Light-emitting device

Abstract

To provide a light-emitting device that includes an adhesive layer of high refractive index and high optical quality disposed on the viewing side of a self-luminescent element.SOLUTION: The provided light-emitting device includes a self-luminescent element, a low-refractive-index layer positioned further toward the viewing side than the self-luminescent element, and a high-refractive-index adhesive layer layered in direct contact with a low-refractive-index adhesive layer. The high-refractive-index adhesive layer has a refractive index n1 of more than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.SELECTED DRAWING: Figure 1

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 viewing side of a self-luminous element.

Background Art

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used for purposes such as joining, fixing, and protecting in various industrial fields from home appliances to automobiles, various machines, electrical equipment, and electronic equipment. As an example of the use of an adhesive, in a display device such as a liquid crystal display device or an organic EL display device, there is a use of joining a polarizing film, a retardation film, a cover window member, and various other light-transmissive members to other members. Patent Documents 1 and 2 are cited as technical documents regarding adhesives for optical members.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Documents 1 and 2 propose an adhesive composition mainly composed of a (meth)acrylic acid ester polymer containing a monomer having a plurality of aromatic rings as monomer units, and an adhesive obtained by crosslinking the adhesive composition, but do not disclose a specific adhesive having a refractive index exceeding 1.570. On the other hand, a technique of blending a resin with particles made of an inorganic material having a high refractive index (for example, inorganic particles such as zirconium oxide particles and titanium oxide particles) to increase the refractive index is also known. However, since an adhesive containing inorganic particles has a trade-off relationship between the refractive index and adhesive properties (for example, peel strength, flexibility, etc.), it is difficult to apply it to the field of adhesives. For example, in increasing the refractive index of the adhesive layer disposed on the viewing side of the self-luminous element in a light-emitting device, it is necessary to consider the influence on optical properties (for example, total light transmittance, haze, etc.) when blending inorganic particles.

[0005] The present invention has been created in view of such circumstances, and an object thereof is to provide a light-emitting device in which a high-refractive-index and optically high-quality adhesive layer is disposed on the viewing side of a self-luminous element.

Means for Solving the Problems

[0006] The light-emitting device provided by this specification includes a self-luminous element, a low-refractive-index layer disposed on the viewing side of the self-luminous 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 exceeding 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

[0007] 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 approximately 1.05 or more.

[0008] In some embodiments, the high-refractive-index adhesive layer preferably has an arithmetic mean roughness Ra of its surface of 100 nm or less.

[0009] 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 approximately 0.5 to 5.

[0010] In some embodiments, the thickness T1 of the high refractive index adhesive layer is preferably 5 μm or more.

[0011] In some embodiments, the laminated sheet (adhesive sheet) composed of the high refractive index adhesive layer and the low refractive index layer preferably has a total light transmittance of 86% or more and a haze value of 3.0% or less.

[0012] In addition, combinations of the various elements described in this specification as appropriate may also be included in the scope of the invention claimed in this patent application.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be understood by those skilled in the art based on the teachings regarding the implementation of the invention described in this specification and the common general knowledge in the art at the time of filing. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. In the following drawings, members and parts having the same function may be denoted by the same reference numerals for description, and duplicate descriptions may be omitted or simplified. In addition, the embodiments shown in the drawings are schematized for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the actually provided product.

[0015] In this specification, the self-luminous element means a light-emitting element capable of controlling the emission luminance according to the value of the flowing current. The self-luminous element may be composed of a single body or an aggregate. Specific examples of the self-luminous element include, but are not limited to, a light-emitting diode (LED) and an organic EL. The light-emitting device disclosed herein includes such a self-luminous element as a component. Examples of the above light-emitting device include, but are not limited to, a light source module device (for example, a surface light-emitting body module) used as lighting and a display device in which pixels are formed.

[0016] The technical matters disclosed by this specification include a light-emitting device, a high refractive index adhesive layer and an adhesive composition used for forming the same, a low refractive index layer and a composition used for forming the same, a laminated sheet (adhesive sheet) including a high refractive index adhesive layer and a low refractive index layer, a laminated sheet with a release liner in which the adhesive surface of the laminated sheet is protected by a release liner, and the like.

[0017] <Configuration Example of Light-Emitting Device> A configuration example of the light-emitting device provided by this specification is shown in FIG. 1. The light-emitting device 100 shown in FIG. 1 includes a self-luminous element 70, a low refractive index layer 12 disposed on the viewing side of the self-luminous 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 viewing side of the high refractive index adhesive layer 11. In the light-emitting device 100 shown in FIG. 1, a laminated sheet 10 composed of a high refractive index adhesive layer 11 and a low refractive index layer 12 is disposed between the self-luminous element 70 and the cover window member 80. Between the self-luminous element 70 and the low refractive index layer 12, between the high refractive index adhesive layer 12 and the cover window member 80, and further on the viewing side of the cover window member 80, layers (not shown) may or may not be interposed independently, one or more. Also, contrary to FIG. 1, the high refractive index adhesive layer 11 may be disposed on the self-luminous element side and the low refractive index layer 12 may be disposed on the cover window member side.

[0018] In the technology disclosed herein, the low refractive index layer may have adhesiveness or may be non-adhesive. In some embodiments, the low refractive index layer is preferably a layer having adhesiveness, that is, a low refractive index adhesive layer. Thereby, a laminated sheet (adhesive sheet) of the low refractive index adhesive layer and the high refractive index adhesive layer becomes double-sided adhesive, and the assemblability in the manufacture of the light-emitting device is improved. Such a laminated sheet is, for example, as shown in FIG. 2, before being incorporated into the light-emitting device, a laminated sheet 10 (substrate-less double-sided adhesive sheet 2) composed of a high refractive index adhesive layer 11 and a low refractive index adhesive layer 12, and the surface (first surface) 10A on the high refractive index adhesive layer 11 side of the laminated sheet 10 is the first adhesive surface, and the surface (second surface) 10B on the low refractive index adhesive layer 12 side is the second adhesive surface, and each of these adhesive surfaces may be in the form of a laminated sheet with release liners protected by release liners 31 and 32.

[0019] <High refractive index adhesive layer> The light-emitting device disclosed herein includes a high refractive index adhesive layer laminated in direct contact with the low refractive index layer included in the light-emitting device. This high refractive index adhesive layer is a layer having a relatively higher refractive index than the above low refractive index layer. It is preferable that the refractive index n1 of the high refractive index adhesive layer is more than 1.570, the total light transmittance is 86% or more, and the haze value is 3.0% or less.

[0020] (Refractive index) The light-emitting device disclosed herein has a high refractive index adhesive layer with a refractive index n1 of more than 1.570. Such a high refractive index adhesive layer can be realized by forming at least one surface (adhesive surface) of the high refractive index adhesive layer with an adhesive (viscoelastic material) having a refractive index of more than 1.570.

[0021] In this specification, the refractive index of the adhesive refers to the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, the model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent can be used. As the measurement sample, an adhesive layer composed of the adhesive to be evaluated can be used. Specifically, the refractive index of the adhesive can be measured by 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 can be used as necessary, etc.).

[0022] The technical matters provided by this specification include an adhesive layer (high refractive index adhesive layer) having a refractive index exceeding 1.570, an adhesive composition capable of forming the adhesive layer, and a laminated sheet including the high refractive index adhesive layer. The laminated sheet may be, for example, a laminated adhesive layer composed of the high refractive index adhesive layer and a low refractive index layer (typically a low refractive index adhesive layer), or may have a configuration in which the high refractive index adhesive layer and the low refractive index layer are laminated in this order or in the reverse order on one surface of a support substrate.

[0023] In some embodiments, the refractive index of the high refractive index adhesive layer is preferably 1.580 or more, more preferably 1.585 or more, and even more preferably 1.590 or more (for example, 1.595 or more). With a high refractive index adhesive layer having such a refractive index, by utilizing the relative refractive index relationship between the high refractive index adhesive layer and the low refractive index layer (typically a low refractive index adhesive layer) directly adjacent thereto, the behavior of light transmitted through the high refractive index adhesive layer can be effectively controlled. In some embodiments of the technology disclosed herein, the refractive index of the high refractive index adhesive layer can be, for example, 1.600 or more or over 1.600, 1.605 or more or over 1.605, or 1.610 or more or over 1.610. The preferred upper limit of the refractive index of the high refractive index adhesive layer is not limited to a specific range as it can vary depending on the refractive index of the adjacent layer and the like. In some embodiments, considering the balance with adhesive properties and transparency, the refractive index of the high refractive index adhesive layer can be, for example, 1.700 or less, 1.670 or less, or 1.650 or less.

[0024] (Total light transmittance) In the technology disclosed herein, the total light transmittance of the high refractive index adhesive layer is preferably 86% or more, more preferably 88% or more, still more preferably 90% or more (for example, more than 90.0%), may be 90.5% or more, may be 93% or more, or may be 95% or more. The upper limit of the total light transmittance is theoretically the value obtained by subtracting the light loss (Fresnel loss) due to reflection occurring at the air interface from 100%. Practically, it may be approximately 98% or less, may be approximately 96% or less, or may be approximately 95% or less. In some embodiments, considering the refractive index and adhesive properties, the total light transmittance of the high refractive index adhesive layer may be approximately 94% or less, may be approximately 93% or less, or may be approximately 92% or less. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a product named "HAZEMETER HM-150" manufactured by Murakami Color Research Laboratory or its equivalent is used. More specifically, for example, the total light transmittance of the high refractive index adhesive layer can be measured according to the examples described below. 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.

[0025] (Haze value) The haze value of the high refractive index adhesive layer is preferably 3.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less, and even more preferably 0.9% or less. A low haze value of the high refractive index adhesive layer is advantageous in applications where high light transmittance is required (for example, optical applications) or in applications where the performance of clearly visualizing the adherend through the high refractive index adhesive layer is required. In some embodiments, the haze value of the high refractive index adhesive layer may be 0.8% or less, 0.5% or less, or 0.3% or less. The lower limit of the haze value of the high refractive index adhesive layer is not particularly limited, and from the perspective of improving transparency, the smaller the haze value, the more preferable. On the other hand, in some embodiments, in consideration of the refractive index and adhesive properties, the haze value of the high refractive index adhesive layer may be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more. These haze values regarding the high refractive index adhesive layer can also be preferably applied to the haze value of a laminated sheet composed of the high refractive index adhesive layer and a low refractive index layer (typically a low refractive index adhesive layer) described later.

[0026] Here, the "haze value" refers to the ratio of the diffused transmitted light to the total transmitted light when the measurement object is irradiated with visible light. It is also called the cloudiness value. The haze value can be expressed by the following formula. Th(%) = Td / Tt × 100 In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total light transmittance. The measurement of the haze value can be performed 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.

[0027] (Storage elastic modulus G') In the technology disclosed herein, the storage elastic modulus G' of the high refractive index adhesive layer at 25°C (hereinafter also referred to as "storage elastic modulus G' V1 (25)") is appropriately set according to the purpose of use, usage mode, etc., and is not limited to a specific range. The storage elastic modulus G' V1(25) may be, for example, approximately 700 kPa or less. In some embodiments, from the perspective of ease of adhesion to the adherend, etc., the storage elastic modulus G’ V1 (25) is advantageously approximately 600 kPa or less, preferably 500 kPa or less, and more preferably 400 kPa or less (for example, 350 kPa or less). In some embodiments, from the perspective of enhancing the flexibility of the high refractive index adhesive layer in the room temperature range (for example, 25 °C) and facilitating adhesion to the adherend, the storage elastic modulus G’ V1 (25) is advantageously approximately 330 kPa or less, preferably 300 kPa or less. In some embodiments where adhesion and flexibility at room temperature are more emphasized, the storage elastic modulus G’ V1 (25) may be, for example, less than 270 kPa or less than 250 kPa, advantageously less than 200 kPa, preferably less than 180 kPa, and more preferably less than 160 kPa (for example, less than 140 kPa). In some embodiments, the storage elastic modulus G’ V1 (25) may be less than 100 kPa or less than 90 kPa. The storage elastic modulus G’ V1 The lower limit of (25) is not particularly limited, but from the perspective of processability and handleability, etc., it may be, for example, 30 kPa or more, 50 kPa or more, or 70 kPa or more. In some embodiments, considering high refractive index, the storage elastic modulus G’ V1 (25) may be 100 kPa or more, 150 kPa or more, 200 kPa or more, 250 kPa or more, or 300 kPa or more.

[0028] In the technology disclosed herein, the storage elastic modulus G’ of the high refractive index adhesive layer at 50 °C (hereinafter, also referred to as "storage elastic modulus G’ V1 (50)").) is not particularly limited and may be, for example, less than 100 kPa. In some embodiments, the storage elastic modulus G’ V1 (50) is suitably less than 60 kPa, preferably less than 40 kPa, and more preferably less than 38 kPa (for example, less than 36 kPa). Thus, the storage elastic modulus G’ V1The high refractive index adhesive layer with (50) restricted can easily enhance the adhesion to the adherend by performing appropriate heating as needed, thereby improving the adhesiveness to the adherend. Storage modulus G’ V1 The lower limit of (50) is not particularly limited. In some embodiments, from the perspective of heat resistance characteristics and the like, the storage modulus G’ V1 (50) may be, for example, 10 kPa or more, 15 kPa or more, 20 kPa or more, or 23 kPa or more.

[0029] In some embodiments of the technology disclosed herein, the high refractive index adhesive layer has the following conditions: (a) The storage modulus G’ V1 (25) is 350 kPa or less (preferably less than 200 kPa, for example, 180 kPa or less); and (b) The storage modulus G’ V1 (50) is less than 60 kPa (preferably less than 50 kPa, more preferably less than 40 kPa, for example, less than 38 kPa); It is preferable to satisfy at least one of them. The high refractive index adhesive layer that satisfies at least the above condition (a) is preferable from the perspective of adhesion and flexibility to the adherend at room temperature (for example, 25 °C). The high refractive index adhesive layer that satisfies at least the above condition (b) is preferable because the adhesion (adhesiveness) to the adherend can be easily improved by heating to a temperature slightly higher than room temperature. An adhesive sheet having a high refractive index adhesive layer that does not satisfy the above condition (a) and satisfies (b) has good reworkability (re-stickability) at the initial stage of pasting at room temperature, and can effectively increase the peel strength from the adherend by heating to a temperature slightly higher than room temperature, and can be used as a heat-activated type adhesive sheet. The above heat activation may be performed by heating the adhesive sheet to a temperature slightly higher than room temperature when pasting to the adherend. The temperature slightly higher than the above room temperature is, for example, about 60 °C or lower, preferably about 55 °C or lower (for example, about 50 °C or lower).

[0030] In some embodiments of the technology disclosed herein, the storage modulus G’ V1Storage elastic modulus G’ with respect to (25) [kPa] V1 Ratio of (50) [kPa], that is, storage elastic modulus ratio G’ V1 (50) / G’ V1 (25) is, for example, 70% or less, may be 40% or less, may be 30% or less, or may be 20% or less. G’ V1 (50) / G’ V1 An adhesive sheet having a high refractive index adhesive layer with a small (25) is suitable for use as the above-mentioned heat-activated type adhesive sheet. G’ V1 (50) / G’ V1 The lower limit of (25) is not particularly limited. G’ V1 (50) / G’ V1 (25) is, for example, 5% or more, preferably 10% or more from the viewpoint of heat resistance characteristics, may be 12% or more, or may be 15% or more.

[0031] Storage elastic modulus G’ V1 (25) and G’ V1 (50) can be determined by dynamic viscoelasticity measurement, and from the results, G’ V1 (50) / G’ V1 (25) can be calculated. The dynamic viscoelasticity measurement can be carried out by a conventional method using a commercially available dynamic viscoelasticity measurement device. For example, it can be carried out under the following measurement conditions using ARES manufactured by TA Instruments or its equivalent. As a sample for measurement, a sample prepared to a thickness of about 1.5 mm by laminating the adhesive layer to be evaluated as necessary is used. [Measurement conditions] Deformation mode: torsion Measurement frequency: 1 Hz Heating rate: 5 °C / min Shape: parallel plate 7.9 mm φ

[0032] Storage elastic modulus G’ V1 (25), G’ V1 (50) and storage elastic modulus ratio (G’ V1 (50) / G’ V1(25) can be adjusted by, for example, the selection of the composition of the monomer components constituting the base polymer of the adhesive (e.g., the selection of the type and content of the monomer (m1) described later), the presence or absence, type, and amount of use of the crosslinking agent, the presence or absence, type, and amount of use of the refractive index improver and plasticizing material described later, etc. For example, as the monomer (m1), in addition to the first monomer that is the main component of the monomer (m1), a relatively small amount of a second monomer having a chemical structure different from that of the first monomer is used in combination with the first monomer. By doing so, in addition to the case where the first monomer is used alone as the monomer (m1), G’ V1 (50) can be reduced, and G’ V1 (50) / G’ V1 (25) can be decreased.

[0033] (Surface smoothness of the adhesive surface) In some embodiments, the surface (adhesive surface) of the high refractive index adhesive layer preferably has high surface smoothness.

[0034] For example, it is preferable that the arithmetic mean roughness Ra of the adhesive surface is limited to a predetermined value or less. A configuration including an adhesive surface designed to have a low arithmetic mean roughness Ra is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic mean roughness Ra, for example, in a usage mode in which light is extracted through the adhesive surface (such as an adhesive sheet disposed on the viewing side of a self-luminous element in a light-emitting device), it is possible to exert an effect of suppressing the occurrence of luminance unevenness due to the surface state of the adhesive layer. A low arithmetic mean roughness Ra of the adhesive surface is also advantageous for suppressing optical distortion, and suppressing optical distortion also contributes to improving optical homogeneity. When the laminated sheet (adhesive sheet) disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface (for example, in the form of a laminated sheet composed of 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 it is more preferable that the arithmetic mean roughness Ra of both adhesive surfaces is limited to a predetermined value or less. By each adhesive surface of the double-sided adhesive sheet having high surface smoothness, adhesion excellent in optical homogeneity can be preferably realized.

[0035] In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is preferably about 70 nm or less, more preferably about 65 nm or less, still 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 perspective of production efficiency and the like, in some embodiments, the arithmetic mean roughness Ra of the adhesive surface may be, for example, about 10 nm or more, about 20 nm or more, or about 30 nm or more (for example, about 40 nm or more). In an embodiment where the laminated sheet has a first adhesive surface and a second adhesive surface, the arithmetic mean roughness Ra of the first adhesive surface and the arithmetic mean roughness Ra of the second adhesive surface may be the same or different.

[0036] Also, for example, it is preferable that the maximum height Rz of the adhesive surface is limited to a predetermined value or less. A configuration including an adhesive surface designed to have a lower maximum height Rz is preferable from the perspective of optical homogeneity. By limiting the maximum height Rz, for example, in a usage mode where light is extracted through the adhesive surface as described above, it is possible to exert an effect of suppressing the occurrence of luminance unevenness caused by the surface state of the adhesive layer. A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion. When the laminated sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferably 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 are limited to a predetermined value or less. By each adhesive surface of the double-sided adhesive sheet having high surface smoothness, adhesion excellent in optical homogeneity can be preferably realized.

[0037] In some embodiments, the maximum height Rz of the adhesive surface is preferably approximately 600 nm or less, more preferably approximately 500 nm or less, still more preferably approximately 450 nm or less, particularly preferably approximately 400 nm or less, and may be less than 350 nm, less than 300 nm, or less than 250 nm. From the perspective of production efficiency and the like, in some embodiments, the maximum height Rz of the adhesive surface may be, for example, approximately 10 nm or more, approximately 50 nm or more, approximately 100 nm or more, or approximately 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.

[0038] The arithmetic mean roughness Ra and the maximum height Rz of the adhesive surface are measured using a non-contact surface roughness measuring device. As the non-contact surface roughness measuring device, a surface roughness measuring device using an optical interference method is used, and for example, a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation) or its equivalent can be used. Specifically, for example, the arithmetic mean roughness Ra and the maximum height Rz can be measured by the following measurement method or by setting the measurement operation and measurement conditions so that results equivalent or corresponding to those obtained by the measurement method are obtained.

[0039] That is, in an environment of 23°C and 50% RH, using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation), the surface shape of the measurement sample is measured under the following conditions. The arithmetic surface roughness Ra is calculated from the measured data in accordance with JIS B 0601-2001. The maximum height Rz is determined as the sum of the height Rp of the highest peak above the average line and the depth Rv of the deepest valley below the average line for the data (roughness curve) obtained by the above measurement. The measurement is performed 5 times (i.e., N = 5), and their average value is used. The above-mentioned measurement sample can be prepared, for example, by cutting an adhesive layer to be measured or an adhesive sheet including the adhesive layer into a size of about 150 mm in length and 50 mm in width. When the adhesive surface is protected by a release liner, the release liner is gently peeled off (for example, under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180°) to expose the adhesive surface. It is desirable to perform the measurement after leaving it to stand for about 30 minutes after exposing the adhesive surface. [Measurement Conditions] Measurement area: 5.62 mm × 4.22 mm (Objective lens: 2.5 times, internal lens: 0.5 times) Analysis mode: Remove: Cylinder Data Fill: ON (Max: 25) Remove Spikes: ON (xRMS: 1) Filter: OFF

[0040] The arithmetic mean roughness Ra and the maximum height Rz of the adhesive surface can be adjusted according to the composition and properties (such as viscosity and leveling property) of the adhesive composition used for forming the adhesive layer, the properties of the surface (peeling surface) of the release liner that protects the adhesive surface, and the like.

[0041] (Water absorption rate) In some embodiments, it is preferable that the water absorption rate of the high refractive index adhesive layer is limited to a predetermined value or less. By limiting the water absorption rate of the high refractive index adhesive layer, dimensional changes of the high refractive index adhesive layer due to fluctuations in the amount of water in the high refractive index adhesive layer (for example, absorption and release of water such as moisture in the environment) tend to be suppressed. Thereby, warping of the high refractive index adhesive layer or the optical laminate including the high refractive index adhesive layer due to a mismatch in dimensional changes between the high refractive index adhesive layer and an adjacent layer (which can be a low refractive index layer, a support substrate, a release liner, an adherend, etc.) can be suppressed. The ability to suppress fluctuations in the amount of water in the high refractive index adhesive layer is also preferable from the viewpoint of maintaining the flatness, transparency, refractive index, etc. of the high refractive index adhesive layer constant. In addition, a high refractive index adhesive layer with a low water absorption rate is suitable as a component of a member or product that contains elements that dislike water, such as an organic EL element, because it is difficult to occlude water.

[0042] In some embodiments, the water absorption rate of the high refractive index adhesive layer is suitably about 1.0% or less, preferably 0.7% or less, more preferably 0.5% or less (for example, less than 0.5%), and may be 0.4% or less, 0.3% or less, or 0.2% or less. The lower limit of the water absorption rate of the high refractive index adhesive layer is not particularly limited, but from a practical viewpoint such as compatibility with adhesive properties, it may 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 may 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 a predetermined value or less.

[0043] Note that the water absorption rate (also referred to as the moisture content) of the high refractive index adhesive layer is measured by the following method. The water absorption rate of the low refractive index layer is also measured by the same method. [Measurement of moisture content] The adhesive layer to be evaluated, together with two release liners disposed on one surface and the other surface thereof, is 4 cm × 5 cm (area: 20 cm 2Cut it out to the size of ), remove the release liner on one side, and laminate it on the aluminum foil that has been pre-weighed. Then, remove the release liner on the other side of the adhesive layer, put it into a thermo-hygrostat chamber at a temperature of 60 °C and a relative humidity of 90%, and take it out after 72 hours. After weighing the test piece in which the adhesive layer and the aluminum foil are laminated, use a moisture meter (Mitsubishi Chemical Analytech CA-200 type) equipped with a heating vaporization device (Mitsubishi Chemical Analytech VA-200 type), and measure the moisture content under the following conditions by the Karl Fischer coulometric titration method. Anolyte: Aquamicron AKX (manufactured by Mitsubishi Chemical) Catholyte: Aquamicron CXU (manufactured by Mitsubishi Chemical) Heating vaporization temperature: 150 °C

[0044] (Gel fraction) The gel fraction of the high refractive index adhesive layer is appropriately set according to the purpose of use, usage mode, etc., and is not limited to a specific range. The above gel fraction is, for example, approximately 99% or less, and preferably approximately 97% or less. From the viewpoint of preferably achieving both a high refractive index and adhesive properties, in some preferred embodiments, the above gel fraction is approximately 95% or less, more preferably approximately 92% or less (for example, approximately 90% or less). The fact that the gel fraction is not too high is also preferable from the viewpoint of appropriately following the unevenness that may exist on the surface of the adherend (for example, the uneven structure provided for the purpose of improving the light extraction efficiency in a light-emitting device) and achieving good adhesion. In some embodiments, the gel fraction may be approximately 88% or less, approximately 75% or less, or approximately 65% or less. Also, from the viewpoint of imparting appropriate cohesiveness to the adhesive and appropriately expressing the adhesive properties, the above gel fraction is, for example, approximately 10% or more, preferably approximately 20% or more, and may be approximately 30% or more. From the viewpoint of the deformation resistance of the adhesive layer (prevention of bubbles due to extrusion by pressure or entrapment of foreign matter), the above gel fraction is preferably approximately 30% or more, more preferably approximately 40% or more, and may be approximately 45% or more, approximately 50% or more, approximately 65% or more, or approximately 75% or more. The gel fraction of the laminated sheet including the high refractive index adhesive layer and the low refractive index layer (typically, a laminated sheet in the form of a substrate-less double-sided adhesive sheet composed of a high refractive index adhesive layer and a low refractive index layer) is also preferably within the range exemplified above. The gel fraction can be adjusted by the molecular weight, molecular structure, concentration, crosslinking degree, etc. of the base polymer. The gel fraction is measured by the following method.

[0045] [Measurement of Gel Fraction] A predetermined amount of the adhesive sample (weight Wg1) is wrapped in a porous polytetrafluoroethylene membrane with an average pore diameter of 0.2 μm (weight Wg2) in a sachet shape, and the mouth is tied with a string (weight Wg3). As the above porous polytetrafluoroethylene (PTFE) membrane, a product named "Nitron (registered trademark) NTF1122" (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Corporation or its equivalent is used. Immerse this package in a sufficient amount of ethyl acetate and keep it at room temperature (typically 23 °C) for 7 days to elute only the sol fraction in the adhesive outside the above-mentioned film. Then, take out the package, wipe off the ethyl acetate adhering to the outer surface, dry the package at 130 °C for 2 hours, and measure the weight (Wg4) of the package. The gel fraction of the adhesive layer is determined by substituting each value into the following formula. Gel fraction (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0046] The gel fraction of the high refractive index adhesive layer and the gel fraction of the low refractive index layer may be the same or different. In some embodiments, the gel fraction of the low refractive index layer can be made lower than the gel fraction of the high refractive index adhesive layer. According to such a configuration, due to the contribution of the low refractive index layer having a relatively low gel fraction, it is easy to enhance the overall flexibility. As a result, it is possible to achieve a good balance between a high refractive index and flexibility.

[0047] In some embodiments of the technology disclosed herein, the peak temperature of tanδ of the adhesive constituting the high refractive index adhesive layer is preferably approximately -50 °C or higher and preferably approximately 50 °C or lower. 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 is measured by sandwiching a disc-shaped adhesive sample with a thickness of about 2 mm and a diameter of 7.9 mm between parallel plates, applying a shear strain at a frequency of 1 Hz using a viscoelasticity testing apparatus, and performing a temperature dispersion test of the adhesive in a shear mode under the conditions of a measurement temperature range of -60 °C to 60 °C and a heating rate of 5 °C / min. The peak temperature of tanδ of the adhesive (hereinafter, sometimes referred to as Tpeak) is determined from the transition of tanδ in the above temperature range. As the viscoelasticity testing apparatus, ARES manufactured by TA Instruments or its equivalent can be used.

[0048] In some embodiments, it is advantageous for the Tpeak of the high refractive index adhesive layer to be 45°C or lower, or 35°C or lower, preferably 30°C or lower (for example, 25°C or lower), and may be 20°C or lower, or 15°C or lower. Adhesives with a lower Tpeak tend to more easily provide good initial adhesiveness and adhesion in the room temperature range. On the other hand, it is preferable that the Tpeak of the adhesive is not too low from the viewpoint of imparting appropriate cohesiveness to the adhesive, and it also tends to be suitable for compatibility with increasing the refractive index. From such a viewpoint, in some embodiments, the Tpeak of the adhesive may be, for example, -40°C or higher, -30°C or higher, -20°C or higher, -5°C or higher, 5°C or higher, 15°C or higher, or even 25°C or higher. An adhesive with a relatively high Tpeak can be preferably used in a mode where, when attaching to an adherend, one or both of the adhesive and the adherend are heated to a temperature slightly higher than room temperature as necessary. The Tpeak of the adhesive can be adjusted by, for example, selecting the composition of the adhesive (such as the composition of the monomer components constituting the base polymer, the presence or absence, type, and amount of use of refractive index improvers and plasticizing materials). The above-described Tpeak of the adhesive is preferably applied at least to the high refractive index adhesive layer, and more preferably applied 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 the same or different.

[0049] (Base polymer) In the technology disclosed herein, the type of the adhesive constituting the high refractive index adhesive layer is not particularly limited. The above-mentioned adhesive may contain one or more of various rubbery polymers such as acrylic polymers, rubber-based polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, polyamide-based polymers, and fluorine-based polymers as a pressure-sensitive adhesive polymer (hereinafter also referred to as "base polymer" in the sense of a structural polymer forming the adhesive). From the viewpoints of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer may be preferably employed. Among them, an adhesive having an acrylic polymer as a base polymer (acrylic adhesive) is preferable. The technology disclosed herein is preferably implemented in a mode using an acrylic adhesive.

[0050] Hereinafter, the high refractive index adhesive layer composed of an acrylic adhesive will be mainly described, but it is not intended to limit the high refractive index adhesive layer in the technology disclosed herein to an acrylic adhesive layer.

[0051] In this specification, the "base polymer" of the adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not construed in any limited sense other than this. The above-mentioned rubbery polymer refers to a polymer exhibiting rubber elasticity in a temperature range near room temperature. Also, in this specification, the "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified. In this specification, the "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. As a typical example of the acrylic polymer, a polymer in which the proportion of acrylic monomers among all the monomers used for the synthesis of the acrylic polymer exceeds 50% by weight (preferably exceeds 70% by weight, for example, exceeds 90% by weight) can be mentioned. In this specification, "(meth)acryloyl" comprehensively refers to acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to acrylic and methacrylic, respectively. Therefore, the concept of the acrylic monomer referred to here can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

[0052] (Acrylic polymer (A)) The high refractive index adhesive layer sheet disclosed herein has a refractive index exceeding 1.570 and a storage elastic modulus G' at 25°C V1It can be preferably implemented in an embodiment including an acrylic pressure-sensitive adhesive layer having 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. As the acrylic polymer which is the base polymer of the acrylic pressure-sensitive adhesive layer, those containing an aromatic ring-containing monomer (m1) as a monomer component constituting the acrylic polymer are preferable. That is, an acrylic polymer containing an aromatic ring-containing monomer (m1) as a monomer unit is preferable. Hereinafter, such an acrylic polymer will also be referred to as "acrylic polymer (A)". Here, in this specification, the "monomer component constituting the acrylic polymer" means a monomer constituting the repeating unit of the acrylic polymer in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition, regardless of whether it is contained in the pressure-sensitive adhesive composition in the form of a polymer (which may be an oligomer) formed in advance or in the form of an unpolymerized monomer. That is, the monomer component constituting the acrylic polymer may be contained in the pressure-sensitive adhesive composition in any form of a polymer, an unpolymerized substance, or a partially polymerized substance. From the viewpoint of ease of preparation of the pressure-sensitive adhesive composition and the like, in some embodiments, a pressure-sensitive adhesive composition containing substantially all (for example, 95% by weight or more, preferably 99% by weight or more) of the monomer component in the form of a polymer is preferable. A pressure-sensitive adhesive composition containing substantially all of the monomer component in the form of a polymer is also preferable from the viewpoint of easily forming a laminated sheet with less distortion and warping.

[0053] (Monomer (m1)) As the monomer (m1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule is used. As the monomer (m1), one kind of such a compound can be used alone or in combination of two or more kinds.

[0054] Examples of the ethylenically unsaturated group include (meth)acryloyl group, vinyl group, (meth)allyl group and the like. From the viewpoint of polymerization reactivity, the (meth)acryloyl group is preferable, and from the viewpoints of flexibility and adhesiveness, the acryloyl group is more preferable. From the viewpoint of suppressing a decrease in flexibility of the pressure-sensitive adhesive, as the monomer (m1), a compound having 1 ethylenically unsaturated group in one molecule (that is, a monofunctional monomer) is preferably used.

[0055] The number of aromatic rings contained in one molecule of the compound used as the monomer (m1) may be 1 or 2 or more. The upper limit of the number of aromatic rings contained in the monomer (m1) is not particularly limited, and may be, for example, 16 or less. In some embodiments, from the viewpoints of ease of preparation of the acrylic polymer (A) and transparency of the pressure-sensitive adhesive, the number of the aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, and may be 5 or less, 4 or less, 3 or less, or 2 or less.

[0056] The aromatic ring of the compound used as the monomer (m1) may be, for example, a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); a condensed ring of a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, a phenanthrene ring; etc. may be a carbocyclic ring, and may be, for example, a heterocyclic ring such as a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a thiophene ring; etc. The heteroatom contained as a ring-constituting atom in the above heterocyclic ring may be 1 or more selected from the group consisting of, for example, nitrogen, sulfur and oxygen. In some embodiments, the heteroatom constituting the above heterocyclic ring may be one or both of nitrogen and sulfur. The monomer (m1) may have a structure in which one or more carbocyclic rings and one or more heterocyclic rings are condensed, such as a dinaphthothiophene structure.

[0057] The above aromatic ring (preferably a carbocyclic ring) may or may not have one or more substituents on the ring-constituting atoms. When having substituents, examples of the substituents include, but are not limited to, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc. In the substituent containing a carbon atom, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the above aromatic ring may be an aromatic ring having no substituent on the ring-constituting atoms or having one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (such as a bromine atom). Note that the fact that the aromatic ring of the monomer (m1) has a substituent on its ring-constituting atoms means that the aromatic ring has a substituent other than the substituent having an ethylenically unsaturated group.

[0058] The aromatic ring and the ethylenically unsaturated group may be directly bonded or may be bonded via a linking group. The above linking group may be, for example, a group containing one or more structures selected from an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, a group having a structure in which one or more hydrogen atoms in these groups are substituted with a hydroxyl group (such as a hydroxyalkylene group), an oxy group (-O- group), a thiooxy group (-S- group), etc. In some embodiments, an aromatic ring-containing monomer having a structure in which the aromatic ring and the ethylenically unsaturated group are directly bonded or are bonded via a linking group selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly(oxyalkylene) group may be preferably employed. The number of carbon atoms in the above alkylene group and the above oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. The number of repetitions of the oxyalkylene unit in the above poly(oxyalkylene) group may be, for example, 2 to 3.

[0059] Examples of compounds that can preferably be employed as monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds can each be used alone or in combination of two or more. One or more aromatic ring-containing (meth)acrylates and one or more aromatic ring-containing vinyl compounds may be used in combination.

[0060] The content of monomer (m1) in the monomer component constituting the acrylic polymer (A) is not particularly limited and can be set so as to realize an adhesive layer that can achieve both a desired refractive index and adhesive properties (such as peel strength, flexibility, etc.) and / or optical properties (such as total light transmittance, haze value, etc.). In some embodiments, the content of monomer (m1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, may be 60% by weight or more, and may be 70% by weight or more. From the viewpoint of facilitating obtaining a higher refractive index, in some preferred embodiments, the content of the monomer (m1) may be, for example, more than 70% by weight, may be 75% by weight or more, may be 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The upper limit of the content of monomer (m1) in the monomer component is 100% by weight. From the viewpoint of achieving a good balance between a high refractive index and adhesive properties and / or optical properties, it is advantageous that the content of the monomer (m1) is less than 100% by weight, for example, preferably approximately 99% by weight or less, more preferably 98% by weight or less, may be 97% by weight or less, and may be 96% by weight or less. In some embodiments, the content of the monomer (m1) may be 93% by weight or less, may be 90% by weight or less, may be 80% by weight or less, and may be 75% by weight or less. In some embodiments that place more emphasis on adhesive properties and / or optical properties, the content of the monomer (m1) in the monomer component may be 70% by weight or less, may be 60% by weight or less, and may be 45% by weight or less.

[0061] In some aspects of the technology disclosed herein, as the monomer (m1), a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be preferably employed because a high refractive index increasing effect is easily obtained. Examples of the monomer having two or more aromatic rings in one molecule (hereinafter, also referred to as "aromatic ring multi-containing monomer") include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly (i.e., without intervening other atoms) chemically bonded, a monomer having a condensed aromatic ring structure, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, and the like. The aromatic ring multi-containing monomers can be used alone or in combination of two or more kinds.

[0062] The above linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2) n - group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n - group, where n is 1 to 3, preferably 1), a linear alkylene group (i.e., -(CH2) n - group, where n is 1 to 6, preferably 1 to 3), a group in which the alkylene group in the above oxyalkylene group, the above thiooxyalkylene group, and the above linear alkylene group is partially halogenated or completely halogenated, and the like. From the viewpoint of the flexibility of the adhesive and the like, preferred examples of the above linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a linear alkylene group. Specific examples of the monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl (meth)acrylate, benzylbenzyl (meth)acrylate, and the like.

[0063] Monomers having a structure in which two or more non-condensed aromatic rings are directly chemically bonded can be, for example, biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, vinyl group-containing biphenyls, and the like. Specific examples include o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, and the like.

[0064] Examples of the monomers having the condensed aromatic ring structure include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, vinyl group-containing anthracenes, and the like. Specific examples include 1-naphthylmethyl (meth)acrylate (alias: 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, and the like.

[0065] Specific examples of the monomers having the fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene (meth)acrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (meth)acrylate, and the like. Since the monomers having the fluorene structure contain a structural part in which two benzene rings are directly chemically bonded, they are included in the concept of the monomers having a structure in which two or more non-condensed aromatic rings are directly chemically bonded.

[0066] Examples of the monomers having the dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophenes, vinyl group-containing dinaphthothiophenes, (meth)allyl group-containing dinaphthothiophenes, and the like. Specific examples include (meth)acryloyloxymethyldinaphthothiophene (for example, a compound having a structure in which CH2CH(R 1 )C(O)OCH2- is bonded to the 5th or 6th position of the dinaphthothiophene ring. Here, R 1 is a hydrogen atom or a methyl group.), (meth)acryloyloxyethyldinaphthothiophene (for example, at the 5th or 6th position of the dinaphthothiophene ring, CH2CH(R1 ) C(O)OCH(CH3)- or CH2CH(R 1 ) A compound having a structure in which C(O)OCH2CH2- is bonded. Here, R 1 is a hydrogen atom or a methyl group.), Vinyldinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, etc. can be mentioned. In addition, the monomer having a dinaphthothiophene structure is included in the concept of the monomer having the above condensed aromatic ring structure by including a naphthalene structure and by having a structure in which a thiophene ring and two naphthalene structures are condensed.

[0067] Examples of the monomer having the above dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene, vinyl group-containing dibenzothiophene, etc. In addition, since the monomer having a dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings are condensed, it is included in the concept of the monomer having the above condensed aromatic ring structure. In addition, neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-condensed aromatic rings are directly chemically bonded.

[0068] As the monomer (m1) in the technology disclosed herein, a monomer having one aromatic ring (preferably a carbocyclic ring) in one molecule may be used. The monomer having one aromatic ring in one molecule can be useful, for example, for improving the flexibility of the adhesive, adjusting the adhesive properties, improving the transparency, etc. In some embodiments, the monomer having one aromatic ring in one molecule is preferably used in combination with a monomer containing a plurality of aromatic rings from the viewpoint of improving the refractive index of the adhesive.

[0069] Examples of monomers having one aromatic ring in the molecule include carbon aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, chlorobenzyl (meth)acrylate; bromine-substituted aromatic ring-containing (meth)acrylates such as 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, 6-(4,6-dibromo-2-s-butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; carbon aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, tert-butylstyrene; compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl oxazole; and the like.

[0070] As the monomer (m1), a monomer having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in various aromatic ring-containing monomers as described above may be used. The monomer having an oxyethylene chain interposed between the ethylenically unsaturated group and the aromatic ring can be regarded as an ethoxylate of the original monomer. The repeating number of oxyethylene units (-CH2CH2O-) in the oxyethylene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, and is, for example, 1. Specific examples of the ethoxylated aromatic ring-containing monomer include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol di(meth)acrylate, and the like.

[0071] The content of the monomer containing a plurality of aromatic rings in the monomer (m1) is not particularly limited, and may be, for example, 5% by weight or more, may be 25% by weight or more, or may be 40% by weight or more. In some embodiments, from the viewpoint of facilitating the realization of an adhesive having a higher refractive index, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be, for example, 50% by weight or more, preferably 70% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. Substantially 100% by weight of the monomer (m1) may be the monomer containing a plurality of aromatic rings. That is, only one or more monomers containing a plurality of aromatic rings may be used as the monomer (m1). Further, in some embodiments, for example, considering the balance between the high refractive index and the adhesive properties and / or optical properties, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 65% by weight or less. In some embodiments, considering the adhesive properties and / or optical properties, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, or may be 10% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of the monomer containing a plurality of aromatic rings in the monomer (m1) is less than 5% by weight. It is not necessary to use the monomer containing a plurality of aromatic rings.

[0072] The content of the monomer containing a plurality of aromatic rings in the monomer components constituting the acrylic polymer is not particularly limited, and can be set so as to realize an adhesive layer that can achieve a desired refractive index and adhesive properties (such as peel strength, flexibility, etc.) and / or optical properties (such as total light transmittance, haze value, etc.). The content of the monomer containing a plurality of aromatic rings in the above monomer components may be, for example, 3% by weight or more, may be 10% by weight or more, and may be 25% by weight or more. In some embodiments, from the perspective of facilitating the realization of an adhesive having a higher refractive index, the content of the monomer containing a plurality of aromatic rings in the above monomer components may be, for example, more than 35% by weight, preferably more than 50% by weight, may be more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The content of the monomer containing a plurality of aromatic rings in the above monomer components can be 100% by weight, but from the perspective of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to be less than 100% by weight, preferably approximately 99% by weight or less, more preferably 98% by weight or less, may be 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, and may be 75% by weight or less. In some embodiments, considering the adhesive properties and / or optical properties, the content of the monomer containing a plurality of aromatic rings in the above monomer components may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, may be 15% by weight or less, and may be 5% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of the monomer containing a plurality of aromatic rings in the above monomer components is less than 3% by weight.

[0073] In some aspects of the technology disclosed herein, a high refractive index monomer may preferably be employed as at least a part of the monomer (m1). Here, the "high refractive index monomer" refers to a monomer having a refractive index of, for example, approximately 1.510 or more, preferably approximately 1.530 or more, more preferably approximately 1.550 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but from the viewpoints of ease of preparation of the adhesive composition and ease of compatibility with flexibility suitable for an adhesive, it is, for example, 3.000 or less, may be 2.500 or less, may be 2.000 or less, may be 1.900 or less, may be 1.800 or less, or may be 1.700 or less. The high refractive index monomer can be used alone or in combination of two or more kinds. The refractive index of the monomer is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, the model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent can be used. When the nominal value of the refractive index at 25°C is provided by the manufacturer or the like, that nominal value can be adopted.

[0074] As the above high refractive index monomer, a compound having a corresponding refractive index can be appropriately adopted from among the compounds (for example, the compounds and compound groups exemplified above) included in the concept of the aromatic ring-containing monomer (m1) disclosed herein. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o-phenylphenol acrylate (number of repeating units of oxyethylene 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), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35°C), 6-acryloyloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793), etc., but are not limited thereto.

[0075] The content of the high refractive index monomer in monomer (m1) (i.e., an aromatic ring-containing monomer having a refractive index of approximately 1.510 or more, preferably approximately 1.530 or more, more preferably approximately 1.550 or more) is not particularly limited and may be, for example, 5% by weight or more, may be 25% by weight or more, may be 35% by weight or more, or may be 40% by weight or more. In some embodiments, from the perspective of making it easier to obtain a higher refractive index, the content of the high refractive index monomer in monomer (m1) may be, for example, 50% by weight or more, preferably 70% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. Substantially 100% by weight of monomer (m1) may be the high refractive index monomer. Also, in some embodiments, for example, from the perspective of achieving a good balance between the high refractive index and the adhesion properties and / or optical properties, the content of the high refractive index monomer in monomer (m1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 65% by weight or less. In some embodiments, considering the adhesion properties and / or optical properties, the content of the high refractive index monomer in monomer (m1) may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, may be 15% by weight or less, or may be 10% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of the high refractive index monomer in monomer component (m1) is less than 5% by weight. It is not necessary to use the high refractive index monomer.

[0076] The content of the high refractive index monomer in the monomer components constituting the acrylic polymer is not particularly limited, and can be set so as to realize an adhesive layer that can achieve both a desired refractive index and adhesive properties (such as peel strength, flexibility, etc.) and / or optical properties (such as total light transmittance, haze value, etc.). The content of the high refractive index monomer in the above monomer components may be, for example, 3% by weight or more, may be 10% by weight or more, and may be 25% by weight or more. In some embodiments, from the perspective of facilitating the realization of an adhesive having a higher refractive index, the content of the high refractive index monomer in the above monomer components may be, for example, more than 35% by weight, preferably more than 50% by weight, may be more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The content of the high refractive index monomer in the above monomer components can be 100% by weight, but from the perspective of achieving a good balance between the high refractive index and the adhesive properties and / or optical properties, it is advantageous to be less than 100% by weight, preferably 99% by weight or less, more preferably 98% by weight or less, may be 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, and may be 75% by weight or less. In some embodiments, considering the adhesive properties and / or optical properties, the content of the high refractive index monomer in the above monomer components may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, may be 15% by weight or less, and may be 5% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of the high refractive index monomer in the above monomer components is less than 3% by weight.

[0077] In some preferred embodiments of the technology disclosed herein, at least a part of the monomer (m1) is an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") having a Tg of the homopolymer of 10 °C or lower (preferably 5 °C or lower, or 0 °C or lower, more preferably -10 °C or lower, still more preferably -20 °C or lower, for example -25 °C or lower). When the content of the aromatic ring-containing monomer (m1) in the monomer component (particularly the aromatic ring-containing monomer (m1) corresponding to one or both of the above-described aromatic ring-containing monomers and high refractive index monomers) is increased, the storage elastic modulus G' of the pressure-sensitive adhesive generally tends to increase. However, by adopting monomer L as part or all of the monomer (m1), an increase in the storage elastic modulus G' can be suppressed. Thereby, while better maintaining the flexibility suitable for a pressure-sensitive adhesive, the refractive index can be improved. The lower limit of the Tg of monomer L is not particularly limited. In consideration of the balance with the refractive index improvement effect, in some embodiments, the Tg of monomer L may be, for example, -70 °C or higher, -55 °C or higher, or -45 °C or higher. Monomer L can be used alone or in combination of two or more kinds.

[0078] As monomer L, a compound having a corresponding Tg can be appropriately adopted from among the compounds (for example, the compounds and compound groups exemplified above) included in the concept of the aromatic ring-containing monomer (m1) disclosed herein. One preferred example of the aromatic ring-containing monomer that can be used as monomer L is m-phenoxybenzyl acrylate (Tg of the homopolymer: -35 °C). Another preferred example is phenoxydiethylene glycol acrylate (Tg of the homopolymer: -35 °C).

[0079] The content of monomer L in monomer (m1) is not particularly limited and may be, for example, 5% by weight or more, may be 25% by weight or more, or may be 40% by weight or more. In some embodiments, from the viewpoint of facilitating the obtainment of an adhesive that better balances high refractive index and flexibility at a higher level, the content of monomer L in monomer (m1) may be, for example, 50% by weight or more, may be 60% by weight or more, may be 70% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. Substantially 100% by weight of monomer (A1) may be monomer L. Also, in some embodiments, from the viewpoint of achieving a good balance between flexibility and high refractive index suitable for an adhesive, for example, the content of monomer L in monomer (m1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, or may be 10% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of monomer L in monomer (m1) is less than 5% by weight. It is not necessary to use monomer L.

[0080] The content of monomer L in the monomer components constituting the acrylic polymer may be, for example, 3% by weight or more, may be 10% by weight or more, and may be 25% by weight or more. In some embodiments, from the viewpoint of facilitating the obtaining of an adhesive that achieves a higher level of compatibility between high refractive index and flexibility, the content of monomer L in the monomer components may be, for example, more than 35% by weight, preferably more than 50% by weight, may be more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The content of monomer L in the above monomer components may be 100% by weight, but in consideration of the balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to be less than 100% by weight, preferably approximately 99% by weight or less, more preferably 98% by weight or less, may be 96% by weight or less, may be 95% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, may be 75% by weight or less. In some embodiments, the content of monomer L in the above monomer components may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, may be 15% by weight or less, and may be 5% by weight or less. The technology disclosed herein can also be implemented in embodiments where the content of monomer L in the above monomer components is less than 3% by weight.

[0081] In some embodiments, the glass transition temperature Tg based on the composition of monomer (m1) m1 is advantageously approximately 20°C or lower, preferably 10°C or lower (for example, 5°C or lower), more preferably 0°C or lower, still more preferably -10°C or lower, may be -20°C or lower, and may be -25°C or lower, from the viewpoint of the flexibility of the adhesive. The glass transition temperature Tg m1 has no particular lower limit. In consideration of the balance with the refractive index improvement effect, in some embodiments, the glass transition temperature Tg m1 may be, for example, -70°C or higher, may be -55°C or higher, and may be -45°C or higher. The technology disclosed herein is applicable to embodiments where the glass transition temperature Tg m1Aspects where it is, for example, -40°C or higher, -35°C or higher, -33°C or higher, -30°C or higher, or -25°C or higher can also be preferably implemented.

[0082] Here, the glass transition temperature Tg based on the composition of monomer (m1) m1 refers to the Tg obtained by the Fox's equation described later based on the composition of only monomer (m1) among the monomer components constituting the acrylic polymer. The glass transition temperature Tg m1 is calculated by applying the Fox's equation described later only to monomer (m1) among the monomer components constituting the acrylic polymer, from 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 an aspect where only one type of monomer is used as monomer (m1), the Tg of the homopolymer of the monomer and the glass transition temperature Tg m1 are the same.

[0083] In some aspects, as the aromatic ring-containing monomer (m1), monomer L (that is, an aromatic ring-containing monomer whose Tg of the homopolymer is 10°C or lower, preferably 5°C or lower or 0°C or lower, more preferably -10°C or lower, still more preferably -20°C or lower, for example -25°C or lower) and monomer H whose Tg is higher than 10°C can be used in combination. The Tg of monomer H can be, for example, above 10°C, above 15°C, or above 20°C. By using monomer L and monomer H in combination, for example, in a configuration where the content of the aromatic ring-containing monomer (m1) in the monomer component is relatively large, the high refractive index and flexibility of the adhesive can be made compatible at a higher level. The usage ratio of monomer L to monomer H can be set so that such an effect is preferably exhibited and is not particularly limited. For example, it is preferable to set the usage ratio of monomer L to monomer H so as to satisfy any of the above-described glass transition temperatures Tg. m1

[0084] In some embodiments, the aromatic ring-containing monomer (m1) can be preferably selected from compounds that do not contain a structure in which two or more non-condensed aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, an acrylic polymer composed of a monomer component having a composition in which the content of a compound containing a structure in which two or more non-condensed aromatic rings are directly chemically bonded is less than 5% by weight (more preferably less than 3% by weight, and may be 0% by weight) is preferred. Limiting the amount of use of a compound containing a structure in which two or more non-condensed aromatic rings are directly chemically bonded in this way can be advantageous from the viewpoint of realizing an adhesive that well balances flexibility, adhesiveness, and a high refractive index.

[0085] (Monomer (m2)) In some embodiments of the technology disclosed herein, the monomer component constituting the acrylic polymer may further contain a monomer (m2) in addition to the above monomer (m1). The above monomer (m2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxyl group-containing monomer). The above hydroxyl group-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The above carboxyl group-containing monomer is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. Monomer (m2) can help introduce 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.

[0086] Examples of the ethylenically unsaturated group of monomer (m2) include a (meth)acryloyl group, a vinyl group, a (meth)allyl group, etc. From the viewpoint of polymerization reactivity, a (meth)acryloyl group is preferred, and from the viewpoints of flexibility and adhesiveness, an acryloyl group is more preferred. From the viewpoint of suppressing a decrease in the flexibility of the adhesive, as monomer (m2), a compound in which the number of ethylenically unsaturated groups contained in one molecule is 1 (that is, a monofunctional monomer) is preferably used.

[0087] Examples of the hydroxyl group-containing monomer include, but are not limited to, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Examples of the hydroxyl group-containing monomer that can be preferably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is more preferable. In a preferred embodiment, 50% by weight or more (for example, more than 50% by weight, more than 70% by weight, or more than 85% by weight) of the monomer (m2) can be 4-hydroxybutyl acrylate. The hydroxyl group-containing monomer can be used alone or in combination of two or more.

[0088] In some embodiments where a hydroxyl group-containing monomer is used as the monomer (m2), the hydroxyl group-containing monomer can be one or more selected from compounds having no methacryloyl group. Preferable examples of the hydroxyl group-containing monomer having no methacryloyl group include the various above-described hydroxyalkyl acrylates. For example, it is preferable that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (m2) is a hydroxyalkyl acrylate. By using a hydroxyalkyl acrylate, a hydroxyl group that helps provide crosslinking points and impart appropriate cohesiveness can be introduced into the acrylic polymer, and an adhesive having good flexibility and adhesiveness in the room temperature range is easily obtained as compared with the case where only the corresponding hydroxyalkyl methacrylate is used.

[0089] Examples of the carboxy group-containing monomer include, but are not limited to, acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. Examples of the carboxy group-containing monomer that can be preferably used include acrylic acid and methacrylic acid. The carboxy group-containing monomer can be used alone or in combination of two or more. The hydroxy group-containing monomer and the carboxy group-containing monomer may be used in combination.

[0090] The content of the monomer (m2) in the monomer components 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 usage effect, in some embodiments, the content of the monomer (A2) is preferably 1% by weight or more, may be 2% by weight or more, and may be 4% by weight or more. The upper limit of the content of the monomer (m2) in the monomer components is set so that the total with the content of other monomers does not exceed 100% by weight. In some embodiments, it is appropriate that the content of the monomer (m2) is, for example, 30% by weight or less or 25% by weight or less. From the viewpoint of relatively increasing the content of the monomer (m1) to facilitate an increase in the refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, may be less than 10% by weight, and may be less than 7% by weight.

[0091] In an embodiment where a hydroxyl group-containing monomer is used as the monomer (m2), the content of the hydroxyl group-containing monomer in the monomer component 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 embodiments, the content of the hydroxyl group-containing monomer is preferably 1% by weight or more of the monomer component, and may be 2% by weight or more, or may be 4% by weight or more. The upper limit of the content of the hydroxyl group-containing monomer in the monomer component is set so that the total 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 relatively increasing the content of the monomer (m1) to facilitate an increase in the refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

[0092] In an embodiment where a carboxyl group-containing monomer is used as the monomer (m2), the content of the carboxyl group-containing monomer in the monomer component 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 embodiments, the content of the carboxyl group-containing monomer may be 1% by weight or more, 2% by weight or more, or 4% by weight or more. The upper limit of the content of the carboxyl group-containing monomer in the monomer component is set so that the total with the amount of other monomers used 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 relatively increasing the content of the monomer (m1) to facilitate an increase in refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight or less than 10% by weight. In some embodiments, from the viewpoint of improving the flexibility of the pressure-sensitive adhesive, it is advantageous that the content of the carboxyl group-containing monomer is less than 7% by weight, preferably less than 5% by weight, and may be less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. The technology disclosed herein can be preferably implemented, for example, in an embodiment where only a hydroxyl group-containing monomer is used as the monomer (m2), that is, an embodiment where a carboxyl group-containing monomer is not used.

[0093] The total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer may be, for example, 31% by weight or more, preferably 51% by weight or more, and may be 61% by weight or more or 71% by weight or more. In some embodiments, the total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer may be, for example, 76% by weight or more from the viewpoint of preferably facilitating the exhibition of the effects of these monomers, and preferably 81% by weight or more, and may be 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.

[0094] (Monomer m3) The monomer components constituting the acrylic polymer may, if necessary, contain monomers other than the above-mentioned monomer (m1) and the above-mentioned monomer (m2). As an example of such an optional component, an alkyl (meth)acrylate (hereinafter also referred to as "monomer (m3)") can be mentioned. Monomer (m3) can be useful for adjusting the flexibility of the adhesive and improving the compatibility within the adhesive.

[0095] As monomer (m3), an alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 20 carbon atoms (i.e., C 1-20 of) at the ester terminal can be preferably used. C 1-20 Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc., but are not limited thereto.

[0096] In some embodiments, at least a part of the monomer (m3) may preferably be an alkyl (meth)acrylate whose homopolymer has a Tg of -20°C or lower (more preferably -40°C or lower, for example -50°C or lower). Such an alkyl (meth)acrylate with a low Tg can help improve the flexibility of the adhesive. The lower limit of the Tg of the above alkyl (meth)acrylate is not particularly limited and may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the above low-Tg alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate (iNA), and the like.

[0097] In some embodiments where the monomer (m3) is used, from the viewpoints of flexibility, adhesiveness, etc., it is preferable that at least a part of the monomer (m3) is an alkyl acrylate. For example, it is preferable that 50 wt% or more (more preferably 75 wt% or more, still more preferably 90 wt% or more) of the monomer (m3) is an alkyl acrylate. An embodiment where only one or more alkyl acrylates are used as the monomer (m3) and no alkyl methacrylate is used may also be possible.

[0098] In an embodiment where the monomer component contains an alkyl (meth)acrylate, the content of the alkyl (meth)acrylate in the monomer component can be set so that its use effect is appropriately exerted. In some embodiments, the content of the above alkyl (meth)acrylate may 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 embodiments, the content of the above alkyl (meth)acrylate may 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 so that the total with the contents of other monomers does not exceed 100% by weight, and can be, for example, less than 50% by weight. In some embodiments, the content of the above monomer (m3) can be, for example, less than 35% by weight. Generally, since the refractive index of alkyl (meth)acrylate is relatively low, in order to increase the 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 such a perspective, the content of monomer (m3) is advantageously 24% by weight or less of the monomer component, preferably less than 23% by weight, more preferably less than 20% by weight, may be less than 17% by weight, may be less than 12% by weight, may be less than 7% by weight, may be less than 3% by weight, or may be less than 1% by weight. It is not necessary to substantially use monomer (m3).

[0099] (Other monomers) The monomer component constituting the acrylic polymer may optionally contain monomers other than the above monomers (m1), (m2), and (m3) (hereinafter referred to as "other monomers"). The above other monomers can be used, for example, for the purpose of adjusting the Tg of the acrylic polymer, adjusting the adhesive performance, improving the compatibility in the adhesive layer, etc. The above other monomers can be used alone or in combination of two or more.

[0100] Examples of the other monomers include monomers having functional groups other than hydroxyl groups and carboxyl groups (functional group-containing monomers). For example, as other monomers that can improve the cohesive strength and heat resistance of the adhesive, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, etc. can be mentioned. Further, a functional group that can serve as a crosslinking point can be introduced into the acrylic polymer, or as a monomer that can contribute to the improvement of the peel strength and the improvement of the compatibility in the adhesive layer, amide group-containing monomers (for example, (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), monomers having a nitrogen atom-containing ring (for example, N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide group-containing monomers, epoxy group-containing monomers, keto group-containing monomers, isocyanate group-containing monomers, alkoxysilyl group-containing monomers, etc. can be mentioned. Among the monomers having a nitrogen atom-containing ring, there are those that also correspond to amide group-containing monomers, such as N-vinyl-2-pyrrolidone. The same applies to the relationship between the monomers having a nitrogen atom-containing ring and the amino group-containing monomers.

[0101] Examples of the other monomers that can be used in addition to the functional group-containing monomers include vinyl ester-based monomers such as vinyl acetate; non-aromatic ring-containing (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; olefin-based monomers such as ethylene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate; vinyl ether-based monomers such as methyl vinyl ether; etc. A preferred example of the other monomers that can be used for the purpose of improving the flexibility of the adhesive is ethoxyethoxyethyl acrylate (alias: ethyl carbitol acrylate, Tg of homopolymer: -67°C).

[0102] When using the above-mentioned other monomers, the amount used is not particularly limited and can be appropriately set within the range where the total amount of the monomer components does not exceed 100% by weight. In some embodiments, from the perspective of facilitating the refractive index improvement effect by using the monomer (m1), the content of the above-mentioned other monomers in the monomer components can be, for example, approximately 35% by weight or less, appropriately approximately 25% by weight or less (e.g., 0 to 25% by weight), may be approximately 20% by weight or less (e.g., 0 to 20% by weight), may be approximately 10% by weight or less, may be approximately 5% by weight or less, and may be, for example, approximately 1% by weight or less. The technology disclosed herein can be preferably implemented in an embodiment where the monomer components substantially do not contain the above-mentioned other monomers.

[0103] In some embodiments, the monomer components constituting the acrylic polymer can have a composition in which the amount of the methacryloyl group-containing monomer used is suppressed to a predetermined level or less. The amount of the methacryloyl group-containing monomer used in the monomer components can be, for example, less than 5% by weight, may be less than 3% by weight, may be less than 1% by weight, or may be less than 0.5% by weight. Limiting the amount of the methacryloyl group-containing monomer used in this way can be advantageous from the perspective of realizing an adhesive that achieves a good balance between flexibility, adhesiveness, and a high refractive index. The monomer components constituting the acrylic polymer may have a composition that does not contain a methacryloyl group-containing monomer (for example, a composition consisting only of acryloyl group-containing monomers).

[0104] In some embodiments, the monomer component constituting the base polymer (e.g., acrylic polymer) of the high refractive index adhesive layer preferably has a limited amount of carboxy group-containing monomer from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the adhesive layer. The amount of the carboxy group-containing monomer in the monomer component may be, for example, less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight, may be less than 0.1% by weight, or may be less than 0.05% by weight. The limitation of the amount of the carboxy group-containing monomer in this way is also advantageous from the viewpoint of suppressing corrosion of metal materials (e.g., metal wirings, metal films, etc. that may be present on the adherend) that can be disposed in contact with or in proximity to the high refractive index adhesive layer. The technology disclosed herein can be preferably implemented in an embodiment where the monomer component does not contain a carboxy group-containing monomer. For the same reason, in some embodiments, the monomer component constituting the base polymer of the high refractive index adhesive layer preferably has a limited amount of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxy groups). As the amount of the acidic functional group-containing monomer in the monomer component of such an embodiment, the preferred amount of the carboxy group-containing monomer described above can be applied. The technology disclosed herein can be preferably implemented in an embodiment where the monomer component does not contain an acidic group-containing monomer (i.e., an embodiment where the base polymer of the high refractive index adhesive layer is acid-free).

[0105] (The glass transition temperature Tg of the base polymer T ) In some embodiments, the base polymer (e.g., acrylic polymer) of the adhesive layer has a glass transition temperature Tg T based on the composition of the monomer component constituting the polymer, which is suitably about 20°C or lower, preferably about 10°C or lower, more preferably 0°C or lower, may be -10°C or lower, may be -20°C or lower, may be -25°C or lower, may be -28°C or lower, or may be -30°C or lower. The glass transition temperature Tg TA low value can be advantageous from the viewpoint of improving the flexibility of the pressure-sensitive adhesive. Also, the glass transition temperature Tg T may be, for example, -60°C or higher, preferably -50°C or higher, more preferably above -45°C, may be above -40°C, may be above -35°C, may be above -25°C, may be above -15°C, or may be above -5°C, from the viewpoint of facilitating an increase in the refractive index of the pressure-sensitive adhesive.

[0106] Here, the glass transition temperature Tg of the polymer T , unless otherwise specified, refers to the glass transition temperature determined by Fox's equation based on the composition of the monomer components constituting the polymer. Fox's equation is a relational expression between the Tg of the copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg = Σ(Wi / Tgi) In the above Fox's equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). As the glass transition temperature of the homopolymer used for calculating Tg, the values described in known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For monomers for which multiple types of values are described in the above Polymer Handbook, the highest value shall be adopted. When the Tg of the homopolymer is not described in known materials, the value obtained by the measurement method described in JP-A-2007-51271 shall be used.

[0107] (Method for preparing the base polymer) In the technology disclosed herein, the method for obtaining the base polymer of the adhesive layer (for example, acrylic polymer (A) composed of monomer components as described above) is not particularly limited, and known polymerization methods such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. can be appropriately adopted. In some embodiments, the solution polymerization method can be preferably adopted. The polymerization temperature when performing solution polymerization can be appropriately selected according to the types of monomers and solvents used, the types of polymerization initiators, etc., and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

[0108] The solvent used for solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetate esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. Any one solvent selected therefrom, or a mixed solvent of two or more kinds can be used.

[0109] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more kinds of azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. 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. Still other examples of polymerization initiators include redox initiators by a combination of a peroxide and a reducing agent. The polymerization initiator can be used alone or in combination of two or more kinds. The amount of the polymerization initiator used can be a normal amount used, and can be selected, for example, from the range of approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) with respect to 100 parts by weight of the monomer component.

[0110] For the above polymerization, various conventionally known chain transfer agents can be used as necessary. For example, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, α-thioglycerol, etc. can be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur-based chain transfer agent) may be used. Examples of non-sulfur-based chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; styrenes such as α-methylstyrene and α-methylstyrene dimer; and the like. The chain transfer agent can be used alone or in combination of two or more. When using a chain transfer agent, the amount used can be, for example, approximately 0.01 to 1 part by weight with respect to 100 parts by weight of the monomer raw material.

[0111] The weight average molecular weight (Mw) of the base polymer is not particularly limited and can be, for example, approximately 10×10 4 ~500×10 4 In view of the adhesion performance, the Mw of the base polymer is approximately 20×10 4 ~400×10 4 (more preferably approximately 30×10 4 ~150×10 4 , for example, approximately 50×10 4 ~130×10 4 ) and is preferably in this range.

[0112] Here, the Mw of the polymer can be determined by converting to polystyrene by gel permeation chromatography (GPC). Specifically, it can be determined by measuring under the following conditions using a GPC measuring device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation). [GPC measurement conditions] Sample concentration: 0.2 wt% (tetrahydrofuran solution) Sample injection volume: 10 μL Eluent: Tetrahydrofuran (THF) Flow rate (flow velocity): 0.6 mL / min Column temperature (measured temperature): 40 °C Column: Sample column: One piece of product name "TSKguardcolumn SuperHZ-H" + two pieces of product name "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation) Reference column: One piece of product name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation) Detector: Differential refractometer (RI) Standard sample: Polystyrene

[0113] (Refractive index improver) In some aspects of the technology disclosed herein, the high refractive index adhesive layer (for example, an acrylic adhesive layer) may contain a refractive index improver, if necessary, in addition to the base polymer. Here, in this specification, the refractive index improver refers to a material that can increase the refractive index of the adhesive layer by its use. As the refractive index improver, a material having a higher refractive index than the refractive index of the adhesive layer containing the refractive index improver can be preferably used. Also, as the refractive index improver, a material having a higher refractive index than the base polymer (for example, acrylic polymer (A)) of the adhesive layer containing the refractive index improver can be preferably used. By appropriately using the refractive index improver, it is possible to preferably achieve both a higher refractive index and practical adhesive performance. In some aspects, the refractive index improver is preferably an organic material. The organic material used as the refractive index improver may be a polymer or a non-polymer. Also, it may or may not have a polymerizable functional group. The refractive index improver can be used alone or in combination of two or more kinds.

[0114] Refractive index improver (for example, additive (H described later ROThe refractive index of (( )) can be set within an appropriate range in relation to the refractive index of the base polymer, and thus is not limited to a specific range. The refractive index of the refractive index improver can be selected from a range, for example, exceeding 1.55, exceeding 1.56 or exceeding 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 embodiments, the refractive index of the refractive index improver is advantageously 1.58 or more, preferably 1.60 or more, more preferably 1.63 or more, may be 1.65 or more, may be 1.70 or more, or may be 1.75 or more. According to a refractive index improver having a higher refractive index, the target refractive index can be achieved even by using a smaller amount of the refractive index improver. This is preferable from the viewpoint of suppressing a decrease in adhesive properties and optical properties. The upper limit of the refractive index of the refractive index improver is not particularly limited, but from the viewpoints of compatibility in the adhesive and ease of achieving both high refractive index and flexibility suitable for an adhesive, for example, it is 3.000 or less, may be 2.500 or less, may be 2.000 or less, may be 1.950 or less, may be 1.900 or less, or may be 1.850 or less.

[0115] In some embodiments, the refractive index improver (for example, the additive (H described later) RO )) has a refractive index n b and the refractive index n a of the base polymer, that is, n b - n a (hereinafter, also referred to as "Δn A ").) is set to be greater than 0. In some embodiments, Δn A is, for example, 0.02 or more, may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, may be 0.20 or more, or may be 0.25 or more. By selecting the base polymer and the refractive index improver so that Δn A becomes larger, the refractive index improving effect by using the refractive index improver tends to be higher. Also, from the viewpoints of compatibility in the adhesive layer and transparency of the adhesive layer, etc., in some embodiments, Δn A may be, for example, 0.70 or less, may be 0.60 or less, may be 0.50 or less, may be 0.40 or less, or may be 0.35 or less.

[0116] In some embodiments, the refractive index n of the refractive index increasing agent (e.g., the additive (H described below RO )) b and the refractive index n of the pressure-sensitive adhesive layer containing the refractive index increasing agent T The difference between them, that is, n b -n T (hereinafter also referred to as "Δn B ").) is set to be greater than 0. In some embodiments, Δn B is, for example, 0.02 or more, may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, may be 0.20 or more or 0.25 or more. By selecting the composition of the pressure-sensitive adhesive layer and the refractive index increasing agent so that Δn B becomes larger, the refractive index increasing effect due to the use of the refractive index increasing agent tends to be higher. Also, from the viewpoints of compatibility within the pressure-sensitive adhesive layer and transparency of the pressure-sensitive adhesive layer, etc., in some embodiments, Δn B may be, for example, 0.70 or less, may be 0.60 or less, may be 0.50 or less, may be 0.40 or less or 0.35 or less.

[0117] The amount of the refractive index improver used with respect to 100 parts by weight of the base polymer (when a plurality of types of refractive index improvers are used, the total amount thereof) is not particularly limited and can be set according to the purpose. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, advantageously 3 parts by weight or more, preferably 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, or may be 20 parts by weight or more. Also, in some embodiments, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and from the viewpoint of achieving a good balance between increasing the refractive index of the pressure-sensitive adhesive and suppressing the deterioration of the adhesive properties and optical properties, it is advantageously 60 parts by weight or less, preferably 45 parts by weight or less. In some embodiments that place more emphasis on the adhesive properties and optical properties, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, may be 20 parts by weight or less, may be 15 parts by weight or less, may be 10 parts by weight or less, may be 5 parts by weight or less, or may be 3 parts by weight or less. The technology disclosed herein can also be preferably implemented in embodiments where the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer is less than 1 part by weight or where the refractive index improver is not substantially used. Here, not substantially using means not using at least intentionally.

[0118] (Additive (H RO )) In some embodiments, as the refractive index improver, an organic material having a higher refractive index than the base polymer can preferably be employed. Hereinafter, such an organic material may be referred to as "additive (H RO )". Here, the above "H RO " represents an organic material having a high refractive index. The base polymer (for example, an acrylic polymer, preferably acrylic polymer (A)) and the additive (H ROBy using in combination with [], an adhesive that more preferably achieves both a refractive index and adhesive properties (peel strength, flexibility, etc.) and / or optical properties (total light transmittance, haze value, etc.) can be realized. Additive (H RO ) The organic material used as may be a polymer or a non-polymer. It may or may not have a polymerizable functional group. Additive (H RO ) can be used alone or in combination of two or more.

[0119] Additive (H RO ) The refractive index of is measured under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 °C using an Abbe refractometer, similar to the refractive index of the monomer. When the nominal value of the refractive index at 25 °C is provided by the manufacturer or the like, that nominal value can be adopted.

[0120] Additive (H RO ) The molecular weight of the organic material used as is not particularly limited and can be selected according to the purpose. The molecular weight of additive (H RO ) can be selected, for example, from the range of 30,000 or less. Also, additive (H RO ) is preferably a polymer or non-polymer having a lower molecular weight than the base polymer. From the viewpoint of achieving a good balance between the effect of increasing the refractive index and other properties (for example, flexibility suitable for an adhesive, optical properties such as haze), in some embodiments, the molecular weight of additive (H RO ) is suitably less than about 10,000, preferably less than 5,000, more preferably less than 3,000 (for example, less than 1,000), and may be less than 800, less than 600, less than 500, or less than 400. The fact that the molecular weight of additive (H RO ) is not too large can be advantageous from the viewpoint of improving compatibility in the adhesive layer. Also, the molecular weight of additive (H RO ) may be, for example, 130 or more, and may also be 150 or more. In some embodiments, the molecular weight of additive (H RO ) is the molecular weight of the additive (H ROFrom the perspective of increasing the refractive index, it is preferably 170 or more, more preferably 200 or more, and may be 230 or more, 250 or more, 270 or more, 500 or more, 1000 or more, or 2000 or more. In some embodiments, a polymer having a molecular weight of about 1000 to 10000 (for example, 1000 or more and less than 5000) is used as the additive (H RO ) can be used. As the molecular weight of the additive (H RO ), for a non-polymer or a polymer with a low degree of polymerization (for example, about a dimer to pentamer), the molecular weight calculated based on the chemical structure can be used. When the additive (H RO ) is a polymer with a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When the nominal value of the molecular weight is provided by the manufacturer or the like, that nominal value can be adopted.

[0121] Examples of the organic materials that can be alternatives for the additive (H RO ) include, but are not limited to, organic compounds having an aromatic ring, organic compounds having a heterocyclic ring (which may be an aromatic ring or a non-aromatic heterocyclic ring).

[0122] The aromatic ring of the above-mentioned organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used as the additive (H RO ) can be selected from the same ones as the aromatic ring of the compound used as the monomer (m1).

[0123] The above aromatic ring may or may not have one or more substituents on the ring-constituting atoms. When having substituents, examples of the substituents include, but are not limited to, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc. In the substituents containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, preferably 1 to 6, more preferably 1 to 4, still more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the above aromatic ring may be an aromatic ring having no substituents on the ring-constituting atoms or having one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (such as a bromine atom).

[0124] Additive (H RO ) Examples of the aromatic ring-containing compound that can be used as include, for example: a compound that can be used as monomer (m1); an oligomer containing a compound that can be used as monomer (m1) as a monomer unit; a compound having a structure in which a group having an ethylenically unsaturated group (which may be a substituent bonded to the ring-constituting atom) or a part constituting the ethylenically unsaturated group in the compound that can be used as monomer (m1) is replaced with a hydrogen atom or a group having no ethylenically unsaturated group (such as a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc.); etc., but are not limited thereto. Additive (H RO)Non-limiting specific examples of the aromatic ring-containing compound that can be used as include aromatic ring-containing monomers such as benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, the monomer having the fluorene structure described above, the monomer having a dinaphthothiophene structure, the monomer having a dibenzothiophene structure; aromatic ring-containing compounds having no ethylenically unsaturated group such as 3-phenoxybenzyl alcohol, dinaphthothiophene and its derivatives (for example, a compound having a structure in which one or more substituents selected from a hydroxy group, a methanol group, a diethanol group, a glycidyl group, etc. are bonded to the dinaphthothiophene ring); etc. may be included. Further, the aromatic ring-containing compound may be an oligomer (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less. For example, a low polymer of about 2 to 5 monomers) containing such an aromatic ring-containing monomer as a monomer unit. The above oligomer may be, for example: a homopolymer of an aromatic ring-containing monomer; a copolymer of one or more aromatic ring-containing monomers; a copolymer of one or more aromatic ring-containing monomers and another monomer; etc. As the above other monomer, one or more monomers having no aromatic ring may be used.

[0125] In some embodiments, the additive (H ROAs for [[ID=]], since it is easy to obtain a high refractive index increasing effect, an organic compound having two or more aromatic rings in one molecule (hereinafter, also referred to as "compound containing a plurality of aromatic rings") can be preferably employed. The compound containing a plurality of aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. Further, the compound containing a plurality of aromatic rings may be a polymer or a non-polymer. Further, the above polymer may be an oligomer (preferably an oligomer having a molecular weight of approximately 5000 or less, more preferably approximately 1000 or less. For example, a low polymer of about 2 to 5 monomers) containing a compound containing a plurality of aromatic rings as a monomer unit. The above oligomer may be, for example: a homopolymer of a compound containing a plurality of aromatic rings; a copolymer of one or more compounds containing a plurality of aromatic rings; a copolymer of one or more compounds containing a plurality of aromatic rings and another monomer; etc. The above other monomer may be an aromatic ring-containing monomer that does not correspond to the compound containing a plurality of aromatic rings, a monomer having no aromatic ring, or a combination thereof.

[0126] Non-limiting examples of the compound containing a plurality of aromatic rings include compounds having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, compounds having a structure in which two or more non-condensed aromatic rings are directly (i.e., without intervening other atoms) chemically bonded, compounds having a condensed aromatic ring structure, compounds having a fluorene structure, compounds having a dinaphthothiophene structure, compounds having a dibenzothiophene structure, and the like. The compound containing a plurality of aromatic rings can be used alone or in combination of two or more.

[0127] Specific examples of the compound having the above fluorene structure include monomers having the above-described fluorene structure, oligomers that are homopolymers or copolymers of such monomers, and 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 the like, including 9,9-bis(phenyl)fluorene and its derivatives.

[0128] Specific examples of the compound having the above dithienothiophene structure include monomers having the above-described dithienothiophene structure, oligomers that are homopolymers or copolymers of such monomers, and dithienothiophene (refractive index: 1.808); hydroxyalkyldithienothiophene such as 6-hydroxymethyldithienothiophene (refractive index: 1.766); dihydroxydithienothiophene such as 2,12-dihydroxydithienothiophene (refractive index: 1.750); dihydroxyalkyloxydithienothiophene such as 2,12-dihydroxyethyloxydithienothiophene (refractive index: 1.677); diglycidyloxydithienothiophene such as 2,12-diglycidyloxydithienothiophene (refractive index 1.723); dithienothiophene having two or more ethylenically unsaturated groups such as 2,12-diallyloxydithienothiophene (abbreviation: 2,12-DAODNT, refractive index 1.729); and the like, including dithienothiophene and its derivatives.

[0129] Specific examples of the compound having the above dibenzothiophene structure include monomers having the above-described dibenzothiophene structure, oligomers that are homopolymers or copolymers of such monomers, and dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), and the like.

[0130] Additive (H RO) Examples of organic compounds having a heterocyclic ring (hereinafter also referred to as heterocyclic ring-containing organic compounds) that can be an option include thioepoxy compounds, compounds having a triazine ring, and the like. Examples of thioepoxy compounds include bis(2,3-epithiopropyl) disulfide and its polymer (refractive index 1.74) described in Japanese Patent No. 3712653. Examples of compounds having a triazine ring include compounds having at least one triazine ring (for example, 3 to 40, preferably 5 to 20) in one molecule. Since the triazine ring has aromaticity, compounds having a triazine ring are also included in the concept of the above aromatic ring-containing compounds, and compounds having a plurality of triazine rings are also included in the concept of the above aromatic ring plurality-containing compounds.

[0131] In some embodiments, as the additive (H RO ), a compound having no ethylenically unsaturated group can be preferably employed. Thereby, alteration of the pressure-sensitive adhesive composition due to heat or light (such as progress of gelation and decrease in leveling property due to increase in viscosity) can be suppressed, and storage stability can be enhanced. Employing an additive (H RO ) having no ethylenically unsaturated group is also preferable from the viewpoint of suppressing dimensional changes, deformation (such as warping and undulation), generation of optical distortion, etc. caused by the reaction of ethylenically unsaturated groups in the pressure-sensitive adhesive layer containing the additive (H RO ) or a laminate (such as a laminated sheet) containing the pressure-sensitive adhesive layer.

[0132] In an embodiment where an oligomer is used as the additive (H RO ), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method. When the above oligomer is produced by radical polymerization, a polymerization initiator, a chain transfer agent, an emulsifier, etc. used for radical polymerization can be appropriately added to the above monomer component to conduct the polymerization. The polymerization initiator, chain transfer agent, emulsifier, etc. used for the above radical polymerization are not particularly limited and can be appropriately selected and used. Note that the weight average molecular weight of the oligomer can be controlled by the amounts of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used is appropriately adjusted according to these types. Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, α-thioglycerol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and the like. The chain transfer agent may be used alone or in combination of two or more. The amount of the chain transfer agent used can be set so that an oligomer having a desired weight average molecular weight can be obtained according to the composition of the monomer components used in the synthesis of the oligomer, the type of the chain transfer agent, and the like. In some embodiments, the amount of the chain transfer agent used relative to 100 parts by weight of the total amount of the monomers used in the synthesis of the oligomer is preferably about 15 parts by weight or less, may be 10 parts by weight or less, or may be about 5 parts by weight or less. The lower limit of the amount of the chain transfer agent used relative to 100 parts by weight of the total amount of the monomers used in the synthesis of the oligomer is not particularly limited, and may be, for example, 0.01 part by weight or more, may be 0.1 part by weight or more, may be 0.5 part by weight or more, or may be 1 part by weight or more.

[0133] In the embodiment of using the additive (H RO ) as the refractive index improver, the amount of the additive (H RO ) used relative to 100 parts by weight of the base polymer (when a plurality of compounds are used, the total amount thereof) is not particularly limited and can be set according to the purpose. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive, the amount of the additive (H RO ) used relative to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, advantageously 3 part by weight or more, preferably 5 part by weight or more, may be 7 part by weight or more, may be 10 part by weight or more, may be 15 part by weight or more, or may be 20 part by weight or more. In some embodiments, the amount of the additive (H RO ) used relative to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and from the viewpoint of achieving a good balance between increasing the refractive index of the pressure-sensitive adhesive and suppressing the deterioration of the adhesive properties and optical properties, it is advantageously 60 parts by weight or less, and preferably 45 parts by weight or less. In some embodiments that place more emphasis on the adhesive properties and optical properties, the additive (H RO ) used relative to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and from the viewpoint of achieving a good balance between increasing the refractive index of the pressure-sensitive adhesive and suppressing the deterioration of the adhesive properties and optical properties, it is advantageously 60 parts by weight or less, and preferably 45 parts by weight or less. In some embodiments that place more emphasis on the adhesive properties and optical properties, the additive (HRO ) may be used in an amount of, for example, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less.

[0134] (plasticizing material) In some embodiments, the high refractive index adhesive layer may contain a plasticizing material having a lower molecular weight than the base polymer of the adhesive layer. By using the plasticizing material, the flexibility of the high refractive index adhesive layer can be increased, and the adhesion to the adherend, the overall flexibility, the followability to deformation, etc. can be improved. From the viewpoints of compatibility and transparency in the adhesive layer, an organic material may preferably be employed as the plasticizing material. The plasticizing material may be a material that can also be used as the refractive index improver described above (for example, the above additive (H RO )) may also be a material that can be used.

[0135] The molecular weight of the plasticizing material only needs to be lower than that of the base polymer and is not particularly limited. In some embodiments, from the viewpoint of facilitating the manifestation of the plasticizing effect, the molecular weight of the plasticizing material may be 30,000 or less, 25,000 or less, less than 10,000, preferably less than 5,000, more preferably less than 3,000 (for example, less than 1,000), may also be less than 800, less than 600, less than 500, or less than 400. The fact that the molecular weight of the plasticizing material is not too large can be advantageous from the viewpoint of improving compatibility in the adhesive layer. Also, in some embodiments, from the viewpoint of facilitating the exertion of a sufficient plasticizing effect, it is appropriate that the molecular weight of the plasticizing material is 130 or more, preferably 150 or more, may also be 170 or more, 200 or more, 250 or more, or 300 or more. In some embodiments, the molecular weight of the plasticizing material may be 500 or more, 1,000 or more, or 2,000 or more. The fact that the molecular weight of the plasticizing material is not too low is also preferable from the viewpoints of the heat resistance performance of the adhesive layer and the suppression of contamination of the adherend.

[0136] Non-limiting examples of compounds that can be alternative plasticizable materials include compounds that can be used as monomer (m1) (e.g., (meth)acrylates having an aromatic ring such as a benzyl group, a phenoxy group, a naphthyl group, etc., monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc.); oligomers containing a compound that can be used as monomer (m1) as a monomer unit; compounds having a structure in which a portion having an ethylenically unsaturated group in a compound that can be used as monomer (m1) is replaced with a hydrogen atom or a group having no ethylenically unsaturated group (e.g., 3-phenoxybenzyl alcohol); and the like. In the oligomers containing a compound that can be used as monomer (m1) as a monomer unit, low-Tg monomers such as n-butyl acrylate and 2-ethylhexyl acrylate may be copolymerized from the viewpoint of improving flexibility. As the plasticizable material, one or more known plasticizers (e.g., phthalate esters, terephthalate esters, adipate esters, adipic acid-based polyesters, benzoic acid glycol esters, etc.) may be used.

[0137] In some embodiments, as the plasticizing material, an organic material having a refractive index of about 1.50 or more (more preferably 1.53 or more) can be preferably used. Specific examples of compounds that can be alternatives for the plasticizing material 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)phenyl 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 (phenylsulfonyl)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 are not limited thereto. From the viewpoints of refractive index and compatibility, for example, diethylene glycol dibenzoate can be preferably employed. The upper limit of the refractive index of the plasticizing material is not particularly limited and can be, for example, 3.00 or less. In some embodiments, from the viewpoints of ease of preparation of the pressure-sensitive adhesive composition and compatibility in the pressure-sensitive adhesive, etc., the refractive index of the plasticizing material is suitably 2.50 or less, advantageously 2.00 or less, may be 1.90 or less, may be 1.80 or less, and may be 1.70 or less. Note that the refractive index of the plasticizing material is measured under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C using an Abbe refractometer, in the same manner as the refractive index of the monomer. When the nominal value of the refractive index at 25°C is provided by the manufacturer or the like, that nominal value can be adopted.

[0138] In the embodiment using a plasticizing material, the amount of the plasticizing material used per 100 parts by weight of the base polymer is not particularly limited and can be set according to the purpose. From the viewpoint of enhancing the plasticizing effect, the amount of the plasticizing material used per 100 parts by weight of the base polymer may be, for example, 0.1 part by weight or more, may be 0.5 part by weight or more, and preferably 1 part by weight or more from the viewpoint of obtaining a higher plasticizing effect, more preferably 3 parts by weight or more, may be 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, or may be 20 parts by weight or more. Further, from the viewpoint of achieving a good balance between increasing the refractive index, transparency, and plasticizing effect of the adhesive, it is appropriate that the amount of the plasticizing material used per 100 parts by weight of the base polymer is approximately 100 parts by weight or less, preferably 80 parts by weight or less, more preferably 60 parts by weight or less, may be 45 parts by weight or less, may be 35 parts by weight or less, or may be 25 parts by weight or less. In some embodiments that place more emphasis on the adhesive properties or optical properties, the amount of the plasticizing material used per 100 parts by weight of the base polymer may be 15 parts by weight or less, may be 10 parts by weight or less, or may be 5 parts by weight or less.

[0139] (Leveling agent) In some embodiments, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain a leveling agent as needed for the purpose of improving the appearance of the pressure-sensitive adhesive layer formed from the composition (for example, improving the thickness uniformity) and improving the coatability of the pressure-sensitive adhesive composition. Non-limiting examples of the leveling agent include acrylic leveling agents, fluorine-based leveling agents, silicone-based leveling agents, and the like. The leveling agent can be selected from commercially available leveling agents, for example, and used by a conventional method.

[0140] In some embodiments, as the leveling agent, a polymer (hereinafter also referred to as "polymer (B)") which is a polymer of a monomer raw material (hereinafter also referred to as "monomer raw material B") containing a monomer having a polyorganosiloxane skeleton (hereinafter also referred to as "monomer S1") and an acrylic monomer can be preferably used. Polymer (B) can be said to be a copolymer of monomer S1 and an acrylic monomer. Polymer (B) can be used alone or in combination of two or more.

[0141] Monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. As monomer S1, those having a structure with a polymerizable reactive group at one end can be preferably used. Among them, monomer S1 having a polymerizable reactive group at one end and no functional group that causes a crosslinking reaction with the base polymer (for example, an acrylic polymer) of the pressure-sensitive adhesive composition in which the leveling agent is blended at the other end can be preferably adopted. Commercially available products include, for example, one-end reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. (for example, product numbers such as X-22-174ASX, X-22-2426, X-22-2475, KF-2012). Monomer S1 can be used alone or in combination of two or more.

[0142] The functional group equivalent of monomer S1 can be, for example, about 100 g / mol to 30000 g / mol. In some preferred embodiments, the above functional group equivalent is, for example, 500 g / mol or more, may be 800 g / mol or more, may be 1500 g / mol or more, or may be 2000 g / mol or more. Also, the above functional group equivalent may be, for example, 20000 g / mol or less, may be less than 10000 g / mol, may be 7000 g / mol or less, or may be 5500 g / mol or less. When the functional group equivalent of monomer S1 is within the above range, a good leveling effect is likely to be exhibited. When using two or more types of 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 type of monomer and their weight fractions.

[0143] Here, the "functional group equivalent" means the weight of the main skeleton (e.g., polydimethylsiloxane) bonded to each functional group. Regarding the unit g / mol, it is converted to 1 mol of the functional group. The functional group equivalent of monomer S1 can be calculated, for example, based on 1 the spectral intensity of 1H-NMR (proton NMR) in nuclear magnetic resonance (NMR). 1 The calculation of the functional group equivalent (g / mol) of monomer S1 based on the spectral intensity of 1H-NMR 1 can be carried out based on general structural analysis methods related to 1H-NMR spectral analysis and referring to the description in Japanese Patent No. 5951153 if necessary. In the functional group equivalent of monomer S1, the above functional group means a polymerizable functional group (e.g., ethylenically unsaturated groups such as (meth)acryloyl group, vinyl group, allyl group, etc.).

[0144] The content of monomer S1 in monomer raw material B can be an appropriate value within the range where the desired effect is exhibited using the monomer S1, and is not limited to a specific range. In some embodiments, the content of monomer S1 in monomer raw material B may be, for example, 5 to 60% by weight, may be 10 to 50% by weight, or may be 15 to 40% by weight.

[0145] In addition to monomer S1, monomer raw material B contains an acrylic monomer copolymerizable with monomer S1. Thereby, the compatibility of polymer (B) in the adhesive layer can be improved. Examples of the acrylic monomer that can be used in monomer raw material B include alkyl acrylates. Here, the "alkyl" refers to a chain (including linear and branched) alkyl (group) and does not include the alicyclic hydrocarbon group described later. In some embodiments, monomer raw material B is (meth)acrylic acid C 4-12 alkyl ester (preferably (meth)acrylic acid C4-10 an alkyl ester, for example a C 6-10 alkyl ester) may be contained. In some other embodiments, the monomer raw material B is a C 1-18 alkyl ester (preferably a C 1-14 alkyl ester, for example a C 1-10 alkyl ester) may be contained. The monomer raw material B may contain, as an acrylic monomer, for example, one or more selected from methyl methacrylate (MMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA).

[0146] Other examples of the above acrylic monomers include (meth)acrylic acid esters having an alicyclic hydrocarbon group. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, etc. can be used. It is not necessary to use a (meth)acrylic acid ester having an alicyclic hydrocarbon group.

[0147] The content of the above (meth)acrylic acid alkyl ester and the (meth)acrylic acid ester having an alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10% by weight or more and 95% by weight or less, may be 20% by weight or more and 95% by weight or less, may be 30% by weight or more and 90% by weight or less, may be 40% by weight or more and 90% by weight or less, or may be 50% by weight or more and 85% by weight or less.

[0148] As other examples of monomers that may be contained in monomer raw material B together with monomer S1, carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, monomers having a nitrogen atom-containing ring, (meth)acrylic acid aminoalkyls, vinyl esters, vinyl ethers, olefins, (meth)acrylic acid esters having an aromatic hydrocarbon group, halogen atom-containing (meth)acrylates, etc., which were exemplified above as monomers that can be used for acrylic polymers, can be mentioned.

[0149] The Mw of polymer (B) may be, for example, 5,000 or more, preferably 10,000 or more, and may also be 15,000 or more. Also, the Mw of polymer (B) may be, for example, 200,000 or less, preferably 100,000 or less, may also be 50,000 or less, and may also be 30,000 or less. By setting the Mw of polymer (B) within an appropriate range, suitable compatibility and leveling properties can be exhibited.

[0150] Polymer (B) can be produced, for example, by polymerizing the above-mentioned monomers by known methods such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. In order to adjust the molecular weight of polymer (B), a chain transfer agent can be used as necessary. Examples of the chain transfer agent to be used include compounds having a mercapto group such as t-dodecyl mercaptan, mercaptoethanol, α-thioglycerol; thioglycolic acid esters such as thioglycolic acid and methyl thioglycolate; α-methylstyrene dimer; etc. The amount of the chain transfer agent used is not particularly limited and can be appropriately set so as to obtain polymer (B) having a desired molecular weight. In some embodiments, the amount of the chain transfer agent used relative to 100 parts by weight of the monomer may be, for example, 0.1 to 5 parts by weight, may also be 0.2 to 3 parts by weight, and may also be 0.5 to 2 parts by weight.

[0151] The amount of polymer (B) used relative to 100 parts by weight of the base polymer (for example, an acrylic polymer) can be, for example, 0.001 part by weight or more, and from the viewpoint of obtaining a higher usage effect, it may be 0.01 part by weight or more, or may be 0.03 part by weight or more. Further, the amount of the polymer (B) used may be, for example, 3 parts by weight or less, and from the viewpoint of reducing the influence on the refractive index, it is appropriate to be 1 part by weight or less, may be 0.5 part by weight or less, or may be 0.1 part by weight or less.

[0152] (Inorganic particles) The technology disclosed herein can be preferably implemented in an embodiment that does not substantially use inorganic particles as a refractive index improver. However, in some embodiments, it may be acceptable to use inorganic particles as a refractive index improver to the extent that desired optical properties (total light transmittance, haze value) are satisfied and the properties as an adhesive are not significantly impaired. Examples of inorganic particles that can be used as a refractive index improver include inorganic particles composed of inorganic oxides (specifically, metal oxides) such as titania (titanium oxide, TiO2), zirconia (zirconium oxide, ZrO2), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide (such as Nb2O5, etc.). The average particle diameter of the above inorganic particles (refers to the 50% volume average particle diameter based on the laser scattering / diffraction method) can be selected, for example, from the range of about 10 nm to 100 nm. The refractive index of the inorganic particles is measured under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 23 °C using a commercially available spectroscopic ellipsometer for a single-layer film (with a film thickness capable of measuring the refractive index) composed of the material constituting the inorganic particles. As the spectroscopic ellipsometer, for example, the product name "EC-400" (manufactured by JA.Woolam) or its equivalent is used. When using inorganic particles as a refractive index improver, the amount used is preferably less than 5 parts by weight, more preferably less than 1 part by weight, based on 100 parts by weight of the base polymer. In the embodiment of using the additive (H RO ), the amount of the above inorganic particles used is preferably 2 times or less, more preferably 1 time or less or 0.5 times or less, based on the weight of the additive (H RO ).

[0153] (Crosslinking agent) In the technology disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain a crosslinking agent as necessary for purposes such as adjusting the cohesive force of the pressure-sensitive adhesive. As the crosslinking agent, known crosslinking agents in the field of pressure-sensitive 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. Among them, isocyanate-based crosslinking agents can be preferably employed. As another example of the crosslinking agent, a monomer having two or more ethylenically unsaturated groups in one molecule, that is, a polyfunctional monomer, can be mentioned. The crosslinking agent can be used alone or in combination of two or more kinds.

[0154] As the isocyanate-based crosslinking agent, polyisocyanate compounds having two or more functional groups can be used. For example, aliphatic polyisocyanates such as trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), dimer acid diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate (XDI); polyisocyanate modified products obtained by modifying the above isocyanate compounds with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds, etc.; and the like. Examples of commercially available products include Takeneate 300S, Takeneate 500, Takeneate 600, Takeneate D165N, Takeneate D178N (manufactured by Takeda Pharmaceutical Company Limited), Sumidule T80, Sumidule L, Desmodule N3400 (manufactured by Sumitomo Bayer Urethane Co., Ltd.), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (manufactured by Tosoh Corporation), and the like. The isocyanate compound can be used alone or in combination of two or more. A bifunctional isocyanate compound and a polyfunctional isocyanate compound having three or more functional groups may be used in combination.

[0155] Examples of the epoxy crosslinking agent include bisphenol A, an epoxy resin of the epichlorohydrin type, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6 - hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diaminoglycidylamine, N,N,N’,N’ - tetraglycidyl - m - xylylenediamine, 1,3 - bis(N,N - diglycidylaminomethyl)cyclohexane, and the like. These can be used alone or in combination of two or more kinds.

[0156] Examples of the polyfunctional monomer 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 (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenoxyethanol fluorene di(meth)acrylate, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (meth)acrylate, hexyl diol di(meth)acrylate, and the like. The polyfunctional monomer can be used alone or in combination of two or more kinds.

[0157] When using a crosslinking agent (which may be a polyfunctional monomer), the amount used is not particularly limited. For example, it can be in the range of about 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the base polymer. From the perspective of improving the flexibility of the adhesive, in some embodiments, the amount of the crosslinking agent used with respect 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 may also be 1.0 part by weight or less, 0.5 part by weight or less, or 0.2 part by weight or less. Also, from the perspective of appropriately exerting the effect of the crosslinking agent, in some embodiments, the amount of the crosslinking agent used with respect to 100 parts by weight of the base polymer may be, for example, 0.005 part by weight or more, may also be 0.01 part by weight or more, 0.05 part by weight or more, or 0.08 part by weight or more.

[0158] In order to make the crosslinking reaction proceed more effectively, a crosslinking catalyst may be used. Examples of the crosslinking catalyst include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, ferric naphthenate, butyltin oxide, dioctyltin dilaurate, etc. Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used with respect to 100 parts by weight of the base polymer can be, for example, in the range of about 0.0001 to 1 part by weight in consideration of the balance between the speed of the crosslinking reaction and the pot life of the adhesive composition, and preferably in the range of 0.001 to 0.5 part by weight.

[0159] In the adhesive composition, a compound that causes keto-enol tautomerism can be contained as a crosslinking retarder. Thereby, the effect of extending the pot life of the adhesive composition can be realized. For example, in an adhesive composition containing an isocyanate-based crosslinking agent, a compound that causes keto-enol tautomerism can be preferably used. As the compound that causes keto-enol tautomerism, various β-dicarbonyl compounds can be used. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetic acid esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably employed. The compound that causes keto-enol tautomerism can be used alone or in combination of two or more. The amount of the compound that causes keto-enol tautomerism used can be, for example, 0.1 part by weight or more and 20 parts by weight or less, preferably 0.5 part by weight or more and 10 parts by weight or less, and more preferably 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the base polymer.

[0160] (Adhesion promoter) In the adhesive layer in the technology disclosed herein, an adhesion promoter may be contained. As the adhesion promoter, known adhesion-promoting resins such as rosin-based adhesion-promoting resins, terpene-based adhesion-promoting resins, phenol-based adhesion-promoting resins, hydrocarbon-based adhesion-promoting resins, ketone-based adhesion-promoting resins, polyamide-based adhesion-promoting resins, epoxy-based adhesion-promoting resins, and elastomer-based adhesion-promoting resins can be used. These can be used alone or in combination of two or more. The amount of the adhesion-promoting resin used is not particularly limited and can be set so as to exhibit appropriate adhesive performance according to the purpose and application. In some embodiments, from the viewpoints of refractive index and transparency, the amount of the adhesion promoter used is suitably 30 parts by weight or less, preferably 10 parts by weight or less, and more preferably 5 parts by weight or less based on 100 parts by weight of the base polymer of the adhesive layer. The technology disclosed herein can be preferably implemented in an embodiment without using an adhesion promoter.

[0161] (Other additives) In the technology disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain, as necessary, known additives that can be used in pressure-sensitive adhesive compositions, such as plasticizers, softeners, colorants, antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, etc., as long as the effects of the present invention are not significantly hindered. Regarding such various additives, those known in the art can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions thereof are omitted.

[0162] (Peel strength) In some embodiments, the peel strength of the pressure-sensitive adhesive layer disclosed herein with respect to the glass plate is preferably about 1.0 N / 25 mm or more (for example, 1.5 N / 25 mm or more), preferably 2 N / 25 mm or more, more preferably 3 N / 25 mm or more, and may 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. The upper limit of the peel strength is not particularly limited and may be, for example, 30 N / 25 mm or less, 25 N / 25 mm or less, or 20 N / 25 mm or less.

[0163] Here, the above peel strength is determined by pressing it onto an alkaline glass plate as an adherend, leaving it in an environment of 23°C and 50% RH for 30 minutes, then putting it into a pressure degassing device (autoclave) and performing an autoclave treatment at a temperature of 50°C and a pressure of 0.5 MPa for 30 minutes, and further leaving it in an atmosphere of 23°C and 50% RH for 24 hours, and then measuring the 180° peel adhesion force under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. In the measurement, if necessary, an appropriate backing material (for example, a polyethylene terephthalate (PET) film with a thickness of about 25 μm to about 50 μm) can be attached to the measurement object for reinforcement. More specifically, the peel strength can be measured according to the method described in the examples below. When the high refractive index adhesive layer disclosed herein is laminated with a low refractive index adhesive layer to form a laminated sheet in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, in some embodiments, the peel strength described above is preferably applied at least to the first adhesive surface (the adhesive surface composed of the high refractive index adhesive layer), and more preferably applied to both the first adhesive surface and the second adhesive surface. The peel strength of the first adhesive surface with respect to the glass plate and the peel strength of the second adhesive surface with respect to the glass may be the same or different.

[0164] <Low refractive index layer> In the technology disclosed herein, the refractive index n2 of the low refractive index layer (preferably the low refractive index adhesive layer) is preferably lower than the refractive index n1 of the high refractive index adhesive layer. Thereby, by utilizing the refractive index difference between the high refractive index adhesive layer and the low refractive index layer, the behavior of light passing through the laminated sheet including these layers can be controlled. The refractive index n2 of the low refractive index layer can be, for example, in the range of about 1.35 to 1.55. In some embodiments, from the viewpoint of increasing the refractive index difference with the refractive index n1 of the high refractive index adhesive layer to facilitate enhancing the front luminance improvement effect described later, the refractive index n2 of the low refractive index layer is preferably, for example, 1.49 or less, more preferably 1.47 or less (for example, 1.46 or less, or 1.45 or less), may be 1.43 or less, may be 1.41 or less, or may be 1.40 or less. Also, from the viewpoints of easy availability of materials and ease of compatibility with adhesive properties, in some embodiments, the refractive index n2 of the low refractive index layer may be, for example, 1.36 or more, may be 1.38 or more, may be 1.40 or more, or may be 1.42 or more.

[0165] 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 may be greater than, for example, 1.00, may be approximately 1.01 or more, and it is suitable that it is approximately 1.02 or more, and may be approximately 1.03 or more. In some embodiments, the ratio (n1 / n2) is advantageously approximately 1.05 or more, preferably approximately 1.07 or more, more preferably approximately 1.10 or more, and may be approximately 1.11 or more. The upper limit of the ratio (n1 / n2) is not particularly limited. In some embodiments, from the viewpoints of adhesive properties, transparency, etc., the ratio (n1 / n2) may be, for example, approximately 1.20 or less, may be approximately 1.18 or less, may be approximately 1.16 or less, may be approximately 1.14 or less, may be approximately 1.12 or less.

[0166] 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, that is, the refractive index difference (n1 - n2), may be greater than, for example, 0.00, may be 0.01 or more, preferably 0.02 or more, may be 0.03 or more, may be 0.05 or more, may be 0.10 or more, may be 0.15 or more, may be 0.20 or more, may be 0.25 or more. The upper limit of the refractive index difference (n1 - n2) is not particularly limited. In some embodiments, from the viewpoints of adhesive properties, transparency, etc., the refractive index difference (n1 - n2) may be, for example, 0.30 or less, may be 0.26 or less, may be 0.21 or less, may be 0.18 or less, may be 0.16 or less.

[0167] In some preferred embodiments, the storage modulus G' at 25°C of the low refractive index layer (hereinafter, may be denoted as "storage modulus G' V2 (25)").) is preferably lower than the storage modulus G' at 25°C of the high refractive index adhesive layer (storage modulus G' V1 (25)). That is, G' V2 (25) < G' V1It is preferably (25). According to such a configuration, by laminating a low refractive index layer on a high refractive index adhesive layer, adhesion and flexibility are imparted, so that step followability and followability to a curved surface or the like are improved, and a laminated sheet (adhesive sheet) that can be preferably applied to various device design applications can be realized.

[0168] Storage elastic modulus G' V2 (25) is not particularly limited and can be, for example, in the range of 1.0 kPa to 500 kPa. From the viewpoint of enhancing the effect of imparting flexibility by the low refractive index layer and improving the followability to deformation, in some aspects, the storage elastic modulus G' V2 (25) is suitably 400 kPa or less, preferably 300 kPa or less, more preferably 200 kPa or less (for example, 180 kPa or less, or 150 kPa or less), may be 120 kPa or less, may be 90 kPa or less, and may be 70 kPa or less. From the viewpoint of imparting appropriate cohesiveness to the low refractive index layer, in some aspects, the storage elastic modulus G' V2 (25) is suitably 5.0 kPa or more, preferably 10 kPa or more, may be 15 kPa or more, may be 25 kPa or more, may be 35 kPa or more, may be 60 kPa or more, and may be 80 kPa or more. From the viewpoint of making it easier to realize higher cohesive force and adhesive characteristics, in some aspects, the storage elastic modulus G' V2 (25) may be 95 kPa or more, may be 110 kPa or more, and may be 140 kPa or more.

[0169] In an embodiment where the low refractive index layer is an adhesive layer, the type of the adhesive constituting the adhesive layer is not particularly limited. The adhesive constituting the low refractive index adhesive layer may include one or more of various rubber-like polymers such as acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers, etc. as base polymers. From the viewpoints of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber polymer as a base polymer may be preferably employed. Among them, an adhesive having an acrylic polymer as a base polymer (acrylic adhesive) is preferred. In an embodiment where the high refractive index adhesive layer is an acrylic adhesive layer, a configuration in which the low refractive index adhesive layer is an acrylic adhesive layer may be preferably adopted from the viewpoint of the adhesion between the high refractive index adhesive layer and the low refractive index adhesive layer.

[0170] In some embodiments, as the above acrylic polymer, for example, a polymer of a monomer raw material containing an alkyl (meth)acrylate and further containing another monomer copolymerizable therewith (copolymerizable monomer) is preferred. The content of the alkyl (meth)acrylate in the monomer 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 above acrylic polymer may be a polymer of a monomer component containing an alkyl (meth)acrylate as a main monomer and further containing the above copolymerizable monomer as a sub monomer. Here, the main monomer refers to a component occupying more than 50% by weight of the monomer composition in the above monomer raw material. More than 55% by weight or more than 60% by weight of the above monomer composition may be alkyl (meth)acrylate.

[0171] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH2=C(R 1 )COOR 2 (1) Here, R in the above formula (1) 1 is a hydrogen atom or a methyl group. Also, R 2 is a linear alkyl group having 1 to 20 carbon atoms (hereinafter, such a carbon atom number range may be expressed as "C 1-20 "). From the viewpoint of the storage elastic modulus of the adhesive, etc., R 2 is C 1-12 (for example, C 2-10 , typically C 4-8 ) alkyl (meth)acrylate which is a linear alkyl group is preferred. The alkyl (meth)acrylate in which the above R 2 is a linear alkyl group of C 1-20 can be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include n-butyl acrylate and 2-ethylhexyl acrylate.

[0172] The above copolymerizable monomer can be useful for introducing crosslinking points into the acrylic polymer or increasing the cohesive force of the acrylic polymer. As the above copolymerizable monomer, for example, one or more of functional group-containing monomers such as carboxy group-containing monomers, hydroxy group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a nitrogen atom-containing ring, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers can be used. Other examples of the copolymerizable monomer include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, non-aromatic ring-containing (meth)acrylate, alkoxy group-containing monomers, etc. Specific examples include those described above as monomers that can be used as the base polymer of the high refractive index adhesive layer, but are not limited thereto. For example, from the viewpoint of improving the cohesive force, an acrylic polymer copolymerized with a carboxy group-containing monomer and / or a hydroxy group-containing monomer as the above copolymerizable monomer is preferred. Preferable examples of the carboxy group-containing monomer include acrylic acid and methacrylic acid. Preferable examples of the hydroxy group-containing monomer include 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

[0173] In some embodiments, in order to lower the refractive index n2 of the low refractive index layer, a fluorine-containing monomer can be used as the copolymerizable monomer. The content of the fluorine-containing monomer in the monomer raw material may be, for example, 10% by weight or more, may be 25% by weight or more, or may be 35% by weight or more. From the viewpoint of facilitating the realization of a low refractive index layer with a lower refractive index, the content of the fluorine-containing monomer is preferably 40% by weight or more, more preferably 45% by weight or more, still more preferably 55% by weight or more, may be 60% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. The upper limit of the content of the fluorine-containing monomer in the monomer raw material is not particularly limited and may be 100% by weight. In some embodiments, from the viewpoint of the cohesiveness of the low refractive index layer, etc., the content of the fluorine-containing monomer is suitably 99.9% by weight or less, preferably 99.5% or less, may be 99% by weight or less, may be 97% by weight or less, or may be 92% by weight or less. The fluorine-containing monomer can be used alone or in combination of two or more.

[0174] As the fluorine-containing monomer, a fluorine-containing acrylic monomer can be preferably used. The fluorine-containing acrylic monomer is not particularly limited as long as it is an acrylic monomer having at least one fluorine atom in the molecule. For example, a fluorine-containing (meth)acrylate can be preferably used. Preferable examples of the fluorine-containing (meth)acrylate include those having a fluorinated hydrocarbon group at the ester terminal. Examples of the fluorinated hydrocarbon group include a fluorinated aliphatic hydrocarbon group, a fluorinated alicyclic hydrocarbon group, and a fluorinated aromatic hydrocarbon group. As the fluorinated hydrocarbon group, a fluorinated aliphatic hydrocarbon group is preferable. Examples of the fluorinated aliphatic hydrocarbon group include a fluorinated alkyl group. In the fluorinated aliphatic hydrocarbon group, the aliphatic hydrocarbon moiety may be linear or branched. Also, in the fluorinated aliphatic hydrocarbon group, the fluorine atom may be bonded to any carbon atom of the aliphatic hydrocarbon group moiety. The number of fluorine atoms bonded to one carbon atom may be single or plural. The number of carbon atoms to which the fluorine atom is bonded is not particularly limited.

[0175] In a fluorinated aliphatic hydrocarbon group (especially a fluorinated alkyl group), the number of carbon atoms in the hydrocarbon group moiety is not particularly limited. In some embodiments, considering the compatibility with other copolymerizable monomers, a fluorinated aliphatic hydrocarbon group having about 1 to 18 (preferably 1 to 12) carbon atoms is preferred. Specific examples of the fluorinated aliphatic hydrocarbon group include fluorinated methyl groups such as trifluoromethyl group, difluoromethyl group, monofluoromethyl group; fluorinated ethyl groups such as pentafluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1-monofluoroethyl group, 2-monofluoroethyl group; and the like. As the fluorinated alkyl group having 3 or more carbon atoms, various fluorinated alkyl groups in which one or more carbon atoms of the carbon atoms in the alkyl group moiety are bonded with one or more fluorine atoms can be exemplified in the same manner as the above-exemplified fluorinated methyl group and fluorinated ethyl group.

[0176] Examples of the fluorinated alicyclic hydrocarbon group include fluorinated cycloalkyl groups. Similar to the above fluorinated aliphatic hydrocarbon group, in the fluorinated alicyclic hydrocarbon group, the fluorine atom may be bonded to any carbon atom of the alicyclic hydrocarbon group, and the number of fluorine atoms bonded to one carbon atom may be either single or plural. Further, the number of carbon atoms to which the fluorine atom is bonded is not particularly limited. The fluorinated alicyclic hydrocarbon group includes, for example, cyclohexyl groups having one fluorine atom such as 2-fluorocyclohexyl group, 3-fluorocyclohexyl group, 4-fluorocyclohexyl group; cyclohexyl groups having two fluorine atoms such as 2,4-difluorocyclohexyl group, 2,6-difluorocyclohexyl group; cyclohexyl groups having three fluorine atoms such as 2,4,6-trifluorocyclohexyl group, etc.

[0177] The fluorinated hydrocarbon group may or may not have a substituent. Such substituents are not particularly limited, and examples include hydrocarbon groups such as alkyl groups, alkoxy groups, hydroxy groups, carboxy groups, amino groups, nitro groups, cyano groups, and halogen atoms. The substituents can be used alone or in combination of two or more.

[0178] The fluorine atom-containing (meth)acrylate [fluorinated (meth)acrylate] includes, for example, fluorine atom-containing alkyl (meth)acrylate [fluorinated alkyl (meth)acrylate], fluorine atom-containing cycloalkyl (meth)acrylate [fluorinated cycloalkyl (meth)acrylate], fluorine atom-containing aryl (meth)acrylate [fluorinated aryl (meth)acrylate], and the like.

[0179] As the fluorine atom-containing (meth)acrylate, fluorinated alkyl (meth)acrylate (particularly, fluorinated alkyl acrylate) is preferred. Examples of the fluorinated alkyl (meth)acrylate include 2,2,2-trifluoroethyl acrylate (trade name "Biscoat 3F" manufactured by Osaka Organic Chemical Industry Co., Ltd., etc.), 2,2,3,3-tetrafluoropropyl acrylate (trade name "Biscoat 4F" manufactured by Osaka Organic Chemical Industry Co., Ltd., etc.), 1H,1H,5H-octafluoropentyl acrylate (trade name "Biscoat 8F" manufactured by Osaka Organic Chemical Industry Co., Ltd., etc.), 1H,1H,5H-octafluoropentyl methacrylate (trade name "Biscoat 8FM" manufactured by Osaka Organic Chemical Industry Co., Ltd., etc.), 2-(heptadecafluorononyl)ethyl acrylate (trade name "FA-108" manufactured by Kyoeisha Chemical Co., Ltd., etc.), 1H,1H,2H,2H-tridecafluorooctyl acrylate (trade name "Biscoat 13F" manufactured by Osaka Organic Chemical Industry Co., Ltd., etc.), and the like.

[0180] From the viewpoints of the low refractive index effect, flexibility, etc., the number of carbon atoms in the fluorinated alkyl group in the fluorinated alkyl (meth)acrylate is advantageously 3 or more, preferably 4 or more, more preferably 5 or more, still more preferably 6 or more or 7 or more, and particularly preferably 8 or more. From the viewpoint of adhesion performance, etc., the number of carbon atoms in the fluorinated alkyl group is advantageously 18 or less, preferably 14 or less, more preferably 12 or less, and may be 10 or less or 9 or less. In some embodiments, the number of carbon atoms in the fluorinated alkyl group may be 7 or less or 5 or less. Further, in some embodiments, as the fluorine atom-containing (meth)acrylic acid ester, a fluorinated alkyl (meth)acrylate in which fluorine is not bonded to the carbon at the 1-position of the alkyl group is preferable, and for example, a fluorinated alkyl (meth)acrylate in which fluorine is not bonded to either the carbon at the 1-position or the carbon at the 2-position of the alkyl group, such as 1H,1H,2H,2H-tridecafluorooctyl acrylate, may be preferably employed.

[0181] In some embodiments, the low refractive index layer is an acrylic pressure-sensitive adhesive layer, and the acrylic polymer that is the base polymer of the pressure-sensitive adhesive is a polymer of a monomer raw material that may at least contain a fluorine-containing acrylic monomer as described above (for example, fluorinated alkyl (meth)acrylate), and may further contain other monomers (copolymerizable monomers) having copolymerizability with the fluorine-containing acrylic monomer. This monomer raw material may or may not contain alkyl (meth)acrylate. The content of the fluorine-containing acrylic monomer in the monomer raw material may be, for example, 10% by weight or more, may be 25% by weight or more, or may be 35% by weight or more. From the viewpoint of facilitating the realization of a low refractive index layer with a lower refractive index, the content of the fluorine-containing acrylic monomer is preferably 40% by weight or more, more preferably 45% by weight or more, still more preferably 55% by weight or more, may be 60% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. The upper limit of the content of the fluorine-containing acrylic monomer in the monomer raw material is not particularly limited and may be 100% by weight. In some embodiments, from the viewpoint of the cohesiveness of the low refractive index layer, etc., the content of the fluorine-containing acrylic monomer is suitably 99.9% by weight or less, preferably 99.5% or less, may be 99% by weight or less, may be 97% by weight or less, or may be 92% by weight or less. The fluorine-containing acrylic monomer can be used alone or in combination of two or more kinds.

[0182] The monomer raw materials for preparing the base polymer of the low refractive index layer can be a composition containing a fluorine-containing acrylic monomer (for example, fluorinated alkyl (meth)acrylate) and further copolymerizable monomers. Examples of the copolymerizable monomers include one or more functional group-containing monomers such as carboxy group-containing monomers, hydroxy group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a nitrogen atom-containing ring (for example, N-vinyl cyclic amides such as N-vinyl-2-pyrrolidone), sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers. Other examples of the copolymerizable monomers include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, non-aromatic ring-containing (meth)acrylates such as cycloalkyl (meth)acrylate and isobornyl (meth)acrylate, and alkoxy group-containing monomers; etc. Specific examples include, but are not limited to, those described above as monomers that can be used as the base polymer of the high refractive index adhesive layer. For example, from the viewpoint of improving cohesion, an acrylic polymer copolymerized with a carboxy group-containing monomer and / or a hydroxy group-containing monomer as the copolymerizable monomer is preferable.

[0183] In some preferred embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer may be a composition containing a fluorine-containing monomer (for example, a fluorine-containing acrylic monomer such as fluorinated alkyl (meth)acrylate) and further containing a hydroxyl group-containing monomer. The hydroxyl group-containing monomer can be useful for improving cohesive force and introducing crosslinking points. Preferred examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate can be more preferably used. The content of the hydroxyl group-containing monomer in the monomer raw material 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 embodiments, the content of the above hydroxyl group-containing monomer may be 0.7% by weight or more, 0.9% by weight or more, or 1.5% by weight or more of the above monomer raw material. The upper limit of the content of the hydroxyl group-containing monomer is not particularly limited and can be, for example, 15% by weight or less or 10% by weight or less. In some embodiments, from the viewpoint of reducing the refractive index, it is appropriate that the content of the hydroxyl group-containing monomer in the above monomer raw material is less than 10% by weight, preferably less than 5% by weight, may be less than 3% by weight, may be less than 2.5% by weight, or may be less than 1.5% by weight.

[0184] In some embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer preferably has a limited content of carboxyl group-containing monomers from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the low refractive index layer. The content of the carboxyl group-containing monomer in the monomer raw material may be, for example, 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 the carboxyl group-containing monomer in this way is also advantageous from the viewpoint of suppressing corrosion of the metal material (e.g., metal wiring, metal film, etc. that may be present on the adherend) that can be disposed in contact with or in proximity to the low refractive index layer. The technology disclosed herein can be preferably implemented in an embodiment where the monomer raw material does not contain a carboxyl group-containing monomer. For the same reason, in some embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer preferably has a limited content of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxyl groups). As the content of the acidic functional group-containing monomer in the monomer raw material of such an embodiment, the preferred content of the carboxyl group-containing monomer described above can be applied. The technology disclosed herein can be preferably implemented in an embodiment where the monomer raw material does not contain an acidic group-containing monomer (i.e., an embodiment where the base polymer of the low refractive index layer is acid-free).

[0185] The base polymer of the low refractive index layer can be prepared by appropriately adopting a known polymerization method, similar to the base polymer of the high refractive index adhesive layer. The weight average molecular weight (Mw) of the base polymer is not particularly limited and may be, for example, approximately 10×10 4 ~500×10 4 and may be in the range of approximately 20×10 4 ~200×10 4 In some embodiments, from the viewpoint of adhesion to the high refractive index adhesive layer and the like, the Mw of the base polymer of the low refractive index adhesive layer is suitably 150×10 4 or less, and 120×10 4The following (for example, 95×10 4 the following) is preferable, 75×10 4 or less may be sufficient, 68×10 4 or less may be sufficient, 60×10 4 or less may be sufficient. Also, in some embodiments, from the perspective of the cohesiveness of the low refractive index adhesive layer, etc., the Mw of the base polymer may be, for example, 30×10 4 or more, 40×10 4 or more may be sufficient, 50×10 4 or more may be sufficient. To prepare the Mw, if necessary, a conventionally known chain transfer agent can be used.

[0186] Although not particularly limited, from the perspective of adhesiveness, the Tg of the base polymer (for example, an acrylic polymer) of the low refractive index layer is advantageously approximately 0°C or lower, preferably approximately -5°C or lower (for example, approximately -15°C or lower, or -25°C or lower). Also, from the perspective of the cohesive force of the adhesive layer, the Tg of the base polymer of the low refractive index layer is approximately -75°C or higher, preferably approximately -70°C or higher (for example, -50°C or higher, and further -30°C or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and usage ratio of the monomers used in the synthesis of the polymer).

[0187] Known crosslinking agents can be used in the low refractive index layer. Also, the low refractive index layer can contain tackifiers and other additives. The crosslinking agents and tackifiers can be appropriately selected from the same ones that can be used in the high refractive index adhesive layer, and appropriate amounts can be used.

[0188] In an embodiment where the pressure-sensitive adhesive composition used for forming the low refractive index pressure-sensitive adhesive layer contains a crosslinking agent, an isocyanate-based crosslinking agent can be preferably adopted as the above crosslinking agent. In some embodiments, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the base polymer of the pressure-sensitive adhesive composition may be, for example, less than 0.5 part by weight, may be less than 0.3 part by weight, may be less than 0.2 part by weight, or may be less than 0.15 part by weight from the viewpoint of adhesion to the high refractive index pressure-sensitive adhesive layer and the like. Also, from the viewpoint of appropriately exerting the effect of the crosslinking agent, in some embodiments, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the base polymer may be, for example, 0.005 part by weight or more, may be 0.01 part by weight or more, may be 0.05 part by weight or more, or may be 0.08 part by weight or more.

[0189] <Production of the pressure-sensitive adhesive layer> In the technology disclosed herein, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer (which may be a high refractive index pressure-sensitive adhesive layer and / or a low refractive index layer. The same applies hereinafter) can be a pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition in a form such as a solvent type, an active energy ray curable type, a water dispersion type, a hot melt type, etc. by drying, crosslinking, polymerization, cooling, etc., that is, a cured product of the above pressure-sensitive adhesive composition. As the curing means of the pressure-sensitive adhesive composition (for example, drying, crosslinking, polymerization, cooling, etc.), only one type may be applied, or two or more types may be applied simultaneously or stepwise. In the case of a solvent type pressure-sensitive adhesive composition, typically, the composition can be dried (preferably, further crosslinked) to form a pressure-sensitive adhesive. In the case of an active energy ray curable type pressure-sensitive adhesive composition, typically, a pressure-sensitive adhesive is formed by irradiating active energy rays to cause a polymerization reaction and / or a crosslinking reaction to proceed. When it is necessary to dry the active energy ray curable type pressure-sensitive adhesive composition, it is advisable to irradiate active energy rays after drying.

[0190] In the technology disclosed herein, the adhesive layer can be formed by applying (e.g., coating) an adhesive composition onto a suitable surface and then curing the composition. The application of the adhesive composition can be carried out using conventional coaters such as, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, etc.

[0191] In the technology disclosed herein, the adhesive layer may be a post-curable adhesive layer or a non-post-curable adhesive layer. Here, the post-curable adhesive layer refers to an adhesive layer that can be further cured by irradiation with heat or active energy rays (e.g., ultraviolet rays). Examples of the post-curable adhesive layer include an adhesive layer having unreacted ethylenically unsaturated groups in the side chain of the base polymer and an adhesive layer containing unreacted polyfunctional monomers. In some embodiments, it is preferable that the adhesive layer is non-post-curable. Since the non-post-curable adhesive layer does not cause dimensional changes associated with the post-curing reaction (i.e., has good dimensional stability), it is easy to suppress warping of the adhesive layer or the adherend to which the adhesive layer is attached. The absence of dimensional changes (e.g., curing shrinkage) due to post-curing can also be advantageous from the viewpoint of suppressing optical distortion of the adhesive layer.

[0192] The thickness of the adhesive layer is not particularly limited and can be, for example, 3 μm or more, preferably 5 μm or more. With an adhesive layer having a thickness of 5 μm or more, good adhesive properties are easily obtained. Further, an adhesive layer having such a thickness can absorb irregularities present on the surface of the adherend and is easily bonded to the adherend with good adhesion. The fact that the thickness of the adhesive layer (for example, the thickness of the high refractive index adhesive layer) is 5 μm or more is also preferable from the viewpoint of preventing coloration and color unevenness due to light interference. In some embodiments, the thickness of the adhesive layer may 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. Also, in some embodiments, the thickness of the adhesive layer may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. The fact that the thickness of the adhesive layer is not too large can be advantageous from the viewpoint of thinning the laminated sheet or the light-emitting device including the adhesive layer. The technology disclosed herein can be preferably implemented, for example, in an embodiment where the thickness of the adhesive layer is in the range of 3 μm to 200 μm (more preferably 5 μm to 100 μm). In some embodiments, the thickness of the adhesive layer described above can be applied at least to 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 described above can be applied to the thickness T2 of the low refractive index layer regardless of whether it is an adhesive layer or not. The thickness T1 of the high refractive index adhesive layer and the thickness T2 of the low refractive index layer may 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 be, for example, 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. Also, the above ratio (T1 / T2) can be, for example, 20 or less, 10 or less, 5 or less, or 3 or less. In some embodiments, the above ratio (T1 / T2) may be less than 2, less than 1.5, or less than 1.

[0193] As a method for obtaining a structure (laminated sheet) in which a high refractive index adhesive layer and a low refractive index layer (typically, a low refractive index adhesive layer) are laminated, for example, a method of forming a high refractive index adhesive layer and a low refractive index layer on a release surface (e.g., the release surface of a release liner) and laminating them, a method of applying a composition for forming a low refractive index layer on the high refractive index adhesive layer and curing it, conversely, a method of applying an adhesive composition for forming a high refractive index adhesive layer on the low refractive index layer and curing it, etc. can be adopted, but it is not limited thereto. When laminating a previously formed high refractive index adhesive layer and a low refractive index layer, a treatment for promoting the adhesion of these layers may be performed as necessary. For example, autoclave treatment, roll press treatment, etc. can be performed, but it is not limited thereto.

[0194] <Support substrate> The high refractive index adhesive layer and the low refractive index layer may be laminated in this order or in the reverse order on one surface of the support substrate. The structure in which the high refractive index adhesive layer and the low refractive index layer are laminated on the support substrate can also be understood as an adhesive sheet with a substrate. Therefore, according to this specification, an adhesive sheet with a substrate (adhesive product) including a laminated sheet composed of a high refractive index adhesive layer and a low refractive index layer (preferably a low refractive index adhesive layer) and a support substrate supporting the laminated sheet is provided.

[0195] The material of the support substrate is not particularly limited and can be appropriately selected according to the purpose of use, usage mode, etc. Non-limiting examples of the support substrate that can be used include polyolefin films mainly composed of polyolefins such as polypropylene (PP) and ethylene-propylene copolymers, polyester films mainly composed of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), plastic films such as polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets made of foams such as polyurethane foams, polyethylene (PE) foams, and polychloroprene foams; various fibrous substances (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc. can be used.) woven fabrics and non-woven fabrics by single or blended spinning, etc.; papers such as Japanese paper, high-quality paper, kraft paper, and crepe paper; metal foils such as aluminum foil and copper foil; etc. A substrate having a composite structure of these may also be used. Examples of such a composite substrate include, for example, a substrate having a structure in which a metal foil and the above plastic film are laminated, and a plastic substrate reinforced with inorganic fibers such as glass cloth.

[0196] In some embodiments, various film substrates can be preferably used. The above film substrate may be a porous substrate such as a foam film or a non-woven fabric sheet, a non-porous substrate, or a substrate having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, as the above film substrate, those containing an independently shape-maintainable (self-supporting or non-dependent) resin film as a base film can be preferably used. Here, the "resin film" means a resin film having a non-porous structure and typically substantially free of air bubbles (voidless). Therefore, the above resin film is a concept distinct from foam films and non-woven fabrics. As the above resin film, an independently shape-maintainable (self-supporting or non-dependent) one can be preferably used. The above resin film may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

[0197] Examples of the material constituting the resin film include polyester resins mainly composed of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins mainly composed of polyolefins 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 (PA) resins such as nylon 6, nylon 66, and partially aromatic polyamide; polyimide (PI) resins; transparent polyimide resins; polyamideimide (PAI); polyetheretherketone (PEEK); polyethersulfone (PES); cyclic polyolefin resins such as 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); fluorine-based resins such as polytetrafluoroethylene (PTFE) and fluorinated polyimide, and the like.

[0198] The above resin film may be formed using a resin material containing only one such resin, or may be formed using a resin material in which two or more are blended. The above resin film may be unstretched, or may be stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, PP / PE blend film, etc. can be preferably used. Examples of resin films preferred from the viewpoints of strength and dimensional stability include PET film, PEN film, PPS film, and PEEK film. PET film and PPS film are particularly preferred from the viewpoint of easy availability, and among them, PET film is preferred.

[0199] In the resin film, known additives such as a light stabilizer, an antioxidant, an antistatic agent, a colorant (dye, pigment, etc.), a filler, a slip agent, and an antiblocking agent can be blended as necessary within a range that does not significantly hinder the effects of the present invention. The blending amount of the additive is not particularly limited and can be appropriately set according to the use of the adhesive sheet and the like.

[0200] The method for manufacturing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding can be appropriately employed.

[0201] The above base material can be substantially composed of such a base film. Alternatively, the above base material may include an auxiliary layer in addition to the above base film. Examples of the above auxiliary layer include an optical property adjustment layer (for example, a coloring layer, an antireflection layer), a printing layer or a laminate layer for imparting a desired appearance to the base material, an antistatic layer, an undercoat layer, and a surface treatment layer such as a release layer.

[0202] In some embodiments, as the support substrate, a substrate having light transmissivity (hereinafter also referred to as a light-transmissive substrate) can be preferably employed. Thereby, it becomes possible to form an adhesive sheet with a light-transmissive substrate. The total light transmittance of the light-transmissive substrate may be, for example, more than 50%, and may also be 70% or more. In some preferred embodiments, the total light transmittance of the support substrate is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). The above total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a product named "HAZEMETER HM-150" manufactured by Murakami Color Research Institute or its equivalent is used. Preferred examples of the above light-transmissive substrate include resin films having light transmissivity. The above light-transmissive substrate may be an optical film.

[0203] The thickness of the substrate is not particularly limited and can be selected according to the purpose of use, usage mode, etc. The thickness of the substrate may be, for example, 500 μm or less, preferably 300 μm or less from the viewpoints of handleability and processability, and may also be 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, or 10 μm or less. When the thickness of the substrate becomes smaller, the followability to the surface shape of the adherend tends to improve. Also, from the viewpoints of handleability, processability, etc., the thickness of the substrate may be, for example, 2 μm or more, and may also be 10 μm or more or 25 μm or more.

[0204] On the surface of the base material on the side where the adhesive layer is laminated, if necessary, conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of an undercoat layer by applying an undercoat agent (primer) may be performed. Such a surface treatment can be a treatment for improving the anchoring property of the adhesive layer to the base material. The composition of the primer used for forming the undercoat layer is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, but usually about 0.01 μm to 1 μm is appropriate, and about 0.1 μm to 1 μm is preferable. Other treatments that can be applied to the base material as necessary include antistatic layer formation treatment, colored layer formation treatment, printing treatment, and the like. These treatments can be applied alone or in combination.

[0205] In the technology disclosed herein, when a high refractive index adhesive layer and a low refractive index layer constitute a pressure-sensitive adhesive sheet with a base material, the thickness of the pressure-sensitive adhesive sheet may 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. Also, from the viewpoint of handleability and the like, the thickness of the above pressure-sensitive adhesive sheet may be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more. Note that the thickness of the pressure-sensitive adhesive sheet refers to the thickness of the portion adhered to the adherend. For example, in the base material-less double-sided pressure-sensitive adhesive sheet 2 having the configuration shown in FIG. 2, it refers to the thickness from the first surface (first adhesive surface) 10A to the second surface (second adhesive surface) 10B of the adhesive layer, and does not include the thickness of the release liners 31 and 32.

[0206] <Laminated Sheet with Release Liner> Before being incorporated into a light-emitting device, the high refractive index adhesive layer and the low refractive index layer disclosed herein can be in the form of a pressure-sensitive adhesive product (a laminated sheet with a release liner) in which the adhesive surface of a laminated sheet including the high refractive index adhesive layer and the low refractive index layer is brought into contact with the release surface of a release liner. Therefore, according to this specification, there is provided a laminated sheet with a release liner (pressure-sensitive adhesive product) including a laminated sheet of a high refractive index adhesive layer and a low refractive index layer, and a release liner having a release surface that contacts the adhesive surface of the laminated sheet.

[0207] The release liner is not particularly limited. For example, a release liner having a release treatment layer on a release liner substrate such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), or a release liner made of a resin film formed of a low-adhesion material such as a fluoropolymer (such as polytetrafluoroethylene) or a polyolefin resin (such as polyethylene or polypropylene) can be used. The release treatment layer can be 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 fluorine-based release treatment agent, or molybdenum(IV) sulfide. In some embodiments, a release liner having a release treatment layer formed by a silicone-based release treatment agent can be preferably employed. The thickness and formation method of the release treatment layer are not particularly limited and can be set so as to exhibit appropriate releasability on the surface on the adhesive side of the release liner.

[0208] In some embodiments, from the viewpoint of the smoothness of the adhesive surface and the like, a release liner (hereinafter also referred to as a release film) having a configuration in which a release treatment layer is provided on a resin film (hereinafter also referred to as a release film substrate) as the release liner substrate can be preferably employed. As the release film substrate, various plastic films can be used. In this specification, a plastic film is typically a non-porous sheet and is, for example, a concept that is distinguished from a non-woven fabric (that is, does not include a non-woven fabric).

[0209] Examples of the material of the plastic film 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; cyclic polyolefin resins such as 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 resins, etc. A release film substrate formed from any one or a mixture of two or more of these resins can be used. Among them, a polyester resin film (e.g., PET film) formed from a polyester resin is preferably used as the release film substrate.

[0210] The plastic film used as the above-described release film substrate may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Also, the plastic film may have a single-layer structure or a multilayer structure including two or more sub-layers. Known additives that can be used for the release film substrate of the adhesive sheet, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, and nucleating agents, may be compounded in the plastic film. In a plastic film having a multilayer structure, each additive may be compounded in all sub-layers or only in some sub-layers.

[0211] In some preferred embodiments, as the release film substrate (typically a plastic film), the content of particles such as inorganic particles (which can be, for example, pigments, lubricants, fillers, etc.) in the layer on the release surface side is restricted, or a substrate substantially free of such particles can be preferably used. Here, being substantially free means that the amount of particles (e.g., inorganic particles) in the layer is less than 1% by weight, preferably less than 0.1% by weight (e.g., 0 to 0.01% by weight). A release film provided with such a release film substrate is likely to have a low arithmetic mean roughness Ra and maximum height Rz of the release surface. When the release film substrate (typically a plastic film) has a multilayer structure, the particle content in the layer on the release surface side can be 1 / 10 or less (e.g., 1 / 50 or less) of the particle content in the layers other than the layer on the release surface side.

[0212] In a laminated sheet with a release liner having a form in which a release liner is provided on each of the first adhesive surface and the second adhesive surface, the release liner disposed on one adhesive surface (hereinafter also referred to as one release liner) and the release liner disposed on the other adhesive surface (hereinafter also referred to as the other release liner) may have the same kind of material and configuration, or may have different materials and configurations.

[0213] The thickness of the release liner (preferably a release film) is not particularly limited and can be, for example, about 10 μm to 500 μm. From the viewpoints of the strength and dimensional stability of the release liner, the thickness of the release liner is suitably 20 μm or more, preferably 30 μm or more, may be 35 μm or more, may be 40 μm or more, or may be 45 μm or more. Also, from the viewpoints of the handleability of the release liner (e.g., ease of winding), etc., the thickness of the release liner is suitably 300 μm or less, preferably 250 μm or less, may be 200 μm or less, may be 150 μm or less, or may be 130 μm or less. In some preferred embodiments, the thickness of the release liner is approximately 125 μm or less, may be approximately 115 μm or less, may be approximately 105 μm or less, may be approximately 90 μm or less, or may be approximately 70 μm or less. By setting the thickness of the release liner to a predetermined value or less, it becomes difficult for winding marks to occur when it is made into a roll shape, the removal from the adhesive sheet becomes smooth, and high surface smoothness is easily obtained on the adhesive surface after the release liner is removed.

[0214] In the laminated sheet with a release liner in an embodiment including one release liner and the other release liner, the thicknesses of those release liners may be the same or different. In some embodiments, from the viewpoints of release workability, etc., it is preferable that one release liner and the other release liner have different thicknesses. For example, it is preferable that the thickness of the thicker release liner is approximately 1.1 times or more (e.g., approximately 1.25 times or more. The upper limit is not particularly limited, but is, for example, 5 times or less) the thickness of the thinner release liner.

[0215] (Arithmetic mean roughness Ra of the surface on the adhesive side) In some embodiments, it is preferable from the viewpoint of realizing a pressure-sensitive adhesive surface having high surface smoothness that the arithmetic mean roughness Ra of the surface on the pressure-sensitive adhesive side of the release liner (preferably a release film) is limited to a predetermined value or less (for example, approximately 100 nm or less, more preferably less than 50 nm). In some embodiments, the arithmetic mean roughness Ra of the surface on the pressure-sensitive adhesive side of the release liner is preferably, for example, approximately 30 nm or less, more preferably approximately 25 nm or less, may be approximately 20 nm or less, or may be approximately 18 nm or less. Also, from the viewpoints of ease of manufacturing and handleability of the release liner, etc., in some embodiments, the arithmetic mean roughness Ra may be, for example, approximately 5 nm or more, may be approximately 10 nm or more, or may be approximately 15 nm or more. In a laminated sheet with a release liner in which release liners are respectively disposed on the first pressure-sensitive adhesive surface and the second pressure-sensitive adhesive surface, it is preferable that the surfaces on the pressure-sensitive adhesive side of both release liners satisfy any of the above-described arithmetic mean roughnesses Ra. The arithmetic mean roughnesses Ra of the surfaces on the pressure-sensitive adhesive side of both release liners may be the same or different.

[0216] (Maximum height Rz of the surface on the pressure-sensitive adhesive side) In some embodiments, it is preferable from the viewpoint of realizing a pressure-sensitive adhesive surface having high surface smoothness that the maximum height Rz of the surface on the pressure-sensitive adhesive side of the release liner (preferably a release film) is 700 nm or less. In some embodiments, the maximum height Rz of the surface on the pressure-sensitive adhesive side of the release liner is preferably approximately 600 nm or less, may be approximately 500 nm or less, may be approximately 400 nm or less, or may be approximately 300 nm or less. Also, from the viewpoints of ease of manufacturing and handleability of the release liner, etc., in some embodiments, the maximum height Rz may be, for example, approximately 50 nm or more, may be approximately 80 nm or more, may be approximately 100 nm or more, may be approximately 200 nm or more, or may be approximately 300 nm or more. In a laminated sheet with a release liner in which release liners are respectively disposed on the first pressure-sensitive adhesive surface and the second pressure-sensitive adhesive surface, it is preferable that the surfaces on the pressure-sensitive adhesive side of both release liners satisfy any of the above-described maximum heights Rz. The maximum heights Rz of the surfaces on the pressure-sensitive adhesive side of both release liners may be the same or different.

[0217] (Surface properties of the back side) The arithmetic mean roughness Ra and the maximum height Rz of the back side (the side opposite to the adhesive layer side) of the release liner (preferably a release film) are not particularly limited. From the viewpoint of productivity and the like, the arithmetic mean roughness Ra of the back side of the release liner may be, for example, more than 30 nm (for example, more than 35 nm, and further, approximately 50 nm or more). The maximum height Rz of the back side of the release liner may be, from the viewpoint of productivity and the like, for example, more than 400 nm (for example, approximately 500 nm or more), and may also be more than 800 nm (for example, 1000 nm or more).

[0218] The arithmetic mean roughness Ra and the maximum height Rz of the surface of the release film can be adjusted by surface treatments such as the selection of film materials, molding methods, and release treatments. For example, adjustment of the smoothness of the layer constituting the release surface (antiblocking layer, hard coat layer, oligomer prevention layer, etc.), reduction or non-use (particle-free) of filler particles in the surface layer or the release film substrate, and adjustment of stretching conditions, etc. can be mentioned.

[0219] The arithmetic mean roughness Ra and the maximum height Rz of the surface of the release liner (preferably a release film) are measured using a non-contact surface roughness measuring device. As the non-contact surface roughness measuring device, a surface roughness measuring device using an optical interference method is used, and for example, a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation) or its equivalent can be used. For example, a glass plate (soda lime glass plate manufactured by MATSUNAMI, thickness 1.3 mm) is bonded and fixed to the surface opposite to the measurement surface of the release liner with an adhesive, and the surface shape can be measured using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation) in an environment of 23°C and 50% RH.

[0220] <Use> In the technology disclosed herein, the high refractive index adhesive layer can be used by being bonded to various adherends constituting a light-emitting device. The constituent material (adherend material) of the adherend is not particularly limited. For example, metals such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, etc., or alloy and other metal materials containing two or more of these, or various resin materials such as polyimide-based resins, acrylic-based resins, polyether nitrile-based resins, polyether sulfone-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 (so-called aramid resins, etc.), polyarylate-based resins, fluorine-based resins, polycarbonate-based resins, cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose, vinyl butyral-based polymers, liquid crystal polymers, carbon materials such as graphene (typically plastic materials), metal oxides such as alumina, zirconia, titania, SiO2, ITO (indium tin oxide), ATO (antimony-doped tin oxide) and their mixtures, nitrides such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, indium nitride and their composites, inorganic materials such as alkali glass, alkali-free glass, quartz glass, borosilicate glass, sapphire glass carbon, etc. can be mentioned. The high refractive index adhesive layer disclosed herein can be used by being attached to a member (for example, an optical member) at least the surface of which is made of the above materials. Further, the low refractive index layer (preferably a low refractive index adhesive layer) in the technology disclosed herein can be used by being laminated (for example, bonded) to the above-described various adherends.

[0221] The high refractive index adhesive layer disclosed herein can be used in an attachment mode that does not require heating to a temperature higher than a temperature range around room temperature (e.g., 20°C to 35°C) after being attached to an adherend. Further, when permitted according to the type of the adherend or the like, a heat treatment may be performed at least at any one of the timing after attachment to the adherend, the timing of attachment, and before attachment. The heat treatment can be performed for the purpose of improving the adhesion of the adhesive to the adherend or promoting adhesion. The heat treatment temperature can be appropriately set within a range permitted according to the constituent materials of the adhesive sheet and the type of the adherend, taking into account the surface state of the adherend or the like, so as to obtain a desired effect. For example, it may be about 100°C or lower, 80°C or lower, 60°C or lower, or 50°C or lower.

[0222] The members or materials to which the adhesive layer is to be attached can be light-transmissive. In such adherends, the advantage that the high refractive index adhesive layer disclosed herein has high transparency is easily obtained. The total light transmittance of the above adherend may be, for example, more than 50%, or may be 70% or more. In some preferred embodiments, the total light transmittance of the above adherend is 80% or more, more preferably 90% or more, and even more preferably 95% or more (e.g., 95 to 100%). The high refractive index adhesive layer disclosed herein can be preferably used in a mode of being attached to an adherend (e.g., an optical member) having a total light transmittance of a predetermined value or more. The above total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a product named "HAZEMETER HM-150" manufactured by Murakami Color Research Laboratory or its equivalent is used.

[0223] 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 in contact with the adherend may be the same or different. For example, by making the refractive index of the adhesive layer relatively higher than that of the adherend, light incident on the adhesive layer from the adherend side at an angle below the critical angle can be refracted to the front side, and the front luminance can be increased. In this case, the refractive index of the adherend may be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, may be less than 1.45, and may be, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. Also, according to an adherend having a relatively high refractive index with respect to the adhesive layer, light incident on the adherend from the adhesive layer side can be refracted to the front side, and the front luminance can be increased. In this case, the refractive index of the adherend may be, for example, 1.60 or more, 1.65 or more, or 1.70 or more, and may be, 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 may be about 1.55 to 1.80, may be about 1.55 to 1.75, or may be about 1.60 to 1.70. The refractive index of the adherend can be measured in the same manner as the refractive index of the adhesive.

[0224] In some preferred embodiments, the above-mentioned adherend may have any of the refractive indices described above and any of the total light transmittances described above. In a light-emitting device in the form in which a high refractive index adhesive layer and / or a low refractive index layer is attached or laminated to such an adherend, the effects of the technology disclosed herein are particularly preferably exhibited.

[0225] The high refractive index adhesive layer and the low refractive index layer disclosed herein can be used by being attached to various adherends as described above in the form of a laminated sheet containing them. As an example of a preferred use, optical applications can be mentioned. More specifically, for example, as an optical adhesive sheet used for applications such as bonding optical members (for bonding optical members) or for manufacturing applications of products (optical products) using the above optical members, the laminated sheet disclosed herein can be preferably used. The laminated sheet used in such a manner can also be understood as an interlayer sheet disposed between the layers of an optical laminate.

[0226] The above optical member refers to a member having optical properties (for example, polarization property, light refraction property, light scattering property, light reflection property, light transmittance, light absorption property, light diffraction property, optical rotation property, visibility, etc.). The above optical member is not particularly limited as long as it is a member having optical properties, and examples thereof include members constituting devices (optical devices) such as display devices (image display devices) and input devices, or members used in these devices. For example, polarizing plates, wavelength plates, retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflection films, antireflection films, hard coat (HC) films, shock absorption films, antifouling films, photochromic films, dimming films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and further members in which these are laminated (these may be collectively referred to as "functional films"). Note that the above "plates" and "films" include plate-like, film-like, sheet-like forms, etc. For example, a "polarizing film" includes a "polarizing plate" and a "polarizing sheet", etc., and a "light guide plate" includes a "light guide film" and a "light guide sheet", etc. Also, the above "polarizing plate" includes a circular polarizing plate.

[0227] Examples of the above display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a micro LED (μLED), a mini LED (miniLED), a PDP (plasma display panel), and an electronic paper. Examples of the above input device include a touch panel.

[0228] The above optical member is not particularly limited. For example, members made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, etc. (for example, sheet-like, film-like, or plate-like members) can be mentioned. In addition, the "optical member" in this specification shall also include members (such as design films, decorative films, and surface protection films) that play a role in decoration and protection while maintaining the visibility of display devices and input devices.

[0229] The high refractive index adhesive layer disclosed herein (which can be in the form of a laminated sheet with a low refractive index layer) can be used, for example, in a manner disposed between an optical film such as a film or a fluorescent film having one or more functions such as light transmission, reflection, diffusion, waveguide, light collection, diffraction, etc., and another optical member (which can be another optical film). Preferably, it can be used to bond the above optical film and the above other optical member. Among them, in the bonding of an optical film having at least one function of light waveguide, light collection, and diffraction, it is desirable that the entire bulk of the bonding layer has a high refractive index, and it can be a preferred application target of the technology disclosed herein.

[0230] The high refractive index adhesive layer disclosed herein can be preferably used for bonding optical films such as a light guide film, a diffusion film, a fluorescent film, a color - tuning film, a prism sheet, a lenticular film, a microlens array film, etc. In these applications, from the viewpoints of the trend towards miniaturization and high - performance of optical members, thinning and improvement of light extraction efficiency are required. As an adhesive layer capable of meeting such requirements, the high refractive index adhesive layer disclosed herein can be preferably utilized. More specifically, for example, in bonding a light guide film or a diffusion film, adjusting (for example, increasing) the refractive index of the adhesive layer as a bonding layer can contribute to thinning. In bonding a fluorescent film, by appropriately adjusting the refractive index difference between the fluorescent emitter and the adhesive, the light extraction efficiency (which can also be grasped as the emission efficiency) can be improved. In bonding a color - tuning film, by appropriately adjusting the refractive index of the adhesive so that the refractive index difference from the color - tuning pigment becomes small, the scattering component can be reduced, contributing to the improvement of light transmittance. In bonding a prism sheet, a lenticular film, a microlens array film, etc., by appropriately adjusting the refractive index of the adhesive, the diffraction of light can be controlled, contributing to the improvement of luminance and / or viewing angle.

[0231] The high refractive index adhesive layer disclosed herein (which may be in the form of a laminated sheet with a low refractive index layer) is preferably used in a manner of being attached to a high refractive index adherend (which may be a high refractive index layer, member, etc.), and can suppress the interfacial reflection with the above adherend. The high refractive index adhesive layer used in such a manner preferably has a small refractive index difference from the high refractive index adherend as described above and high adhesion at the interface with the adherend. Further, from the viewpoint of enhancing the homogeneity of the appearance, it is preferable that the thickness uniformity of the adhesive layer is high. For example, it is preferable that the surface smoothness of the adhesive surface is high. When the thickness of the high refractive index adherend is relatively small (for example, 5 μm or less, 4 μm or less, or 2 μm or less), it is particularly meaningful to suppress the reflection at the interface from the viewpoint of suppressing coloration and color unevenness due to the interference of reflected light. As an example of such a usage mode, in a polarizing plate with a retardation layer including a polarizer, a first retardation layer, and a second retardation layer in this order, a mode used for bonding the above polarizer and the above first retardation layer and / or bonding the above first retardation layer and the above second retardation layer can be mentioned.

[0232] Further, the high refractive index adhesive layer disclosed herein can be preferably used in a manner of being attached to a light-emitting layer such as an optical semiconductor (for example, a high refractive index light-emitting layer mainly composed of an inorganic material). By reducing the refractive index difference between the light-emitting layer and the high refractive index adhesive layer, the reflection at their interface can be suppressed, and the light extraction efficiency can be improved. Further, from the viewpoint of preventing the deterioration of the self-luminous element due to moisture, it is preferable that the water absorption rate of the high refractive index adhesive layer is low. From the viewpoint of improving the luminance, it is preferable that the high refractive index adhesive layer has low coloration. This can also be advantageous from the viewpoint of suppressing unintentional coloration caused by the high refractive index adhesive layer.

[0233] The high refractive index adhesive layer disclosed herein can be preferably used as a coating layer covering the lens surface, a bonding layer with a member facing the lens surface (for example, a member having a surface shape corresponding to the lens surface), a filling layer filled between the lens surface and the member, etc. in a microlens or other lens members (for example, microlenses constituting a microlens array film, lens members such as microlenses for cameras) used as components of a camera, a light emitting device, etc. The high refractive index adhesive layer disclosed herein can reduce the refractive index difference from a lens (for example, a lens made of a high refractive index resin or a lens having a surface layer made of a high refractive index resin) even when it is disposed in contact with the high refractive index lens. This is advantageous from the viewpoint of thinning the lens and the product provided with the lens, and can also contribute to suppression of aberration and improvement of the Abbe number. In the technology disclosed herein, the adhesive (viscoelastic material) constituting the high refractive index adhesive layer can itself be used as a lens resin, for example, in a form filled in a concave portion or a void of a suitable transparent member.

[0234] As a mode of bonding optical members using the adhesive layer (a high refractive index adhesive layer and / or a low refractive index adhesive layer, preferably a high refractive index adhesive layer which may be laminated on the low refractive index layer) disclosed herein, it is not particularly limited. For example, (1) a mode of bonding optical members via the adhesive layer disclosed herein, (2) a mode of bonding an optical member to a member other than an optical member via the adhesive layer disclosed herein, or (3) a mode in which the adhesive layer disclosed herein is in the form of an adhesive sheet containing an optical member and the adhesive sheet is bonded to an optical member or a member other than an optical member may be used. In the mode of (3) above, the adhesive sheet in the form containing an optical member may be, for example, an adhesive sheet whose support is an optical member (e.g., an optical film). Thus, the adhesive sheet in the form containing an optical member as the support can also be regarded as a pressure-sensitive adhesive type optical member (e.g., a pressure-sensitive adhesive type optical film). Further, when the adhesive layer disclosed herein constitutes an adhesive sheet having a support, and the above 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.

[0235] From the above, according to the technology disclosed herein, an optical laminate including the adhesive layer disclosed herein and a member (e.g., a resin film such as an optical film) laminated by pasting or the like of the adhesive layer is provided. The member laminated by pasting or the like of the adhesive layer may have the refractive index of the adherend material described above. Further, the difference in refractive index (refractive index difference) between the refractive index of the adhesive layer and the refractive index of the member may be the refractive index difference between the adherend and the adhesive layer described above. Regarding the members constituting the laminate, since they are as described above for the members, materials, and adherends, repeated explanations will not be repeated.

[0236] As can be understood from the above description and the following examples, the matters disclosed by this specification include the following. [1] An adhesive sheet containing an adhesive layer, having an adhesive surface constituted by the above adhesive layer, The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a refractive index exceeding 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less. 〔2〕 The pressure-sensitive adhesive sheet according to 〔1〕 above, wherein the pressure-sensitive adhesive layer has a thickness of 5 μm or more. 〔3〕 The pressure-sensitive adhesive sheet according to 〔1〕 or 〔2〕 above, having a peel strength (adhesive force) to a glass plate of 3 N / 25 mm or more. 〔4〕 The pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔3〕 above, wherein the adhesive surface has an arithmetic mean roughness Ra of 100 nm or less. 〔5〕 The pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔4〕 above, wherein the pressure-sensitive adhesive layer has a water absorption rate of 1.0% or less. 〔6〕 The pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔5〕 above, which is configured as a laminate including the pressure-sensitive adhesive layer and a light-transmissive substrate. 〔7〕 The pressure-sensitive adhesive sheet according to 〔6〕 above, wherein the light-transmissive substrate is a resin film. 〔8〕 The pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔5〕 above, which is a double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer. 〔9〕 The pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔8〕 above, a release liner disposed on the adhesive surface of the pressure-sensitive adhesive sheet, and a pressure-sensitive adhesive sheet with a release liner including the same. 〔10〕 An adhesive composition used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of 〔1〕 to 〔8〕 above.

[0237] 〔11〕 An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit, and an additive (H RO ) which is an organic material having a higher refractive index than the acrylic polymer (A), and an adhesive composition including the same. 〔12〕 The adhesive composition according to 〔11〕 above, wherein the refractive index of the additive (H RO ) is 1.60 or more. 〔13〕 With respect to 100 parts by weight of the acrylic polymer (A), the above additive (H ROThe content of 〔14〕 The above additive (H RO ) contains at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocyclic ring-containing compound, and is the pressure-sensitive adhesive composition according to any one of the above

[11] to

[13] . 〔15〕 The above additive (H RO ) contains a compound having two or more aromatic rings in one molecule, and is the pressure-sensitive adhesive composition according to any one of the above

[11] to

[14] . 〔16〕 The above additive (H RO ) is, as the compound having two or more aromatic rings in one molecule, (i) contains a structure in which two non-condensed aromatic rings are directly chemically bonded, and (ii) contains a structure in which two aromatic rings are condensed, and is the pressure-sensitive adhesive composition according to the above

[15] , which contains a compound satisfying at least one of them. 〔17〕 In the monomer component constituting the above acrylic polymer (A), the content of the above aromatic ring-containing monomer (m1) is 50% by weight or more, and is the pressure-sensitive adhesive composition according to any one of the above

[11] to

[16] . 〔18〕 In the monomer component constituting the above acrylic polymer (A), the content of the above aromatic ring-containing monomer (m1) exceeds 70% by weight and is less than 100% by weight, and 50% by weight or more of the above aromatic ring-containing monomer (m1) is a monomer having a glass transition temperature of 10°C or lower for the homopolymer, and is the pressure-sensitive adhesive composition according to any one of the above

[11] to

[17] . 〔19〕 The monomer component constituting the above acrylic polymer (A) further contains a monomer (m2) having at least one of a hydroxyl group and a carboxyl group, and is the pressure-sensitive adhesive composition according to any one of the above

[11] to

[18] . 〔20〕 The pressure-sensitive adhesive composition according to any one of the above

[11] to

[18] , which is used to form the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of the above [1] to [8]. An adhesive formed from the adhesive composition according to any one of the above

[11] to

[20] , having a refractive index higher than 1.570. 〔22〕 An adhesive sheet including an adhesive layer composed of an adhesive formed from the adhesive composition according to any one of the above

[11] to

[20] . 〔23〕 The adhesive sheet according to the above

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

[0238] 〔24〕 An interlayer sheet used by being disposed between layers of a laminate in optical applications, including a viscoelastic layer V1 having a refractive index n1 of 1.570 or more, and having a total light transmittance of 86% or more; having a haze value of 1.0% or less; and, having a storage elastic modulus G' at 25°C of 30 kPa to 700 kPa; An interlayer sheet satisfying the above conditions. 〔25〕 The interlayer sheet according to the above

[24] , having a thickness of 5 μm or more. 〔26〕 The interlayer sheet according to the above

[24] or

[25] , wherein the viscoelastic layer V1 includes a main polymer and a plasticizing material having a lower molecular weight than the main polymer. 〔27〕 The interlayer sheet according to the above

[26] , wherein the weight average molecular weight of the plasticizing material is 30,000 or less. 〔28〕 Further including a viscoelastic layer V2 laminated on the viscoelastic layer V1, wherein the storage elastic modulus G' at 25°C of the viscoelastic layer V2 V2 is lower than the storage elastic modulus G' at 25°C of the viscoelastic layer V1 V1 The interlayer sheet according to any one of the above

[24] to

[27] . 〔29〕 The interlayer sheet according to the above

[28] , wherein the refractive index n2 of the viscoelastic layer V2 is lower than the refractive index n1 of the viscoelastic layer V1. 〔30〕 The interlayer sheet according to any one of the above

[24] to

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

[11] to

[18] .

[31] The viscoelastic layer V1 is an interlayer sheet according to any one of the above

[24] to

[29] , which is an adhesive layer in the pressure-sensitive adhesive sheet according to any one of the above [1] to [5].

[32] An interlayer sheet according to any one of the above

[24] to

[31] , and a resin film laminated on the interlayer sheet, An optical laminate comprising:

[33] An interlayer sheet according to any one of the above

[24] to

[31] , and a release liner covering at least one surface of the interlayer sheet, An interlayer sheet with a release liner comprising:

[0239]

[34] A self-luminous element, a low refractive index layer disposed on the viewing side of the self-luminous element, a high refractive index pressure-sensitive adhesive layer laminated in direct contact with the low refractive index layer, Comprising, The high refractive index pressure-sensitive adhesive layer has a refractive index n1 of more than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less. A light-emitting device.

[35] The light-emitting device according to the above

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

[36] The light-emitting device according to the above

[35] or

[36] , wherein the arithmetic mean roughness Ra of the surface of the high refractive index pressure-sensitive adhesive layer is 100 nm or less.

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

[34] to

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

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

[34] to

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

[39] The laminated sheet composed of the high refractive index pressure-sensitive adhesive layer and the low refractive index layer has a total light transmittance of 86% or more and a haze value of 3.0% or less. The light-emitting device according to any one of the above

[34] to

[38] . 〔40〕The light-emitting device according to any one of 〔34〕~〔39〕, wherein the high refractive index adhesive layer is a layer formed from the adhesive composition according to any one of 〔11〕~〔18〕. 〔41〕The light-emitting device according to any one of 〔34〕~〔40〕, wherein the high refractive index adhesive layer is an adhesive layer in the adhesive sheet according to any one of 〔1〕~〔5〕.

[0240] 〔101〕An adhesive containing an acrylic polymer (F) containing a fluorine-containing acrylic monomer (M1) as a monomer unit, having a refractive index of 1.46 or less, and having a storage elastic modulus G' at 25 °C of 1.0 kPa or more and 400 kPa or less. 〔102〕The adhesive according to 〔101〕, wherein the content of the fluorine-containing acrylic monomer (M1) in the monomer components constituting the acrylic polymer (F) is 25% by weight or more. 〔103〕The adhesive according to 〔101〕 or 〔102〕, wherein the fluorine-containing acrylic monomer (M1) contains a fluorine atom-containing (meth)acrylic acid alkyl ester. 〔104〕The adhesive according to any one of 〔101〕~〔103〕, wherein the acrylic polymer (F) contains a hydroxyl group-containing monomer as a monomer unit. 〔105〕A low refractive index adhesive layer formed from the adhesive according to any one of 〔101〕~〔104〕, and a high refractive index adhesive layer laminated on the low refractive index adhesive layer, and a laminated sheet containing the same. 〔106〕The laminated sheet according to 〔105〕, 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 adhesive layer is 1.02 or more. 〔107〕The laminated sheet according to 〔105〕 or 〔106〕, wherein the refractive index n1 of the high refractive index adhesive layer is more than 1.570. 〔108〕The laminated sheet according to any one of 〔105〕~〔107〕, wherein the high refractive index adhesive layer has a storage elastic modulus G' at 25 °C of 700 kPa or less. [

[109] ] The laminated sheet according to any one of [

[105] ] to [

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

[110] ] A self-luminous element and, the laminated sheet according to any one of [

[105] ] to [

[109] ] above, and a light-emitting device including the same, wherein the laminated sheet is disposed on the visible side of the self-luminous element. [

[111] ] The pressure-sensitive adhesive according to any one of [

[101] ] to [

[104] ] above, which is used to form the viscoelastic layer V2 in the interlayer sheet according to any one of [

[28] ] to [

[31] ] above. [

[112] ] The pressure-sensitive adhesive according to any one of [

[101] ] to [

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

[34] ] to [

[41] ] above.

Examples

[0241] Hereinafter, some experimental aspects related to the present invention will be described. In the following description, "parts" and "%" representing the amount used and the content are based on weight unless otherwise specified.

[0242] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C1> Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 95 parts of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A", refractive index: 1.566, Tg of homopolymer: -35°C. Hereinafter abbreviated as "POB-A"), 5 parts of 4-hydroxybutyl acrylate (4HBA), 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 100 parts of toluene as a polymerization solvent were charged. While gently stirring, nitrogen gas was introduced, and the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature in the flask at around 60°C to prepare a solution (50%) of acrylic polymer A1. The polymerization average molecular weight (Mw) of this acrylic polymer A1 was 500,000. The above acrylic polymer A1 has a Tg (i.e., Tg T) is -35°C, and Tg (i.e., Tg m1 ) based on the composition of the aromatic ring-containing monomer is -35°C. The solution (50%) of the above acrylic polymer A1 was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts of non-volatile matter), 10 parts of a 1% ethyl acetate solution of an isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", a trifunctional isocyanate compound) as a crosslinking agent (0.1 part of non-volatile matter), 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of ferric naphthenate as a crosslinking catalyst (0.01 part of non-volatile matter) were added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C1.

[0243] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C2> Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 72 parts of POB-A, 23 parts of 1-naphthylmethyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate NMT-A", refractive index: 1.595, Tg of homopolymer: 31°C. Hereinafter abbreviated as "NMT-A"), 5 parts of 4HBA, 0.2 part of AIBN as a polymerization initiator, and 100 parts of toluene as a polymerization solvent were charged. While gently stirring, nitrogen gas was introduced, and the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature in the flask at around 60°C to prepare a solution (50%) of acrylic polymer A2. The polymerization average molecular weight (Mw) of this acrylic polymer A2 was 500,000. Into a separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 20 parts of POB-A, 80 parts of NMT-A as monomer components, 0.2 part of AIBN as a polymerization initiator, 3.5 parts of α-thioglycerol as a chain transfer agent, and 67 parts of methyl ethyl ketone were charged. Then, nitrogen gas was passed through, and nitrogen substitution was carried out for about 1 hour while stirring. Thereafter, the flask was heated to 70°C and reacted for 12 hours to obtain an acrylic oligomer (oligomer B) having a weight average molecular weight (Mw) of 4000 and a refractive index of 1.63. The solution (50%) of the above acrylic polymer A2 was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts of non-volatile matter), 20 parts of the oligomer B prepared above, 10 parts of a 1% ethyl acetate solution of an isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", a trifunctional isocyanate compound) (0.1 part of non-volatile matter) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of ferric naphthenate (0.01 part of non-volatile matter) as a crosslinking catalyst were added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C2.

[0244] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C3> Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a 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: Biscoat 8F), 3 parts of N-vinyl-2-pyrrolidone (NVP, manufactured by Nippon Shokubai), 2 parts of 4HBA, 0.2 part of AIBN as a polymerization initiator, and 200 parts of ethyl acetate as a polymerization solvent were charged. While gently stirring, nitrogen gas was introduced, and the polymerization reaction was carried out for 9 hours while maintaining the liquid temperature in the flask at around 60°C to prepare a solution (33%) of an acrylic polymer A3. The polymerization average molecular weight (Mw) of the above acrylic polymer A3 was 550,000. The solution (33%) of the above acrylic polymer A3 was diluted to 30% with ethyl acetate. To 100 parts of non-volatile matter (solid content), 10 parts of a 1% ethyl acetate solution of an isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", a trifunctional isocyanate compound) (0.1 part of non-volatile matter) as a crosslinking agent was added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C3.

[0245] <Production of Adhesive Sheet> (Example 1) The acrylic pressure-sensitive adhesive composition C1 prepared above was applied to the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (thickness: 50 μm) having silicone treatment on one side, and heated at 130°C for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 25 μm. The silicone-treated surface of a PET film R2 (thickness: 38 μm) having silicone treatment on one side was bonded to the surface of the pressure-sensitive adhesive layer. In this way, a pressure-sensitive adhesive layer (high refractive index pressure-sensitive adhesive layer) protected by PET films (release liners) R1 and R2 on both sides was obtained. Note that the release liner R2 has relatively easy peelability compared to the release liner R1. Also, the acrylic pressure-sensitive adhesive composition C3 prepared above was applied to the silicone-treated surface of a PET film R1 (thickness: 50 μm) having silicone treatment on one side, and heated at 130°C for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 10 μm. The silicone-treated surface of a PET film R2 (thickness: 38 μm) having silicone treatment on one side was bonded to the surface of the pressure-sensitive adhesive layer. In this way, a pressure-sensitive adhesive layer (low refractive index pressure-sensitive adhesive layer) protected by PET films (release liners) R1 and R2 on both sides was obtained. The release liner R2 was peeled off from the high refractive index pressure-sensitive adhesive layer and the low refractive index pressure-sensitive adhesive layer, and the adhesive surfaces were bonded together and crimped with a hand roller. The laminate was subjected to autoclave treatment at 50°C and 0.60 MPa for 30 minutes, and then aged in an environment at 50°C for 48 hours. In this way, a laminated sheet (substrate-free double-sided pressure-sensitive adhesive sheet) having a two-layer structure of a high refractive index pressure-sensitive adhesive layer / low refractive index pressure-sensitive adhesive layer was obtained. The surface of this pressure-sensitive adhesive sheet is protected by two release liners R1.

[0246] (Example 2) A laminated sheet (substrate-free double-sided pressure-sensitive adhesive sheet) having a two-layer structure of a high refractive index pressure-sensitive adhesive layer / low refractive index pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the type of the pressure-sensitive adhesive composition used for forming each pressure-sensitive adhesive layer and the thickness of each pressure-sensitive adhesive layer were changed as shown in Table 1.

[0247] (Examples 3 to 5) In the same manner as in Example 1, adhesive layers having a single-layer structure each composed of acrylic adhesive compositions C1 to C3 and having the thicknesses shown in Table 1 were produced to obtain the pressure-sensitive adhesive sheets according to Examples 3 to 5.

[0248] After sufficiently acclimating the obtained pressure-sensitive adhesive sheets to an environment of 23°C and 50% RH, they were used for the following measurements and evaluations.

[0249] <Measurement and Evaluation (1)> (Refractive Index) For each adhesive layer, the refractive index was measured using an Abbe refractometer (manufactured by ATAGO Co., Ltd., 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.

[0250] (Storage Elastic Modulus G') Samples for measurement were prepared by laminating each adhesive layer to a thickness of approximately 1.5 mm. Dynamic viscoelasticity measurement was performed using ARES manufactured by TA Instruments under the following conditions. From the measurement results, the storage elastic modulus G' at 25°C was read. The results are shown in Table 1. [Measurement Conditions] Deformation Mode: Torsion Measurement Frequency: 1 Hz Temperature Increase Rate: 5°C / min Shape: Parallel Plate 7.9 mmφ

[0251] (Total Light Transmittance and Haze Value) Using test pieces prepared by bonding the pressure-sensitive adhesive sheets according to each example to non-alkali glass (thickness 0.8 - 1.0 mm, total light transmittance 92%, haze 0.4%), the total light transmittance and haze of the above test pieces were measured using a haze meter (manufactured by Murakami Color Technology Laboratory, product name "HAZEMETER HM-150") under a measurement environment of 23°C. The values obtained by subtracting the total light transmittance and haze of the above non-alkali glass from the measured values were taken as the total light transmittance and haze values of the pressure-sensitive adhesive sheets. The results are shown in Table 1.

[0252] (Peeling Strength from Glass Plate) Under the measurement environment of 23°C and 50% RH, the release liner was peeled off from one side of the adhesive sheet according to each example (in Examples 1 and 2, the surface of the adhesive layer formed from the adhesive composition C3), and after laminating and backing with a 50-μm-thick PET film, a test piece was cut into a size of 25 mm in width and 100 mm in length. The release liner on the other side was peeled off from the test piece, and a 2-kg roller was reciprocated once to press-bond it to the surface of an alkali glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35 mm, blue plate edge-ground product) as the adherend. This was left in the same environment for 30 minutes, then put into a pressure degassing device (autoclave), and autoclave treatment was performed for 30 minutes under the conditions of a temperature of 50°C and a pressure of 0.5 MPa. After further leaving it in an atmosphere of 23°C and 50% RH for 24 hours, using a universal tensile-compression testing machine, in accordance with JIS Z 0237:2000, the peel strength (adhesive force) [N / 25 mm] was measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. As the universal tensile-compression testing machine, the "Tensile-Compression Testing Machine, TG-1kN" manufactured by Minebea Co., Ltd. was used.

[0253]

Table 1

[0254] As shown in Table 1, the adhesive sheets of Examples 1 to 4 included an adhesive layer V1 (high refractive index adhesive layer) having a refractive index n V1 higher than 1.570 and showed high transparency in the adhesive sheet. These adhesive sheets showed practical peel strengths suitable for bonding optical members.

[0255] <Evaluation of the front luminance improvement effect> The pressure-sensitive adhesive sheet according to each example was attached onto a white LED light-emitting light source. After the light source was turned on for 30 minutes or more in a dark room environment to stabilize it, the front luminance at the portion where the pressure-sensitive adhesive sheet was attached was measured using a spectro-radiometer SR-UL1R (manufactured by Topcon Techno House Co., Ltd.). The average value of the luminance measured three times was used, and those having a luminance improvement effect of 10% or more with respect to the luminance of the light source without the pressure-sensitive adhesive sheet attached were evaluated as G (Good), and those with a luminance improvement of less than 10% were evaluated as P (Poor). The results are shown in Table 2.

[0256]

Table 2

[0257] As shown in Table 2, according to the pressure-sensitive adhesive sheets (laminated sheets) of Examples 1 and 2 having a laminated structure pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer of Example 5 with a low refractive index was combined with the pressure-sensitive adhesive layers of Examples 3 and 4 with a high refractive index, a front luminance improvement effect of 10% or more was recognized as compared with the case where the pressure-sensitive adhesive sheet was not used. In the pressure-sensitive adhesive sheets of Examples 3 to 5 in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was a single-layer structure, no front luminance improvement effect was recognized by the pressure-sensitive adhesive sheet alone.

[0258] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C4> Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler, 79 parts of POB-A as a monomer component, 20 parts of n-butyl acrylate, 1 part of 4HBA, 0.2 part of AIBN as a polymerization initiator, and 100 parts of toluene as a polymerization solvent were charged. While gently stirring, nitrogen gas was introduced, and the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature in the flask at around 60 °C to prepare a solution (50%) of acrylic polymer A4. The Mw of this acrylic polymer A4 was 520,000. The solution (50%) of the above acrylic polymer A4 was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts of non-volatile matter), 10 parts (0.1 part of non-volatile matter) of a 1% ethyl acetate solution of coronate HX as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part (0.01 part of non-volatile matter) of a 1% ethyl acetate solution of ferric naphthenate as a crosslinking catalyst were added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C4.

[0259] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C5> The composition (weight ratio) of the monomer components was changed to POB-A / ethyl carbitol acrylate (CBA) / 4HBA = 79 / 20 / 1. Otherwise, in the same manner as the preparation of the solution of acrylic polymer A4, a solution (50%) of acrylic polymer A5 was prepared. The Mw of this acrylic polymer A5 was 460,000. An acrylic pressure-sensitive adhesive composition C5 was prepared in the same manner as the preparation of acrylic pressure-sensitive adhesive composition C4, except that a solution of acrylic polymer A5 was used instead of the solution of acrylic polymer A4.

[0260] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C6> The composition (weight ratio) of the monomer components was changed to P2H-A / 4HBA = 99 / 1. Otherwise, in the same manner as the preparation of the solution of acrylic polymer A4, a solution (50%) of acrylic polymer A6 was prepared. "P2H-A" in the composition of the above monomer components represents phenoxydiethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate P2H-A", refractive index: 1.510, Tg of homopolymer: -35°C). The Mw of this acrylic polymer A6 was 1,000,000. The solution (50%) of acrylic polymer A6 was diluted to 30% with ethyl acetate. To 334 parts of this solution (100 parts of non-volatile matter), an additive (H RO) As 20 parts of 6-ethyl acrylate-dinaphtho[2,1-b:1’,2’-d]thiophene (6-acryloyloxyethyl dinaphthothiophene manufactured by Sugai Chemical Industry Co., Ltd., abbreviation: 6EDNTA, refractive index: 1.722), 10 parts of a 1% ethyl acetate solution of Coronate HX (nonvolatile content 0.1 part) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of ferric naphthenate (nonvolatile content 0.01 part) as a crosslinking catalyst were added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C6.

[0261] <Preparation of Acrylic Pressure-Sensitive Adhesive Composition C7> An acrylic polymer A7 solution (50%) was prepared in the same manner as the preparation of the acrylic polymer A3 solution, except that the composition (weight ratio) of the monomer components was changed to 2EHA / Biscote 13F / 4HBA = 49 / 50 / 1. In the composition of the above monomer components, “Biscote 13F” represents 1H,1H,2H,2H-tridecafluorooctyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name “Biscote 13F”). The Mw of this acrylic polymer A7 was 550,000. An acrylic pressure-sensitive adhesive composition C7 was prepared in the same manner as the preparation of the acrylic pressure-sensitive adhesive composition C3, except that the acrylic polymer A7 solution was used instead of the acrylic polymer A3 solution.

[0262] <Production of Adhesive Sheet> (Examples 6 to 8) A laminated sheet (substrate-free double-sided adhesive sheet) having a two-layer structure of a high refractive index adhesive layer / low refractive index adhesive layer was obtained in the same manner as in Example 1, except that the type of the adhesive composition used for forming each adhesive layer and the thickness of each adhesive layer were as shown in Table 3.

[0263] After sufficiently conditioning the adhesive sheets obtained in Examples 6 to 8 in an environment of 23°C and 50% RH, the measurement and evaluation of each item were performed in the same manner as in the above-mentioned “Measurement and Evaluation (1)”. The results are shown in Table 3.

[0264]

Table 3

[0265] As shown in Table 3, the pressure-sensitive adhesive sheets of Examples 6 to 8 exhibited high transparency in a laminated structure of a pressure-sensitive adhesive layer (high refractive index pressure-sensitive adhesive layer) having a refractive index n1 higher than 1.570 and a low refractive index layer. These pressure-sensitive adhesive sheets exhibited a practical peel strength suitable for bonding optical members.

[0266] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Explanation of Reference Numerals

[0267] 2 Substrate-free double-sided pressure-sensitive adhesive sheet 10 Laminated sheet (pressure-sensitive adhesive sheet) 10A First surface (first pressure-sensitive adhesive surface) 10B Second surface (second pressure-sensitive adhesive surface) 11 High refractive index pressure-sensitive adhesive layer 12 Low refractive index pressure-sensitive adhesive layer (low refractive index layer) 70 Self-luminous element 80 Cover window member 100 Light-emitting device

Claims

1. A self-luminous element, a low refractive index layer disposed on the viewing side of the self-luminous element, a high refractive index adhesive layer laminated in direct contact with the low refractive index layer, comprising: The high refractive index adhesive layer contains, as a base polymer, an acrylic polymer containing a plurality of aromatic ring-containing monomers having two or more aromatic rings in one molecule and hydroxyalkyl acrylate as monomer units, In the monomer components constituting the acrylic polymer, the content of the plurality of aromatic ring-containing monomers is 70% by weight or more and 99% by weight or less, and the content of the hydroxyalkyl acrylate is 1% by weight or more and less than 7% by weight, The high refractive index adhesive layer has a refractive index n １ is greater than 1.570, the total light transmittance is 86% or more, and the haze value is 3.0% or less, a light emitting device.

2. The refractive index n of the high refractive index adhesive layer １ and the refractive index n of the low refractive index layer ２ The ratio (n １ / n ２ ) is 1.05 or more. The light emitting device according to claim 1

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

4. The thickness T of the high refractive index adhesive layer １ and the ratio (T １ / T ２ ) to the thickness T2 of the low refractive index layer is 0.5 to 5. The light emitting device according to any one of claims 1 to 3.

5. The thickness T of the high refractive index adhesive layer １ The light-emitting device according to any one of claims 1 to 4, wherein the thickness T is 5 μm or more.

6. The light-emitting device according to any one of claims 1 to 5, wherein the laminated sheet composed of the high refractive index adhesive layer and the low refractive index layer has a total light transmittance of 86% or more and a haze value of 3.0% or less.

Images