Light emitting device

Abstract

The provided light emitting device includes a self-light emitting element, a low refractive index layer disposed on a visual recognition side of the self-light emitting element, and a high refractive index adhesive layer laminated in direct contact with the low refractive index adhesive layer. The high refractive index adhesive layer has a refractive index n1 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] The present invention relates to a light-emitting device, and more particularly, to a light-emitting device having an adhesive layer disposed on the visual recognition side of a self-emitting element.

[0002] This application claims priority based on Japanese Patent Application No. 2020-052408 filed on March 24, 2020, Japanese Patent Application No. 2020-166428 filed on September 30, 2020, and Japanese Patent Application No. 2021-049061 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 having multiple aromatic rings as monomer units, but no 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, the refractive index of adhesives incorporating inorganic particles is a trade-off between adhesive properties (e.g., peel strength, flexibility, etc.), making them difficult to apply in the field of adhesives. For example, when increasing the refractive index of an adhesive layer disposed on the visual recognition side of a self-emissive element in a light-emitting device, the influence on optical properties (e.g., total transmittance, haze, etc.) must be considered when incorporating inorganic particles.

[0010] The present invention was made in view of the above-mentioned situation, and its object is to provide a light-emitting device having an adhesive layer with high refractive index and optical quality disposed on the visual recognition side of the self-emitting element.

[0011] Solution for solving the problem

[0012] The light-emitting device provided in this specification includes: a self-emissive element, a low-refractive-index layer disposed on the visual recognition side of the self-emissive element, and a high-refractive-index adhesive layer laminated in direct contact with the low-refractive-index layer. The high-refractive-index adhesive layer has a refractive index n1 greater than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

[0013] In some embodiments, the ratio (n1 / n2) of the refractive index n1 of the high refractive index adhesive layer to the refractive index n2 of the low refractive index layer is preferably about 1.05 or more.

[0014] In some embodiments, the aforementioned high-refractive-index adhesive layer preferably has an arithmetic mean roughness Ra of its surface of less than 100 nm.

[0015] In some embodiments, the ratio (T1 / T2) of the thickness T1 of the high-refractive-index adhesive layer to the thickness T2 of the low-refractive-index layer is preferably in the range of about 0.5 to 5.

[0016] In some embodiments, the thickness T1 of the aforementioned high-refractive-index adhesive layer is preferably 5 μm or more.

[0017] In some embodiments, the laminate (adhesive sheet) comprising the above-mentioned high refractive index adhesive layer and the above-mentioned low refractive index layer preferably has a total light transmittance of 86% or more and a haze value of 3.0% or less.

[0018] 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

[0019] Figure 1 A cross-sectional view illustrating the configuration of a light-emitting device according to one embodiment is shown for illustrative purposes.

[0020] Figure 2 A cross-sectional view illustrating the configuration of the laminated sheet used in a light-emitting device according to one embodiment is shown for illustrative purposes. Detailed Implementation

[0021] 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.

[0022] 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 proportions of the actual product provided.

[0023] 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. The light-emitting devices disclosed herein incorporate such self-emissive elements as constituent elements. 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.

[0024] The technical items disclosed in this specification include: light-emitting devices, high-refractive-index adhesive layers and adhesive compositions for their formation, low-refractive-index layers and compositions for their formation, laminates (adhesive sheets) comprising high-refractive-index adhesive layers and low-refractive-index layers, and laminates with release liner whose adhesive surfaces are protected by release liner.

[0025] <Example of Light-Emitting Device Configuration>

[0026] Figure 1 An example of the configuration of the light-emitting device provided in this instruction manual is shown. Figure 1The light-emitting device 100 shown includes: a self-emissive element 70, a low-refractive-index layer 12 disposed on the visual recognition side of the self-emissive element 70, and a high-refractive-index adhesive layer 11 laminated in direct contact with the low-refractive-index layer 12. The light-emitting device 100 may further include a cover window member 80 disposed on the visual recognition side of the high-refractive-index adhesive layer 11. Figure 1 In the illustrated light-emitting device 100, a laminate 10 comprising a high-refractive-index adhesive layer 11 and a low-refractive-index layer 12 is disposed between the self-emitting element 70 and the cover window member 80. One or more layers (not shown) may be independently sandwiched between the self-emitting element 70 and the low-refractive-index layer 12, between the high-refractive-index adhesive layer 12 and the cover window member 80, and on the further visual recognition side of the cover window member 80, or none may be sandwiched. Additionally, it may be combined with... Figure 1 Conversely, the high-refractive-index adhesive layer 11 is disposed on the self-luminous element side, and the low-refractive-index layer 12 is disposed on the cover window member side.

[0027] In the technology disclosed herein, the low-refractive-index layer can be adhesive or non-adhesive. In some embodiments, the low-refractive-index layer is preferably an adhesive layer, i.e., a low-refractive-index adhesive layer. Thus, the laminate (adhesive sheet) of the low-refractive-index adhesive layer and the high-refractive-index adhesive layer becomes double-sided adhesive, improving the assemblability in the manufacture of the light-emitting device. This laminate is, for example, as shown in... Figure 2 As shown, the laminate with release liner can be in the following form: before being assembled into the light-emitting device, it is a laminate 10 (substrate-free double-sided adhesive sheet 2) containing a high refractive index adhesive layer 11 and a low refractive index adhesive layer 12. The surface (first surface) 10A on the side of the high refractive index adhesive layer 11 of the laminate 10 becomes the first adhesive surface, and the surface (second surface) 10B on the side of the low refractive index adhesive layer 12 becomes the second adhesive surface. These adhesive surfaces are protected by release liners 31 and 32, respectively.

[0028] <High Refractive Index Adhesive Layer>

[0029] The light-emitting device disclosed herein includes a high-refractive-index adhesive layer laminated in direct contact with a low-refractive-index layer contained in the light-emitting device. This high-refractive-index adhesive layer is a layer with a relatively high refractive index compared to the aforementioned low-refractive-index layer. Preferably, the high-refractive-index adhesive layer has a refractive index n1 higher than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

[0030] (Refractive index)

[0031] The light-emitting device disclosed herein has a high refractive index adhesive layer with a refractive index n1 greater than 1.570. This high refractive index adhesive layer can be achieved by using an adhesive (viscoelastic material) with a refractive index greater than 1.570 to form at least one surface (adhesive surface) of the high refractive index adhesive layer.

[0032] It should be noted that, in this specification, the refractive index of the adhesive refers to the refractive index of the adhesive surface (adhesive surface). The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) at a measurement wavelength of 589 nm and a measurement temperature of 25°C. For example, the Abbe refractometer can be the ATAGO "DR-M4" or its equivalent. As the test sample, an adhesive layer formed from the adhesive of the object being evaluated can be used. Specifically, the refractive index of the adhesive can be measured using the method described in the examples below. The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive (e.g., the composition of the monomer components constituting the base polymer, additives that may be used as needed, etc.).

[0033] The technical details provided in this specification include: an adhesive layer with a refractive index higher than 1.57 (a high-refractive-index adhesive layer), an adhesive composition capable of forming the adhesive layer, and a laminate containing the aforementioned high-refractive-index adhesive layer. The laminate may be, for example, a laminated adhesive layer formed from the aforementioned high-refractive-index adhesive layer and a low-refractive-index layer (typically a low-refractive-index adhesive layer), or it may be configured such that the high-refractive-index adhesive layer and the low-refractive-index layer are laminated sequentially or in reverse order on one side of a supporting substrate.

[0034] In some embodiments, the refractive index of the high-refractive-index adhesive layer is preferably 1.580 or higher, more preferably 1.585 or higher, and even more preferably 1.590 or higher (e.g., 1.595 or higher). Based on the high-refractive-index adhesive layer having this refractive index, the behavior of light transmitted through the high-refractive-index adhesive layer can be effectively controlled by utilizing the relative refractive index relationship between the high-refractive-index adhesive layer and its directly adjacent low-refractive-index layer (typically a low-refractive-index adhesive layer). In some embodiments of the technology disclosed herein, the refractive index of the high-refractive-index adhesive layer can, for example, be 1.600 or higher, 1.605 or higher, or 1.610 or higher. The preferred upper limit of the refractive index of the high-refractive-index adhesive layer can vary depending on the refractive index of adjacent layers, and is therefore not limited to a specific range. In some embodiments, considering the balance with adhesive properties and transparency, the refractive index of the high-refractive-index adhesive layer can, for example, be 1.700 or lower, 1.670 or lower, or 1.650 or lower.

[0035] (Total light transmittance)

[0036] In the technology disclosed herein, a total light transmittance of 86% or more for the high-refractive-index adhesive layer is appropriate, 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 light 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 refractive index and adhesive properties, the total light transmittance of the high-refractive-index adhesive layer can be about 94% or less, about 93% or less, or about 92% or less. The 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 can be used. More specifically, the total light transmittance of the high-refractive-index adhesive layer can be measured, for example, according to the embodiments described later. The total light transmittance of the high-refractive-index adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc., of the high-refractive-index adhesive layer.

[0037] (Haze value)

[0038] A haze value of 3.0% or less for the high-refractive-index adhesive layer is suitable, preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.9% or less. A low haze value is advantageous in applications requiring high light transmittance (e.g., optical applications) and applications requiring good visual identification of the adhered object through the high-refractive-index adhesive layer. In some embodiments, the haze value of the high-refractive-index adhesive layer 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 high-refractive-index adhesive layer; from the viewpoint of improving transparency, a lower haze value is more preferred. On the other hand, in some embodiments, considering refractive index and adhesive properties, the haze value of the high-refractive-index adhesive layer can, for example, be 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more. These haze values ​​associated with the high refractive index adhesive layer can also preferably be applied to the haze values ​​of a laminate formed by the high refractive index adhesive layer and a low refractive index layer (typically a low refractive index adhesive layer) described later.

[0039] 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 known as turbidity. The haze value can be expressed by the following formula.

[0040] Th(%)=Td / Tt×100

[0041] 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.

[0042] (Storage modulus G')

[0043] In the technology disclosed herein, the storage modulus G' of the high refractive index adhesive layer at 25°C (hereinafter also referred to as "storage modulus G'") V1 (25)) This can be set appropriately according to the purpose and method of use, and is not limited to a specific range. Energy storage modulus G' V1 (25) For example, it can be below approximately 700 kPa. In some methods, from the viewpoint of ease of adhesion to the adhered object, the storage modulus G' V1 (25) A pressure of about 600 kPa or less is advantageous, preferably 500 kPa or less, and more preferably 400 kPa or less (e.g., 350 kPa or less). In some ways, from the viewpoint of improving the flexibility of the high refractive index adhesive layer in the room temperature region (e.g., 25°C) and making it easier to bond with the substrate, the storage modulus G' V1 (25) A pressure of approximately 330 kPa or less is advantageous, and preferably 300 kPa or less. In some approaches that place greater emphasis on adhesion and flexibility in the room temperature range, the storage modulus G' V1 (25) For example, it can be below 270 kPa or below 250 kPa, below 200 kPa is advantageous, below 180 kPa is preferred, and below 160 kPa (e.g., below 140 kPa) is more preferred. In some embodiments, the energy storage modulus G' V1 (25) It can be below 100 kPa or below 90 kPa. Storage modulus G' V1 (25) has no particular lower limit. From the perspective of processability and handling, it can be above 30 kPa, above 50 kPa, or above 70 kPa. In some methods, considering the high refractive index, the storage modulus G' V1 (25) It can be above 100 kPa, above 150 kPa, above 200 kPa, above 250 kPa, or above 300 kPa.

[0044] In the technology disclosed herein, the storage modulus G' of the high refractive index adhesive layer at 50°C (hereinafter also referred to as "storage modulus G'") V1 (50)) There are no particular limitations; for example, it can be below 100 kPa. In some methods, the energy storage modulus G' V1(50) A pressure below 60 kPa is appropriate, preferably below 40 kPa, and more preferably below 38 kPa (e.g., below 36 kPa). This limits the energy storage modulus G'. V1 (50) The high refractive index adhesive layer, by appropriate heating as needed, can easily improve the adhesion to the substrate, thereby enhancing the bonding strength. Storage modulus G' V1 (50) has no particular lower limit. In some approaches, from the perspective of heat resistance and other factors, the storage modulus G' V1 (50) For example, it can be above 10 kPa, above 15 kPa, above 20 kPa, or above 23 kPa.

[0045] In some of the techniques disclosed herein, the high-refractive-index adhesive layer preferably satisfies at least one of the following conditions:

[0046] (a) Energy storage modulus G' V1 (25) is below 350 kPa (preferably below 200 kPa, for example below 180 kPa); and

[0047] (b) Energy storage modulus G' V1 (50) Less than 60 kPa (preferably less than 50 kPa, more preferably less than 40 kPa, for example less than 38 kPa).

[0048] A high-refractive-index adhesive layer that at least satisfies condition (a) above is preferred from the viewpoint of adhesion and flexibility to the adherend at room temperature (e.g., 25°C). A high-refractive-index adhesive layer that at least satisfies condition (b) above is preferred because its adhesion to the adherend can be easily improved by heating it to a temperature slightly higher than room temperature. For an adhesive sheet having a high-refractive-index adhesive layer that does not satisfy condition (a) above but satisfies condition (b) above, it exhibits good reprocessability (re-adhesion) at the initial bonding stage at room temperature and can be used as a heat-activated adhesive sheet that can effectively improve its peel strength from the adherend by heating it to a temperature slightly higher than room temperature. The aforementioned heat activation can be performed by heating the adhesive sheet to a temperature slightly higher than room temperature when bonding it to the adherend. The temperature slightly higher than room temperature is, for example, around 60°C or less, preferably around 55°C or less (e.g., around 50°C or less).

[0049] In some of the techniques disclosed herein, the energy storage modulus G' V1 (50) [kPa] relative to storage modulus G' V1 (25) The ratio of [kPa], i.e., the energy storage modulus ratio G' V1 (50) / G' V1(25) For example, it can be below 70%, below 40%, below 30%, or below 20%. It has G' V1 (50) / G' V1 (25) Adhesive sheets with small high-refractive-index adhesive layers are suitable for use as the aforementioned thermally activated adhesive sheets. G' V1 (50) / G' V1 (25) has no particular lower limit. V1 (50) / G' V1 (25) For example, it is 5% or more. From the viewpoint of heat resistance, it is preferably 10% or more, and it can be 12% or more or 15% or more.

[0050] Energy storage modulus G' V1 (25) and G' V1 (50) It can be determined by dynamic viscoelasticity measurement, and G' can be calculated from the result. V1 (50) / G' V1 (25). Dynamic viscoelasticity determination can be performed using a commercially available dynamic viscoelasticity measuring device by conventional methods, such as the ARES manufactured by TA Instruments or its equivalent, under the following testing conditions. As the sample for testing, a sample with a thickness of approximately 1.5 mm is prepared by laminating the adhesive layer of the object being evaluated as needed.

[0051] [Measurement Conditions]

[0052] Deformation mode: Torsion

[0053] Measurement frequency: 1Hz

[0054] Heating rate: 5℃ / minute

[0055] Shape: Parallel plate

[0056] Energy storage modulus G' V1 (25) G' V1 (50) and energy storage modulus ratio (G' V1 (50) / G' V1(25) This 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) described later), whether to use the crosslinking agent, the type and amount used, whether to use the refractive index enhancer, the type and amount used, and the plasticizer. For example, as monomer (m1), by using a first monomer as the main component of the first monomer (m1) and combining it with a second monomer with a different chemical structure than the first monomer in a smaller amount, it is possible to reduce G' when the first monomer is used alone as monomer (m1). V1 (50) Reduce G' V1 (50) / G' V1 (25).

[0057] (Surface smoothness of the adhesive surface)

[0058] In some approaches, the surface (adhesive surface) of the high-refractive-index adhesive layer preferably has high surface smoothness.

[0059] 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 aforementioned adhesive surface (such as an adhesive sheet arranged on the viewpoint side of a light-emitting device, closer to 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. When the laminate (adhesive sheet) disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface (e.g., a laminate containing a high-refractive-index adhesive layer and a low-refractive-index adhesive layer), it is preferable that at least the arithmetic mean roughness Ra of 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 ensuring high surface smoothness on each adhesive surface of the double-sided adhesive sheet, it is possible to preferably achieve an adhesive with excellent optical homogeneity.

[0060] In some embodiments, the arithmetic mean roughness Ra of the bonding 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 bonding 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 embodiments where the laminate has a first bonding surface and a second bonding surface, the arithmetic mean roughness Ra of the first bonding surface and the arithmetic mean roughness Ra of the second bonding surface may be the same or different.

[0061] 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 applications where light is extracted through the aforementioned adhesive surface, it is possible to suppress uneven brightness caused by the surface condition of the adhesive layer. A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion. When the laminate disclosed herein is in the form of a double-sided adhesive sheet 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 sheet have high surface smoothness, it is preferable to achieve adhesion with excellent optical homogeneity.

[0062] 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 embodiments 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.

[0063] 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) or its equivalent. Specifically, the arithmetic mean roughness Ra and maximum height Rz can be measured, for example, by setting the measurement operation and measurement conditions in a manner equivalent to or corresponding to the results obtained using the measurement method.

[0064] That is, the surface shape of the sample was measured under the following conditions using a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) at 23°C and 50% RH. Based on the measured data, the arithmetic surface roughness Ra was calculated according to JIS B0601-2001. Regarding the maximum height Rz, it was calculated 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, based on the data obtained from the above measurements (roughness curve). The measurements were performed 5 times (i.e., N=5), and their average value was used.

[0065] The sample used for the above-mentioned test can be prepared by cutting the adhesive layer of the test object or the adhesive sheet containing the adhesive layer into a size of approximately 150 mm in length and 50 mm in width. With the adhesive surface protected by a release liner, the release liner is gently peeled off (for example, at a stretching speed of 300 mm / min and a peeling angle of 180°) to expose the adhesive surface. Ideally, the test should be performed after allowing the sample to stand for approximately 30 minutes after the adhesive surface has been exposed.

[0066] [Measurement Conditions]

[0067] Measurement area: 5.62mm × 4.22mm

[0068] (Objective lens: 2.5x, internal lens: 0.5x)

[0069] Parsing mode:

[0070] Remove: Cylinder

[0071] Data Fill: ON (Max: 25)

[0072] Remove Spikes: ON (xRMS: 1)

[0073] Filter: OFF

[0074] 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).

[0075] (Water absorption rate)

[0076] In some embodiments, the water absorption rate of the high-refractive-index adhesive layer is preferably limited to a specified value or below. By limiting the water absorption rate of the high-refractive-index adhesive layer, dimensional changes in the high-refractive-index adhesive layer caused by variations in the amount of moisture in the adhesive layer (e.g., absorption and release of moisture from the environment) tend to be suppressed. This suppresses warping of the high-refractive-index adhesive layer or the optical laminate containing the high-refractive-index adhesive layer due to inconsistencies in dimensional changes between the high-refractive-index adhesive layer and its adjacent layers (which may be low-refractive-index layers, support substrates, release liner, adherends, etc.). From the viewpoint of maintaining the flatness, transparency, refractive index, etc., of the high-refractive-index adhesive layer at a certain level, it is also preferable to suppress variations in the amount of moisture in the high-refractive-index adhesive layer. Furthermore, high-refractive-index adhesive layers with low water absorption rates are suitable as constituent elements in components or articles containing moisture-sensitive elements, such as organic EL elements, because they do not easily absorb moisture.

[0077] In some embodiments, the water absorption rate of the high-refractive-index adhesive layer is preferably about 1.0% or less, 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 high-refractive-index 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. The water absorption rate of the low-refractive-index layer can be the same as or different from that of the high-refractive-index adhesive layer. From the viewpoint of obtaining a higher effect, it is more preferable that the water absorption rates of both the high-refractive-index adhesive layer and the low-refractive-index layer are limited to specified values ​​or less.

[0078] It should be noted that the water absorption rate (also known as moisture content) of the high refractive index adhesive layer is determined using the following method. The water absorption rate of the low refractive index layer is also determined using the same method.

[0079] [Moisture content determination]

[0080] 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. 2The 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.

[0081] Anode solution: AQUAMICRON AKX (manufactured by Mitsubishi Chemical)

[0082] Cathodic solution: AQUAMICRON CXU (manufactured by Mitsubishi Chemical)

[0083] Heating and vaporization temperature: 150℃

[0084] (Gel ratio)

[0085] The gelation rate of the high-refractive-index adhesive layer is appropriately set according to the intended use and application method, 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 about 10% or more, or about 20% or more, is suitable, and may also be about 30% or more. From the viewpoint of the adhesive layer's resistance to deformation (preventing overflow due to pressure, air bubbles due to 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 of the laminate comprising a high-refractive-index adhesive layer and a low-refractive-index layer (typically a laminate in the form of a substrate-free double-sided adhesive sheet formed by a high-refractive-index adhesive layer and a low-refractive-index layer) is also preferably set within the range exemplified above. The gelation rate can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc., of the base polymer. The gelation rate is measured by the following method.

[0086] [Determination of gelation rate]

[0087] 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.

[0088] 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.

[0089] Gelation rate (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0090] The gelation rates of the high-refractive-index adhesive layer and the low-refractive-index layer can be the same or different. In some cases, the gelation rate of the low-refractive-index layer can be lower than that of the high-refractive-index adhesive layer. According to this configuration, the overall softness is easily improved by the contribution of the relatively low-refractive-index layer with its low gelation rate. Thus, a good balance can be achieved between high refractive index and softness.

[0091] In some embodiments of the technology disclosed herein, the peak temperature of the tanδ of the adhesive constituting the high refractive index adhesive layer is preferably above about -50°C, and more preferably below about 50°C. Here, the tanδ (loss tangent) of the adhesive refers to the ratio of the loss modulus G” to the storage modulus G’ of the adhesive. That is, tanδ = G” / G’. The tanδ of the adhesive can be determined as follows: A disk-shaped adhesive sample with a thickness of about 2 mm and a diameter of 7.9 mm is held between parallel plates. Using a viscoelastic testing apparatus, a temperature dispersion test of the adhesive is performed in shear mode under the conditions of a measurement temperature range of -60°C to 60°C and a heating rate of 5°C / min, while applying a shear strain at a frequency of 1 Hz. The tanδ is then determined based on the storage modulus G’ (Pa) and the loss modulus G” (Pa) at this time, using the following formula: tanδ = G” / G’. The peak temperature of the tanδ of the adhesive (hereinafter sometimes referred to as Tpeak) can be determined from the shift of tanδ within the above temperature range. As a viscoelasticity testing apparatus, ARES or its equivalent, manufactured by TA Instruments, can be used.

[0092] In some methods, it is advantageous for the Tpeak of the high-refractive-index adhesive layer 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 Tpeak of the adhesive is not too low, and it is also suitable to achieve a high refractive index. From this viewpoint, in some methods, the Tpeak of the adhesive is, for example, above -40°C, above -30°C, above -20°C, above -5°C, above 5°C, above 15°C, and even 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).

[0093] The Tpeak of the aforementioned adhesive is preferably applied at least to the high-refractive-index adhesive layer, and more preferably to both the high-refractive-index adhesive layer and the low-refractive-index layer. The Tpeak of the high-refractive-index adhesive layer and the Tpeak of the low-refractive-index layer may be of the same or different degree.

[0094] (Basic Polymer)

[0095] In the technology disclosed herein, the type of adhesive constituting the high-refractive-index 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 (natural rubber, synthetic rubber, mixtures thereof, etc.), 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"), and which are structural polymers that shape 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.

[0096] The following description focuses primarily on high refractive index adhesive layers made of acrylic adhesives, but is not intended to limit the high refractive index adhesive layers in the art disclosed herein to acrylic adhesive layers.

[0097] It should be noted that in this specification, the term "base polymer" in the adhesive refers to the main component of the rubber-like polymer contained in the adhesive, and is not interpreted in any other limiting way. The aforementioned rubber-like 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 greater than 50% by weight unless otherwise specified.

[0098] 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 listed.

[0099] 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).

[0100] (Acrylic polymer (A))

[0101] The high refractive index binder sheets disclosed herein can preferably contain a storage modulus G' with a refractive index higher than 1.570 and at 25°C. V1The method is to implement an acrylic adhesive layer with a pressure of 30 kPa to 700 kPa, a total light transmittance of 86% or more, and a haze value of 1.0% or less. For the acrylic polymer used as the base polymer of the aforementioned acrylic adhesive layer, it is preferable to use a polymer containing an aromatic ring-containing monomer (m1) as a monomeric component of the acrylic polymer. That is, it is preferable to use 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 the repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition, whether it is 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 laminates with minimal deformation and warping.

[0102] (Single(m1))

[0103] 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.

[0104] 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 adhesion, 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 containing one olefin unsaturated group per molecule (i.e., a monofunctional monomer).

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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) is, for example, higher than 70% by weight, such as 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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: 6°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.

[0127] 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.

[0128] 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.

[0129] 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, further 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. By using monomer L as part or all of the monomer (m1), the increase in storage modulus G' can be suppressed. Thus, 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] (Single (m2))

[0138] 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.

[0139] 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).

[0140] 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 a monomer concentration of 50% by weight or more (e.g., more than 50% by weight, more than 70% by weight, or more than 85% by weight). One hydroxyl-containing monomer may be used alone or in combination of two or more.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] (Single m3)

[0148] 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.

[0149] 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.

[0150] 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).

[0151] 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) without using alkyl methacrylates.

[0152] 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.

[0153] (Other monomers)

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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).

[0159] In some embodiments, for the monomer component of the base polymer (e.g., an acrylic polymer) constituting the high refractive index adhesive layer, from the viewpoint of suppressing coloration or discoloration (e.g., yellowing) of the adhesive layer, it is preferable to limit the amount of carboxyl-containing monomers used. The amount of carboxyl-containing monomers used in the monomer component can be, for example, 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 object) that may come into contact with or approach the high refractive index adhesive layer. The techniques disclosed herein can preferably be implemented in a manner where the aforementioned monomer component does not contain carboxyl-containing monomers.

[0160] 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) is preferably limited in the monomer component constituting the high refractive index adhesive layer. 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 high refractive index adhesive layer is acid-free).

[0161] (glass transition temperature Tg of the basic polymer) T )

[0162] 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.T For 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.

[0163] 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.

[0164] 1 / Tg=Σ(Wi / Tgi)

[0165] 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).

[0166] 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.

[0167] (Preparation methods of basic polymers)

[0168] 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).

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] [GPC Measurement Conditions]

[0175] Sample concentration: 0.2% by weight (tetrahydrofuran solution)

[0176] Sample injection volume: 10 μL

[0177] Eluent: Tetrahydrofuran (THF)

[0178] Flow rate: 0.6 mL / min

[0179] Column temperature (measurement temperature): 40℃

[0180] column:

[0181] Sample column: 1 brand name "TSKguardcolumn SuperHZ-H" + 2 pieces "TSKgel SuperHZM-H" brand name (manufactured by Tosoh Corporation)

[0182] Reference column: 1 product name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation)

[0183] Detector: Differential refractometer (RI)

[0184] Standard sample: polystyrene

[0185] (Refractive index enhancer)

[0186] In some embodiments of the technology disclosed herein, the high-refractive-index adhesive layer (e.g., an acrylic adhesive layer) may contain a refractive index enhancer in addition to the base polymer, as needed. 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] (additives (H) RO ))

[0192] 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.

[0193] 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.

[0194] 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. Additives (H...) RO The molecular weight of the additive (H) can be selected, for example, from a range below 30,000. Additionally, the additive (H) RO Preferably, the additive (H) is a polymer or non-polymer with a molecular weight lower than that of the base polymer. From the viewpoint of achieving a good balance between the effect of increasing the refractive index and other properties (such as suitability for the adhesive's softness, haze, and other optical properties), in some methods, the additive (H) RO The molecular weight of the additive (H) is preferably below about 10,000, more preferably below 5,000, more preferably below 3,000 (e.g., below 1,000), and can be below 800, below 600, below 500, or below 400. RO When the molecular weight of the additive (H) is not too large, it can be advantageous from the viewpoint 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 ).

[0195] 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). RO When the polymer is of 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.

[0196] It can be used as an additive (H) ROExamples 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).

[0197] As an additive (H) RO The 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).

[0198] 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, glycidoxy, 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).

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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 of 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 their derivatives are also listed.

[0203] 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.

[0204] 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, dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), etc., can also be listed.

[0205] 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.

[0206] 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 olefinic unsaturated groups in adhesive layers and laminates (e.g., laminates) containing such adhesive layers, additives (H) without olefinic unsaturated groups are also preferred. RO ).

[0207] 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.

[0208] Examples of chain transfer agents include lauryl thiol, glycidyl thiol, thioglycolic 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 synthesis of the oligomer, the type of chain transfer agent, etc., to obtain an oligomer 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 synthesis of the oligomer; 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 synthesis of the oligomer; 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.

[0209] 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.

[0210] (Plasticized materials)

[0211] In some embodiments, the high-refractive-index adhesive layer may contain a plasticizer with a molecular weight lower than that of the base polymer of the adhesive layer. The use of a plasticizer can improve the flexibility of the high-refractive-index adhesive layer, enhance adhesion to the adhered objects, improve overall flexibility, and improve conformability to deformation. From the viewpoint of compatibility and transparency within the adhesive layer, organic materials are preferred as plasticizers. The plasticizer can be, or can be used as, the aforementioned refractive index enhancer (e.g., the aforementioned additive (H...). RO Materials.

[0212] The molecular weight of the plasticizing material 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 plasticizing material 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 relatively low molecular weight of the plasticizing material 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 is appropriate for the plasticizing material, 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 plasticizing material can be 500 or more, 1,000 or more, or 2,000 or more. When the molecular weight of the plasticizer is not too low, it is also preferred from the perspective of the heat resistance of the adhesive layer and the inhibition of contamination of the adhered material.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] (Leveling agent)

[0218] 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.

[0219] In some embodiments, a polymer (hereinafter also referred to as "polymer (B)") may be preferably used as the leveling agent. This polymer is a monomer raw material 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.

[0220] 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. Among these, monomer S1 with a structure that has a polymerizable reactive group at one end and does not have a functional group at the other end that would cause a crosslinking reaction with the base polymer (e.g., an acrylic polymer) of the adhesive composition to which the leveling agent is to be mixed. Commercially available examples include, for instance, single-end 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.

[0221] 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.

[0222] 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.

[0223] 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 above-mentioned functional groups refer to polymerizable functional groups (e.g., (meth)acryloyl, vinyl, allyl and other olefinic unsaturated groups).

[0224] 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.

[0225] 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 esters (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.

[0226] 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.

[0227] The content of the above-mentioned alkyl methacrylate and the above-mentioned methacrylate having alicyclic hydrocarbon group in monomer raw material B may 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] (Inorganic particles)

[0234] 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, 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 a binder. 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. 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.

[0235] (Cross-linking agent)

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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, butyl glycol (meth)acrylate, and hexyl glycol di(meth)acrylate. Multifunctional monomers can be used alone or in combination of two or more.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] (Thickening agent)

[0244] 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.

[0245] (Other additives)

[0246] 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.

[0247] (Peel strength)

[0248] In some embodiments, it is suitable for the adhesive layer disclosed herein 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 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 less than 30 N / 25 mm, less than 25 N / 25 mm, or less than 20 N / 25 mm.

[0249] Here, the peel strength can be determined as follows: The material is pressed onto an alkaline glass plate as the adherend, placed in an environment of 23°C and 50% RH for 30 minutes, 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 180° peel adhesion force is measured at a peel angle of 180 degrees 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 test object for reinforcement. Specifically, the peel strength can be measured according to the method described in the examples below.

[0250] When the high-refractive-index adhesive layer and the low-refractive-index adhesive layer disclosed herein are laminated to form a double-sided adhesive sheet 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 (the adhesive surface composed of the high-refractive-index adhesive layer), 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.

[0251] <Low Refractive Index Layer>

[0252] In the technology disclosed herein, the refractive index n2 of the low-refractive-index layer (preferably a low-refractive-index adhesive layer) is preferably lower than the refractive index n1 of the high-refractive-index adhesive layer. Therefore, the behavior of light transmitted through the laminate containing these layers can be controlled by utilizing the refractive index difference between the high-refractive-index adhesive layer and the low-refractive-index layer. The refractive index n2 of the low-refractive-index layer can, for example, be in the range of approximately 1.35 to 1.55. In some embodiments, from the viewpoint of easily improving the front brightness enhancement effect described later by increasing the refractive index difference with the high-refractive-index adhesive layer n1, the refractive index n2 of the low-refractive-index layer is preferably 1.49 or less, more preferably 1.47 or less (e.g., 1.46 or less, or 1.45 or less), and can be 1.43 or less, 1.41 or less, or 1.40 or less. Furthermore, from the viewpoint of balancing material availability and adhesive properties, in some embodiments, the refractive index n2 of the low-refractive-index layer can, for example, be 1.36 or more, 1.38 or more, 1.40 or more, or 1.42 or more.

[0253] In some embodiments, the ratio (n1 / n2) of the refractive index n1 of the high-refractive-index adhesive layer to the refractive index n2 of the low-refractive-index layer can, for example, be greater than 1.00, preferably about 1.01 or more, about 1.02 or more, or even about 1.03 or more. In some embodiments, a ratio (n1 / n2) of about 1.05 or more is advantageous, preferably about 1.07 or more, more preferably about 1.10 or more, or even about 1.11 or more. There is no particular upper limit to the ratio (n1 / n2). In some embodiments, from the viewpoint of adhesive properties, transparency, etc., the ratio (n1 / n2) can, for example, be about 1.20 or less, about 1.18 or less, about 1.16 or less, about 1.14 or less, or even about 1.12 or less.

[0254] In some embodiments, the difference between the refractive index n1 of the high-refractive-index adhesive layer and the refractive index n2 of the low-refractive-index layer, i.e., the refractive index difference (n1-n2), can be greater than 0.00, greater than 0.01, preferably greater than 0.02, 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. There is no particular upper limit to the refractive index difference (n1-n2). In some embodiments, from the viewpoint of adhesion properties, transparency, etc., the refractive index difference (n1-n2) can be less than 0.30, less than 0.26, less than 0.21, less than 0.18, or less than 0.16.

[0255] In some preferred embodiments, the storage modulus G' of the low refractive index layer at 25°C (hereinafter sometimes referred to as "storage modulus G'") V2(25)) Preferably, the storage modulus G' is lower than that of the high refractive index adhesive layer at 25°C (storage modulus G'). V1 (25)). That is, G' is preferred. V2 (25) <G’ V1 (25). According to this configuration, by laminating a low-refractive-index layer on a high-refractive-index adhesive layer, adhesion and flexibility are imparted, thereby improving height difference tracking and surface tracking, etc., and enabling the realization of a laminate (adhesive sheet) that can be preferentially applied in a variety of device designs.

[0256] Energy storage modulus G' V2 (25) There are no particular limitations; for example, it can be in the range of 1.0 kPa to 500 kPa. From the viewpoint of improving the flexibility imparted by the low-refractive-index layer and the effect of improving the follow-through of deformation, in some ways, the storage modulus G' V2 (25) A pressure of 400 kPa or less is appropriate, preferably 300 kPa or less, more preferably 200 kPa or less (e.g., 180 kPa or less, or 150 kPa or less), and can be 120 kPa or less, 90 kPa or less, or 70 kPa or less. Furthermore, from the viewpoint of imparting appropriate cohesion to the low refractive index layer, in some embodiments, the storage modulus G' V2 (25) A value of 5.0 kPa or higher is appropriate, preferably 10 kPa or higher, but can be 15 kPa or higher, 25 kPa or higher, 35 kPa or higher, 60 kPa or higher, or 80 kPa or higher. From the viewpoint of easily achieving higher cohesion and adhesive properties, in some methods, the storage modulus G' V2 (25) It can be above 95 kPa, above 110 kPa, or above 140 kPa.

[0257] In the case where the low-refractive-index layer is the adhesive layer, the type of adhesive constituting this adhesive layer is not particularly limited. The adhesive constituting the low-refractive-index adhesive layer can be one or more of the following rubber-like polymers used in the adhesive field: 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 base polymer. From the viewpoints of adhesive performance and cost, adhesives containing either 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. In the case where the high-refractive-index adhesive layer is the acrylic adhesive layer, from the viewpoint of the adhesion between the high-refractive-index adhesive layer and the low-refractive-index adhesive layer, it is preferable to use a low-refractive-index adhesive layer as the acrylic adhesive layer.

[0258] In some embodiments, the acrylic polymer described above is preferably a polymer containing alkyl (meth)acrylate and may further contain other monomers (copolymeric monomers) that are copolymerizable with the alkyl (meth)acrylate. The content of the alkyl (meth)acrylate in the monomeric raw material may be, for example, 10% by weight or more, 25% by weight or more, 35% by weight or more, or 45% by weight or more. The acrylic polymer described above may be a polymer containing alkyl (meth)acrylate as a main monomer and may further contain the aforementioned copolymeric monomer as a secondary monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomeric raw material. Alternatively, the monomer composition may be more than 55% by weight or more than 60% by weight of alkyl (meth)acrylate.

[0259] As an alkyl methacrylate, for example, the compound shown in formula (1) below can be preferred.

[0260] CH2=C(R 1 COOR 2 (1)

[0261] Here, R in equation (1) above 1 It can be a hydrogen atom or a methyl group. Additionally, R... 2 A chain alkyl group having 1 to 20 carbon atoms (hereinafter, this range of carbon atoms is sometimes expressed as "C"). 1-20 From the perspective of the storage modulus of the adhesive, R is preferred. 2 C 1-12 (e.g., C) 2-10 Typically, C 4-8Alkyl (meth)acrylates of chain-like alkyl groups. The above R 2 C 1-20 Alkyl (meth)acrylates with chain-like alkyl groups can be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include n-butyl acrylate and 2-ethylhexyl acrylate.

[0262] The aforementioned comonomers can be used to introduce crosslinking points into acrylic polymers or to improve the cohesive strength of acrylic polymers. Examples of comonomers include one or more monomers containing functional groups such as carboxyl-containing monomers, hydroxyl-containing monomers, anhydride-containing monomers, amide-containing monomers, amino-containing monomers, monomers with nitrogen-containing rings, sulfonic acid-containing monomers, and phosphate-containing monomers. Other examples of comonomers include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, (meth)acrylates containing non-aromatic rings, and alkoxy-containing monomers. Specific examples include the aforementioned substances that can be used as monomers in base polymers for high-refractive-index adhesive layers, but are not limited to these. For example, from the viewpoint of improving cohesive strength, acrylic polymers copolymerized with carboxyl-containing monomers and / or hydroxyl-containing monomers are preferred. Suitable examples of carboxyl-containing monomers include acrylic acid and methacrylic acid. Suitable examples of hydroxyl-containing monomers include 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

[0263] In some embodiments, to reduce the refractive index n2 of the low-refractive-index layer, a fluorinated monomer can be used as the aforementioned copolymerizable monomer. The content of the fluorinated monomer in the monomer raw material can be, for example, 10% by weight or more, 25% by weight or more, or 35% by weight or more. From the viewpoint of easily achieving a low-refractive-index layer with an even lower refractive index, the content of the aforementioned fluorinated monomer is preferably 40% by weight or more, more preferably 45% by weight or more, even more preferably 55% by weight or more, and can be 60% 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. There is no particular upper limit to the content of the fluorinated monomer in the monomer raw material, and it can be 100% by weight. In some embodiments, from the viewpoint of the cohesiveness of the low-refractive-index layer, the content of the aforementioned fluorinated monomer is appropriate to be 99.9% by weight or less, preferably 99.5% by weight or less, 99% by weight or less, 97% by weight or less, or 92% by weight or less. One type of fluorinated monomer can be used alone, or two or more types can be used in combination.

[0264] Fluorinated acrylic monomers can be suitably used as fluorinated monomers. There are no particular restrictions on whether the fluorinated acrylic monomer has at least one fluorine atom within its molecule. For example, fluorinated (meth)acrylates can be suitably used. Suitable examples of fluorinated (meth)acrylates include substances with a fluorinated hydrocarbon group at the ester terminus. Examples of fluorinated hydrocarbon groups include fluorinated aliphatic hydrocarbon groups, fluorinated alicyclic hydrocarbon groups, and fluorinated aromatic hydrocarbon groups. Fluorinated aliphatic hydrocarbon groups are suitable as fluorinated hydrocarbon groups. Fluorinated alkyl groups are examples of fluorinated aliphatic hydrocarbon groups. In fluorinated aliphatic hydrocarbon groups, the aliphatic hydrocarbon site can be linear or branched. Furthermore, in fluorinated aliphatic hydrocarbon groups, the fluorine atom can be bonded to any carbon atom of the aliphatic hydrocarbon group site. The fluorine atom bonded to one carbon atom can be single or multiple. There are no particular restrictions on the number of carbon atoms bonded with fluorine atoms.

[0265] In fluorinated aliphatic hydrocarbon groups (especially fluorinated alkyl groups), the number of carbon atoms at the hydrocarbon group site is not particularly limited. In some embodiments, considering compatibility with other comonomers, fluorinated aliphatic hydrocarbon groups with a carbon number of, for example, about 1 to 18 (preferably 1 to 12) are preferred. Specific examples of fluorinated aliphatic hydrocarbon groups include fluorinated methyl groups such as trifluoromethyl, difluoromethyl, and monofluoromethyl; fluorinated ethyl groups such as pentafluoroethyl, 1,1,2,2-tetrafluoroethyl, 1,2,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl, 1,2,2-trifluoroethyl, 2,2,2-trifluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, 2,2-difluoroethyl, 1-monofluoroethyl, and 2-monofluoroethyl; etc. As fluoroalkyl groups having 3 or more carbon atoms, similar to the fluoromethyl and fluoroethyl groups exemplified above, various fluoroalkyl groups in which one or more carbon atoms in the alkyl group are bonded to a single or multiple fluorine atoms can be exemplified.

[0266] Examples of fluorinated alicyclic hydrocarbon groups include fluorinated cycloalkyl groups. Similar to the aforementioned fluorinated alicyclic hydrocarbon groups, in fluorinated alicyclic hydrocarbon groups, the fluorine atom can be bonded to any carbon atom of the alicyclic hydrocarbon group; the number of fluorine atoms bonded to one carbon atom can be single or multiple. Furthermore, there is no particular limitation on the number of carbon atoms bonded with fluorine atoms. Examples of fluorinated alicyclic hydrocarbon groups include: cyclohexyl groups with one fluorine atom, such as 2-fluorocyclohexyl, 3-fluorocyclohexyl, and 4-fluorocyclohexyl; cyclohexyl groups with two fluorine atoms, such as 2,4-difluorocyclohexyl and 2,6-difluorocyclohexyl; and cyclohexyl groups with three fluorine atoms, such as 2,4,6-trifluorocyclohexyl.

[0267] Fluorinated hydrocarbon groups may or may not have substituents. There are no particular restrictions on the types of substituents; examples include alkyl groups, alkoxy groups, hydroxyl groups, carboxyl groups, amino groups, nitro groups, cyano groups, and halogen atoms. Substituents may be used alone or in combination of two or more.

[0268] Fluorine-containing (meth)acrylates [fluoro(meth)acrylates] include, for example, fluorine-containing alkyl (meth)acrylates [fluoroalkyl (meth)acrylates], fluorine-containing cycloalkyl (meth)acrylates [fluorocycloalkyl (meth)acrylates], fluorine-containing aryl (meth)acrylates [fluoroaryl (meth)acrylates], etc.

[0269] As a fluorine-containing (meth)acrylate, a fluoroalkyl (meth)acrylate (especially a fluoroalkyl acrylate) is suitable. Examples of fluoroalkyl esters of (meth)acrylate include 2,2,2-trifluoroethyl acrylate (trade name "Viscoat 3F" manufactured by Osaka Organic Chemical Industry Co., Ltd.), 2,2,3,3-tetrafluoropropyl acrylate (trade name "Viscoat 4F" manufactured by Osaka Organic Chemical Industry Co., Ltd.), 1H,1H,5H-octafluoropentyl acrylate (trade name "Viscoat 8F" manufactured by Osaka Organic Chemical Industry Co., Ltd.), 1H,1H,5H-octafluoropentyl methacrylate (trade name "Viscoat 8FM" manufactured by Osaka Organic Chemical Industry Co., Ltd.), 2-(heptadecylfluorononyl)ethyl acrylate (trade name "FA-108" manufactured by Kyoeisha Chemical Co., Ltd.), and 1H,1H,2H,2H-tridecylfluorooctyl acrylate (trade name "Viscoat 13F" manufactured by Osaka Organic Chemical Industry Co., Ltd.).

[0270] From the viewpoints of low refractive index effect and flexibility, it is advantageous for the fluoroalkyl group in the (meth)acrylate to have 3 or more carbon atoms, preferably 4 or more, more preferably 5 or more, further preferably 6 or 7 or more, and particularly preferably 8 or more. From the viewpoints of adhesive properties, it is advantageous for the fluoroalkyl group to have 18 or less carbon atoms, preferably 14 or less, more preferably 12 or less, and may be 10 or less, or 9 or less. In some embodiments, the fluoroalkyl group may have 7 or less carbon atoms, or 5 or less. Furthermore, in some embodiments, as the (meth)acrylate containing fluorine atoms, it is preferable to be a (meth)acrylate fluoroalkyl group without fluorine bonded to the carbon at the 1-position of the alkyl group, such as 1H,1H,2H,2H-tridecylfluorooctyl acrylate, which is a (meth)acrylate fluoroalkyl group without fluorine bonded to either the carbon at the 1-position or the carbon at the 2-position of the alkyl group.

[0271] In some embodiments, the low-refractive-index layer is an acrylic adhesive layer. The acrylic polymer used as the base polymer of this adhesive can be a polymer of a monomer raw material that contains at least the fluorinated acrylic monomer (e.g., fluoroalkyl (meth)acrylate) as described above, and also contains other monomers (copolymerizable monomers) that are copolymerizable with the fluorinated acrylic monomer. This monomer raw material may or may not contain alkyl (meth)acrylate. The content of the fluorinated acrylic monomer in the aforementioned monomer raw material can be, for example, 10% by weight or more, 25% by weight or more, or 35% by weight or more. From the viewpoint of easily achieving a low-refractive-index layer with a lower refractive index, the content of the aforementioned fluorinated acrylic monomer is preferably 40% by weight or more, more preferably 45% by weight or more, further preferably 55% by weight or more, and can be 60% 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. There is no particular upper limit to the content of the fluorinated acrylic monomer in the monomer raw material; it can be 100% by weight. In some embodiments, from the viewpoint of the cohesiveness of the low-refractive-index layer, it is appropriate for the content of the aforementioned fluorinated acrylic monomer to be 99.9% by weight or less, preferably 99.5% by weight or less, and can be 99% by weight or less, 97% by weight or less, or 92% by weight or less. One type of fluorinated acrylic monomer can be used alone or in combination of two or more types.

[0272] The monomer raw materials for the base polymer used to prepare the low refractive index layer can include a composition containing comonomers in addition to fluorinated acrylic monomers (e.g., fluoroalkyl methacrylates). As such comonomers, one or more monomers containing functional groups, such as carboxyl-containing monomers, hydroxyl-containing monomers, anhydride-containing monomers, amide-containing monomers, amino-containing monomers, monomers with a nitrogen-containing ring (e.g., N-vinyl-2-pyrrolidone and other N-vinylcyclic amides), sulfonic acid-containing monomers, and phosphate-containing monomers, can be used. Other examples of comonomers include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, cycloalkyl methacrylates, (meth)acrylates containing non-aromatic rings such as isobornyl methacrylate, and alkoxy-containing monomers; etc. Specific examples include the above-mentioned substances as monomers for base polymers that can be used as high refractive index adhesive layers, but are not limited to these. For example, from the viewpoint of improving cohesion, acrylic polymers copolymerized with carboxyl-containing monomers and / or hydroxyl-containing monomers as the comonomers are preferred.

[0273] In some preferred embodiments, the monomer raw material of the base polymer used to prepare the low refractive index layer can be a composition containing fluorinated monomers (e.g., fluorinated acrylic monomers such as fluoroalkyl methacrylates) and also containing hydroxyl monomers. Hydroxyl monomers can contribute to improved cohesion and the introduction of crosslinking points. Suitable examples of hydroxyl monomers include hydroxyalkyl methacrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. From the viewpoint of improved flexibility in the room temperature range, 4-hydroxybutyl acrylate is more preferably used. The content of the hydroxyl monomer in the monomer raw material is not particularly limited, and for example, it can be 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.5% by weight or more). In some embodiments, the content of the hydroxyl monomer can be 0.7% by weight or more, 0.9% by weight or more, or 1.5% by weight or more of the monomer raw material. The upper limit of the content of the hydroxyl monomer is not particularly limited, and for example, it can be 15% by weight or less or 10% by weight or less. In some approaches, from the viewpoint of reducing refractive index, it is appropriate for the content of hydroxyl-containing monomers in the aforementioned monomer raw materials to be less than 10% by weight, preferably less than 5% by weight, less than 3% by weight, less than 2.5% by weight, or less than 1.5% by weight.

[0274] In some approaches, from the viewpoint of suppressing coloration or discoloration (e.g., yellowing) of the low-refractive-index layer, the monomer raw material used to prepare the base polymer of the low-refractive-index layer preferably has a limited content of carboxyl-containing monomers. The content of carboxyl-containing monomers in the aforementioned monomer raw material can, for example, be less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight, and even more preferably less than 0.1% by weight (e.g., less than 0.05% by weight). Limiting the content 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 adherend) that may come into contact with or approach the low-refractive-index layer. The techniques disclosed herein can preferably be implemented in a manner where the aforementioned monomer raw material does not contain carboxyl-containing monomers.

[0275] For the same reason, in some methods, the monomer raw materials used to prepare the base polymer of the low refractive index layer preferably limit the content of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxyl groups). The preferred content of the acidic functional group-containing monomers in the monomer raw materials of this method can be applied using the aforementioned preferred content of carboxyl-containing monomers. The technology disclosed herein can preferably be implemented in a manner where the aforementioned monomer raw materials do not contain monomers containing acidic groups (i.e., the base polymer of the low refractive index layer is acid-free).

[0276] The base polymer for the low-refractive-index layer, like that for the high-refractive-index binder layer, can be prepared using well-known polymerization methods. The weight-average molecular weight (Mw) of the base polymer is not particularly limited; for example, it can be approximately 10 × 10⁻⁶. 4 ~500×10 4 The range can also be approximately 20 × 10 4 ~200×10 4 The range. In some approaches, from the viewpoint of adhesion to high-refractive-index adhesive layers, the Mw of the base polymer of the low-refractive-index adhesive layer is 150 × 10. 4 The following is appropriate, preferably 120×10 4 The following (e.g., 95×10) 4 (The following) can be 75×10 4 The following can be 68×10 4 The following can also be 60×10 4 Below. Additionally, in some approaches, from the viewpoint of the cohesiveness of the low-refractive-index adhesive layer, the Mw of the base polymer can, for example, be 30 × 10⁻⁶. 4 The above can be 40×10 4 The above can also be 50×10 4 That's all. To prepare Mw, conventionally known chain transfer agents can be used as needed.

[0277] While not specifically limited, from an adhesive viewpoint, it is advantageous for the base polymer (e.g., an acrylic polymer) of the low-refractive-index layer to have a Tg of about 0°C or less, preferably about -5°C or less (e.g., about -15°C or less, or -25°C or less). Furthermore, from the viewpoint of the cohesive strength of the adhesive layer, the base polymer of the low-refractive-index layer should have a Tg of about -75°C or more, preferably about -70°C or more (e.g., -50°C or more, and further -30°C or more). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and proportions of monomers used in the synthesis of the polymer).

[0278] Known crosslinking agents can be used in low-refractive-index layers. Additionally, low-refractive-index layers may contain other additives such as tackifiers. Crosslinking agents and tackifiers can be appropriately selected from the same substances used in high-refractive-index adhesive layers and used in suitable amounts.

[0279] In adhesive compositions used to form low-refractive-index adhesive layers that include a crosslinking agent, isocyanate-based crosslinking agents are preferably used, for example. In some embodiments, from the viewpoint of good adhesion to high-refractive-index adhesive layers, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer of the adhesive composition may be less than, for example, 0.5 parts by weight, less than 0.3 parts by weight, less than 0.2 parts by weight, or less than 0.15 parts by weight. Furthermore, from the viewpoint of appropriately utilizing the crosslinking agent, in some embodiments, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer may 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.

[0280] <Preparation of Adhesive Layer>

[0281] In the technology disclosed herein, the adhesive constituting the adhesive layer (which may be a high-refractive-index adhesive layer and / or a low-refractive-index adhesive layer, hereinafter the same) 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 means of the adhesive composition (e.g., drying, crosslinking, polymerization, cooling, etc.) may be applied only once, or two or more may be applied simultaneously or in 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 a polymerization reaction and / or crosslinking reaction is 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.

[0282] The adhesive layer in the technology disclosed herein can be formed by applying (e.g., coating) an adhesive composition to a suitable surface and then curing the composition. The application of the adhesive composition can be carried out, for example, 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.

[0283] The adhesive layer 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 warping of the adhesive layer or the substrate to which it is adhered. It is also advantageous from the viewpoint of suppressing optical distortion of the adhesive layer when no dimensional changes (e.g., curing shrinkage) occur due to post-curing.

[0284] 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 tight bond with the adherend. From the viewpoint of preventing coloring and uneven color due to light interference, a thickness of 5 μm or more for the adhesive layer (e.g., the thickness of a high-refractive-index adhesive layer) 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. When the thickness of the adhesive layer is not too large, it can be advantageous from the viewpoint of thinning the laminate containing the adhesive layer and the light-emitting device. The techniques disclosed herein can be implemented, for example, preferably with the thickness of the adhesive layer ranging from 3 μm to 200 μm (more preferably from 5 μm to 100 μm).

[0285] In some embodiments, the thickness of the adhesive layer can be at least the thickness T1 of the high-refractive-index adhesive layer. The thickness T2 of the low-refractive-index adhesive layer can also be selected from the same range. The thickness of the adhesive layer can also be applied to the thickness T2 of the low-refractive-index layer, regardless of whether it is an adhesive layer. The thickness T1 of the high-refractive-index adhesive layer and the thickness T2 of the low-refractive-index layer can be the same or different. The ratio (T1 / T2) of the thickness T1 of the high-refractive-index adhesive layer to the thickness T2 of the low-refractive-index layer can, for example, be 0.1 or more, 0.3 or more, 0.5 or more, 0.8 or more, 1.2 or more, or 1.5 or more. Furthermore, the ratio (T1 / T2) can, for example, be 20 or less, 10 or less, 5 or less, or 3 or less. In some embodiments, the ratio (T1 / T2) can be less than 2, less than 1.5, or less than 1.

[0286] As a method for obtaining a structure (laminated sheet) consisting of a high-refractive-index adhesive layer and a low-refractive-index layer (typically a low-refractive-index adhesive layer), methods may include: forming a high-refractive-index adhesive layer and a low-refractive-index layer respectively on a release surface (e.g., the release surface of a release liner) and bonding them together; applying a composition for forming the low-refractive-index layer onto the high-refractive-index adhesive layer and curing it; or, conversely, applying an adhesive composition for forming the high-refractive-index adhesive layer onto the low-refractive-index layer and curing it, etc., but are not limited to these methods. When bonding the pre-formed high-refractive-index adhesive layer and the low-refractive-index layer, treatments to promote adhesion between these layers may be performed as needed. For example, autoclaving, rolling, etc., may be performed, but are not limited to these methods.

[0287] <Supporting substrate>

[0288] The high-refractive-index adhesive layer and the low-refractive-index layer can be stacked sequentially or in reverse order on one side of the supporting substrate. This configuration, in which a high-refractive-index adhesive layer and a low-refractive-index layer are stacked on the supporting substrate, can also be used as an adhesive sheet with a substrate. Therefore, according to this specification, an adhesive sheet (adhesive article) with a substrate is provided, comprising: a laminate formed of a high-refractive-index adhesive layer and a low-refractive-index layer (preferably a low-refractive-index adhesive layer), and a supporting substrate supporting the laminate.

[0289] There are no particular limitations on the material of the supporting substrate; it can be selected appropriately based on the intended use and method of application. Non-limiting examples of usable substrates include polyolefin films with polyolefins as the main component, such as polypropylene (PP) and ethylene-propylene copolymer; polyester films with polyesters as the main component, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); and polyvinyl chloride films with polyvinyl chloride as the main component. Examples of plastic films include: foamed sheets formed from polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; woven and nonwoven fabrics based on various fibrous materials (such as natural fibers like hemp and cotton, synthetic fibers like polyester and vinylon, and semi-synthetic fibers like acetate); paper types such as Japanese paper, high-quality paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil. Substrates composed of these composites are also acceptable. Examples of such composite substrates include substrates with structures formed by laminating metal foil and the aforementioned plastic film, and plastic substrates reinforced with inorganic fibers such as glass cloth.

[0290] In some embodiments, various film substrates can be preferably used. These film substrates can be porous substrates such as foamed films or nonwoven sheets, or non-porous substrates, or substrates with a structure consisting of laminated porous and non-porous layers. In some embodiments, a substrate comprising a self-supporting or independent resin film capable of independently maintaining its shape can be preferably used as the base film. Here, "resin film" refers to a non-porous structure, typically a substantially bubble-free (non-porous) resin film. Therefore, the resin film is a concept distinct from foamed films and nonwoven fabrics. As the resin film, a self-supporting or independent film capable of independently maintaining its shape can be preferably used. The resin film can be a single-layer structure or a multi-layer structure with two or more layers (e.g., a three-layer structure).

[0291] 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 triacetyl cellulose; 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), and norbornene resins; (meth)acrylic 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.

[0292] 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). Examples of preferred resin films include 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, and PP / PE blend film. From the viewpoint of strength and dimensional stability, preferred examples of resin films 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.

[0293] In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and anti-blocking 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 sheet.

[0294] 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.

[0295] The aforementioned substrate may be substantially composed of such a base film. Alternatively, the aforementioned substrate 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 to the substrate, laminated layers, antistatic layers, primer layers, release layers, and other surface treatment layers.

[0296] In some embodiments, a light-transmitting substrate (hereinafter also referred to as a light-transmitting substrate) is preferably used as the supporting substrate. This allows for the formation of a light-transmitting adhesive sheet with a substrate. The total light transmittance of the light-transmitting substrate can be, for example, higher than 50%, or higher than 70%. In some preferred embodiments, the total light transmittance of the supporting substrate is 80% or higher, more preferably 90% or higher, and may also be 95% or higher (e.g., 95-100%). The aforementioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. The transmittance meter used is the Murakami Color Technology Research Institute's trade name "HAZEMETER HM-150" or its equivalent. A suitable example of the aforementioned light-transmitting substrate is a light-transmitting resin film. The aforementioned light-transmitting substrate can be an optical film.

[0297] The thickness of the substrate is not particularly limited and can be selected according to the intended use and application method. For example, the substrate thickness can be 500 μm or less, but from the viewpoint of processability and workability, 300 μm or less is preferred; it can also be 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, or even 10 μm or less. A smaller substrate thickness tends to improve the ability to follow the surface shape of the adhered object. Furthermore, from the viewpoint of processability and workability, the substrate thickness can, for example, be 2 μm or more, 10 μm or more, or 25 μm or more.

[0298] For one side of the laminated adhesive layer in the substrate, conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and the formation of a primer-based coating can be performed as needed. Such surface treatments can be used to improve the anchoring of the adhesive layer to the substrate. The composition of the primer used in the formation of the primer coating is not particularly limited and can be appropriately selected from known compositions. The thickness of the primer coating 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 substrate as needed include antistatic layer formation treatment, coloring layer formation treatment, and printing treatment. These treatments can be applied individually or in combination.

[0299] In the technology disclosed herein, when a high-refractive-index adhesive layer and a low-refractive-index layer constitute an adhesive sheet with a substrate, the thickness of the adhesive sheet 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 aforementioned adhesive sheet can be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

[0300] It should be noted that the thickness of the adhesive sheet refers to the thickness of the portion that is adhered to the object being bonded. For example, for Figure 2 The substrate-free double-sided adhesive sheet 2 shown refers to the thickness from the first surface (first adhesive surface) 10A to the second surface (second adhesive surface) 10B of the adhesive layer, excluding the thickness of the release liner 31, 32.

[0301] <Laminated sheet with release liner>

[0302] The high-refractive-index adhesive layer and low-refractive-index layer disclosed herein can be in the form of an adhesive article (laminated sheet with release liner) in which the adhesive surface of the laminate containing the high-refractive-index adhesive layer and the low-refractive-index layer abuts against the release surface of the release liner before being assembled to a light-emitting device. Therefore, according to this specification, a laminate (adhesive article) with release liner is provided, comprising: a laminate of a high-refractive-index adhesive layer and a low-refractive-index layer, and a release liner having a release surface abutting against the adhesive surface of the laminate.

[0303] 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.

[0304] 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).

[0305] 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 triacetyl cellulose; 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.

[0306] 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.

[0307] 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.

[0308] For a laminate with release liner in the form of release liners on a first adhesive surface and a second adhesive surface, 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 composition, or they may have different materials and compositions.

[0309] 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 sheet smoother, and a high surface smoothness can be easily obtained on the adhesive surface after the release liner is removed.

[0310] In a laminated sheet with release liner and another release liner, the thicknesses of these release liners can be the same or different. In some embodiments, from the viewpoint of ease of release operation, it is preferable that one release liner has a different thickness from 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).

[0311] (Arithmetic mean roughness Ra of the bonding surface side)

[0312] 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 aforementioned 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 a laminate with 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 aforementioned 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.

[0313] (Maximum height Rz of the adhesive side surface)

[0314] 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 manufacture 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 200 nm or more, or about 300 nm or more. For a laminate with release liners in the form of release liners disposed on both the first adhesive surface and the second adhesive surface, 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.

[0315] (Surface characteristics of the reverse side)

[0316] 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).

[0317] 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.

[0318] 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.

[0319] <Applications>

[0320] In the technology disclosed herein, a high-refractive-index adhesive layer can be bonded to various adherends constituting a light-emitting device. The materials constituting these adherends (adhesion 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-based resins, acrylic-based resins, polyether nitrile-based resins, polyethersulfone-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate-based resins, etc.), polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyether ether ketone-based resins, polyamide-based resins (such as aramid resins), polyarylate-based resins, and fluorine-based resins. This includes various resin materials (typically plastic materials), such as resins, polycarbonate resins, cellulose polymers like diacetyl cellulose and triacetyl cellulose, vinyl butyral polymers, liquid crystal polymers, and carbon materials like graphene; metal oxides and mixtures thereof, 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; and inorganic materials such as alkaline glass, alkali-free glass, quartz glass, borosilicate glass, and sapphire glass carbon. The high-refractive-index adhesive layer disclosed herein can be adhered to components (e.g., optical components) whose surfaces are at least made of the aforementioned materials. Furthermore, the low-refractive-index layer (preferably a low-refractive-index adhesive layer) disclosed herein can be laminated (e.g., bonded) to the aforementioned various adhered materials.

[0321] The high-refractive-index adhesive layer 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 applied to the substrate. Furthermore, depending on the type of substrate, heating treatment can be performed at least at any time after application, at the point of application, or before application, where permissible. Heating treatment can be performed to improve the adhesion of the adhesive to the substrate, promote bonding, etc. Regarding the heating treatment temperature, it can be appropriately set within permissible limits, taking into account the surface condition of the substrate, etc., to obtain the desired effect, depending on the constituent materials of the adhesive sheet 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.

[0322] The component or material to which the adhesive layer is applied can be translucent. In such adhered objects, the high refractive index adhesive layer disclosed herein readily offers the advantage of high transparency. The total light transmittance of the adhered object can, for example, be higher than 50%, or even higher than 70%. In some preferred embodiments, the total light transmittance of the adhered object 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 high refractive index adhesive layer disclosed herein can preferably be used to adhere to an object (e.g., an optical component) with a total light transmittance of a specified value or higher. The total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. The transmittance meter used is the Murakami Color Technology Research Institute's trade name "HAZEMETER HM-150" or an equivalent thereof.

[0323] The refractive index of the adherend and the refractive index of the adhesive layer (high-refractive-index adhesive layer or low-refractive-index layer) disposed against 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 towards 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 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 towards 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, 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. In this case, the refractive index of the adherend can be approximately 1.55–1.80, 1.55–1.75, or 1.60–1.70. The refractive index of the adherend can be measured using the same method as that used for the adhesive.

[0324] In some preferred embodiments, the adherend may have any of the aforementioned refractive indices and any of the aforementioned total transmittance. The effects of the techniques disclosed herein are particularly preferably achieved in light-emitting devices in which a high-refractive-index adhesive layer and / or a low-refractive-index layer are bonded or laminated to such an adherend.

[0325] The high-refractive-index adhesive layer and low-refractive-index layer disclosed herein can be used in the form of a laminate containing them to adhere to various substrates as described above. Optical applications are an example of preferred uses. More specifically, for example, the laminate disclosed herein is preferably used as an optical adhesive sheet for bonding optical components (optical component bonding), manufacturing articles using the aforementioned optical components (optical articles), etc. The laminate used in this manner can be held as an interlayer sheet disposed between the layers of an optical laminate.

[0326] 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.

[0327] 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.

[0328] 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 the term "optical component" in this specification also includes components that maintain the visual legibility of the display device and input device and serve decorative and protective functions (such as outer films, decorative films, and surface protective films).

[0329] The high-refractive-index adhesive layer disclosed herein (which may be in the form of a laminate with a low-refractive-index layer) can be used, for example, as an optical thin film such as a thin film or fluorescent thin film having one or more functions such as light transmission, reflection, diffusion, waveguide, light collection, and diffraction, and other optical components (which may be other optical thin films). It is preferably used for bonding the aforementioned optical thin film and the aforementioned other optical components. In the bonding of optical thin films having at least one function of light waveguide, light collection, or diffraction, it is ideal that the entire volume of the bonding layer is of high refractive index, which is a preferred application of the technology disclosed herein.

[0330] The high-refractive-index adhesive layer disclosed herein is preferably used for bonding 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 high-refractive-index adhesive layer disclosed herein is preferably used as an adhesive layer to meet this demand. 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.

[0331] The high-refractive-index adhesive layer disclosed herein (which may be in the form of a laminate with a low-refractive-index layer) 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 high-refractive-index adhesive layer used in this manner preferably has a small refractive index difference with the high-refractive-index 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 adhesive layer has high uniformity of thickness, for example, high surface smoothness of the adhesive surface. 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 phase difference layer and / or the first phase difference layer to the second phase difference layer can be cited in a polarizing plate with a phase difference layer having a polarizing element, a first phase difference layer and a second phase difference layer in sequence.

[0332] Furthermore, the high-refractive-index adhesive layer disclosed herein 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 high-refractive-index adhesive layer, reflection at their interface can be suppressed, and light extraction efficiency can be improved. Additionally, from the viewpoint of preventing deterioration of the self-emissive element due to moisture, a low water absorption rate of the high-refractive-index adhesive layer is preferred. From the viewpoint of improving brightness, a low-coloring high-refractive-index adhesive layer is preferred. This is also advantageous from the viewpoint of suppressing unintentional coloring caused by the high-refractive-index adhesive layer.

[0333] The high-refractive-index adhesive layer disclosed herein can preferably be used as a coating layer covering the lens surface, a bonding layer to a component opposite the lens surface (e.g., a component having a surface shape corresponding to the lens surface), or a filler layer filling the space between the lens surface and the component in microlenses and other lens components used as constituent components of cameras, light-emitting devices, etc.

[0334] There are no particular limitations on the method of bonding optical components using the adhesive layer disclosed herein (which may be a high-refractive-index adhesive layer and / or a low-refractive-index adhesive layer, preferably a high-refractive-index adhesive layer optionally laminated on a low-refractive-index layer). For example, it may be (1) bonding optical components to each other using the adhesive layer disclosed herein, (2) bonding optical components to components other than optical components using the adhesive layer disclosed herein, or (3) the adhesive layer disclosed herein is in the form of an adhesive sheet containing optical components, and the adhesive sheet is bonded to an optical component or a component other than an optical component. It should be noted that in the above-mentioned (3) method, the adhesive sheet in the form of an optical component may be, for example, an adhesive sheet in the form of an optical component (e.g., an optical film) as a support. Such an adhesive sheet in the form of an optical component as a support can also be regarded as an adhesive-type optical component (e.g., an adhesive-type optical film). In addition, when the adhesive layer disclosed herein constitutes an adhesive sheet of the type having a support, and the above-mentioned functional film is used as the support, the adhesive sheet can also be regarded as an "adhesive-type functional film" having the adhesive layer disclosed herein on at least one side of the functional film.

[0335] As described above, according to the technology disclosed herein, an optical laminate is provided, comprising an adhesive layer disclosed herein, and a component (e.g., a resin film such as an optical film) to which the adhesive layer is laminated by bonding or the like. The component to which the adhesive layer is laminated by bonding or the like can have the refractive index of the aforementioned adhered material. Furthermore, the difference between the refractive index of the adhesive layer and the refractive index of the component (refractive index difference) can be the difference between the refractive index of the adhered material and the adhesive layer. Regarding the components constituting the laminate, as described above as components, materials, and adhered materials, they will not be described again.

[0336] As can be understood from the above description and the following embodiments, the matters disclosed in this specification include the following.

[0337] [1] An adhesive sheet comprising an adhesive layer,

[0338] It has an adhesive surface composed of the aforementioned adhesive layer.

[0339] 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%.

[0340] [2] The adhesive sheet according to [1] above, wherein the thickness of the adhesive layer is 5 μm or more.

[0341] [3] The adhesive sheet described in [1] or [2] above has a peel strength (adhesive force) of 3 N / 25 mm or more on the glass plate.

[0342] [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.

[0343] [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.

[0344] [6] The adhesive sheet according to any one of [1] to [5] above is formed in the form of a laminate comprising the adhesive layer and the light-transmitting substrate.

[0345] [7] The adhesive sheet according to [6] above, wherein the light-transmitting substrate is a resin film.

[0346] [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.

[0347] [9] An adhesive sheet with a release liner, comprising:

[0348] The adhesive sheet described in any one of [1] to [8] above, and

[0349] A release liner disposed on the adhesive surface of the aforementioned adhesive sheet.

[0350]

[10] An adhesive composition for forming an adhesive layer of the adhesive sheet described in any one of [1] to [8] above.

[0351]

[11] An adhesive composition comprising:

[0352] An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit; and

[0353] Additives (H) RO ), which is an organic material with a higher refractive index compared to the aforementioned acrylic polymer (A).

[0354]

[12] The adhesive composition according to

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

[0355]

[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.

[0356]

[14] The adhesive composition according to any one of

[11] to

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

[0357]

[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.

[0358]

[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:

[0359] (i) A structure comprising two non-fused aromatic rings directly chemically bonded together; and

[0360] (ii) A structure consisting of two fused aromatic rings.

[0361]

[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.

[0362]

[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.

[0363] 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.

[0364]

[19] The adhesive composition according to any one of

[11] to

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

[0365]

[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.

[0366]

[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.

[0367]

[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.

[0368]

[23] The adhesive sheet according to

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

[0369]

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

[0370] It contains a viscoelastic layer V1 with a refractive index n1 of 1.570 or higher, and

[0371] The interlayer sheet satisfies the following condition: total light transmittance of 86% or higher;

[0372] The haze value is below 1.0%; and,

[0373] The energy storage modulus G' at 25℃ is 30kPa~700kPa.

[0374]

[25] The interlayer sheet described in

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

[0375]

[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.

[0376]

[27] According to the interlayer sheet described in

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

[0377]

[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.

[0378] 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 .

[0379]

[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.

[0380]

[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.

[0381]

[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.

[0382]

[32] An optical laminate comprising:

[0383] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0384] A resin film laminated on the above interlayer sheet.

[0385]

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

[0386] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0387] A release liner covering at least one surface of the aforementioned interlayer sheet.

[0388]

[34] A light-emitting device comprising:

[0389] Self-emitting elements

[0390] A low-refractive-index layer disposed on the visual recognition side, which is closer to the self-emissive element mentioned above, and

[0391] The high-refractive-index adhesive layer is laminated in direct contact with the aforementioned low-refractive-index layer.

[0392] The aforementioned high-refractive-index adhesive layer has a refractive index n1 higher than 1.570, a total light transmittance of more than 86%, and a haze value of less than 3.0%.

[0393]

[35] According to the light-emitting device described in

[34] above, the ratio (n1 / n2) of the refractive index n1 of the high refractive index adhesive layer to the refractive index n2 of the low refractive index layer is 1.05 or more.

[0394]

[36] In the light-emitting device according to

[35] or

[36] above, the arithmetic mean roughness Ra of the surface of the high refractive index adhesive layer is less than 100 nm.

[0395]

[37] The light-emitting device according to any one of

[34] to

[36] above, wherein the ratio (T1 / T2) of the thickness T1 of the high refractive index adhesive layer to the thickness T2 of the low refractive index layer is 0.5 to 5.

[0396]

[38] The light-emitting device according to any one of

[34] to

[37] above, wherein the thickness T1 of the high refractive index adhesive layer is 5 μm or more.

[0397]

[39] The light-emitting device according to any one of

[34] to

[38] above, wherein the total light transmittance of the laminate comprising the high refractive index adhesive layer and the low refractive index layer is 86% or more and the haze value is 3.0% or less.

[0398]

[40] The light-emitting device according to any one of

[34] to

[39] above, wherein the high refractive index adhesive layer is a layer formed from the adhesive composition according to any one of

[11] to

[18] above.

[0399]

[41] The light-emitting device according to any one of

[34] to

[40] above, wherein the high refractive index adhesive layer is the adhesive layer in any one of [1] to [5] above.

[0400]

[101] An adhesive comprising an acrylic polymer (F), wherein the acrylic polymer (F) contains a fluorinated acrylic monomer (M1) as a monomer unit.

[0401] The adhesive has a refractive index of less than 1.46, and

[0402] The energy storage modulus G' at 25℃ is above 1.0 kPa and below 400 kPa.

[0403]

[102] According to the adhesive described in

[101] above, the content of the aforementioned fluorinated acrylic monomer (M1) in the monomer components constituting the aforementioned acrylic polymer (F) is 25% by weight or more.

[0404]

[103] The adhesive according to

[101] or

[102] above, wherein the aforementioned fluorinated acrylic monomer (M1) contains a fluorinated alkyl (meth)acrylate.

[0405]

[104] The adhesive according to any one of

[101] to

[103] above, wherein the aforementioned acrylic polymer (F) contains a hydroxyl-containing monomer as a monomer unit.

[0406]

[105] A laminated sheet comprising

[0407] The low refractive index adhesive layer formed by the adhesive described in any one of

[101] to

[104] above, and

[0408] A high-refractive-index adhesive layer is laminated on top of the aforementioned low-refractive-index adhesive layer.

[0409]

[106] According to the laminate described in

[105] above, the ratio (n1 / n2) of the refractive index n1 of the aforementioned high refractive index adhesive layer to the refractive index n2 of the aforementioned low refractive index adhesive layer is 1.02 or more.

[0410]

[107] The laminate according to

[105] or

[106] above, wherein the refractive index n1 of the aforementioned high refractive index adhesive layer is higher than 1.570.

[0411]

[108] The laminate according to any one of

[105] to

[107] above, wherein the storage modulus G' of the aforementioned high refractive index adhesive layer at 25°C is 700 kPa or less.

[0412]

[109] The laminate according to any one of

[105] to

[108] above has a total light transmittance of 86% or more and a haze value of 3.0% or less.

[0413]

[110] A light-emitting device comprising:

[0414] Self-emissive elements, and

[0415] The laminated sheet described in any one of

[105] to

[109] above,

[0416] The aforementioned stacked sheet is positioned closer to the visual recognition side than the aforementioned self-emissive element.

[0417]

[111] The adhesive according to any one of

[101] to

[104] above is used to form the viscoelastic layer V2 in any one of

[28] to

[31] above.

[0418]

[112] The adhesive according to any one of

[101] to

[104] above is used to form the low refractive index layer in the light-emitting device according to any one of

[34] to

[41] above.

[0419] Example

[0420] The following describes some experiments related to this invention. It should be noted that, in the following description, the terms "parts" and "%" indicating the amount used or the content are by weight unless otherwise specified.

[0421] <Preparation of Acrylic Adhesive Composition C1>

[0422] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 95 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"), 5 parts 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 weight-average molecular weight (Mw) of this acrylic polymer A1 is 500,000. The Tg of the above acrylic polymer A1 based on the above monomer composition (i.e., Tg) is...T The temperature is -35℃, based on the Tg (i.e., Tg) of the monomer containing the aromatic ring. m1 The temperature is -35℃.

[0423] 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.

[0424] <Preparation of Acrylic Adhesive Composition C2>

[0425] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 72 parts of POB-A (monomer), 23 parts of 1-naphthyl methyl acrylate (manufactured by Kyoei Chemical Co., Ltd., trade name "LIGHT ACRYLATE NMT-A", refractive index: 1.595, Tg of homopolymer: 31℃, hereinafter referred to as "NMT-A"), 5 parts of 4HBA, 0.2 parts of AIBN (polymer initiator), and 100 parts of toluene (polymer 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 A2. The weight-average molecular weight (Mw) of this acrylic polymer A2 is 500,000.

[0426] In a detachable flask equipped with a thermometer, stirrer, reflux condenser, and nitrogen inlet, 20 parts of POB-A (monomer), 80 parts of NMT-A, 0.2 parts of AIBN (polymer initiator), 3.5 parts of α-thioglycerol (chain transfer agent), and 67 parts of methyl ethyl ketone were added. Nitrogen gas was then introduced, and nitrogen purging was carried out for approximately 1 hour with stirring. The flask was then heated to 70°C and reacted for 12 hours to obtain an acrylic oligomer (oligomer B) with a weight-average molecular weight (Mw) of 4000 and a refractive index of 1.63.

[0427] The above-mentioned acrylic polymer A2 solution (50%) was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts of non-volatile component), 20 parts of the oligomer B prepared above, 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 of non-volatile component) were added and stirred to prepare acrylic adhesive composition C2.

[0428] <Preparation of Acrylic Adhesive Composition C3>

[0429] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 65 parts of 2-ethylhexyl acrylate, 30 parts of 1H,1H,5H-octafluoropentyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Viscoat 8F), 3 parts of N-vinyl-2-pyrrolidone (NVP, manufactured by Nippon Shokubai), and 2 parts of 4HBA were added as monomer components, 0.2 parts of AIBN as a polymerization initiator, and 200 parts of ethyl acetate as a polymerization solvent. Nitrogen gas was introduced while stirring slowly, and the liquid temperature in the flask was maintained at approximately 60°C for 9 hours to prepare a 33% solution of acrylic polymer A3. The weight-average molecular weight (Mw) of the acrylic polymer A3 was 550,000.

[0430] The above-mentioned acrylic polymer A3 solution (33%) was diluted to 30% with ethyl acetate. 10 parts of a 1% ethyl acetate solution (0.1 parts of non-volatile component) of hexamethylene diisocyanate isocyanurate (manufactured by Tosoh Corporation, trade name "Coronate HX", a 3-functional isocyanate compound) as a crosslinking agent were added relative to 100 parts of the non-volatile component (solid component) and stirred to prepare acrylic adhesive composition C3.

[0431] <Making Adhesive Sheets>

[0432] (Example 1)

[0433] The acrylic adhesive composition C1 prepared above was coated onto the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (50 μm thick) with one side treated with silicone. The film was then heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 25 μm. A silicone-treated PET film R2 (38 μm thick) with one side treated with silicone was then bonded to the surface of the adhesive layer. This process yields an adhesive layer (high refractive index adhesive layer) protected on both sides by PET films (release liner) R1 and R2. It should be noted that release liner R2 peels relatively easily compared to release liner R1.

[0434] Furthermore, the acrylic adhesive composition C3 prepared above was coated onto the silicone-treated surface of a PET film R1 (50 μm thick) that had undergone silicone treatment on one side, and heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 10 μm. A PET film R2 (38 μm thick) that had undergone silicone treatment on one side was then bonded to the surface of the adhesive layer. This process yields an adhesive layer (low refractive index adhesive layer) that is protected on both sides by PET films (release liner) R1 and R2.

[0435] The release liner R2 is peeled off from the high-refractive-index adhesive layer and the low-refractive-index adhesive layer, and the adhesive surfaces are then pressed together using a manual roller. The laminate is then autoclaved at 50°C and 0.60 MPa for 30 minutes, followed by curing at 50°C for 48 hours. This process yields a laminate (substrate-free double-sided adhesive sheet) formed from a two-layer structure of a high-refractive-index adhesive layer and a low-refractive-index adhesive layer. The surface of this adhesive sheet is protected by two release liners R1.

[0436] (Example 2)

[0437] The type of adhesive composition used to form each adhesive layer and the thickness of each adhesive layer are changed as shown in Table 1. Otherwise, a laminate (substrate-free double-sided adhesive sheet) formed of a two-layer structure of a high-refractive-index adhesive layer / low-refractive-index adhesive layer is obtained in the same manner as in Example 1.

[0438] (Examples 3~5)

[0439] Similar to Example 1, adhesive layers with a single-layer structure formed from acrylic adhesive compositions C1 to C3 and having the thicknesses shown in Table 1 were prepared as adhesive sheets for Examples 3 to 5.

[0440] 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.

[0441] <Measurement and Evaluation (1)>

[0442] (Refractive index)

[0443] For each adhesive layer, 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.

[0444] (Storage modulus G')

[0445] Each adhesive layer was stacked to a thickness of approximately 1.5 mm, and this was used as the test sample. Dynamic viscoelasticity was measured using an ARES instrument manufactured by TA Instruments under the following conditions. The storage modulus G' at 25°C was read from the measurement results. The results are shown in Table 1.

[0446] [Measurement Conditions]

[0447] Deformation mode: Torsion

[0448] Measurement frequency: 1Hz

[0449] Heating rate: 5℃ / minute

[0450] Shape: Parallel plate

[0451] (Total transmittance and haze value)

[0452] Test pieces were prepared by bonding the adhesive sheets 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 sheets 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.

[0453] (Peel strength of glass plate)

[0454] Under a test environment of 23°C and 50% RH, the release liner was peeled off from one side of the adhesive sheet in each example (the surface of the adhesive layer formed by adhesive composition C3 in Examples 1 and 2), and a 50 μm thick PET film was laminated on it. The sheet 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 a 2 kg roller was used to press the sheet against the surface of an alkaline glass plate (Matsunami Glass Industry Co., Ltd., 1.35 mm thick, with ground edges) once. The sample was placed in this environment for 30 minutes, then placed in a pressure degassing device (autoclave) and subjected to autoclaving at 50°C and 0.5 MPa for 30 minutes. Afterward, it was placed at 23°C and 50% RH for 24 hours. The peel strength (adhesive force) [N / 25 mm] was then measured using a universal tensile and compression testing machine according to JIS Z0237:2000, at a tensile speed of 300 mm / min and a peel angle of 180 degrees. A Minebea TG-1kN universal tensile and compression testing machine was used.

[0455] [Table 1]

[0456] Table 1

[0457]

[0458] C1: POB-A / 4HBA (95 / 5)

[0459] C2: 100 parts of POB-A / NMT-A / 4HBA (72 / 23 / 5) + 20 parts of oligomer B

[0460] C3: 2EHA / Viscoat 8F / NVP / 4HBA(65 / 30 / 3 / 2)

[0461] As shown in Table 1, the adhesive sheets in Examples 1-4 contain a refractive index n V1 The adhesive layer V1 (high refractive index adhesive layer) has a refractive index greater than 1.570, and the adhesive sheet exhibits high transparency. These adhesive sheets demonstrate practical peel strength suitable for bonding optical components.

[0462] <Evaluation of the effect of improving front brightness>

[0463] Adhesive sheets were attached to white LED light sources for each example. After stabilizing the light source in a dark room for more than 30 minutes, the frontal luminance of the portion with the adhesive sheet attached was measured using a spectroradiometer SR-UL1R (manufactured by TOPCON TECHNOHOUSE CORPORATION). The average of the three luminance measurements was used. A luminance improvement of more than 10% compared to the luminance of the light source without the adhesive sheet was rated as G (Good), and a luminance improvement of less than 10% was rated as P (Poor).

[0464] The results are shown in Table 2.

[0465] [Table 2]

[0466] Table 2

[0467] example 1 2 3 4 5 Improved front brightness G G P P P

[0468] As shown in Table 2, for the adhesive sheets (laminated sheets) of Examples 1 and 2, which have a laminated structure of adhesive layers with a combined low-refractive-index adhesive layer (Example 5) and high-refractive-index adhesive layers (Examples 3 and 4), a front brightness improvement of more than 10% was confirmed compared to the case where no adhesive sheet was used. For the interlaminated sheets of Examples 3 to 5, where the adhesive layer of the adhesive sheet is a single-layer structure, no front brightness improvement effect was confirmed by the adhesive sheet alone.

[0469] <Preparation of Acrylic Adhesive Composition C4>

[0470] A four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet pipe, and condenser was filled with 79 parts of POB-A (monomer), 20 parts of n-butyl acrylate, 1 part of 4HBA, 0.2 parts of AIBN (polymer initiator), and 100 parts of toluene (polymer solvent). Nitrogen gas was introduced while the mixture was slowly stirred, and the liquid temperature in the flask was maintained at approximately 60°C for 6 hours to prepare a 50% solution of acrylic polymer A4. The Mw of this acrylic polymer A4 was 520,000.

[0471] The above-mentioned acrylic polymer A4 solution (50%) was diluted to 30% with ethyl acetate. 10 parts of a 1% ethyl acetate solution of Coronate HX 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) were added to 334 parts of this solution (100 parts of non-volatile component). The mixture was stirred and mixed to prepare acrylic adhesive composition C4.

[0472] <Preparation of Acrylic Adhesive Composition C5>

[0473] The monomer composition (weight ratio) was changed to POB-A / ethyl carbitol acrylate (CBA) / 4HBA = 79 / 20 / 1. Otherwise, a solution of acrylic polymer A5 (50%) was prepared in the same manner as the solution of acrylic polymer A4. The Mw of acrylic polymer A5 was 460,000. Acrylic adhesive composition C5 was prepared in the same manner as the preparation of acrylic adhesive composition C4, except that the solution of acrylic polymer A5 was used instead of acrylic polymer A4.

[0474] <Preparation of Acrylic Adhesive Composition C6>

[0475] The monomer composition (weight ratio) was changed to P2H-A / 4HBA = 99 / 1. Otherwise, a solution of acrylic polymer A6 (50%) was prepared in the same manner as the solution of acrylic polymer A4. In the monomer composition above, "P2H-A" represents phenoxydiethylene glycol acrylate (manufactured by Kyoei Chemical Co., Ltd., trade name "LIGHTACRYLATE P2H-A", refractive index: 1.510, Tg of homopolymer: -35℃). The Mw of this acrylic polymer A6 is 1 million.

[0476] A 50% solution of acrylic polymer A6 was diluted to 30% with ethyl acetate. Additive (H) was then added to 334 parts of this solution (100 parts of non-volatile components). RO Acrylic adhesive composition C6 was prepared by mixing 20 parts 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), 10 parts of a 1% ethyl acetate solution of Coronate HX 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).

[0477] <Preparation of Acrylic Adhesive Composition C7>

[0478] The monomer composition (weight ratio) was changed to 2EHA / Viscoat 13F / 4HBA = 49 / 50 / 1. Otherwise, a solution of acrylic polymer A7 (50%) was prepared in the same manner as the solution of acrylic polymer A3. In the above monomer composition, "Viscoat 13F" represents 1H,1H,2H,2H-tridecylfluorooctyl acrylate (manufactured by Osaka Organic Chemicals Co., Ltd., trade name "Viscoat 13F"). The Mw of acrylic polymer A7 is 550,000. The acrylic adhesive composition C7 was prepared in the same manner as the preparation of acrylic adhesive composition C3, except that the solution of acrylic polymer A7 was used instead of acrylic polymer A3.

[0479] <Making Adhesive Sheets>

[0480] (Examples 6~8)

[0481] The types of adhesive compositions used to form each adhesive layer and the thickness of each adhesive layer are set as shown in Table 3. Otherwise, a laminate (substrate-free double-sided adhesive sheet) formed of a two-layer structure of a high-refractive-index adhesive layer / low-refractive-index adhesive layer is obtained in the same manner as in Example 1.

[0482] After the adhesive sheets obtained from Examples 6 to 8 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.

[0483] [Table 3]

[0484] Table 3

[0485]

[0486] C4: POB-A / BA / 4HBA (79 / 20 / 1)

[0487] C5: POB-A / CBA / 4HBA (79 / 20 / 1)

[0488] C6: 100 servings of P2H-A / 4HBA (99 / 1) + 20 servings of 6EDNTA

[0489] C7:2EHA / Viscoat13F / 4HBA(49 / 50 / 1)

[0490] As shown in Table 3, the adhesive sheets of Examples 6-8 exhibit high transparency in a laminate structure of an adhesive layer with a refractive index n1 higher than 1.570 (high refractive index adhesive layer) and a low refractive index layer. These adhesive sheets demonstrate practical peel strength suitable for bonding optical components.

[0491] 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.

[0492] Explanation of reference numerals in the attached figures

[0493] 2. Substrate-free double-sided adhesive sheet

[0494] 10-layer laminate (adhesive sheet)

[0495] 10A First Surface (First Adhesive Surface)

[0496] 10B Second Surface (Second Adhesive Surface)

[0497] 11 High-refractive-index adhesive layer

[0498] 12. Low-refractive-index adhesive layer (low-refractive-index layer)

[0499] 70 Self-illuminating elements

[0500] 80 Cover window components

[0501] 100 Light-emitting devices

Claims

1. A light-emitting device comprising: Self-emitting elements A low-refractive-index layer disposed on the visual recognition side, and The high-refractive-index adhesive layer is laminated in direct contact with the low-refractive-index layer. The high-refractive-index adhesive layer comprises an acrylic polymer containing monomers with aromatic rings and hydroxyl-containing monomers as monomer units. The monomers with aromatic rings are monomers containing multiple aromatic rings, having two or more aromatic rings per molecule. The hydroxyl-containing monomers are hydroxyalkyl acrylates. In the monomer components constituting the acrylic polymer, the content of the aromatic ring-containing monomer is 70% to 99% by weight or more, and the content of the hydroxyl-containing monomer is 1% to 7% by weight or more. The high refractive index adhesive layer has a refractive index n1 higher than 1.570, a total light transmittance of more than 86%, and a haze value of less than 3.0%.

2. The light emitting device of claim 1, wherein, The ratio (n1 / n2) of the refractive index n1 of the high refractive index adhesive layer to the refractive index n2 of the low refractive index layer is 1.05 or higher.

3. The light-emitting device according to claim 1 or 2, wherein, The arithmetic mean roughness Ra of the surface of the high refractive index adhesive layer is less than 100 nm.

4. The light-emitting device according to claim 1 or 2, wherein, The ratio (T1 / T2) of the thickness T1 of the high refractive index adhesive layer to the thickness T2 of the low refractive index layer is 0.5 to 5.

5. The light-emitting device according to claim 1 or 2, wherein, The thickness T1 of the high refractive index adhesive layer is greater than 5 μm.

6. The light-emitting device according to claim 1 or 2, wherein, The total light transmittance of the laminate containing the high refractive index adhesive layer and the low refractive index layer is above 86%, and the haze value is below 3.0%.

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