalkyloxy, cycloglycidoxy, etc., but are not limited to these. Among the substituents containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, advantageously 1 to 6, preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. In some embodiments, the aromatic ring described above may be an aromatic ring that does not have substituents on the cyclizing atom, or has one or more substituents selected from the group consisting of alkyl, alkoxy, and halogen atoms (e.g., bromine atoms).

[0196] As an additive (H) RO Examples of aromatic ring-containing compounds include, for example, compounds that can be used as monomers (m1); oligomers containing compounds that can be used as monomers (m1) as monomer units; compounds formed by removing and replacing a group having an olefinically unsaturated group (which may be a substituent bonded to a cyclic atom) or a portion of that group constituting the olefinically unsaturated group with a hydrogen atom or a group not having an olefinically unsaturated group (e.g., hydroxyl, amino, halogen atom, alkyl, alkoxy, hydroxyalkyl, hydroxyalkyloxy, glycidoxy, etc.) from a compound that can be used as a monomer (m1); etc., but not limited to these. RONon-limiting examples of aromatic ring-containing compounds may include: benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxy polyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc., aromatic ring-containing monomers; 3-phenoxybenzyl alcohol, dinaphthothiophene and its derivatives (e.g., compounds with a structure in which one or more substituents selected from hydroxyl, methanol, diethanol, glycidyl, etc., are bonded to the dinaphthothiophene ring), etc., aromatic ring-containing compounds without olefinic unsaturated groups; etc. Furthermore, aromatic ring-containing compounds may be oligomers containing such aromatic ring-containing monomers as monomer units (preferably oligomers with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, oligomers of about 2 to 5 polymers). The aforementioned oligomers may be, for example, homopolymers of monomers containing aromatic rings; copolymers of one or more monomers containing aromatic rings; copolymers of one or more monomers containing aromatic rings with other monomers; etc. As the aforementioned other monomers, one or more monomers without aromatic rings may be used.

[0197] In some methods, as an additive (H) RO From the perspective of easily obtaining a high refractive index effect, organic compounds having two or more aromatic rings per molecule (hereinafter also referred to as "compounds containing multiple aromatic rings") are preferred. Compounds containing multiple aromatic rings may or may not have polymerizable functional groups such as olefinic unsaturated groups. Furthermore, compounds containing multiple aromatic rings can be polymers or non-polymers. Additionally, the aforementioned polymers can be oligomers containing monomers containing multiple aromatic rings as monomer units (preferably oligomers with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, oligomers of about 2 to 5 polymers). The aforementioned oligomers can be, for example, homopolymers of monomers containing multiple aromatic rings; copolymers of one or more monomers containing multiple aromatic rings; copolymers of one or more monomers containing multiple aromatic rings with other monomers; etc. The aforementioned other monomers can be monomers containing aromatic rings that are not monomers containing multiple aromatic rings, monomers without aromatic rings, or combinations thereof.

[0198] Non-limiting examples of compounds containing multiple aromatic rings include: compounds having a structure in which two or more non-fused aromatic rings are bonded together by a linking group; compounds having a structure in which two or more non-fused aromatic rings are directly (i.e., without the aid of other atoms) chemically bonded together; compounds having a fused aromatic ring structure; compounds having a fluorene structure; compounds having a dinaphthothiophene structure; and compounds having a dibenzothiophene structure. Compounds containing multiple aromatic rings may be used alone or in combination of two or more.

[0199] As specific examples of the compounds having the fluorene structure, in addition to the monomers having the fluorene structure and the oligomers of the homopolymers or copolymers thereof, examples include 9,9-bis(4-hydroxyphenyl)fluorene (refractive index: 1.68), 9,9-bis(4-aminophenyl)fluorene (refractive index: 1.73), 9,9-bis(4-hydroxy-3-methylphenyl)fluorene (refractive index: 1.68), 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (refractive index: 1.65), and other 9,9-bisphenylfluorene and their derivatives.

[0200] As specific examples of compounds having the dinaphthothiophene structure, in addition to the monomers having the dinaphthothiophene structure and oligomers of homopolymers or copolymers thereof, examples include dinaphthothiophene (refractive index: 1.808); 6-hydroxymethyl dinaphthothiophene (refractive index: 1.766) and other hydroxyalkyl dinaphthothiophenes; 2,12-dihydroxydinaphthothiophene (refractive index: 1.750) and other dihydroxydinaphthothiophenes; 2,12-di... Dihydroxyalkyloxydinaphthothiophene (refractive index: 1.677) and other dihydroxyalkyloxydinaphthothiophenes; 2,12-diglycidyloxydinaphthothiophene (refractive index: 1.723) and other diglycidyloxydinaphthothiophenes; 2,12-diallyloxydinaphthothiophene (abbreviation: 2,12-DAODNT, refractive index: 1.729) and other dinaphthothiophenes having two or more olefinic unsaturated groups; and other dinaphthothiophenes and their derivatives.

[0201] As specific examples of compounds having the dibenzothiophene structure, in addition to the monomers having the dibenzothiophene structure and the oligomers that are homopolymers or copolymers of the monomers, examples include dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), and 4,6-dimethyldibenzothiophene (refractive index: 1.617).

[0202] As a potential additive (H) ROExamples of heterocyclic organic compounds (hereinafter also referred to as heterocyclic organic compounds) that are options for the following can be listed: thioepoxides, compounds having triazine rings, etc. As an example of a thioepoxide, the bis(2,3-cyclothiopropyl) disulfide and its polymer (refractive index 1.74) disclosed in Japanese Patent No. 3712653 can be listed. As an example of a compound having a triazine ring, a compound having at least one (e.g., 3 to 40, preferably 5 to 20) triazine ring per molecule can be listed. It should be noted that triazine rings are aromatic; therefore, compounds having triazine rings are also included in the above concept of compounds containing aromatic rings. Furthermore, compounds having multiple triazine rings are also included in the above concept of compounds containing multiple aromatic rings.

[0203] In some methods, as an additive (H) RO The preferred choice is a compound without olefinic unsaturated groups. This suppresses the deterioration of the adhesive composition caused by heat and light (due to gelation and increased viscosity leading to decreased leveling properties) and improves storage stability. From the presence of this additive (H... RO From the viewpoint of suppressing dimensional changes, deformations (warping, undulations, etc.), and optical distortions caused by the reaction of olefin unsaturated groups in adhesive optical films and laminates containing such adhesive optical films, it is also preferable to use additives (H) that do not have olefin unsaturated groups. RO ).

[0204] Using oligomers as additives (H) RO In this process, the oligomer can be obtained by polymerizing the corresponding monomer components using known methods. When manufacturing the above-mentioned oligomer via free radical polymerization, polymerization initiators, chain transfer agents, emulsifiers, etc., used for free radical polymerization can be appropriately added to the monomer components to carry out polymerization. There are no particular limitations on the polymerization initiators, chain transfer agents, emulsifiers, etc., used for free radical polymerization, and they can be selected and used appropriately. It should be noted that the weight-average molecular weight of the oligomer can be controlled by the amount of polymerization initiator and chain transfer agent used, and the reaction conditions; their amounts should be adjusted appropriately according to their types.

[0205] Examples of chain transfer agents include lauryl thiol, glycidyl thiol, mercaptoacetic acid, 2-mercaptoethanol, α-thioglycerol, mercaptoacetic acid, 2-ethylhexyl mercaptoacetic acid, and 2,3-dimercapto-1-propanol. One chain transfer agent can be used alone, or two or more can be used in combination. The amount of chain transfer agent used can be set according to the composition of the monomer components used in the oligomer synthesis, the type of chain transfer agent, etc., to obtain oligomers with the desired weight-average molecular weight. In some cases, it is appropriate to set the amount of chain transfer agent to about 15 parts by weight or less relative to 100 parts by weight of the total amount of monomers used in the oligomer synthesis; it can be 10 parts by weight or less, or about 5 parts by weight or less. There is no particular limitation on the lower limit of the amount of chain transfer agent used relative to 100 parts by weight of the total amount of monomers used in the oligomer synthesis; for example, it can be 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more.

[0206] Using additives (H) RO In the case of additives (H) acting as refractive index enhancers, the additives (H) RO The amount of additive (H) used relative to 100 parts by weight of the base polymer (or the total amount of multiple compounds when using them) is not particularly limited and can be set according to the purpose. From the viewpoint of increasing the refractive index of the adhesive, the additive (H) RO The amount used relative to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, 3 parts by weight or more, preferably 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. In some methods, the additive (H) RO The amount used relative to 100 parts by weight of the base polymer can be set to, for example, 80 parts by weight or less. From the viewpoint of achieving a good balance between increasing the refractive index of the adhesive and suppressing the reduction of adhesive and optical properties, setting it to 60 parts by weight or less is advantageous, and preferably 45 parts by weight or less. In some approaches that place greater emphasis on adhesive and optical properties, the additive (H... RO The amount used relative to 100 parts by weight of the base polymer can be, for example, less than 30 parts by weight, less than 20 parts by weight, less than 15 parts by weight, or less than 10 parts by weight.

[0207] (Plasticized materials)

[0208] In some embodiments of the adhesive optical film disclosed herein, the adhesive layer may contain, in addition to the base polymer (e.g., acrylic polymer (A)) as described above, a plasticizing material with a molecular weight lower than that of the base polymer. The use of the plasticizing material improves the flexibility of the adhesive layer, enhances adhesion to the adhered object, improves the overall flexibility of the adhesive optical film, and increases its adaptability to deformation. From the viewpoint of compatibility and transparency within the adhesive layer, organic materials are preferred as the plasticizing material. The plasticizing material can be, or can also be, the aforementioned refractive index enhancer (e.g., the aforementioned additive (H)). RO Materials.

[0209] The molecular weight of the plasticizer can be lower than that of the base polymer, and there is no particular limitation. In some embodiments, from the viewpoint of easily exhibiting a plasticizing effect, the molecular weight of the plasticizer can be less than 30,000, less than 25,000, less than 10,000, preferably less than 5,000, more preferably less than 3,000 (e.g., less than 1,000), less than 800, less than 600, less than 500, or less than 400. A lower molecular weight of the plasticizer is advantageous from the viewpoint of improved compatibility within the adhesive layer. Furthermore, in some embodiments, from the viewpoint of easily achieving a sufficient plasticizing effect, a molecular weight of 130 or more of the plasticizer is appropriate, preferably 150 or more, and can be 170 or more, 200 or more, 250 or more, or 300 or more. In some embodiments, the molecular weight of the plasticizer can be 500 or more, 1,000 or more, or 2,000 or more. A lower molecular weight of the plasticizer is also preferred from the viewpoint of heat resistance and suppression of contamination of the adhered material.

[0210] Non-limiting examples of compounds that can be used as plasticizing materials include: compounds that can be used as monomers (m1) (e.g., (meth)acrylates having aromatic rings such as benzyl, phenoxy, and naphthyl; monomers having a fluorene structure; monomers having a dinaphthothiophene structure; monomers having a dibenzothiophene structure, etc.); oligomers containing compounds that can be used as monomers (m1) as monomer units; compounds with structures formed by removing and replacing the portion having an olefinically unsaturated group from compounds that can be used as monomers (m1) with a hydrogen atom or a group that does not have an olefinically unsaturated group (e.g., 3-phenoxybenzyl alcohol); etc. For oligomers containing compounds that can be used as monomers (m1) as monomer units, from the viewpoint of improving flexibility, low Tg monomers such as n-butyl acrylate and 2-ethylhexyl acrylate can also be copolymerized, for example. As a plasticizing material, one or more of the known plasticizers (such as phthalate esters, terephthalate esters, adipate esters, adipate polyesters, dibenzoic acid esters, etc.) can be used.

[0211] In some methods, organic materials with a refractive index of about 1.50 or higher (more preferably 1.53 or higher) are preferably used as plasticizers. Specific examples of compounds that can be used as plasticizers include: diethylene glycol dibenzoate (refractive index 1.55), dipropylene glycol dibenzoate (refractive index 1.54), 3-phenoxytoluene (refractive index 1.57), 3-ethylbiphenyl (refractive index 1.59), 3-methoxybiphenyl (refractive index 1.61), 4-methoxybiphenyl (refractive index 1.57), polyethylene glycol dibenzoate, 3-phenoxybenzyl alcohol (refractive index 1.59), triphenyl phosphate (refractive index 1.56), benzyl benzoate (refractive index 1.57), 4-(tert-butyl) Phenylacetic diphenyl phosphate (refractive index 1.56), trimethylphenyl phosphate (refractive index 1.55), butyl benzyl phthalate (refractive index 1.54), rosin methyl ester (refractive index 1.53), alkyl benzyl phthalate (refractive index 1.53), butyl(benzenesulfonyl)amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2-ethylhexyl diphenyl phosphate (refractive index 1.51), tris(2,4-di-tert-butylphenyl) phosphite, etc., but not limited to these. From the viewpoint of refractive index and compatibility, diethylene glycol dibenzoate, for example, may be preferred. There is no particular upper limit to the refractive index of the plasticizing material, for example, it can be below 3.00. In some approaches, from the viewpoints of ease of preparation of the adhesive composition and compatibility within the adhesive, it is appropriate for the refractive index of the plasticizing material to be below 2.50, advantageous to be below 2.00, below 1.90, below 1.80, or below 1.70.

[0212] It should be noted that the refractive index of the plasticized material, like that of the monomer, was measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C. If the manufacturer provides a nominal value for the refractive index at 25°C, that value can be used.

[0213] In using plasticizing materials, the amount of plasticizing material relative to 100 parts by weight of the base polymer is not particularly limited and can be set according to the purpose. From the viewpoint of improving the plasticizing effect, the amount of plasticizing material relative to 100 parts by weight of the base polymer can be, for example, 0.1 parts by weight or more, or 0.5 parts by weight or more. From the viewpoint of obtaining a higher plasticizing effect, it is preferable to set it to 1 part by weight or more, more preferably 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. In addition, from the viewpoint of achieving a good balance between the high refractive index and transparency of the adhesive and the plasticizing effect, it is appropriate to set the amount of plasticizing material relative to 100 parts by weight of the base polymer to about 100 parts by weight or less, preferably 80 parts by weight or less, more preferably 60 parts by weight or less, 45 parts by weight or less, 35 parts by weight or less, or 25 parts by weight or less. In some approaches that place greater emphasis on adhesive and optical properties, the amount of plasticizer used relative to 100 parts by weight of the base polymer can be less than 15 parts by weight, less than 10 parts by weight, or less than 5 parts by weight.

[0214] (Leveling agent)

[0215] In some embodiments, the adhesive composition used to form the adhesive layer may contain a leveling agent as needed to improve the appearance of the adhesive layer formed by the composition (e.g., to improve the uniformity of thickness) and to improve the coatability of the adhesive composition. Non-limiting examples of leveling agents include acrylic leveling agents, fluorinated leveling agents, and silicone leveling agents. For example, suitable substances can be selected from commercially available leveling agents and used by conventional methods.

[0216] In some embodiments, the leveling agent described above may preferably be a polymer (hereinafter referred to as "polymer (B)") comprising a monomer having a polyorganosiloxane backbone (hereinafter also referred to as "monomer S1") and an acrylic monomer (hereinafter also referred to as "monomer raw material B"). Polymer (B) may refer to a copolymer of monomer S1 and an acrylic monomer. Polymer (B) may be used alone or in combination of two or more.

[0217] There are no particular limitations on monomer S1, and any monomer containing a polyorganosiloxane backbone can be used. Monomer S1 is preferably a monomer with a polymerizable reactive group at one end. Specifically, monomer S1 with a polymerizable reactive group at one end and no functional group at the other end that would crosslink with the base polymer (the base polymer of the adhesive composition to which the leveling agent is to be formulated, such as an acrylic polymer) is preferably used. Commercially available examples include single-terminal reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. (e.g., trade names X-22-174ASX, X-22-2426, X-22-2475, KF-2012, etc.). Monomer S1 can be used alone or in combination of two or more.

[0218] The functional group equivalent of monomer S1 can be, for example, around 100 g / mol to 30,000 g / mol. In some preferred embodiments, the functional group equivalent is, for example, 500 g / mol or more, 800 g / mol or more, 1500 g / mol or more, or 2000 g / mol or more. Alternatively, the functional group equivalent can be, for example, below 20,000 g / mol, below 10,000 g / mol, below 7,000 g / mol, or below 5,500 g / mol. When the functional group equivalent of monomer S1 is within the above range, it is easy to achieve good leveling effect.

[0219] It should be noted that when using two or more monomers with different functional group equivalents as monomer S1, the functional group equivalent of monomer S1 can be the sum of the products of the functional group equivalents of each monomer and the weight fraction of that monomer.

[0220] Here, "functional group equivalent" refers to the weight of the backbone (e.g., polydimethylsiloxane) bonded by each functional group. The unit g / mol is used to convert to 1 mol of functional groups. The functional group equivalent of monomer S1 can be determined, for example, based on nuclear magnetic resonance (NMR)... 1 It is calculated from the spectral intensity of H-NMR (proton NMR). 1 The calculation of the functional group equivalent (g / mol) of monomer S1 from the spectral intensity of H-NMR can be based on 1 The usual structural analysis methods in H-NMR spectroscopy are performed with reference to the description in Japanese Patent No. 5951153 when necessary. In the functional group equivalent of monomer S1, the aforementioned functional groups refer to polymerizable functional groups (e.g., olefinic unsaturated groups such as (meth)acryloyl, vinyl, allyl, etc.).

[0221] The content of monomer S1 in monomer raw material B can be an appropriate value within the range that allows the desired effect to be achieved using monomer S1, and is not limited to a specific range. In some embodiments, the content of monomer S1 in monomer raw material B can be, for example, 5-60% by weight, 10-50% by weight, or 15-40% by weight.

[0222] In addition to monomer S1, monomer raw material B also contains acrylic monomers capable of copolymerizing with monomer S1. This improves the compatibility of the polymer (B) within the adhesive layer. Examples of acrylic monomers that can be used in monomer raw material B include alkyl acrylates. Here, "alkyl" refers to chain-like (including linear and branched) alkyl groups, excluding alicyclic hydrocarbon groups described later. In some embodiments, monomer raw material B may contain (meth)acrylic acid C. 4-12 Alkyl ester (preferably (meth)acrylic acid C) 4-10 Alkyl esters, such as (meth)acrylic acid C 6-10 At least one of alkyl esters. In some other embodiments, monomer raw material B may contain methacrylic acid C. 1-18 Alkyl ester (preferably C methacrylate) 1-14 Alkyl esters, such as C methacrylate 1-10 At least one of alkyl esters. Monomer raw material B may, for example, contain one or more of methyl methacrylate (MMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA) as acrylic monomers.

[0223] Other examples of the aforementioned acrylic monomers include (meth)acrylates having alicyclic hydrocarbon groups. Examples include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, and 1-adamantyl (meth)acrylate. Alternatively, (meth)acrylates without alicyclic hydrocarbon groups may also be used.

[0224] The content of the above-mentioned alkyl methacrylate and the above-mentioned methacrylate having alicyclic hydrocarbon group in monomer raw material B can be, for example, 10% or more and 95% or less by weight, 20% or more and 95% or less by weight, 30% or more and 90% or less by weight, 40% or more and 90% or less by weight, or 50% or more and 85% or less by weight.

[0225] Other examples of monomers that can be included together with monomer S1 in monomer raw material B include: carboxyl-containing monomers, anhydride-containing monomers, hydroxyl-containing monomers, epoxy-containing monomers, cyano-containing monomers, isocyanate-containing monomers, amide-containing monomers, monomers having a ring containing a nitrogen atom, aminoalkyl esters of (meth)acrylate, vinyl esters, vinyl ethers, olefins, (meth)acrylates having an aromatic hydrocarbon group, (meth)acrylates containing a halogen atom, etc.

[0226] The Mw of polymer (B) can be, for example, 5000 or more, preferably 10000 or more, or 15000 or more. Alternatively, the Mw of polymer (B) can be, for example, 200000 or less, preferably 100000 or less, 50000 or less, or 30000 or less. By setting the Mw of polymer (B) within an appropriate range, suitable compatibility and leveling properties can be achieved.

[0227] Polymer (B) can be produced, for example, by polymerizing the aforementioned monomers using known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization.

[0228] To adjust the molecular weight of polymer (B), chain transfer agents can be used as needed. Examples of chain transfer agents include compounds with thiol groups such as n-dodecyl mercaptan, mercaptoethanol, and α-thioglycerol; thioglycolic acid esters such as thioglycolic acid and methyl thioglycolate; α-methylstyrene dimers; etc. There are no particular limitations on the amount of chain transfer agent used; it can be appropriately set to obtain polymer (B) with the desired molecular weight. In some methods, the amount of chain transfer agent used relative to 100 parts by weight of the monomer can be, for example, 0.1 to 5 parts by weight, 0.2 to 3 parts by weight, or 0.5 to 2 parts by weight.

[0229] The amount of polymer (B) used relative to the base polymer (e.g., an acrylic polymer) per 100 parts by weight can be set to 0.001 parts by weight or more. From the viewpoint of obtaining a better performance, it can be set to 0.01 parts by weight or more, or 0.03 parts by weight or more. Alternatively, the amount of polymer (B) used can be, for example, 3 parts by weight or less. From the viewpoint of reducing the influence on the refractive index, it is appropriate to set it to 1 part by weight or less, or 0.5 parts by weight or less, or 0.1 parts by weight or less.

[0230] (Inorganic particles)

[0231] The technology disclosed herein can preferably be implemented in a manner that substantially does not use inorganic particles as refractive index enhancers. Of course, in some embodiments of the adhesive optical thin films disclosed herein, inorganic particles can be used as refractive index enhancers to the extent that desired optical properties (total transmittance, haze value) are met without significantly impairing the properties as an adhesive. Examples of inorganic particles that can be used as refractive index enhancers include inorganic particles composed of inorganic oxides (specifically metal oxides) such as titanium oxides (titanium oxide, TiO2), zirconium oxides (zirconia, ZrO2), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide (Nb2O5, etc.). The average particle size of the aforementioned inorganic particles (referring to the 50% volume average particle size based on laser scattering / diffraction) can, for example, be selected from the range of approximately 10 nm to 100 nm. It should be noted that, regarding the refractive index of the inorganic particles, the measurement was performed using a commercially available spectroellipsometer on a single-layer film (set as the film thickness for which the refractive index can be measured) of the material constituting the inorganic particles, under conditions of a measurement wavelength of 589 nm and a measurement temperature of 23°C. As the spectroellipsometer, for example, product name "EC-400" (manufactured by JA. Woolam) or its equivalent can be used. When using inorganic particles as a refractive index enhancer, the amount used is preferably less than 5 parts by weight relative to 100 parts by weight of the base polymer, more preferably less than 1 part by weight. Furthermore, when using additives (H... RO In the method described above, the amount of the inorganic particles used, on a weight basis, is preferably set to the amount of the additive (H) RO The dosage is less than twice that of the original dosage, preferably less than once or less than 0.5 times.

[0232] (Cross-linking agent)

[0233] In the technology disclosed herein, the adhesive composition used to form the adhesive layer may contain a crosslinking agent as needed for purposes such as adjusting the cohesive strength of the adhesive. As a crosslinking agent, crosslinking agents known in the field of adhesives, such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based resins, and metal chelate-based crosslinking agents, can be used. Isocyanate-based crosslinking agents are preferred. Other examples of crosslinking agents include monomers having two or more olefinic unsaturated groups per molecule, i.e., multifunctional monomers. One type of crosslinking agent may be used alone, or two or more may be used in combination.

[0234] As isocyanate-based crosslinking agents, isocyanate compounds with two or more functionalities can be used, such as aliphatic polyisocyanates like trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), and dimer diisocyanate; alicyclic isocyanates like cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and 1,3-bis(isocyanate-methyl)cyclohexane; aromatic isocyanates like 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenylenediamine diisocyanate (XDI); and polyisocyanate modifiers that have been modified using urea-formate bonds, biuret bonds, isocyanurate bonds, urea-dione bonds, urea bonds, carbodiimide bonds, urea-ketimide bonds, and oxadiazine-trione bonds; etc. Examples of commercially available products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N (and above, manufactured by Takeda Pharmaceutical Company Limited), Sumidur T80, Sumidur L, Desmodur N3400 (and above, manufactured by Sumika Bayer Urethane Co., Ltd.), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (and above, manufactured by Tosoh Corporation), etc. Isocyanate compounds can be used alone or in combination of two or more. They can also be used in combination of difunctional isocyanate compounds and trifunctional or higher isocyanate compounds.

[0235] Examples of epoxy-based crosslinking agents include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These can be used alone or in combination of two or more.

[0236] Examples of multifunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl methacrylate, vinyl methacrylate, divinylbenzene, bisphenoxyethanol fluorene di(meth)acrylate, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol (meth)acrylate, hexanediol di(meth)acrylate, etc. Multifunctional monomers can be used alone or in combination of two or more.

[0237] When using a crosslinking agent (which can be a multifunctional monomer), the amount used is not particularly limited; for example, it can be set to a range of about 0.001 parts by weight to 5.0 parts by weight relative to 100 parts by weight of the base polymer. From the viewpoint of improving the flexibility of the adhesive, in some embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the base polymer is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and can be 1.0 parts by weight or less, 0.5 parts by weight or less, or 0.2 parts by weight or less. Furthermore, from the viewpoint of appropriately maximizing the effect of the crosslinking agent, in some embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the base polymer can be, for example, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.08 parts by weight or more.

[0238] To facilitate the crosslinking reaction more efficiently, a crosslinking catalyst can also be used. Examples of crosslinking catalysts include tetrabutyl titanate, tetraisopropyl titanate, and ferric acetylacetone. Metal-based crosslinking catalysts such as iron(III)), butyltin oxide, and dioctyltin dilaurate are preferred. Among these, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. There is no particular limitation on the amount of crosslinking catalyst used. Considering the balance between the rate of the crosslinking reaction and the pot life of the adhesive composition, the amount of crosslinking catalyst used relative to 100 parts by weight of the base polymer can be set to, for example, a range of about 0.0001 parts by weight and less than 1 part by weight, preferably a range of 0.001 parts by weight and less than 0.5 parts by weight.

[0239] The adhesive composition may contain a keto-enol tautomer as a crosslinking delay agent. This extends the pot life of the adhesive composition. For example, in adhesive compositions containing isocyanate-based crosslinking agents, a keto-enol tautomer is preferably used. Various β-dicarbonyl compounds can be used as keto-enol tautomers. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) are preferred. One keto-enol tautomer can be used alone or in combination of two or more. The amount of the keto-enol tautomer relative to 100 parts by weight of the base polymer can be, for example, 0.1 parts by weight or more and 20 parts by weight or less, 0.5 parts by weight or more and 10 parts by weight or less, or 1 part by weight or more and 5 parts by weight or less.

[0240] (Thickening agent)

[0241] The adhesive layer in the technology disclosed herein may contain a tackifier. Known tackifiers such as rosin-based, terpene-based, phenolic, hydrocarbon-based, ketone-based, polyamide-based, epoxy-based, and elastic-system tackifiers can be used as tackifiers. One or more of these can be used alone or in combination. The amount of tackifier used is not particularly limited and can be set according to the purpose and application to achieve appropriate adhesive properties. In some embodiments, from the viewpoint of refractive index and transparency, it is appropriate for the amount of tackifier used to be 30 parts by weight or less relative to 100 parts by weight of the base polymer of the adhesive layer, preferably 10 parts by weight or less, and more preferably 5 parts by weight or less. The technology disclosed herein can preferably be implemented without the use of a tackifier.

[0242] (Other additives)

[0243] In the technology disclosed herein, the adhesive composition used to form the adhesive layer may, as needed, include plasticizers, softeners, colorants, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, and other known additives that can be used in adhesive compositions, to a extent that does not significantly impair the effects of the present invention. Regarding these various additives, conventionally known substances can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

[0244] (Creating the adhesive layer)

[0245] In the technology disclosed herein, the adhesive constituting the adhesive layer can be an adhesive formed by curing a solvent-based, active energy ray-curable, water-dispersible, or hot-melt adhesive composition through drying, crosslinking, polymerization, cooling, etc., i.e., a cured product of the aforementioned adhesive composition. The curing method of the adhesive composition (e.g., drying, crosslinking, polymerization, cooling, etc.) can be applied in only one way, or in two or more ways simultaneously or at multiple stages. For solvent-based adhesive compositions, typically the composition can be dried (preferably further crosslinked) to form an adhesive. For active energy ray-curable adhesive compositions, typically, polymerization and / or crosslinking reactions are carried out by irradiation with active energy rays to form the adhesive. When drying is required for active energy ray-curable adhesive compositions, irradiation with active energy rays after drying is preferable.

[0246] The adhesive layer of the adhesive-type optical film disclosed herein can be formed by applying (e.g., coating) an adhesive composition to a suitable surface and then curing the composition. The coating of the adhesive composition can be carried out using conventional coating machines such as gravure roller coaters, reverse roller coaters, licker coaters, dip roller coaters, bar coaters, doctor blade coaters, and spray coaters.

[0247] The adhesive layer of the adhesive optical film disclosed herein can be either a post-curing adhesive layer or a non-post-curing adhesive layer. Here, a post-curing adhesive layer refers to an adhesive layer that can be further cured by irradiation with heat or active energy rays (e.g., ultraviolet light). Examples of post-curing adhesive layers include adhesive layers having unreacted olefinic unsaturated groups in the side chains of the base polymer, and adhesive layers containing unreacted polyfunctional monomers. In some embodiments, the adhesive layer preferably does not have post-curing properties. An adhesive layer without post-curing properties does not produce dimensional changes associated with post-curing reactions (i.e., good dimensional stability), thus easily suppressing warpage of the adhesive optical film or the laminate containing it. The absence of dimensional changes (e.g., curing shrinkage) caused by post-curing is also advantageous from the viewpoint of suppressing optical distortion of the adhesive layer.

[0248] The thickness of the adhesive layer is not particularly limited, but can be set to 3 μm or more, preferably 5 μm or more. With an adhesive layer thickness of 5 μm or more, good adhesive properties are easily obtained. Furthermore, an adhesive layer of this thickness readily absorbs any unevenness that may exist on the surface of the adherend, thus achieving a good bond with the adherend. From the viewpoint of preventing coloring and uneven coloring caused by light interference, a thickness of 5 μm or more is also preferred. In some embodiments, the thickness of the adhesive layer can be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 85 μm or more. In other embodiments, the thickness of the adhesive layer can be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. A less excessive thickness of the adhesive layer is advantageous from the viewpoint of achieving thinner adhesive optical films. The techniques disclosed herein can preferably be implemented with the adhesive layer thickness ranging from 3 μm to 200 μm (more preferably 5 μm to 100 μm). For adhesive optical films having a first adhesive layer and a second adhesive layer on the first and second surfaces of a light-transmitting member, the thickness of the adhesive layer can be at least the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from the same range.

[0249] (Peel strength)

[0250] In some embodiments of the adhesive optical film disclosed herein, it is suitable for the adhesive optical film to have a peel strength to the glass plate of about 1.0 N / 25 mm or more (e.g., 1.5 N / 25 mm or more), preferably 2 N / 25 mm or more, more preferably 3 N / 25 mm or more, and it can be 4 N / 25 mm or more, 6 N / 25 mm or more, 8 N / 25 mm or more, 10 N / 25 mm or more, or 12 N / 25 mm or more. There is no particular limitation on the upper limit of the peel strength; for example, it can be 30 N / 25 mm or less, 25 N / 25 mm or less, or 20 N / 25 mm or less.

[0251] Here, the peel strength can be determined as follows: The film is pressed onto an alkaline glass plate (the substrate), placed at 23°C and 50% RH for 30 minutes, then immersed in a pressure degassing apparatus (autoclave) for 30 minutes at 50°C and 0.5 MPa. After being placed at 23°C and 50% RH for 24 hours, the 180° peel adhesion force is measured at a peel angle of 180° and a tensile speed of 300 mm / min. During the measurement, if necessary, a suitable lining material (e.g., a polyethylene terephthalate (PET) film with a thickness of approximately 25 μm to 50 μm) can be applied to the adhesive optical film of the test object to reinforce it. Specifically, the peel strength can be measured according to the method described in the examples below.

[0252] When the adhesive optical film disclosed herein is in the form of a double-sided adhesive optical film having a first adhesive surface and a second adhesive surface, in some embodiments, the aforementioned peel strength preferably applies at least to the first adhesive surface, and more preferably to both the first and second adhesive surfaces. The peel strength of the first adhesive surface to the glass plate and the peel strength of the second adhesive surface to the glass can be the same or different.

[0253] <Translucent Components>

[0254] In the technology disclosed herein, the material of the light-transmitting component is not particularly limited and can be appropriately selected according to the purpose and method of use of the adhesive optical film. Examples of light-transmitting components constituting the adhesive optical film include optical components described later (such as functional films such as polarizing plates).

[0255] In some embodiments, various thin film substrates are preferably used as the light-transmitting component. As the aforementioned thin film substrate, a resin film capable of independently maintaining its shape (self-supporting or independent) is preferably used as the base film. Here, "resin film" refers to a non-porous structure, typically substantially free of air bubbles (non-porous). Therefore, the aforementioned resin film is a concept distinct from foamed films and nonwoven fabrics. As the aforementioned resin film, a film capable of independently maintaining its shape (self-supporting or independent) is preferably used. The aforementioned resin film can be a single-layer structure or a multi-layer structure with two or more layers (e.g., a three-layer structure).

[0256] Materials constituting resin films include, for example, polyester resins with polyesters as the main component, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins with polyolefins as the main component, such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as cellulose triacetate; acetate resins; polysulfone resins; polyethersulfone resins; polycarbonate resins; nylon 6; nylon 66; some aromatic polyamides and other polyamide (PA) resins; and polyimide (…). Cyclic polyolefin resins such as PI (polyimide) resins, transparent polyimide resins, polyamide-imide (PAI), polyether ether ketone (PEEK), polyether sulfone (PES), norbornene resins, (meth)acrylic acid resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyarylate resins, polyphenylene sulfide (PPS) resins, polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE), and fluorinated polyimide resins.

[0257] The aforementioned resin film can be a film formed using a resin material containing only one such resin, or a film formed using a blend of two or more resin materials. The resin film can be unstretched or stretched (e.g., uniaxially or biaxially stretched). In some embodiments, PET film, PBT film, PEN film, unstretched polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, PP / PE blend film, etc., are preferred. Examples of resin films preferred from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film, and PEEK film. From the viewpoint of ease of acquisition, PET film and PPS film are particularly preferred, with PET film being the most preferred.

[0258] In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and antiblocking agents may be added as needed, without significantly impairing the effects of the present invention. The amount of additives added is not particularly limited and can be appropriately set according to the intended use of the adhesive optical film.

[0259] There are no particular limitations on the manufacturing method of resin films. For example, commonly known resin film forming methods such as extrusion molding, blow molding, T-die casting, and calendering can be appropriately used.

[0260] The aforementioned light-transmitting component may be substantially composed of such a base film. Alternatively, the aforementioned light-transmitting component may also include auxiliary layers in addition to the aforementioned base film. Examples of such auxiliary layers include optical property adjustment layers (e.g., coloring layers, anti-reflective layers), printing layers for imparting a desired appearance, laminated layers, antistatic layers, primer layers, release layers, and other surface treatment layers.

[0261] In some embodiments, the total light transmittance of the light-transmitting component can be, for example, higher than 50%, or higher than 70%. In some preferred embodiments, the total light transmittance of the light-transmitting component is 80% or higher, more preferably 90% or higher, and may also be 95% or higher (e.g., 95-100%). The above-mentioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. As a transmittance meter, the trade name "HAZEMETER HM-150" or its equivalent manufactured by Murakami Color Technology Research Institute is used. As a suitable example of the above-mentioned light-transmitting component, a resin film with light transmittance can be cited. The above-mentioned light-transmitting component can be an optical film.

[0262] In some embodiments, materials that can be used to constitute the aforementioned translucent components include: metallic materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, or alloys containing two or more of these; and polyimide resins, acrylic resins, polyether nitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (such as aramid resins), polyarylate resins, fluorine resins, polycarbonate resins, cellulose polymers such as cellulose diacetate and cellulose triacetate. Carbon materials such as vinyl butyral polymers, liquid crystal polymers, carbon nanotubes, and graphene; various resin materials (typically plastic materials) such as PEDOT (poly(3,4-ethylenedioxythiophene)) and polyaniline; metal oxides and their mixtures such as alumina, zirconium oxide, titanium oxide, SiO2, ITO (indium tin oxide), and ATO (antimony-doped tin oxide); nitrides and their complexes such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride; inorganic materials such as alkaline glass, alkali-free glass, quartz glass, borosilicate glass, and sapphire glass; their mixtures and complexes; but not limited to these.

[0263] The thickness of the light-transmitting component is not particularly limited and can be selected according to the intended use and application method of the adhesive optical film. For example, the thickness of the light-transmitting component can be 500 μm or less, but from the viewpoint of processability and workability, it is preferably 300 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, or even 10 μm or less. As the thickness of the light-transmitting component decreases, there is a tendency to improve the ability to follow the surface shape of the adhered object. Furthermore, from the viewpoint of processability and workability, the thickness of the light-transmitting component can, for example, be 2 μm or more, 10 μm or more, or 25 μm or more.

[0264] For one side of the laminated adhesive layer in a translucent component, conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and the formation of a base coat based on a primer can be performed as needed. Such surface treatments can be used to improve the anchoring of the adhesive layer to the translucent component. The composition of the primer used in the formation of the base coat is not particularly limited and can be appropriately selected from known compositions. The thickness of the base coat is not particularly limited, but is typically suitable at around 0.01 μm to 1 μm, preferably around 0.1 μm to 1 μm. Other treatments that can be performed on the translucent component as needed include antistatic layer formation treatment, coloring layer formation treatment, and printing treatment. These treatments can be applied individually or in combination.

[0265] The thickness of the adhesive optical film disclosed herein can be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, 120 μm or less, 75 μm or less, or 50 μm or less. Furthermore, from the viewpoint of processability, the thickness of the adhesive optical film can be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

[0266] It should be noted that the thickness of adhesive optical films refers to the thickness of the portion adhered to the substrate. For example, for Figure 1 The adhesive optical film 1 shown refers to the thickness from the first surface (adhesive surface) 10A of the adhesive layer to the second surface 20B of the light-transmitting member, excluding the thickness of the release liner 30.

[0267] <Adhesive optical films with release liner>

[0268] The adhesive optical film disclosed herein can be in the form of an adhesive article obtained by abutting the surface (adhesive surface) of an adhesive layer against the release surface of a release liner. Therefore, according to this specification, an adhesive optical film (adhesive article) with a release liner is provided, comprising: any adhesive optical film disclosed herein, and a release liner having a release surface abutting against the adhesive surface of the adhesive optical film.

[0269] The release liner is not particularly limited; for example, a release liner with a release treatment layer on a release liner substrate such as a resin film or paper (which may be paper laminated with resins such as polyethylene) can be used, or a release liner containing a resin film formed from a low-adhesion material such as a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.). The release treatment layer can be a layer formed by surface-treating the release liner substrate with a release treatment agent. The release treatment agent can be a known release treatment agent such as a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorinated release treatment agent, or molybdenum sulfide (IV). In some embodiments, a release liner having a release treatment layer based on a silicone-based release treatment agent is preferred. The thickness and formation method of the release treatment layer are not particularly limited, and can be set in a way that provides appropriate peelability on the adhesive side surface of the release liner.

[0270] In some embodiments, from the viewpoint of smoothness of the adhesive surface, a release liner (hereinafter also referred to as a release film) having a release treatment layer on a resin film (hereinafter also referred to as a release film substrate) serving as the release liner substrate is preferred. Various plastic films can be used as the release film substrate. In this specification, the plastic film is typically a non-porous sheet, a concept distinguished, for example, from nonwoven fabrics (i.e., excluding nonwoven fabrics).

[0271] Examples of materials used for the aforementioned plastic films include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as cellulose triacetate; acetate resins; polysulfone resins; polyethersulfone resins; polycarbonate resins; polyamide resins; polyimide resins; norbornene resins; cyclic polyolefin resins such as (meth)acrylic acid resins; polyvinyl chloride resins; polyvinylidene chloride resins; polystyrene resins; polyvinyl alcohol resins; ethylene-vinyl acetate copolymer resins; ethylene-vinyl alcohol copolymer resins; polyarylate resins; and polyphenylene sulfide resins. A release film substrate formed from one or more of these resins can be used. Among these, polyester resin films (e.g., PET films) formed from polyester resins are preferred release film substrates.

[0272] The plastic film used as the release film substrate can be an unstretched film, a uniaxially stretched film, or a biaxially stretched film. Furthermore, the plastic film can be a single-layer structure or a multi-layer structure containing two or more sub-layers. The plastic film can be formulated with known additives that can be used in the release film substrate of adhesive sheets, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, dyes, colorants, lubricants, fillers, antistatic agents, and nucleating agents. In multi-layer plastic films, each additive can be incorporated into all sub-layers or only into a portion of the sub-layers.

[0273] In some preferred embodiments, the release film substrate (typically a plastic film) is preferably a substrate whose content of particles such as inorganic particles (e.g., pigments, lubricants, fillers, etc.) is limited in the layers on its release surface side, or which substantially does not contain such particles. Here, "substantially does not contain" means that the amount of particles (e.g., inorganic particles) in that layer is less than 1% by weight, preferably less than 0.1% by weight (e.g., 0 to 0.01% by weight). Release films with such release film substrates tend to be films with low arithmetic mean roughness Ra and low maximum height Rz of the release surface. When the release film substrate (typically a plastic film) comprises a multilayer structure, the particle content in the layers on the release surface side can be less than 1 / 10 (e.g., less than 1 / 50) of the particle content in the layers other than the layers on the release surface side.

[0274] For an adhesive optical film with release liner on both the first and second adhesive surfaces, the release liner disposed on one adhesive surface (hereinafter also referred to as a release liner) and the release liner disposed on the other adhesive surface (hereinafter also referred to as another release liner) may have the same material and structure, or they may have different materials and structures.

[0275] The thickness of the release liner (preferably a release film) is not particularly limited, and can be, for example, around 10 μm to 500 μm. From the viewpoint of the strength and dimensional stability of the release liner, a thickness of 20 μm or more is suitable, preferably 30 μm or more, and can be 35 μm or more, 40 μm or more, or 45 μm or more. Furthermore, from the viewpoint of the processability of the release liner (e.g., ease of winding), a thickness of 300 μm or less is suitable, preferably 250 μm or less, and can be 200 μm or less, 150 μm or less, or 130 μm or less. In some preferred embodiments, the thickness of the release liner is about 125 μm or less, about 115 μm or less, about 105 μm or less, about 90 μm or less, or about 70 μm or less. By keeping the thickness of the release liner below a specified value, it is less likely to form winding marks when rolled up, making the removal of the self-adhesive layer smoother, and high surface smoothness can be easily obtained on the adhesive surface after the release liner is removed.

[0276] In configurations that include one release liner and another release liner, the thicknesses of these release liners may be the same or different. In some configurations, from the viewpoint of ease of release operation, it is preferable that one release liner has a different thickness than the other release liner; for example, the thickness of the thicker release liner is preferably at least about 1.1 times the thickness of the thinner release liner (e.g., at least about 1.25 times. There is no particular upper limit, for example, less than 5 times).

[0277] (Arithmetic mean roughness Ra of the bonding surface side)

[0278] In some embodiments, from the viewpoint of achieving an adhesive surface with high surface smoothness, the arithmetic mean roughness Ra of the adhesive side surface of the release liner (preferably a release film) is preferably limited to a specified value or less (e.g., about 100 nm or less, and further less than 50 nm). In some embodiments, the arithmetic mean roughness Ra of the adhesive side surface of the release liner is preferably about 30 nm or less, more preferably about 25 nm or less, can be about 20 nm or less, or can be about 18 nm or less. Furthermore, from the viewpoint of ease of manufacture and processability of the release liner, in some embodiments, the above-mentioned arithmetic mean roughness Ra can be, for example, about 5 nm or more, about 10 nm or more, or about 15 nm or more. For an adhesive optical film with a release liner in the form of having release liners disposed on the first adhesive surface and the second adhesive surface respectively, it is preferable that the adhesive side surfaces of both release liners satisfy any of the above-mentioned arithmetic mean roughness Ra. The arithmetic mean roughness Ra of the adhesive side surfaces of the two release liners can be the same or different.

[0279] (Maximum height Rz of the adhesive side surface)

[0280] In some embodiments, from the viewpoint of achieving an adhesive surface with high surface smoothness, the maximum height Rz of the adhesive side surface of the release liner (preferably a release film) is preferably 700 nm or less. In some embodiments, the maximum height Rz of the adhesive side surface of the release liner is preferably about 600 nm or less, but can be about 500 nm or less, about 400 nm or less, or about 300 nm or less. Furthermore, from the viewpoint of ease of manufacturing and processability of the release liner, in some embodiments, the aforementioned maximum height Rz can be, for example, about 50 nm or more, about 80 nm or more, about 100 nm or more, about 150 nm or more, or about 200 nm or more. For an adhesive optical film with release liners disposed on both the first and second adhesive surfaces, it is preferable that the adhesive side surfaces of both release liners satisfy any of the aforementioned maximum height Rz. The maximum height Rz of the adhesive side surfaces of the two release liners can be the same or different.

[0281] (Surface characteristics of the reverse side)

[0282] The arithmetic mean roughness Ra and maximum height Rz of the back side (opposite to the adhesive layer side) of the release liner (preferably the release film) are not particularly limited. From a productivity point of view, the arithmetic mean roughness Ra of the back side of the release liner can, for example, be higher than 30 nm (e.g., higher than 35 nm, and further, about 50 nm or more). From a productivity point of view, the maximum height Rz of the back side of the release liner can, for example, be higher than 400 nm (e.g., about 500 nm or more), or higher than 800 nm (e.g., 1000 nm or more).

[0283] The arithmetic mean roughness Ra and maximum height Rz of the release film surface can be adjusted by selecting the film material, forming method, and surface treatments such as release treatment. For example, the smoothness of the layers constituting the release surface (anti-adhesion layer, hard coating, oligomer anti-adhesion layer, etc.) can be adjusted; the amount of filler particles in the surface layer and the release film substrate can be reduced or eliminated (no particle formation); and other tensile conditions can be adjusted.

[0284] The arithmetic mean roughness Ra and maximum height Rz of the surface of the release liner (preferably the release film) are measured using a non-contact surface roughness measuring device. As a non-contact surface roughness measuring device, an optical interference method surface roughness measuring device can be used, for example, a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) or its equivalent. For example, a glass plate (1.3 mm thick, calcium-sodium glass plate manufactured by MATSUNAMI) can be adhered to and fixed on the side opposite to the measurement surface of the release liner using an adhesive, and the surface shape can be measured using a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) at 23°C and 50% RH.

[0285] <Applications>

[0286] The adhesive optical film disclosed herein can be adhered to various substrates. The constituent materials of these substrates (substrate materials) are not particularly limited, but can include: for example, metallic materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, or alloys containing two or more of these materials; and resins such as polyimide resins, acrylic resins, polyether nitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (such as aramid resins), and polyaramid resins. This includes various resin materials (typically plastic materials) such as ester resins, fluorine resins, polycarbonate resins, cellulose polymers such as cellulose diacetate and cellulose triacetate, vinyl butyral polymers, liquid crystal polymers, and carbon materials such as graphene; metal oxides and mixtures thereof such as alumina, zirconium oxide, titanium oxide, SiO2, ITO, and ATO; nitrides and their complexes such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride; and inorganic materials such as alkaline glass, alkali-free glass, quartz glass, borosilicate glass, and sapphire glass. The adhesive optical films disclosed herein can be adhered to components (e.g., optical components) whose surfaces are at least composed of the aforementioned materials for use.

[0287] The adhesive optical film disclosed herein can be used in a bonding method that does not require heating to a temperature range higher than room temperature (e.g., 20°C to 35°C) after being bonded to the substrate. Furthermore, depending on the constituent materials of the adhesive optical film (e.g., the material of the light-transmitting component) and the type of substrate, heating treatment may be performed at least at any time after bonding to the substrate, at the moment of bonding, and before bonding, where permissible. Heating treatment may be performed for purposes such as improving the adhesion of the adhesive to the substrate and promoting bonding. Regarding the heating treatment temperature, it can be appropriately set within permissible range, taking into account the surface condition of the substrate, etc., to obtain the desired effect, depending on the constituent materials of the adhesive optical film and the type of substrate; for example, it can be around 100°C or below, below 80°C, below 60°C, or below 50°C.

[0288] The components and materials to which the adhesive optical film is adhered (for double-sided adhesive optical films, at least one of the adhered materials) can be transparent. In such adhered materials, the techniques disclosed herein readily provide the advantage of suppressing the reduction of optical properties (transparency, etc.) and increasing the refractive index. The total transmittance of the aforementioned adhered material can, for example, be higher than 50%, or higher than 70%. In some preferred embodiments, the total transmittance of the aforementioned adhered material is 80% or higher. More preferably, it is 90% or higher, and even more preferably, it is 95% or higher (e.g., 95-100%). The adhesive optical film disclosed herein can preferably be used by adhering it to an adhered material (e.g., an optical component) with a total transmittance of a specified value or higher. The aforementioned total transmittance is measured using a commercially available transmittance meter according to JISK 7136:2000. The transmittance meter used is the Murakami Color Technology Research Institute's trade name "HAZEMETER HM-150" or an equivalent thereof.

[0289] The refractive index of the adhesive layer and the refractive index of the adherend can be the same or different. For example, by relatively increasing the refractive index of the adhesive layer compared to the refractive index of the adherend, light incident on the adhesive layer at an angle below the critical angle from the adherend side can be refracted on the front side, increasing the front brightness. In this case, the refractive index of the adherend can be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, or even less than 1.45; and, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. Alternatively, by using an adherend with a relatively high refractive index compared to the adhesive layer, light incident on the adherend from the adhesive layer side can be refracted on the front side, increasing the front brightness. In this case, the refractive index of the adherend can be, for example, 1.60 or more, 1.65 or more, or 1.70 or more; and, for example, 3.00 or less, or 2.50 or less, or 2.00 or less. On the other hand, by reducing the refractive index difference between the adhesive layer and the adherend, light reflection at the interface can be suppressed. At this point, the refractive index of the adhered material can be approximately 1.55–1.80, 1.55–1.75, or 1.60–1.70. The refractive index of the adhered material can be determined using the same method as that used for the refractive index of the adhesive.

[0290] In some preferred embodiments, the adherend may have any of the aforementioned refractive indices and any of the aforementioned total light transmittance. The effects of the techniques disclosed herein can be particularly preferably achieved in the manner of adhesion to such an adherend.

[0291] As an example of preferred applications, optical applications can be cited. More specifically, for example, optical adhesive sheets used in applications such as bonding optical components (optical component bonding) and manufacturing articles using the aforementioned optical components (optical articles) may preferably use the adhesive-type optical film disclosed herein.

[0292] The aforementioned optical components refer to components possessing optical properties (such as polarization, refraction, scattering, reflection, transmission, absorption, diffraction, rotation, and visual recognition). There is no particular limitation on the term "optical component" as long as it possesses optical properties. Examples include components constituting display devices (image display devices), input devices, and other equipment (optical devices), or components used in these devices. Examples include polarizing plates, wavelength plates, phase retardation plates, optical compensation films, brightness-enhancing films, light guide plates, reflective films, anti-reflective films, hard-coated (HC) films, impact-absorbing films, anti-fouling films, photochromic films, dimming films, transparent conductive films (ITO films), exterior films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and components further laminated with these (sometimes collectively referred to as "functional films"). It should be noted that the terms "plate" and "film" mentioned above each include plate-like, film-like, and sheet-like forms. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet," and "light guide plate" includes "light guide film" and "light guide sheet." In addition, the term "polarizing plate" mentioned above includes circular polarizing plate.

[0293] Examples of display devices include liquid crystal displays, organic EL (electroluminescent) displays, micro LEDs (μLEDs), mini LEDs, PDPs (plasma display panels), and electronic paper. Additionally, examples of input devices include touch panels.

[0294] The term "optical component" is not particularly limited, and examples include components formed from glass, acrylic resins, polycarbonate, polyethylene terephthalate, metal films, etc. (e.g., sheet-like, film-like, plate-like components). It should be noted that "optical component" in this specification also includes components that maintain the visual legibility of the display device and input device and serve a decorative or protective function (such as outer films, decorative films, surface protective films, etc.).

[0295] The techniques disclosed herein are preferably used, for example, to bond optical thin films, such as thin films and fluorescent thin films, which have one or more functions of light transmission, reflection, diffusion, waveguide, light collection, and diffraction to other optical components (which may be other optical thin films). For example, by attaching an adhesive optical thin film having the aforementioned optical thin film as a light-transmitting component to the aforementioned other optical component as the adherend, a structure can be formed in which the light-transmitting component is bonded to the aforementioned other optical component by means of a high-refractive-index adhesive layer (bonding layer). Furthermore, by attaching an adhesive optical thin film having the aforementioned other optical components as light-transmitting components to the aforementioned optical thin film as the adherend, a structure can be formed in which the aforementioned other optical components are bonded to the aforementioned light-transmitting component by means of a high-refractive-index adhesive layer. In the bonding of optical thin films having at least one function of light waveguide, light collection, and diffraction, it is ideal for the bonding layer to have an overall high refractive index, which is a preferred application of the techniques disclosed herein.

[0296] The techniques disclosed herein are preferably used, for example, in the bonding of optical films such as light guide films, diffusion films, fluorescent films, color-matching films, prism sheets, lens-shaped films, and microlens array films. In these applications, from the perspective of miniaturization and high performance of optical components, there is a demand for thinner designs and improved light extraction efficiency. The techniques disclosed herein are preferably used as adhesive-type optical films that possess an adhesive capable of meeting these requirements. More specifically, for example, in the bonding of light guide films and diffusion films, adjusting the refractive index of the adhesive layer as the bonding layer (e.g., increasing the refractive index) can contribute to thinning. In the bonding of fluorescent films, appropriately adjusting the refractive index difference between the phosphor and the adhesive can improve light extraction efficiency (which can also be considered as luminous efficiency). In the bonding of color-matching films, appropriately adjusting the refractive index of the adhesive to have a small refractive index difference with the color-matching pigment can reduce scattering components and contribute to improved light transmittance. In the bonding of prism sheets, lens-shaped films, microlens array films, etc., by appropriately adjusting the refractive index of the adhesive, it is possible to control the diffraction of light and contribute to the improvement of brightness and / or viewing angle.

[0297] The adhesive optical film disclosed herein is preferably used by adhering it to a high-refractive-index substrate (which may be a high-refractive-index layer, component, etc.) to suppress interfacial reflection with the substrate. As described above, the adhesive optical film used in this manner preferably has a small refractive index difference with the substrate and high adhesion at the interface with the substrate. Furthermore, from the viewpoint of improving the uniformity of appearance, it is preferable that the thickness uniformity of the adhesive layer is high, for example, it is preferable that the surface smoothness of the adhesive surface is high. When the thickness of the high-refractive-index substrate is small (e.g., 5 μm or less, 4 μm or less, or 2 μm or less), suppressing reflection at the interface is particularly meaningful from the viewpoint of suppressing coloring and color unevenness caused by interference of reflected light. As an example of this usage, a method for bonding the polarizing element to the first retardation layer and / or the first retardation layer to the second retardation layer can be cited in a polarizing plate with a retardation layer comprising a polarizing element, a first retardation layer, and a second retardation layer in sequence.

[0298] Furthermore, the adhesive-type optical film disclosed herein is suitable for having a high refractive index adhesive layer, and therefore can preferably be used by adhering it to a light-emitting layer (e.g., a high-refractive-index light-emitting layer mainly composed of inorganic materials) of a photonic semiconductor. By reducing the refractive index difference between the light-emitting layer and the adhesive layer, reflection at their interface can be suppressed, and light extraction efficiency can be improved. The adhesive-type optical film used in this manner preferably has an adhesive layer with a high refractive index. In addition, from the viewpoint of preventing the degradation of the self-emitting element due to moisture, it is preferable that the adhesive layer has a low water absorption rate. From the viewpoint of improving brightness, it is preferable that the adhesive-type optical film has low coloration. This is also advantageous from the viewpoint of suppressing unintentional coloration caused by the adhesive-type optical film.

[0299] The adhesive disclosed in this specification can be preferably used as a coating layer covering the lens surface, a bonding layer to a component (e.g., a microlens constituting a microlens array film, a camera microlens, etc.) in microlenses and other lens components used as constituent parts of cameras, light-emitting devices, etc., as well as a filler layer filling the space between the lens surface and the component. The adhesive disclosed herein is suitable for high refractive index applications, thus reducing the refractive index difference even with high refractive index lenses (e.g., lenses made of high refractive index resin, lenses with a surface layer made of high refractive index resin). This is advantageous from the viewpoint of thinning the lens and the article containing the lens, and also contributes to the suppression of aberrations and the improvement of the Abbe number. The adhesive disclosed herein can also be used itself as a lens resin, for example, by filling recesses or gaps in suitable transparent components.

[0300] The adhesive optical film disclosed herein can also be considered as an adhesive optical component. Furthermore, when the aforementioned functional film is used as a light-transmitting component in the adhesive optical film disclosed herein, the adhesive optical film disclosed herein can also be considered as an "adhesive functional film" having an adhesive layer disclosed herein on at least one side of the functional film.

[0301] As described above, according to the technology disclosed herein, a laminate is provided which includes the adhesive optical film disclosed herein. The component to which the adhesive optical film is adhered may have the refractive index of the aforementioned adherent material. Furthermore, the difference between the refractive index of the adhesive optical film and the refractive index of the component (refractive index difference) may be the difference between the refractive index of the adherent and the adhesive optical film. Regarding the components constituting the laminate, as described above as components, materials, and adherents, further description is unnecessary.

[0302] As can be understood from the above description and the following embodiments, the matters disclosed in this specification include the following.

[0303] [1] An adhesive sheet comprising an adhesive layer,

[0304] It has an adhesive surface composed of the aforementioned adhesive layer.

[0305] The refractive index of the adhesive layer is higher than 1.570, the total light transmittance is above 86%, and the haze value is below 3.0%.

[0306] [2] The adhesive sheet according to [1] above, wherein the thickness of the adhesive layer is 5 μm or more.

[0307] [3] The adhesive sheet described in [1] or [2] above has an adhesive force of 3 N / 25 mm or more.

[0308] [4] The adhesive sheet according to any one of [1] to [3] above, wherein the arithmetic mean roughness Ra of the adhesive surface is 100 nm or less.

[0309] [5] The adhesive sheet according to any one of [1] to [4] above, wherein the water absorption rate of the adhesive layer is 1.0% or less.

[0310] [6] The adhesive sheet according to any one of [1] to [5] above is constructed in the form of a laminate comprising the adhesive layer and the light-transmitting member.

[0311] [7] The adhesive sheet according to [6] above, wherein the light-transmitting component is a resin film.

[0312] [8] The adhesive sheet according to any one of [1] to [5] above is a double-sided adhesive sheet formed by the adhesive layer described above.

[0313] [9] An adhesive sheet with a release liner, comprising:

[0314] The adhesive sheet described in any one of [1] to [8] above, and

[0315] A release liner disposed on the adhesive surface of the aforementioned adhesive sheet.

[0316]

[91] An adhesive optical film comprising a light-transmitting component and an adhesive layer laminated on the light-transmitting component.

[0317] The adhesive optical film has an adhesive surface composed of the aforementioned adhesive layer.

[0318] The aforementioned adhesive layer has a refractive index higher than 1.570, a total light transmittance of more than 86%, and a haze value of less than 3.0%.

[0319]

[92] According to the adhesive optical film described in

[91] above, the thickness of the adhesive layer is 5 μm or more.

[0320]

[93] The adhesive optical film according to

[91] or

[92] above has a peel strength to the glass plate of 3 N / 25 mm or more.

[0321]

[94] An adhesive optical film according to any one of

[91] to

[93] above, wherein the arithmetic mean roughness Ra of the adhesive surface is 100 nm or less.

[0322]

[95] An adhesive optical film according to any one of

[91] to

[94] above, wherein the water absorption rate of the adhesive layer is 1.0% or less.

[0323]

[96] An adhesive optical film according to any one of

[91] to

[95] above, wherein the light-transmitting member is a resin film.

[0324]

[97] An adhesive optical film according to any one of

[91] to

[96] above, wherein the light-transmitting member is selected from the group consisting of a polarizing plate, a protective film and a cover window member.

[0325]

[98] An adhesive optical film with a release liner, comprising:

[0326] The adhesive optical film described in any one of

[91] to

[97] above, and

[0327] A release liner disposed on the adhesive surface of the aforementioned adhesive optical film.

[0328]

[10] An adhesive composition for forming an adhesive layer of an adhesive sheet as described in any one of [1] to [8] above or an adhesive layer of an adhesive optical film as described in any one of

[91] to

[97] above.

[0329]

[11] An adhesive composition comprising:

[0330] An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit; and

[0331] Additives (H) RO ), which is an organic material with a higher refractive index compared to the aforementioned acrylic polymer (A).

[0332]

[12] The adhesive composition according to

[11] above, wherein the above-mentioned additive (H) RO The refractive index is above 1.60.

[0333]

[13] According to the adhesive composition described in

[11] or

[12] above, wherein, relative to 100 parts by weight of the acrylic polymer (A) described above, the additive (H) RO The content of ) is higher than 0 parts by weight and lower than 60 parts by weight.

[0334]

[14] The adhesive composition according to any one of

[11] to

[13] above, wherein the above-mentioned additive (H) RO It includes at least one compound selected from the group consisting of compounds containing aromatic rings and compounds containing heterocycles.

[0335]

[15] The adhesive composition according to any one of

[11] to

[14] above, wherein the above-mentioned additive (H) RO (A) Compounds containing two or more aromatic rings within one molecule.

[0336]

[16] The adhesive composition according to

[15] above, wherein the above-mentioned additive (H) RO A compound comprising at least one of the following is a compound having two or more aromatic rings within one molecule:

[0337] (i) A structure comprising two non-fused aromatic rings directly chemically bonded together; and

[0338] (ii) A structure consisting of two fused aromatic rings.

[0339]

[17] The adhesive composition according to any one of

[11] to

[16] above, wherein the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the acrylic polymer (A) is 50% by weight or more.

[0340]

[18] The adhesive composition according to any one of

[11] to

[17] above, wherein, in the monomer component constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is higher than 70% by weight and lower than 100% by weight.

[0341] More than 50% by weight of the aromatic ring-containing monomers (m1) mentioned above are homopolymers with a glass transition temperature of less than 10°C.

[0342]

[19] The adhesive composition according to any one of

[11] to

[18] above, wherein the monomer component constituting the acrylic polymer (A) further contains a monomer (m2) having at least one of hydroxyl and carboxyl groups.

[0343]

[20] The adhesive composition according to any one of

[11] to

[18] above is used to form the adhesive layer of the adhesive sheet according to any one of [1] to [8] above or the adhesive layer of the adhesive optical film according to any one of

[91] to

[97] above.

[0344]

[21] An adhesive formed from any one of the adhesive compositions described in

[11] to

[20] above, having a refractive index higher than 1.570.

[0345]

[22] An adhesive sheet comprising an adhesive layer made of an adhesive, said adhesive being formed from any one of the adhesive compositions described in

[11] to

[20] above.

[0346]

[23] The adhesive sheet according to

[22] above, wherein the haze value of the adhesive layer is 1.0% or less.

[0347]

[24] An interlayer sheet, which is used as an interlayer sheet disposed between the layers of a laminate for optical applications.

[0348] It contains a viscoelastic layer V1 with a refractive index n1 of 1.570 or higher, and

[0349] The interlayer sheet satisfies the following condition: total light transmittance of 86% or higher;

[0350] The haze value is below 1.0%; and,

[0351] The energy storage modulus G' at 25℃ is 30kPa~700kPa.

[0352]

[25] The interlayer sheet described in

[24] above has a thickness of 5 μm or more.

[0353]

[26] According to the interlayer sheet described in

[24] or

[25] above, wherein the viscoelastic layer V1 comprises a main polymer and a plasticizing material with a molecular weight lower than that of the main polymer.

[0354]

[27] According to the interlayer sheet described in

[26] above, the weight-average molecular weight of the plasticizing material is 30,000 or less.

[0355]

[28] The interlayer sheet according to any one of

[24] to

[27] above further comprises a viscoelastic layer V2 laminated on the viscoelastic layer V1.

[0356] The storage modulus G' of the viscoelastic layer V2 at 25°C V2 The energy storage modulus G' of the viscoelastic layer V1 at 25°C is lower than that of the above viscoelastic layer V1. V1 .

[0357]

[29] According to the interlayer sheet described in

[28] above, wherein the refractive index n2 of the viscoelastic layer V2 is lower than the refractive index n1 of the viscoelastic layer V1.

[0358]

[30] The interlayer sheet according to any one of

[24] to

[29] above, wherein the viscoelastic layer V1 is a layer formed by the adhesive composition according to any one of

[11] to

[18] above.

[0359]

[31] The interlayer sheet according to any one of

[24] to

[29] above, wherein the viscoelastic layer V1 is the adhesive layer in the adhesive sheet according to any one of [1] to [5] above.

[0360]

[32] An optical laminate comprising:

[0361] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0362] A resin film laminated on the above interlayer sheet.

[0363]

[33] An interlayer sheet with a release liner, comprising:

[0364] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0365] A release liner covering at least one surface of the aforementioned interlayer sheet.

[0366] Example

[0367] The following describes some experimental examples related to this invention. It should be noted that, in the following description, the terms "parts" and "%" indicating the amount used and the content are by weight unless otherwise specified.

[0368] <Example 1>

[0369] (Preparation of acrylic polymer solutions)

[0370] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 99 parts of m-phenoxybenzyl acrylate (manufactured by Kyoei Chemical Co., Ltd., trade name "LIGHT ACRYLATE POB-A", refractive index: 1.566, Tg of homopolymer: -35℃, hereinafter referred to as "POB-A"), 1 part of 4-hydroxybutyl acrylate (4HBA), 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as polymerization initiator, and 100 parts of toluene as polymerization solvent were added. Nitrogen gas was introduced while stirring slowly, and the liquid temperature in the flask was maintained at approximately 60℃ for 6 hours to prepare a 50% solution of acrylic polymer A1. The Tg of the above acrylic polymer A1 based on the above monomer components (i.e., Tg) was measured. T The temperature is -35℃, based on the Tg (i.e., Tg) of the monomer containing the aromatic ring. m1 The temperature is -35℃.

[0371] (Preparation of the adhesive composition)

[0372] The above-mentioned acrylic polymer A1 solution (50%) was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts non-volatile components), 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate (manufactured by Tosoh Corporation, trade name "Coronate HX", a 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking delay agent, and 1 part of a 1% ethyl acetate solution of iron acetylacetone as a crosslinking catalyst (0.01 parts non-volatile components) were added and stirred to prepare the acrylic adhesive composition C1.

[0373] (Making the adhesive sheet)

[0374] The acrylic adhesive composition C1 prepared above was coated onto the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (50 μm thick, arithmetic mean roughness Ra of 21 nm, and maximum height Rz of 233 nm) that had undergone silicone treatment on one side. The film was then heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 20 μm. Next, a silicone-treated PET film R2 (25 μm thick, arithmetic mean roughness Ra of 15 nm, and maximum height Rz of 180 nm) that had undergone silicone treatment on one side was bonded to the surface of the adhesive layer (first adhesive surface). This process yielded a substrate-free double-sided adhesive sheet S1 formed from the adhesive layer. Both sides of the adhesive sheet S1 were protected by PET films (release liner) R1 and R2. The release liner R2 bonded to the first adhesive surface peeled off relatively easily compared to the release liner R1 (the release liner coated with the adhesive composition) protecting the second adhesive surface.

[0375] <Examples 2~3, 7~8, 10~14>

[0376] The composition of the monomer components was changed as shown in Table 1. Otherwise, solutions of acrylic polymers A2-3, 7-8, and 10-14 in each example were prepared in the same manner as the preparation of the acrylic polymer solution in Example 1.

[0377] The acrylic polymer solutions of the above examples were used instead of the acrylic polymer A1 solution. Otherwise, the acrylic adhesive compositions C2-3, 7-8, and 10-14 of the examples were prepared in the same manner as the preparation of the adhesive composition in Example 1.

[0378] The acrylic adhesive composition of each of the above examples was used instead of acrylic adhesive composition C1, and the thickness of the adhesive layer was as shown in Table 1. Otherwise, the adhesive sheets (substrate-free double-sided adhesive sheets formed by the adhesive layer) S2-3, 7-8, 10-14 of each example were made in the same manner as the adhesive sheet in Example 1.

[0379] It should be noted that in the composition of the monomer components shown in Table 1, "NMT-A" represents 1-naphthyl methyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "LIGHT ACRYLATE NMT-A", refractive index: 1.595, Tg of homopolymer: 31℃), HEA represents 2-hydroxyethyl acrylate, BA represents n-butyl acrylate, and 2EHA represents 2-ethylhexyl acrylate.

[0380] <Example 4>

[0381] The 50% solution of acrylic polymer A3 prepared in Example 3 was diluted to 30% with ethyl acetate, and H was added as an additive to 334 parts of the solution (100 parts of non-volatile components). RO An acrylic adhesive composition C4 was prepared by mixing 5 parts of 6-acryloyloxymethyl dinaphthothiophene (6-methacrylate body manufactured by Sugai Chemical IND.CO.,LTD., trade name "6MDNTA", refractive index 1.75), 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate body (manufactured by Tosoh Corporation, trade name "Coronate HX", 3-functional isocyanate compound) as a crosslinking agent (0.1 parts of non-volatile component), 2 parts of acetylacetone as a crosslinking delay agent, and 1 part of a 1% ethyl acetate solution of iron acetylacetone as a crosslinking catalyst (0.01 parts of non-volatile component).

[0382] Instead of acrylic adhesive composition C1, acrylic adhesive composition C4 is used, and the thickness of the adhesive layer is set to 25 μm. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed by the adhesive layer) S4 of this example is made in the same manner as the adhesive sheet in Example 1.

[0383] <Examples 5~6>

[0384] Additive (H) RO The types of acrylic polymers and the amount used relative to 100 parts of acrylic polymer (phr; per hundred resin) were changed as shown in Table 1. Except that, acrylic adhesive compositions C5 and C6 of Examples 5 and 6 were prepared in the same manner as the preparation of acrylic adhesive composition C4 in Example 4. Here, in Table 1, “BPFL” represents 9,9-bis(4-hydroxyphenyl)fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.68) and “BAFL” represents 9,9-bis(4-aminophenyl)fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.73).

[0385] Acrylic adhesive compositions C5 and C6 were used instead of acrylic adhesive composition C4, and otherwise, adhesive sheets (substrate-free double-sided adhesive sheets formed of adhesive layers) were made in Examples 5 and 6 in the same manner as the adhesive sheet in Example 4.

[0386] <Example 9>

[0387] The 50% solution of acrylic polymer A8 prepared in Example 8 was diluted to 30% with ethyl acetate, and 334 parts (100 parts of non-volatile components) of this solution were added as an additive (H). ROThe acrylic adhesive composition C9 was prepared by mixing 10 parts of BPFL, 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate (manufactured by Tosoh Corporation, trade name "Coronate HX", a 3-functional isocyanate compound) as a crosslinking agent (0.1 parts of non-volatile component), 2 parts of acetylacetone as a crosslinking delay agent, and 1 part of a 1% ethyl acetate solution of iron acetylacetone as a crosslinking catalyst (0.01 parts of non-volatile component).

[0388] Acrylic adhesive composition C9 is used instead of acrylic adhesive composition C8. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed of adhesive layer) S9 of this example is made in the same way as the adhesive sheet in Example 8.

[0389] <Example 15>

[0390] The composition of the monomer components was changed to 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of 4HBA. Otherwise, a solution of acrylic polymer A14 (40%) was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1.

[0391] A 40% solution of the above-mentioned acrylic polymer A14 was diluted to 20% with ethyl acetate. To 500 parts of this solution (100 parts non-volatile components), 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate (manufactured by Tosoh Corporation, trade name "Coronate HX", a 3-functional isocyanate compound) (0.1 parts non-volatile components), 2 parts of acetylacetone (a crosslinking delay agent), and 1 part of a 1% ethyl acetate solution of iron acetylacetone (0.01 parts non-volatile components) (a crosslinking catalyst) were added and stirred to prepare the acrylic adhesive composition C15. As the above-mentioned zirconia particle dispersion, a surface-treated zirconia particle dispersion (average particle size 20 nm, solid component refractive index: 1.64, surface treatment: carboxylic acid-based / phosphoric acid-based hydrophobic treatment, manufactured by Kyoei Chemical Co., Ltd.) was obtained by dispersing surface-treated zirconia particles in propylene glycol monomethyl ether (PGME).

[0392] Acrylic adhesive composition C15 is used instead of acrylic adhesive composition C14. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed of adhesive layer) S15 of Example 15 is made in the same manner as the adhesive sheet of Example 14.

[0393] After the obtained adhesive sheet was fully adapted to an environment of 23°C and 50% RH, it was used for the following determinations and evaluations.

[0394] <Measurement and Evaluation (1)>

[0395] (Refractive index)

[0396] For each example of adhesive layer (substrate-free double-sided adhesive sheet), the refractive index was measured using an Abbe refractometer (ATAGO, model "DR-M4") under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 °C. The results are shown in Table 1.

[0397] (Total transmittance and haze value)

[0398] Test pieces were prepared by bonding the adhesive layer of each example to alkali-free glass (thickness 0.8–1.0 mm, total transmittance 92%, haze 0.4%). The total transmittance and haze of these test pieces were measured using a haze meter (manufactured by Murakami Color Technology Research Institute, trade name "HAZEMETER HM-150") at 23°C. The total transmittance and haze values ​​of the adhesive layer were obtained by subtracting the total transmittance and haze of the alkali-free glass from the measured values. The results are shown in Table 1.

[0399] (Water absorption rate)

[0400] The water absorption rate of the adhesives in each example was determined using the method described above. The results are shown in Table 1.

[0401] It should be noted that the storage modulus G'(25) of the adhesive layer in each example was measured using the above method, and the results confirmed that it was below 350 kPa in Examples 1 to 14. On the other hand, the storage modulus G'(25) of the adhesive layer in Example 15, which increased the refractive index by mixing in inorganic particles with a high refractive index, was high at 750 kPa, indicating insufficient flexibility and adhesion.

[0402] [Table 1]

[0403] Table 1

[0404]

[0405] <Example 16>

[0406] The coating amount of acrylic adhesive composition C3 was adjusted in such a way as to form an adhesive layer with a thickness of 5 μm. Otherwise, the substrate-free double-sided adhesive sheet S16 of this example was obtained in the same manner as the substrate-free double-sided adhesive sheet S3 of Example 3.

[0407] <Measurement and Evaluation (2)>

[0408] The following measurements and evaluations were conducted on some of the adhesive sheets prepared above. The results are shown in Table 2.

[0409] (Arithmetic mean roughness (Ra) and maximum height (Rz) of the bonding surface)

[0410] Each example of substrate-free double-sided adhesive sheet, along with release liner R1 and R2 protecting the first and second adhesive surfaces, was cut into dimensions of 150 mm in length and 50 mm in width to prepare a test sample. The release liner R1 side of this test sample was fixed to a test plate, and the release liner R2 was peeled off from the first adhesive surface of the test sample using a tensile testing machine (Autograph AG-IS, manufactured by Shimadzu Corporation) at 23°C and 50% RH, at a tensile speed of 300 mm / min and a peel angle of 180°, exposing the first adhesive surface. After standing for 30 minutes, the surface shape of the first adhesive surface was measured using a three-dimensional optical profilometer (NewView7300, manufactured by ZYGO Corporation) at 23°C and 50% RH. Based on the measured data, the arithmetic surface roughness Ra was calculated according to JIS B 0601-2001.

[0411] Furthermore, regarding the maximum height (Rz), it is calculated from the data obtained from the above measurements (roughness curve) as the sum of the height Rp of the highest peak above the average line of the roughness curve and the depth Rv of the deepest valley below the average line. The measurement conditions are as follows.

[0412] Ra and Rz were measured 5 times (i.e., N=5), and their average value was used.

[0413] [Measurement Conditions]

[0414] Measurement area: 5.62mm × 4.22mm

[0415] (Objective lens: 2.5x, internal lens: 0.5x)

[0416] Parsing mode:

[0417] Remove: Cylinder

[0418] Data Fill: ON (Max: 25)

[0419] Remove Spikes: ON (xRMS: 1)

[0420] Filter: OFF

[0421] (Optical distortion)

[0422] A commercially available mirror (2mm thick) made from unplated glass using a silver plating method was prepared. The mirror was confirmed to be distortion-free by visual inspection and by projecting the reflected image onto a screen using the same method described later. In a clean room, the surface of the mirror was wiped with a clean cloth to remove foreign matter. The release film R2 was peeled off from the substrate-free double-sided adhesive sheet in each example, exposing the first adhesive surface. Appropriate tension was applied to prevent the introduction of foreign matter, air bubbles, or distorted streaks, and the sheet was adhered to the surface of the mirror. To remove the influence of micro-air bubbles, a degassing treatment was performed using a pressure degassing device (autoclave) (treatment conditions: 50°C, 0.5MPa, 30 minutes). After cooling at room temperature for at least 30 minutes, the release film R1 was peeled off, exposing the second adhesive surface, thereby creating an optical distortion evaluation sample (a laminate formed by the adhesive sheet and the mirror). The evaluation sample was positioned such that its adhesive sheet side faced the point light source side at an angle of approximately 45 degrees relative to the light from the point light source. A white screen was placed in front of the light source to reflect the reflected image. As a point light source, the product "Xenon Lamp C2577" manufactured by Hamamatsu Photonics KK or an equivalent can be used. In this experiment, the product "Xenon Lamp C2577" was used. The point light source, the evaluation sample, and the screen were arranged such that the distance from the evaluation sample to the point light source and the distance from the evaluation sample to the screen were both approximately 50 cm.

[0423] The point light source is lit up, and the image reflected from the sample and projected onto the screen is observed visually. The presence and degree of optical distortion are then evaluated according to the following three levels.

[0424] E: No optical distortion was detected.

[0425] A: Some optical distortion has been identified, but it is within a practically permissible range.

[0426] P: Obvious optical distortion was confirmed.

[0427] (Peel strength of glass plate)

[0428] Under a test environment of 23°C and 50% RH, the release liner was peeled off from one side of the adhesive sheet, and a 50 μm thick PET film was laminated on top. The film was then cut into pieces 25 mm wide and 100 mm long to serve as test pieces. The release liner was peeled off from the other side of the test piece, and the surface of an alkaline glass plate (Matsunami Glass Industry Co., Ltd., 1.35 mm thick, with ground edges) was pressed once by a 2 kg roller. The plate was placed in this environment for 30 minutes, and then placed in a pressure degassing device (autoclave) for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. After being placed in an atmosphere of 23°C and 50% RH for 24 hours, the peel strength (adhesive force) [N / 25 mm] was measured using a universal tensile and compression testing machine according to JIS Z 0237:2000, at a tensile speed of 300 mm / min and a peel angle of 180 degrees. As a universal tensile and compression testing machine, the "Tensile and Compression Testing Machine TG-1kN" manufactured by Minebea is used.

[0429] [Table 2]

[0430] Table 2

[0431]

[0432] The adhesive sheets shown in Tables 1 and 2 (Examples 1-13 and 16) exhibit a high refractive index greater than 1.570 and high transparency. Furthermore, as shown in Table 2, they demonstrate excellent peel strength and surface smoothness, making them practical as adhesives. In a comparison between Example 3 and Example 16, which used the same adhesive composition, Example 16 showed better results in the evaluation of optical distortion. It should be noted that although not shown in Table 2, Example 16 has a water absorption rate of 0.2%. By attaching these adhesive sheets (substrate-free adhesive sheets) to any light-transmitting component, adhesive-type optical films with an adhesive layer on the light-transmitting component having a refractive index greater than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less can be easily fabricated.

[0433] On the other hand, compared with Examples 1 to 13, Example 15, which increased the refractive index by mixing with high-refractive-index inorganic particles, showed significantly poorer transparency (especially significantly higher haze), as shown in Table 2. It also had low surface smoothness, significant optical distortion, and did not show adhesive properties (peel strength) suitable for practical applications as an adhesive.

[0434] <Example 17, 18, 23>

[0435] The monomer composition is shown in Table 3. Except as in Example 1, solutions of the acrylic polymers of Examples 17, 18, and 23 were prepared to prepare acrylic adhesive compositions. The acrylic adhesive composition of each example was used instead of acrylic adhesive composition C1, and the thickness of the adhesive layer was set to 25 μm. Except as in Example 1, the adhesive sheets of each example were prepared in the same manner.

[0436] It should be noted that in the monomer composition shown in Table 3, "BZA" represents benzyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat#160", refractive index (nD20): 1.519, Tg of homopolymer: 6℃), "PEA" represents phenoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat#192", refractive index (nD20): 1.517, Tg of homopolymer: 2℃), "P2H-A" represents phenoxydiethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "LIGHT ACRYLATE P2H-A", refractive index: 1.510, Tg of homopolymer: -35℃), HEMA represents 2-hydroxyethyl methacrylate, and CBA represents ethyl carbitol acrylate.

[0437] <Example 19>

[0438] The monomer composition is as shown in Table 3. Otherwise, the solution of acrylic polymer A19 in this example is prepared in the same manner as in Example 1. The solution of acrylic polymer A19 is used instead of the solution of acrylic polymer A3 as an additive (H). RO Using 10 phr of 2,12-diallyloxydinathothiophene (manufactured by Sugai Chemical IND.CO.,LTD., abbreviation: 2,12-DAODNT, refractive index: 1.729), the acrylic adhesive composition of this example was prepared in the same manner as in Example 4, and an adhesive sheet was made.

[0439] <Examples 20~22>

[0440] The monomer composition was as shown in Table 3. Except as in Example 1, solutions of the acrylic polymers of Examples 20-22 were prepared. The solutions of the acrylic polymers of each example were used instead of the solution of acrylic polymer A3 as additives (H). ROUsing 20 phr of 6-ethyl acrylate-dinaphtho[2,1-b:1',2'-d]thiophene (6-acryloyloxyethyl dinaphthothiophene manufactured by Sugai Chemical IND.CO.,LTD., No.: 6EDNTA, refractive index: 1.722), the acrylic adhesive compositions of each example were prepared in the same manner as in Example 4 to make adhesive sheets.

[0441] After the adhesive sheets obtained from Examples 17 to 23 were fully acclimatized in an environment of 23°C and 50% RH, the measurements and evaluations of each item were performed in the same manner as in "Measurement and Evaluation (1)" above. The results are shown in Table 3.

[0442] [Table 3]

[0443] Table 3

[0444]

[0445] The adhesive sheets shown in Table 3 (Examples 17-23) all exhibited a high refractive index greater than 1.570 and high transparency. Among these, the adhesive sheet of Example 23 had a harder feel and higher water absorption compared to the adhesive sheets of Examples 17-22.

[0446] Based on the above, the adhesive sheets (substrate-free double-sided adhesive sheets formed by adhesive layers) of Examples 1-14, 16, and 17-23 can suppress the reduction of optical properties and increase the refractive index. Therefore, in the form of an adhesive optical film with the above-mentioned adhesive layer laminated on a light-transmitting component, it is suitable for applications such as bonding of optical components (e.g., optical films with at least one function of light waveguide, light collection, or diffraction).

[0447] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The scope of the claims includes various modifications and alterations to the specific examples described above.

[0448] Explanation of reference numerals in the attached figures

[0449] 1. Adhesive-type optical thin film

[0450] 10 Adhesive Layer

[0451] 10A First Surface (Adhesive Surface)

[0452] 10B Second Surface

[0453] 20 Translucent components

[0454] 20A Side 1

[0455] 20B, Side 2 (Back)

[0456] 30, 31, 32 Peeling gaskets

[0457] 50 Adhesive optical films with release liner

[0458] 70 Optical components (attached objects)

[0459] 100 optical laminates

Claims

1. An adhesive optical film comprising a light-transmitting component and an adhesive layer laminated on the light-transmitting component. The adhesive optical film has an adhesive surface formed by the adhesive layer. The adhesive layer has a refractive index higher than 1.570, a total light transmittance of 86% or higher, and a haze value of 3.0% or lower. The adhesive layer contains an acrylic polymer as the base polymer and does not contain plasticizers. The monomer components constituting the acrylic polymer include more than 50% by weight of aromatic ring-containing monomers, and also include hydroxyl-containing monomers. in, The monomeric component satisfies at least one of the following conditions: (A) More than 50% by weight of the hydroxyl-containing monomer is a hydroxyalkyl acrylate, the content of the hydroxyalkyl acrylate in the monomer component is more than 1% by weight and less than 7% by weight, and the content of the aromatic ring-containing monomer with a Tg below 0°C in the monomer component is more than 3% by weight; and (B) The hydroxyl-containing monomer comprises 4-hydroxybutyl acrylate, wherein the content of 4-hydroxybutyl acrylate in the monomer component is more than 1% by weight and less than 7% by weight.

2. The adhesive optical film according to claim 1, wherein, The thickness of the adhesive layer is 5 μm or more.

3. The adhesive optical film according to claim 1 or 2 has a peel strength to the glass plate of 3N / 25mm or higher.

4. The adhesive optical film according to claim 1 or 2, wherein, The arithmetic mean roughness Ra of the bonding surface is below 100 nm.

5. The adhesive optical film according to claim 1 or 2, wherein, The water absorption rate of the adhesive layer is less than 1.0%.

6. The adhesive optical film according to claim 1 or 2, wherein, The light-transmitting component is a resin film.

7. The adhesive optical film according to claim 1 or 2, wherein, The light-transmitting component is selected from the group consisting of a polarizing plate, a protective film, and a cover window component.

8. An adhesive optical film with a release liner, comprising: The adhesive optical film according to any one of claims 1 to 7, and the release liner disposed on the adhesive surface of the adhesive optical film.

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