CN115335634A

CN115335634A - Light emitting device

Info

Publication number: CN115335634A
Application number: CN202180024072.8A
Authority: CN
Inventors: 形见普史; 片冈贤一; 西野智哉; 山本祐辅; 野依慎太郎
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-03-24
Filing date: 2021-03-24
Publication date: 2022-11-11
Also published as: TW202146229A; WO2021193721A1; KR20220153646A

Abstract

The provided light emitting device includes: the adhesive layer includes a self-light emitting element, a low refractive index layer disposed on a side of the self-light emitting element from which a user can visually recognize the self-light emitting element, and a high refractive index adhesive layer stacked in direct contact with the low refractive index adhesive layer. Refractive index n of the high refractive index adhesive layer ₁ Higher than 1.570, total light transmittance of 86% or more, and haze value of 3.0% or less.

Description

Light emitting device

Technical Field

The present invention relates to a light-emitting device, and more particularly, to a light-emitting device having an adhesive layer disposed on a viewing side of a self-light-emitting element.

Priority is claimed for this application based on japanese patent application No. 2020-052408, filed on 3/24/2020, japanese patent application No. 2020-166428, filed on 9/30/2020, and japanese patent application No. 2021-049061, filed on 3/23/2021, which are all incorporated by reference into this specification.

Background

In general, an adhesive (also referred to as a pressure-sensitive adhesive hereinafter) has a property of exhibiting a soft solid (viscoelastic body) state in a temperature region near room temperature and simply adhering to an adherend by pressure. By utilizing such properties, adhesives are widely used for the purpose of bonding, fixing, protection, and the like in various industrial fields from home electric appliances to automobiles, various machines, electric devices, electronic devices, and the like. Examples of the application of the adhesive include the application of bonding a polarizing film, a retardation film, a cover window member, and other various light-transmitting members to other members in a display device such as a liquid crystal display device or an organic EL display device. Patent documents 1 and 2 are cited as technical documents relating to adhesives for optical members.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-169383

Patent document 2: japanese patent laid-open publication No. 2017-128732

Disclosure of Invention

Problems to be solved by the invention

Patent documents 1 and 2 propose an adhesive composition containing a (meth) acrylate polymer as a main component, the (meth) acrylate polymer containing a monomer having a plurality of aromatic rings as a monomer unit, but do not disclose an adhesive having a refractive index higher than 1.570, and an adhesive obtained by crosslinking the adhesive composition. On the other hand, a technique of increasing the refractive index by blending particles made of an inorganic material having a high refractive index (for example, inorganic particles such as zirconia particles and titania particles) with a resin is also known, but the refractive index of a pressure-sensitive adhesive in which inorganic particles are blended is in a trade-off relationship with the adhesive properties (for example, peel strength, flexibility, and the like), and therefore, it is difficult to apply the pressure-sensitive adhesive to the field of pressure-sensitive adhesives. For example, in a light-emitting device, in order to increase the refractive index of a pressure-sensitive adhesive layer disposed on the viewing side of a self-light-emitting element, it is necessary to consider the influence on optical characteristics (for example, total light transmittance, haze, and the like) when inorganic particles are blended.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a light-emitting device in which a pressure-sensitive adhesive layer having a high refractive index and optical quality is disposed on the viewing side of a self-light-emitting element.

Means for solving the problems

The specification provides a light emitting device comprising: the adhesive layer includes a self-light emitting element, a low refractive index layer disposed on a side of the self-light emitting element from which a user can visually recognize the self-light emitting element, and a high refractive index adhesive layer stacked in direct contact with the low refractive index layer. Refractive index n of the high refractive index adhesive layer ₁ Higher than 1.570, total light transmittance of 86% or more, and haze value of 3.0% or less.

In some embodiments, the refractive index n of the high refractive index adhesive layer is ₁ Refractive index n of the low refractive index layer ₂ Ratio of (n) ₁ /n ₂ ) Preferably about 1.05 or more.

In some embodiments, the high refractive index pressure-sensitive adhesive layer preferably has an arithmetic average roughness Ra of 100nm or less on the surface.

In some embodiments, the thickness T of the high refractive index adhesive layer ₁ Thickness T of the low refractive index layer ₂ Ratio of (T) ₁ /T ₂ ) Preferably in the range of about 0.5 to 5.

In some embodiments, the thickness T of the high refractive index adhesive layer ₁ Preferably 5 μm or more.

In some embodiments, the laminate sheet (adhesive sheet) including 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.

It should be noted that the technical means of appropriately combining the respective elements described in the present specification may be included in the scope of the claims of the present patent application.

Drawings

Fig. 1 is a sectional view schematically showing a configuration of a light-emitting device according to an embodiment.

Fig. 2 is a sectional view schematically showing the configuration of a laminate sheet used in a light-emitting device of an embodiment.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described. Matters necessary for carrying out the present invention other than the matters specifically mentioned in the present specification can be understood by those skilled in the art based on the teaching of the practice of the invention described in the present specification and the common general knowledge at the time of application. The present invention can be implemented based on the contents disclosed in the present specification and the common general knowledge in the art.

In the following drawings, members and portions that exhibit the same function are sometimes described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately show the size and the ratio of a product to be actually provided.

In this specification, the self-light emitting element refers to a light emitting element capable of controlling light emission luminance by a value of current flowing therethrough. The self-luminous element may be formed of a single body or an aggregate. Specific examples of the self-light emitting 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-light-emitting element as a constituent element. Examples of the light-emitting device include a light source module device (for example, a planar light-emitting module) used for illumination and a display device in which pixels are formed, but are not limited thereto.

Technical matters disclosed by the specification include: a light-emitting device, a high refractive index adhesive layer and an adhesive composition for forming the same, a low refractive index layer and a composition for forming the same, a laminate sheet (adhesive sheet) comprising a high refractive index adhesive layer and a low refractive index layer, a release liner-equipped laminate sheet in which the adhesive surface of the laminate sheet is protected by a release liner, and the like.

< example of light emitting device construction >

Fig. 1 shows one configuration example of a light-emitting device provided by this specification. The light-emitting device 100 shown in fig. 1 includes: the light-emitting device includes a self-light-emitting element 70, a low refractive index layer 12 disposed on a side of the self-light-emitting element 70 from which a user can visually recognize, and a high refractive index adhesive layer 11 stacked 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 visually recognizing side of the high refractive index adhesive layer 11. In the light-emitting device 100 shown in fig. 1, a laminate sheet 10 including a high refractive index adhesive layer 11 and a low refractive index layer 12 is disposed between the self-light-emitting element 70 and the cover window member 80. The self-light emitting element 70 and the low refractive index layer 12, the high refractive index adhesive layer 12 and the cover window member 80, and the cover window member 80 may or may not be provided with 1 or 2 or more layers, not shown, on the further visual recognition side thereof. In contrast to fig. 1, the high refractive index adhesive layer 11 may be disposed on the self-light emitting element side and the low refractive index layer 12 may be disposed on the cover window member side.

In the technique disclosed herein, the low refractive index layer may be adhesive or non-adhesive. In some embodiments, the low refractive index layer is preferably a layer having adhesiveness, that is, a low refractive index adhesive layer. This makes the laminated sheet (adhesive sheet) of the low refractive index adhesive layer and the high refractive index adhesive layer double-sided adhesive, and improves the ease of assembly in the production of the light-emitting device. The laminate may be a release liner-bearing laminate, for example, as shown in fig. 2, in the form of: before the light-emitting device is incorporated, a laminate sheet 10 (substrate-less double-sided adhesive sheet 2) including a high refractive index adhesive layer 11 and a low refractive index adhesive layer 12 is provided, a surface (1 st surface) 10A on the high refractive index adhesive layer 11 side of the laminate sheet 10 serves as a1 st adhesive surface, and a surface (2 nd surface) 10B on the low refractive index adhesive layer 12 side serves as a2 nd adhesive surface, and these adhesive surfaces are protected by

release liners

31 and 32, respectively.

< high refractive index adhesive layer >

The light-emitting device disclosed herein includes a high refractive index adhesive layer laminated in direct contact with a low refractive index layer included in the light-emitting device. The high refractive index adhesive layer is a layer having a relatively higher refractive index than the low refractive index layer. The refractive index n of the high refractive index adhesive layer is preferably set ₁ Higher than 1.570 and total light transmittance of 86%And a haze value of 3.0% or less.

(refractive index)

The light emitting devices disclosed herein have a refractive index n ₁ A high refractive index adhesive layer higher than 1.570. Such a high refractive index adhesive layer can be realized by constituting at least one surface (adhesive surface) of the high refractive index adhesive layer with an adhesive (viscoelastic material) having a refractive index higher than 1.570.

In the present specification, the refractive index of the adhesive refers to the refractive index of the surface (bonding surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring apparatus (Abbe refractometer) at a measurement wavelength of 589nm and a measurement temperature of 25 ℃. As the Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO or a product equivalent thereof can be used. As the measurement sample, an adhesive layer formed of an adhesive to be evaluated may be used. The refractive index of the binder can be measured specifically by the method described in the examples below. The refractive index of the binder can be adjusted by, for example, the composition of the binder (for example, the composition of monomer components constituting the base polymer, additives that can be used as needed, and the like).

The technical items provided by this specification include: a pressure-sensitive adhesive layer having a refractive index of higher than 1.57 (high-refractive-index pressure-sensitive adhesive layer), a pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive layer, and a laminate sheet comprising the high-refractive-index pressure-sensitive adhesive layer. The laminate sheet may be a laminate pressure-sensitive adhesive layer formed of the high refractive index pressure-sensitive adhesive layer and the low refractive index layer (typically, a low refractive index pressure-sensitive adhesive layer), or may be a laminate sheet in which a high refractive index pressure-sensitive adhesive layer and a low refractive index layer are laminated in this order or in the reverse order on one surface of a support base.

In some aspects, the refractive index of the high refractive index adhesive layer may be preferably 1.580 or more, more preferably 1.585 or more, and further preferably 1.590 or more (e.g., 1.595 or more). According to the high-refractive-index adhesive layer having such a refractive index, the behavior of light transmitted through the high-refractive-index adhesive layer can be effectively controlled by utilizing the relative refractive index relationship between the high-refractive-index adhesive layer and the low-refractive-index layer (typically, the low-refractive-index adhesive layer) directly adjacent thereto. In some versions of the technology disclosed herein, the refractive index of the high refractive index adhesive layer may be, for example, 1.600 or greater, 1.605 or greater, or 1.610 or greater, than 1.600. The preferable upper limit of the refractive index of the high refractive index adhesive layer may vary depending on the refractive index of the adjacent layer, and is not limited to a specific range. In some embodiments, the refractive index of the high refractive index adhesive layer may be, for example, 1.700 or less, 1.670 or less, or 1.650 or less, in consideration of the balance between the adhesive property and the transparency.

(Total light transmittance)

In the technique disclosed herein, the total light transmittance of the high refractive index pressure-sensitive adhesive layer is suitably 86% or more, preferably 88% or more, more preferably 90% or more (for example, higher than 90.0%), and may be 90.5% or more, 93% or more, or 95% or more. The upper limit of the total light transmittance is theoretically a value obtained by subtracting the optical loss (fresnel loss) due to reflection occurring at the air interface from 100%, and may be practically about 98% or less, about 96% or less, or about 95% or less. In some embodiments, the total light transmittance of the high refractive index adhesive layer may be about 94% or less, about 93% or less, or about 92% or less, in consideration of the refractive index and the adhesive property. Total light transmittance was measured according to JIS K7136: 2000, measured by using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETER HM-150" available from the color technology research on villages or a product equivalent thereof can be used. More specifically, the total light transmittance of the high refractive index adhesive layer can be measured, for example, in accordance with examples described later. The total light transmittance of the high-refractive-index adhesive layer can be adjusted by, for example, selection of the composition, thickness, and the like of the high-refractive-index adhesive layer.

(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 still more preferably 0.9% or less. In applications where high light transmittance is required (for example, optical applications) and where good visual recognition of an adherend through the high refractive index pressure-sensitive adhesive layer is required, a low haze value of the high refractive index pressure-sensitive adhesive layer is advantageous. In some embodiments, the haze value of the high refractive index adhesive layer may be 0.8% or less, may be 0.5% or less, and may also be 0.3% or less. The lower limit of the haze value of the high refractive index pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the more preferable. On the other hand, in some embodiments, the haze value of the high refractive index pressure-sensitive 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, in consideration of the refractive index and the adhesive property. These haze values for the high-refractive-index adhesive layer can also be preferably applied to the haze value of a laminate sheet formed of the high-refractive-index adhesive layer and a low-refractive-index layer (typically, a low-refractive-index adhesive layer) described later.

Here, the "haze value" refers to a ratio of diffuse transmitted light to total transmitted light when the measurement target is irradiated with visible light. Also known as turbidity. The haze value can be expressed by the following equation.

Th(％)＝Td/Tt×100

In the above formula, th is a haze value (%), td is a scattered light transmittance, and Tt is a total light transmittance. The haze value can be measured by the method described in examples below. The haze value of the adhesive layer can be adjusted by, for example, selecting the composition, thickness, and the like of the adhesive layer.

(storage modulus G')

In the technique disclosed herein, the high refractive index adhesive layer has a storage modulus G ' at 25 ℃ ' (hereinafter also referred to as "storage modulus G ' _V1 (25) ". ) The range is not limited to a specific range, and may be appropriately set according to the purpose of use, the mode of use, and the like. Storage modulus G' _V1 (25) For example, about 700kPa or less. In some embodiments, the storage modulus G 'is from the viewpoint of ease of adhesion to an adherend, and the like' _V1 (25) Advantageously, the pressure is about 600kPa or less, preferably 500kPa or less, and more preferably 400kPa or less (for example 350kPa or less). In some ways, flexibility of the high refractive index adhesive layer in the region from elevated room temperature (e.g., 25℃.)Storage modulus G 'for softness and easy adhesion to an adherend' _V1 (25) Advantageously, the pressure is about 330kPa or less, preferably 300kPa or less. In some embodiments where adhesiveness and flexibility in the room temperature region are more important, the storage modulus G' _V1 (25) For example, may be below 270kPa or below 250kPa, advantageously below 200kPa, preferably below 180kPa, more preferably below 160kPa (for example below 140 kPa). In some forms, storage modulus G' _V1 (25) May be less than 100kPa, or may be less than 90kPa. Storage modulus G' _V1 (25) The lower limit of (B) is not particularly limited, and may be, for example, 30kPa or more, 50kPa or more, or 70kPa or more from the viewpoints of processability, handleability, and the like. In some embodiments, the storage modulus G 'is taken into consideration for the increase in refractive index' _V1 (25) May be 100kPa or more, may be 150kPa or more, may be 200kPa or more, may be 250kPa or more, or may be 300kPa or more.

In the technique disclosed herein, the high refractive index adhesive layer has a storage modulus G ' at 50 ℃ ' (hereinafter also referred to as "storage modulus G ' _V1 (50) ". ) The pressure is not particularly limited, and may be, for example, less than 100kPa. In some forms, storage modulus G' _V1 (50) Suitably, less than 60kPa, preferably less than 40kPa, more preferably less than 38kPa (e.g. less than 36 kPa). Thus limiting the storage modulus G' _V1 (50) The high refractive index pressure-sensitive adhesive layer of (2) can easily improve the adhesiveness to an adherend by appropriately heating as necessary, and thus can improve the adhesiveness to an adherend. Storage modulus G' _V1 (50) The lower limit of (b) is not particularly limited. In some embodiments, the storage modulus G 'is from the viewpoint of heat resistance characteristics and the like' _V1 (50) For example, the pressure may be 10kPa or higher, 15kPa or higher, 20kPa or higher, or 23kPa or higher.

In some versions of the technology disclosed herein, the high refractive index adhesive layer preferably satisfies at least one of the following conditions:

(a) Storage modulus G' _V1 (25) 350kPa or less (preferably less than 200kPa, for example, 180kPa or less); and

(b) Storage modulus G' _V1 (50) Below 60kPa (preferably below 50kPa, more preferably below 40kPa, for example below 38 kPa).

A high refractive index pressure-sensitive adhesive layer satisfying at least the above condition (a) is preferable from the viewpoint of adhesion to an adherend and flexibility in a room temperature region (e.g., 25 ℃). The high refractive index pressure-sensitive adhesive layer satisfying at least the above condition (b) is preferable because the adhesiveness (adhesiveness) to an adherend can be easily improved by heating to a temperature slightly higher than room temperature. The pressure-sensitive adhesive sheet having a high refractive index pressure-sensitive adhesive layer which does not satisfy the above condition (a) and satisfies the above condition (b) has good reworkability (re-adherability) at the initial stage of adhesion at room temperature, and can be used as a heat-activated pressure-sensitive adhesive sheet which can be heated to a temperature slightly higher than room temperature to effectively improve the peel strength from an adherend. The heat activation can be performed by heating the pressure-sensitive adhesive sheet to a temperature slightly higher than room temperature at the time of attachment to an adherend. The temperature slightly higher than room temperature is, for example, about 60 ℃ or lower, preferably about 55 ℃ or lower (for example, about 50 ℃ or lower).

In some versions of the technology disclosed herein, storage modulus G' _V1 (50)[kPa]Relative to storage modulus G' _V1 (25)[kPa]Of storage modulus to G' _V1 (50)/G’ _V1 (25) For example, the content is 70% or less, may be 40% or less, may be 30% or less, or may be 20% or less. Is of G' _V1 (50)/G’ _V1 (25) The pressure-sensitive adhesive sheet having a small high refractive index pressure-sensitive adhesive layer is suitable for use as the above-mentioned heat-activatable pressure-sensitive adhesive sheet. G' _V1 (50)/G’ _V1 (25) The lower limit of (b) is not particularly limited. G' _V1 (50)/G’ _V1 (25) For example, 5% or more, preferably 10% or more, and may be 12% or more, and may be 15% or more, from the viewpoint of heat resistance.

Storage modulus G' _V1 (25) And G' _V1 (50) Can be obtained by dynamic viscoelasticity measurement, and G 'can be calculated from the result' _V1 (50)/G’ _V1 (25). The dynamic viscoelasticity can be measured by a conventional method using a commercially available dynamic viscoelasticity measuring apparatusThe method can be carried out, for example, using ARES manufactured by TA Instruments or its equivalent under the following measurement conditions. As a sample for measurement, a sample prepared to have a thickness of about 1.5mm by laminating the adhesive layer to be evaluated as necessary, or the like, was used.

[ measurement conditions ]

Deformation mode: torsion

Measuring frequency: 1Hz

Temperature rise rate: 5 ℃ per minute

Shape: parallel plates

Storage modulus G' _V1 (25)、G’ _V1 (50) And storage modulus ratio (G' _V1 (50)/G’ _V1 (25) Can be adjusted by selection of the composition of the monomer component constituting the base polymer of the adhesive (for example, selection of the type and content of the monomer (m 1) described later), use/non-use of the crosslinking agent, selection of the type and amount of the crosslinking agent, use/non-use of the refractive index improver and the plasticizing material described later, selection of the type and amount of the plasticizing material, and the like. For example, by using a1 st monomer as a main component of the monomer (m 1) as the monomer (m 1) and using a2 nd monomer different in chemical structure from the 1 st monomer in a smaller amount in combination with the 1 st monomer, G 'can be reduced in the case of using the 1 st monomer alone as the monomer (m 1)' _V1 (50) G 'is reduced' _V1 (50)/G’ _V1 (25)。

(surface smoothness of pressure-sensitive adhesive surface)

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

For example, the adhesive surface is preferably limited to have an arithmetic average roughness Ra of a predetermined value or less. A configuration having a pressure-sensitive adhesive surface designed to have a low arithmetic average roughness Ra is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic average roughness Ra, for example, in a use mode (an adhesive sheet or the like disposed closer to the viewpoint than the self-luminous element in the light-emitting device) in which light is extracted through the adhesive surface, an effect of suppressing the occurrence of luminance unevenness due to the surface state of the adhesive layer can be exhibited. When the arithmetic average roughness Ra of the adhesive surface is low, it is also advantageous to suppress optical distortion, and suppression of optical distortion contributes to improvement of optical homogeneity. When the laminate (adhesive sheet) disclosed herein is in the form of a double-sided adhesive sheet having a1 st adhesive surface and a2 nd adhesive surface (for example, in the form of a laminate comprising a high refractive index adhesive layer and a low refractive index adhesive layer), the arithmetic average roughness Ra of at least the 1 st adhesive surface is preferably limited to a predetermined value or less, and more preferably, the arithmetic average roughness Ra of both adhesive surfaces is limited to a predetermined value or less. By providing each adhesive surface of the double-sided adhesive sheet with high surface smoothness, adhesion with excellent optical homogeneity can be preferably achieved.

In some embodiments, the arithmetic average roughness Ra of the adhesive surface is preferably about 70nm or less, more preferably about 65nm or less, further preferably about 55nm or less, and may be less than 50nm, may be less than 45nm, or may be less than 40nm. From the viewpoint of production efficiency and the like, the arithmetic average roughness Ra of the adhesive surface may be, for example, about 10nm or more, about 20nm or more, or about 30nm or more (for example, about 40nm or more) in some embodiments. In the embodiment where the laminate sheet has the 1 st adhesive surface and the 2 nd adhesive surface, the arithmetic average roughness Ra of the 1 st adhesive surface and the arithmetic average roughness Ra of the 2 nd adhesive surface may be the same or different.

For example, the maximum height Rz of the pressure-sensitive adhesive surface is preferably limited to a predetermined value or less. A configuration having a pressure-sensitive adhesive surface designed to have a low maximum height Rz is preferable from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example, in the use mode in which light is extracted through the pressure-sensitive adhesive surface, the effect of suppressing the occurrence of luminance unevenness due to the surface state of the pressure-sensitive adhesive layer can be exhibited. When the maximum height Rz of the pressure-sensitive adhesive surface is low, suppression of optical distortion is also advantageous. When the laminate sheet disclosed herein is in the form of a double-sided adhesive sheet having a1 st adhesive surface and a2 nd adhesive surface, the maximum height Rz of at least the 1 st adhesive surface is preferably limited to a predetermined value or less, and more preferably, the maximum heights Rz of both adhesive surfaces are limited to a predetermined value or less. By providing each adhesive surface of the double-sided adhesive sheet with high surface smoothness, adhesion with excellent optical homogeneity can be preferably achieved.

In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600nm or less, more preferably about 500nm or less, further preferably about 450nm or less, particularly preferably about 400nm or less, and may be less than 350nm, less than 300nm, or less than 250nm. From the viewpoint of production efficiency and the like, in some embodiments, the maximum height Rz of the adhesive surface may be, for example, about 10nm or more, about 50nm or more, about 100nm or more, or about 200nm or more. In the embodiment having the 1 st adhesive surface and the 2 nd adhesive surface, the maximum height Rz of the 1 st adhesive surface and the maximum height Rz of the 2 nd adhesive surface may be the same or different.

The arithmetic average roughness Ra and the maximum height Rz of the adhesion surface were measured using a noncontact surface roughness measuring apparatus. As the noncontact surface roughness measuring device, a surface roughness measuring device using an optical interference system, for example, a three-dimensional optical profiler (trade name "new view7300", manufactured by ZYGO) or a product equivalent thereof can be used. Specifically, the arithmetic average roughness Ra and the maximum height Rz can be measured, for example, by the following measurement method or by setting the measurement operation and measurement conditions so as to obtain results equivalent to or corresponding to those obtained by using the measurement method.

That is, the surface shape of the measurement sample was measured under the following conditions using a three-dimensional optical profiler (trade name "New View7300", manufactured by ZYGO Co., ltd.) in an environment of 23 ℃ and 50% RH. From the measured data, the arithmetic surface roughness Ra was calculated in accordance with JIS B0601-2001. The maximum height Rz is obtained as the sum of the height Rp of the highest peak on the upper side from the average line of the roughness curve and the depth Rv of the deepest valley on the lower side from the average line, with respect to the data (roughness curve) obtained by the above measurement. The assay was performed 5 times (i.e. N = 5), and their average value was used.

The measurement sample can be prepared by, for example, cutting a pressure-sensitive adhesive layer to be measured or a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer into a size of about 150mm in length and about 50mm in width. When the pressure-sensitive adhesive surface is protected by the release liner, the pressure-sensitive adhesive surface is exposed by peeling off the release liner gently (for example, under conditions of a stretching speed of 300 mm/min and a peeling angle of 180 °). It is preferable to perform the measurement after leaving the adhesive surface to stand for about 30 minutes after exposing the adhesive surface.

[ measurement conditions ]

Area measurement: 5.62mm by 4.22mm

(Objective lens: 2.5 times, inner lens: 0.5 times)

Analysis mode:

Remove：Cylinder

Data Fill：ON(Max：25)

Remove Spikes：ON(xRMS：1)

Filter：OFF

the arithmetic average roughness Ra and the maximum height Rz of the pressure-sensitive adhesive surface can be adjusted by the composition and properties (viscosity, leveling property, etc.) of the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer, the properties of the surface (release surface) of the release liner protecting the pressure-sensitive adhesive surface, and the like.

(Water absorption)

In some aspects, the high refractive index adhesive layer preferably has a water absorption limited to a predetermined value or less. By limiting the water absorption rate of the high refractive index pressure-sensitive adhesive layer, the dimensional change of the high refractive index pressure-sensitive adhesive layer due to the fluctuation of the moisture amount in the high refractive index pressure-sensitive adhesive layer (for example, absorption and release of moisture such as moisture in the environment) tends to be suppressed. Thus, warpage of the high refractive index pressure-sensitive adhesive layer or the optical laminate including the high refractive index pressure-sensitive adhesive layer due to non-uniformity in dimensional change between the high refractive index pressure-sensitive adhesive layer and a layer adjacent thereto (which may be a low refractive index layer, a support base, a release liner, an adherend, or the like) can be suppressed. From the viewpoint of maintaining the flatness, transparency, refractive index, and the like of the high refractive index pressure-sensitive adhesive layer at a constant level, it is also preferable that the variation in the amount of water in the high refractive index pressure-sensitive adhesive layer be suppressed. The high refractive index pressure-sensitive adhesive layer having a low water absorption rate is less likely to absorb moisture, and therefore is suitable as a component of a member or a product including a component which is offensive to moisture, such as an organic EL element.

In some embodiments, the water absorption 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 (e.g., 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 pressure-sensitive adhesive layer is not particularly limited, and 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, from the viewpoint of practical use, for example, in consideration of compatibility with adhesive properties. The water absorption of the low refractive index layer may be the same as or different from the water absorption of the high refractive index adhesive layer. From the viewpoint of obtaining higher effects, 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.

The water absorption rate (also referred to as a water content rate) of the high refractive index adhesive layer was measured by the following method. The water absorption of the low refractive index layer was also measured by the same method.

[ measurement of moisture content ]

The pressure-sensitive adhesive layer to be evaluated was cut out to 4cm × 5cm (area: 20 cm) together with 2 sheets of release liners disposed on one surface and the other surface thereof ² ) The release liner on one side was removed, and the sheet was attached to a previously weighed aluminum foil. Then, the release liner on the other side of the adhesive layer was removed, and the resulting assembly was put into a constant temperature and humidity bath at a temperature of 60 ℃ and a relative humidity of 90%, and taken out after 72 hours. After weighing a test piece in which an adhesive layer and an aluminum foil were laminated, the moisture content was measured by karl fischer coulometry using a moisture meter (model CA-200 of mitsubishi chemical Analytech) equipped with a heat vaporizer (model VA-200 of mitsubishi chemical Analytech).

Anolyte: AQUAMICRON AKX (Mitsubishi chemical)

And (3) catholyte: AQUAMICRON CXU (Mitsubishi chemical)

Heating and gasifying temperature: 150 ℃ C

(gel fraction)

The gel fraction of the high refractive index pressure-sensitive adhesive layer is appropriately set depending on the purpose of use, the mode of use, and the like, and is not limited to a specific range. The gel fraction is preferably about 99% or less, and about 97% or less, for example. In some preferred embodiments, the gel fraction is about 95% or less, and more preferably about 92% or less (for example, about 90% or less), from the viewpoint of easily and suitably achieving both of the high refractive index and the adhesive property. The gel fraction is preferably not too high from the viewpoint of suitably following irregularities that may be present on the surface of an adherend (for example, an irregular structure provided in a light-emitting device for the purpose of improving light extraction efficiency) and achieving good adhesion. In some embodiments, the gel fraction may be about 88% or less, may be about 75% or less, and may be about 65% or less. From the viewpoint of imparting appropriate cohesive properties to the pressure-sensitive adhesive and appropriately exhibiting adhesive properties, the gel fraction is, for example, about 10% or more, preferably about 20% or more, and may be about 30% or more. From the viewpoint of deformation resistance of the pressure-sensitive adhesive layer (prevention of overflow due to pressure, bubbles due to mixing of foreign substances, and the like), the gel fraction is preferably about 30% or more, more preferably about 40% or more, and may be about 45% or more, and may be about 50% or more, and may be about 65% or more, and may be about 75% or more. The gel fraction of the laminate sheet comprising the high-refractive-index pressure-sensitive adhesive layer and the low-refractive-index layer (typically, a laminate sheet in the form of a substrate-free double-sided pressure-sensitive adhesive sheet formed of the high-refractive-index pressure-sensitive adhesive layer and the low-refractive-index layer) is also preferably in the above-exemplified range. The gel fraction can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc. of the base polymer. The gel fraction was measured by the following method.

[ measurement of gel fraction ]

A prescribed amount of the adhesive sample (weight Wg) ₁ ) A porous polytetrafluoroethylene film (weight Wg) having an average pore diameter of 0.2 μm was used ₂ ) Wrapping into a purse shape, and using kite line (weight Wg) for mouth ₃ ) And (6) tightening. As the porous Polytetrafluoroethylene (PTFE) membrane, a product of NITOFLON (registered trademark) NTF1122 (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) available from Ninto electric corporation or a product equivalent thereof was used.

The coating was immersed in a sufficient amount of ethyl acetate, and kept at room temperature (typically 23 ℃) for 7 days to elute only the sol component in the binder out of the film, and then the coating was taken out and wiped off the ethyl acetate adhered to the outer surface, and the coating was dried at 130 ℃ for 2 hours to measure the weight (Wg) of the coating ₄ ). The gel fraction of the pressure-sensitive adhesive layer was determined by substituting each value into the following formula.

Gel fraction (%) = [ (Wg) ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

The gel fraction of the high refractive index adhesive layer may be the same as or different from the gel fraction of the low refractive index layer. In some approaches, the low refractive index layer may be made to have a lower gel fraction than the high refractive index adhesive layer. According to this configuration, the flexibility of the whole can be easily improved by the contribution of the low refractive index layer having a relatively low gel fraction. This makes it possible to achieve both high refractive index and flexibility in a well-balanced manner.

In some embodiments of the technology disclosed herein, the peak temperature of tan δ of the adhesive constituting the high refractive index adhesive layer is preferably about-50 ℃ or higher, and further preferably about 50 ℃ or lower. Here, tan δ (loss tangent) of an adhesive refers to the ratio of the loss modulus G ″ of the adhesive to the storage modulus G'. Namely, tan δ = G "/G'. The tan δ of the adhesive can be determined as follows: a disk-shaped adhesive sample having a thickness of about 2mm and a diameter of 7.9mm was sandwiched between parallel plates, and a temperature dispersion test of the adhesive was performed in a shear mode using a viscoelasticity test apparatus under conditions of a measurement temperature range of-60 ℃ to 60 ℃ and a temperature rise rate of 5 ℃/min while applying a shear strain having a frequency of 1Hz, and based on the storage modulus G' (Pa) and the loss modulus G "(Pa) at that time, the following formula was applied: tan δ = G "/G'; and then the result is obtained. The peak temperature of tan δ (hereinafter sometimes referred to as tpeak.) of the adhesive can be determined from the transition of tan δ in the above temperature range. As the viscoelasticity test apparatus, ARES manufactured by TA Instruments, inc. or a product equivalent thereto can be used.

In some embodiments, the high refractive index adhesive layer advantageously has a Tpeak of 45 ℃ or less or 35 ℃ or less, preferably 30 ℃ or less (e.g., 25 ℃ or less), and may be 20 ℃ or less or 15 ℃ or less. With a binder having a lower Tpeak, good initial adhesiveness and adhesion tend to be easily obtained in a room temperature region. On the other hand, from the viewpoint of imparting appropriate cohesive properties to the adhesive, it is preferable that Tpeak of the adhesive is not too low, and that the adhesive is also suitable for achieving a high refractive index. From this viewpoint, in some embodiments, the Tpeak of the binder may be, for example, -40 ℃ or higher, may be-30 ℃ or higher, may be-20 ℃ or higher, may be-5 ℃ or higher, may be 15 ℃ or higher, and may be 25 ℃ or higher. The adhesive having a high Tpeak can be preferably used in such a manner that one or both of the adhesive and the adherend are heated to a temperature slightly higher than room temperature as needed at the time of adhesion to the adherend. The Tpeak of the binder can be adjusted by selecting the composition of the binder (for example, the composition of the monomer components constituting the base polymer, the refractive index improver, and the selection of whether or not the plasticizing material is used, the type of the plasticizing material, and the amount of the plasticizing material to be used).

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

(base Polymer)

In the technique disclosed herein, the type of the adhesive constituting the high refractive index adhesive layer is not particularly limited. The pressure-sensitive adhesive may be one containing 1 or 2 or more of various rubbery polymers such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, a mixture thereof, and the like), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers, and the like, which are used in the field of pressure-sensitive adhesives, as a pressure-sensitive adhesive polymer (which is defined as a structural polymer to be shaped into a pressure-sensitive adhesive, and hereinafter may be referred to as a "base polymer"). From the viewpoint of adhesive performance, cost, and the like, an adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably used. Among them, an adhesive (acrylic adhesive) containing an acrylic polymer as a base polymer is preferable. The techniques disclosed herein are preferably implemented using acrylic adhesives.

The following description will be mainly made of a high refractive index pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive, but the high refractive index pressure-sensitive adhesive layer in the technology disclosed herein is not intended to be limited to the acrylic pressure-sensitive adhesive layer.

In this specification, the "base polymer" of the pressure-sensitive adhesive is a main component of the rubber-like polymer contained in the pressure-sensitive adhesive, and is not to be construed in any way as limiting other than the above. The rubbery polymer is a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" means a component contained in an amount of more than 50% by weight unless otherwise specified.

In this specification, the "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least 1 (meth) acryloyl group in 1 molecule. Hereinafter, a monomer having at least 1 (meth) acryloyl group in 1 molecule is also referred to as an "acrylic monomer". Accordingly, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. As a typical example of the acrylic polymer, a polymer in which the ratio of the acrylic monomer in all monomers used for the synthesis of the acrylic polymer is higher than 50% by weight (preferably higher than 70% by weight, for example, higher than 90% by weight) can be cited.

In this specification, "(meth) acryloyl group" means an acryloyl group and a methacryloyl group as a whole. Similarly, "(meth) acrylate" is used in the sense of generically referring to both acrylate and methacrylate, and "(meth) acrylic acid" is used in the sense of generically referring to both acrylic acid and methacrylic acid. Therefore, the concept of the acrylic monomer as referred to herein may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

(acrylic Polymer (A))

The high index adhesive plies disclosed herein may preferably comprise a storage modulus G 'at 25 ℃ having a refractive index higher than 1.570' _V1 An acrylic pressure-sensitive adhesive layer having a total light transmittance of 86% or more and a haze value of 1.0% or less, wherein the acrylic pressure-sensitive adhesive layer has a thickness of 30kPa to 700kPa. The acrylic polymer as the base polymer of the acrylic pressure-sensitive adhesive layer is preferably a polymer containing an aromatic ring-containing monomer (m 1) as a monomer component constituting the acrylic polymer. That is, an acrylic polymer containing an aromatic ring-containing monomer (m 1) as a monomer unit is preferable. This acrylic polymer is also referred to as "acrylic polymer (a)" hereinafter. In the present specification, the term "monomer component constituting the acrylic polymer" refers to a monomer constituting a repeating unit of the acrylic polymer in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition, and is not limited to a monomer contained in the pressure-sensitive adhesive composition in the form of a polymer (which may be an oligomer) formed in advance or a monomer contained in the pressure-sensitive adhesive composition in the form of an unpolymerized monomer. That is, the monomer component constituting the acrylic polymer may be contained in the adhesive composition in any form of a polymer, an unpolymerized polymer, and a partially polymerized polymer. From the viewpoint of ease of production of the adhesive composition, and the like, in some embodiments, an adhesive composition containing substantially all (for example, 95 wt% or more, preferably 99 wt% or more) of the monomer component in the form of a polymer is preferable. The pressure-sensitive adhesive composition containing substantially all of the monomer components in the form of a polymer is also preferable from the viewpoint of easy formation of a laminate sheet with less deformation and warpage.

(monomer (m 1))

As the monomer (m 1), a compound containing at least 1 aromatic ring and at least 1 ethylenically unsaturated group in 1 molecule is used. As the monomer (m 1), 1 kind of the compound may be used alone or 2 or more kinds may be used in combination.

Examples of the ethylenically unsaturated group include a (meth) acryloyl group, a vinyl group, and a (meth) allyl group. From the viewpoint of polymerization reactivity, a (meth) acryloyl group is preferable, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferable. From the viewpoint of suppressing the decrease in flexibility of the adhesive, it is preferable to use, as the monomer (m 1), a compound having 1 number of ethylenically unsaturated groups contained in 1 molecule (i.e., a monofunctional monomer).

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

The aromatic ring of the compound used as the monomer (m 1) may be, for example, a benzene ring (may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); fused rings of naphthalene ring, indene ring, azulene ring, anthracene ring and phenanthrene ring; and the like carbon rings, for example, may be 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; and the like. The hetero atom contained as a ring-forming atom in the above-mentioned hetero ring may be, for example, 1 or 2 or more selected from the group consisting of nitrogen, sulfur and oxygen. In some embodiments, the heteroatom comprising the heterocyclic ring can be one or both of nitrogen and sulfur. The monomer (m 1) may have a structure in which 1 or 2 or more carbocyclic rings and 1 or 2 or more heterocyclic rings are fused, for example, as in a dinaphthothiophene structure.

The aromatic ring (preferably, carbocyclic ring) may have 1 or 2 or more substituents on the ring-constituting atoms, or may have no substituent. When a substituent is present, examples of the substituent include, but are not limited to, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (e.g., a fluorine atom, a chlorine atom, and a bromine atom), a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group. 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 1 or 2, for example. In some forms, the above aromatic ring may have no substituent on the ring-forming atoms, or 1 or 2 or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (e.g., a bromine atom). Note that the aromatic ring of the monomer (m 1) having a substituent on a ring-forming atom thereof means that the aromatic ring has a substituent other than a substituent containing an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be bonded directly or via a linking group. The linking group may be, for example, a group having 1 or 2 or more structures selected from alkylene groups, oxyalkylene groups, poly (oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups having a structure in which 1 or 2 or more hydrogen atoms in these groups are substituted with a hydroxyl group (for example, hydroxyalkylene groups), oxy groups (-O-groups), and thiooxy groups (-S-groups). In some modes, it may be preferable to employ an aromatic ring-containing monomer of a structure in which an aromatic ring is bonded to an ethylenically unsaturated group directly or via a linking group selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly (oxyalkylene) group. The number of carbon atoms in the alkylene group and the oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. The number of repeating oxyalkylene units in the poly (oxyalkylene) group may be, for example, 2 to 3.

Examples of the compound that can be preferably used as the monomer (m 1) include aromatic ring-containing (meth) acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth) acrylate and the aromatic ring-containing vinyl compound may be used singly or in combination of 1 or more. It is also possible to use 1 or 2 or more kinds of aromatic ring-containing (meth) acrylates in combination with 1 or 2 or more kinds of aromatic ring-containing vinyl compounds.

The content of the monomer (m 1) in the monomer component constituting the acrylic polymer (a) is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). In some embodiments, the content of the monomer (m 1) 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, or may be 70% by weight or more. In some preferable embodiments, the content of the monomer (m 1) is, for example, higher 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, from the viewpoint of easily obtaining a higher refractive index. The upper limit of the content of the monomer (m 1) in the monomer component is 100% by weight. From the viewpoint of achieving a good balance between the high refractive index and the adhesive and/or optical properties, the content of the monomer (m 1) is favorably less than 100% by weight, and is preferably about 99% by weight or less, more preferably 98% by weight or less, and may be 97% by weight or less, and may be 96% by weight or less, for example. In some embodiments, the content of the monomer (m 1) may be 93% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 75% by weight or less. In some embodiments where the adhesive property and/or the optical property are more important, the content of the monomer (m 1) in the monomer component may be 70 wt% or less, 60 wt% or less, or 45 wt% or less.

In some embodiments of the technology disclosed herein, a monomer having 2 or more aromatic rings (preferably carbocyclic rings) in 1 molecule can be preferably used as the monomer (m 1) in view of easily obtaining a high refractive index increasing effect. Examples of the monomer having 2 or more aromatic rings in 1 molecule (hereinafter, also referred to as "monomer having a plurality of aromatic rings") include: a monomer having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded (i.e., without via other atoms), 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-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds.

The above-mentioned linking group may be, for example, an oxy group (-O-) -) sulfo-oxo (-S-), oxoAlkyl (e.g. -O- (CH) ₂ ) _n A group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g. -S- (CH) ₂ ) _n A radical, where n is from 1 to 3, preferably 1), a linear alkylene radical (i.e. - (CH) ₂ ) _n A group wherein n is 1 to 6, preferably 1 to 3), a group in which an alkylene group in the oxyalkylene group, the thiooxyalkylene group and the straight-chain alkylene group is partially halogenated or fully halogenated, or the like. From the viewpoint of flexibility of the adhesive and the like, suitable examples of the linking group include an oxy group, a thioxo group, an oxyalkylene group, and a linear alkylene group. Specific examples of the monomer having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth) acrylate (e.g., m-phenoxybenzyl (meth) acrylate), thiophenyloxybenzyl (meth) acrylate, and benzylbenzyl (meth) acrylate).

The monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded may be, for example, (meth) acrylate having a biphenyl structure, (meth) acrylate having a triphenyl structure, biphenyl having a vinyl group, or the like. Specific examples thereof include o-phenylphenol (meth) acrylate and biphenylmethyl (meth) acrylate.

Examples of the monomer having a condensed aromatic ring structure include (meth) acrylate having a naphthalene ring, (meth) acrylate having an anthracene ring, naphthalene having a vinyl group, anthracene having a vinyl group, and the like. Specific examples thereof include 1-naphthylmethyl (meth) acrylate (also known as 1-naphthylmethyl (meth) acrylate), hydroxyethylated β -naphthol acrylate, 2-naphthylethyl (meth) acrylate, 2-naphthyloxyethyl acrylate, and 2- (4-methoxy-1-naphthyloxy) ethyl (meth) acrylate.

Specific examples of the monomer having a fluorene structure include 9,9-bis (4-hydroxyphenyl) fluorene (meth) acrylate, 9,9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene (meth) acrylate, and the like. The monomer having a fluorene structure includes a structural portion in which 2 benzene rings are directly chemically bonded to each other, and therefore, the monomer is included in the concept of the monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded to each other.

Examples of the monomer having a dinaphthothiophene structure include (meth) acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth) allyl group-containing dinaphthothiophene. Specific examples thereof include (meth) acryloyloxymethyl dinaphthothiophenes (for example, a dinaphthothiophene ring having CH bonded to the 5-or 6-position ₂ CH(R ¹ )C(O)OCH ₂ A compound of the structure of (a-b). Here, R ¹ Is a hydrogen atom or a methyl group. ) (meth) acryloyloxyethyl dinaphthothiophene (for example, CH is bonded to the 5-or 6-position of the dinaphthothiophene ring ₂ CH(R ¹ )C(O)OCH(CH ₃ ) -or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ A compound of the structure of (a-b). Here, R ¹ Is a hydrogen atom or a methyl group. ) Vinyl dinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5-or 6-position of a naphthothiophene ring), and (meth) allyloxydianhthothiophene. The monomer having a dinaphthothiophene structure includes a naphthalene structure and also has a structure in which 2 naphthalene structures are fused to a thiophene ring, and therefore, the monomer having a fused aromatic ring structure is included in the concept of the monomer having a fused aromatic ring structure.

Examples of the monomer having the dibenzothiophene structure include (meth) acryloyl group-containing dibenzothiophene and vinyl group-containing dibenzothiophene. The monomer having a dibenzothiophene structure has a structure in which 2 benzene rings are fused to a thiophene ring, and therefore, the monomer is included in the concept of the monomer having a fused aromatic ring structure.

The dinaphthothiophene structure and the dibenzothiophene structure do not belong to a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded.

As the monomer (m 1) in the technology disclosed herein, a monomer having 1 aromatic ring (preferably, a carbocyclic ring) in 1 molecule may also be used. The monomer having 1 aromatic ring in 1 molecule can contribute to, for example, improvement of flexibility, adjustment of adhesive properties, improvement of transparency, and the like of the adhesive. In some embodiments, from the viewpoint of improving the refractive index of the adhesive, a monomer having 1 aromatic ring in 1 molecule is preferably used in combination with a monomer containing a plurality of aromatic rings.

Examples of the monomer having 1 aromatic ring in 1 molecule include (meth) acrylates containing a carbon aromatic ring such as benzyl (meth) acrylate, methoxybenzyl (meth) acrylate, phenyl (meth) acrylate, ethoxylated phenol (meth) acrylate, phenoxypropyl (meth) acrylate, phenoxybutyl (meth) acrylate, cresol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and chlorobenzyl (meth) acrylate; bromine-substituted aromatic ring-containing (meth) acrylates such as 2- (4,6-dibromo-2-sec-butylphenyloxy) ethyl (meth) acrylate, 2- (4,6-dibromo-2-isopropylphenoxy) ethyl (meth) acrylate, 6- (4,6-dibromo-2-sec-butylphenyloxy) hexyl (meth) acrylate, 6- (4,6-dibromo-2-isopropylphenoxy) hexyl (meth) acrylate, 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; vinyl compounds containing a carbon aromatic ring such as styrene, α -methylstyrene, vinyltoluene and t-butylstyrene; compounds having a vinyl substituent on the heteroaromatic ring, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; and the like.

As the monomer (m 1), a monomer having an oxyethylene chain structure between the ethylenically unsaturated group and the aromatic ring in the above-described various aromatic ring-containing monomers can be used. Such a monomer having an oxyethylene chain sandwiched between an ethylenically unsaturated group and an aromatic ring can be grasped as an ethoxylate of the original monomer. Oxyethylene unit (-CH) in the above oxyethylene chain ₂ CH ₂ The number of repetitions of O-) is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, 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.

The content of the monomer having a plurality of aromatic rings in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer (m 1) may be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. Substantially 100% by weight of the monomer (m 1) may be a monomer containing a plurality of aromatic rings. That is, as the monomer (m 1), only 1 or 2 or more kinds of monomers containing a plurality of aromatic rings may be used. In some embodiments, for example, in view of the balance between the high refractive index and the adhesive property and/or the optical property, the content of the monomer containing a plurality of aromatic rings in the monomer (m 1) 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, the content of the monomer having a plurality of aromatic rings in the monomer (m 1) 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 in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the monomer having a plurality of aromatic rings in the monomer (m 1) is less than 5% by weight. A monomer containing a plurality of aromatic rings may not be used.

The content of the monomer containing a plurality of aromatic rings in the monomer components constituting the acrylic polymer is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). The content of the monomer having a plurality of aromatic rings in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, higher than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. The content of the monomer having a plurality of aromatic rings in the monomer component may be 100% by weight, but from the viewpoint of well-balanced compatibility between the high refractive index and the adhesive property and/or the optical property, it is favorably less than 100% by weight, preferably about 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, or may be 75% by weight or less. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer component may be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the monomer having a plurality of aromatic rings in the monomer components is less than 3% by weight.

In some aspects of the technology disclosed herein, it may be preferable to employ a high refractive index monomer as at least a part of the monomer (m 1). Here, the "high refractive index monomer" refers to a monomer having a refractive index of, for example, about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, and is, for example, 3.000 or less, 2.500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less, from the viewpoint of ease of preparation of the pressure-sensitive adhesive composition and ease of compatibility with flexibility suitable as a pressure-sensitive adhesive. The high refractive index monomer may be used alone in 1 kind or in combination of 2 or more kinds.

The refractive index of the monomer was measured using an Abbe refractometer at a measurement wavelength of 589nm and a measurement temperature of 25 ℃. As the Abbe refractometer, model number "DR-M4" manufactured by ATAGO or its equivalent can be used. In the case where a nominal value of the refractive index at 25 ℃ is provided by the manufacturer or the like, the nominal value may be adopted.

As the high refractive index monomer, a compound having a suitable refractive index can be suitably used from among compounds (for example, the compounds and compound groups exemplified above) included in the concept of the aromatic ring-containing monomer (m 1) disclosed herein. Specific examples thereof 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 (repetition number of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD 20): 1.519, tg of homopolymer: 6 ℃ C.), phenoxyethyl acrylate (refractive index (nD 20): 1.517, tg of homopolymer: 2 ℃ C.), phenoxydiglycol acrylate (refractive index: 1.510, tg of homopolymer: -35 ℃ C.), 6-acryloyloxymethyl dinaphthothiophene (6 MDNTA, refractive index: 1.75), 6-methacryloyloxymethyl dinaphthothiophene (6 MDNTMA, refractive index: 1.726), 5-acryloyloxyethyl dinaphthothiophene (5 EDNTA, refractive index: 1.786), 6-acryloyloxyethyl dinaphthothiophene (6 MDNTA, 3532), vinyldinaphthothiophene (5 EDNTNT), vinyldinaphthothiophene (refractive index: 3425: 3432, VDNTNT), etc., but these refractive indexes are not limited to VDNTNT 2, VDNTNT).

The content of the high-refractive-index monomer (i.e., aromatic ring-containing monomer having a refractive index of about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more) in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer (m 1) may be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily obtaining a higher refractive index. Substantially 100% by weight of the monomer (m 1) may be a high refractive index monomer. In some embodiments, for example, from the viewpoint of achieving a good balance between the high refractive index and the adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer (m 1) 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, and may be 65% by weight or less. In some aspects, the content of the high refractive index monomer in the monomer (m 1) may be 70 wt% or less, may be 50 wt% or less, may be 25 wt% or less, may be 15 wt% or less, and may be 10 wt% or less in consideration of adhesive characteristics and/or optical characteristics. The technique disclosed herein may also be carried out in such a manner that the content of the high refractive index monomer in the monomer component (m 1) is less than 5% by weight. The high refractive index monomer may not be used.

The content of the high refractive index monomer in the monomer component constituting the acrylic polymer is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both a desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). The content of the high refractive index monomer in the monomer component may be, for example, 3 wt% or more, 10 wt% or more, or 25 wt% or more. In some embodiments, the content of the high refractive index monomer in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, may be higher 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, or may be 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. The content of the high refractive index monomer in the monomer component may be 100% by weight, but from the viewpoint of achieving a good balance between the high refractive index and the adhesive and/or optical properties, it is advantageously less than 100% by weight, preferably 99% by weight or less, more preferably 98% by weight or less, and may be 96% by weight or less, and may be 93% by weight or less, and may be 90% by weight or less, and may be 85% by weight or less, and may be 80% by weight or less, and may be 75% by weight or less. In some embodiments, the content of the high refractive index monomer in the monomer component may be 70 wt% or less, may be 50 wt% or less, may be 25 wt% or less, may be 15 wt% or less, and may be 5 wt% or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the high refractive index monomer in the above monomer components is less than 3% by weight.

In some preferred embodiments of the technology disclosed herein, an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") having a homopolymer Tg of 10 ℃ or less (preferably 5 ℃ or less or 0 ℃ or less, more preferably-10 ℃ or less, further preferably-20 ℃ or less, for example-25 ℃ or less) is used as at least a part of the monomer (m 1). When the content of the aromatic ring-containing monomer (m 1) (particularly, the aromatic ring-containing monomer (m 1) corresponding to one or both of the aromatic ring-containing monomer and the high refractive index monomer) in the monomer component is increased, the storage modulus G 'of the adhesive tends to be generally increased, and by using the monomer L as a part or the whole of the monomer (m 1), the increase in the storage modulus G' can be suppressed. This can improve the refractive index while maintaining flexibility suitable as a binder more favorably. The lower limit of the Tg of the monomer L is not particularly limited. In some embodiments, the Tg of the monomer L may be, for example, -70 ℃ or higher, may be-55 ℃ or higher, or may be-45 ℃ or higher, in view of the balance with the refractive index-improving effect. The monomers L may be used alone in 1 kind or in combination of 2 or more kinds.

As the monomer L, a compound having a Tg corresponding to that of the compound included in the concept of the aromatic ring-containing monomer (m 1) disclosed herein (for example, the compound and the compound group exemplified above) can be appropriately used. As a suitable example of the aromatic ring-containing monomer usable as the monomer L, m-phenoxybenzyl acrylate (homopolymer Tg: -35 ℃ C.) can be mentioned. As another suitable example, phenoxy diethylene glycol acrylate (homopolymer Tg: -35 ℃ C.) may be mentioned.

The content of the monomer L in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer L in the monomer (m 1) may be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily obtaining a binder having both a high refractive index and flexibility at a higher level. The monomer L may be substantially 100% by weight of the monomer (A1). In some embodiments, for example, from the viewpoint of achieving both flexibility and high refractive index which are suitable as a binder in a good balance, the content of the monomer L in the monomer (m 1) 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 technique disclosed herein can also be carried out in such a manner that the content of the monomer L in the monomer (m 1) is less than 5% by weight. The monomer L may not be used.

The content of the monomer L in the monomer components constituting the acrylic polymer may be, for example, 3 wt% or more, 10 wt% or more, or 25 wt% or more. In some embodiments, the content of the monomer L in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, may be higher 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, or may be 95% by weight or more, from the viewpoint of easily obtaining a binder having both a high refractive index and flexibility at a higher level. The content of the monomer L in the monomer component may be 100% by weight, but in consideration of the balance between the high refractive index and the adhesive property and/or the optical property, it is favorably less than 100% by weight, preferably about 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, or may be 75% by weight or less. In some embodiments, the content of the monomer L in the monomer component may be 70 wt% or less, may be 50 wt% or less, may be 25 wt% or less, may be 15 wt% or less, or may be 5 wt% or less. The technique disclosed herein can also be carried out in such a manner that the content of the monomer L in the above-mentioned monomer components is less than 3% by weight.

In some embodiments, based on the composition of the monomer (m 1) from the viewpoint of flexibility of the adhesiveGlass transition temperature Tg _m1 Advantageously, the temperature is about 20 ℃ or lower, preferably 10 ℃ or lower (e.g., 5 ℃ or lower), more preferably 0 ℃ or lower, still more preferably-10 ℃ or lower, and may be-20 ℃ or lower, or may be-25 ℃ or lower. Glass transition temperature Tg _m1 The lower limit of (b) is not particularly limited. In some ways, the glass transition temperature Tg is taken into consideration in balance with the refractive index-increasing effect _m1 For example, the temperature may be-70 ℃ or higher, may be-55 ℃ or higher, or may be-45 ℃ or higher. The techniques disclosed herein may also be used at the glass transition temperature Tg _m1 For example, at-40 ℃ or higher, -35 ℃ or higher, -33 ℃ or higher, -30 ℃ or higher, or-25 ℃ or higher.

Here, the glass transition temperature Tg based on the composition of the monomer (m 1) _m1 The method comprises the following steps: the Tg determined by the following Fox equation is used based only on the composition of the monomer (m 1) in the monomer components constituting the acrylic polymer. Glass transition temperature Tg _m1 The following Fox formula can be applied to only the monomer (m 1) among the monomer components constituting the acrylic polymer, and the glass transition temperature of the homopolymer of each aromatic ring-containing monomer used as the monomer (m 1) and the weight fraction of each aromatic ring-containing monomer in the total amount of the monomer (m 1) can be calculated. In the mode of using only 1 monomer as the monomer (m 1), tg and glass transition temperature Tg of a homopolymer of the monomer _m1 And (5) the consistency is achieved.

In some embodiments, as the aromatic ring-containing monomer (m 1), a monomer L (i.e., an aromatic ring-containing monomer having a homopolymer Tg of 10 ℃ or less, preferably 5 ℃ or less, or 0 ℃ or less, more preferably-10 ℃ or less, further preferably-20 ℃ or less, for example-25 ℃ or less) and a monomer H having a Tg of more than 10 ℃ may be used in combination. The Tg of the monomer H may be, for example, higher than 10 ℃, higher than 15 ℃ or higher than 20 ℃. By using the monomer L and the monomer H in combination, for example, in a configuration in which the content of the aromatic ring-containing monomer (m 1) in the monomer component is large, it is possible to achieve both high refractive index and flexibility of the adhesive at a higher level. The amount ratio of the monomer L to the monomer H used is not particularly limited, and may be set so as to exhibit the above-mentioned effects. For example, it is preferable to satisfy the aboveAny glass transition temperature Tg _m1 The ratio of the amount of the monomer L to the amount of the monomer H used is set as described in (1).

In some embodiments, the aromatic ring-containing monomer (m 1) may preferably be selected from compounds that do not include a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, the acrylic polymer is preferably composed of a monomer component having a composition in which the content of a compound having a structure in which 2 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). From the viewpoint of achieving an adhesive agent that has flexibility, adhesiveness, and a high refractive index in a well-balanced manner, it may be advantageous to limit the amount of the compound having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded to each other.

(monomer (m 2))

In some embodiments of the technology disclosed herein, the monomer component constituting the acrylic polymer may further contain a monomer (m 2) in addition to the monomer (m 1). The monomer (m 2) is a monomer belonging 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-mentioned hydroxyl group-containing monomer is a compound having at least 1 hydroxyl group and at least 1 ethylenically unsaturated group in 1 molecule. The above carboxyl group-containing monomer is a compound containing at least 1 carboxyl group and at least 1 ethylenically unsaturated group in 1 molecule. The monomer (m 2) can contribute to introduction of a crosslinking point into the acrylic polymer or to impart appropriate cohesive properties to the adhesive. The monomer (m 2) may be used alone in 1 kind or in combination of 2 or more kinds. The monomer (m 2) is typically a monomer containing no aromatic ring.

Examples of the ethylenically unsaturated group of the monomer (m 2) include a (meth) acryloyl group, a vinyl group, and a (meth) allyl group. From the viewpoint of polymerization reactivity, a (meth) acryloyl group is preferable, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferable. From the viewpoint of suppressing the decrease in flexibility of the adhesive, it is preferable to use, as the monomer (m 2), a compound having 1 number of ethylenically unsaturated groups contained in 1 molecule (i.e., a monofunctional monomer).

Examples of the hydroxyl group-containing monomer include, but are not limited to, hydroxyalkyl (meth) acrylates such as 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 which can be preferably used include 4-hydroxybutyl acrylate (Tg: -40 ℃) and 2-hydroxyethyl acrylate (Tg: -15 ℃). From the viewpoint of improving flexibility in the room temperature region, 4-hydroxybutyl acrylate having a lower Tg is more preferable. In a preferred embodiment, it is possible that 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 (m 2) is 4-hydroxybutyl acrylate. The hydroxyl group-containing monomers may be used singly in 1 kind or in combination of 2 or more kinds.

In some modes of using a hydroxyl group-containing monomer as the monomer (m 2), the above hydroxyl group-containing monomer may be 1 or 2 or more selected from compounds having no methacryloyl group. Suitable examples of the hydroxyl group-containing monomer having no methacryloyl group include the above-mentioned various 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 monomers used as the monomer (m 2) is hydroxyalkyl acrylate. By using the hydroxyalkyl acrylate, a hydroxyl group contributing to providing a crosslinking point and imparting appropriate cohesive property can be introduced into the acrylic polymer, and a pressure-sensitive adhesive having good flexibility and adhesion in a room temperature region can be easily obtained as compared with a case where only the corresponding hydroxyalkyl methacrylate is used.

Examples of the carboxyl group-containing monomer include, but are not limited to, acrylic monomers such as (meth) acrylic acid, carboxyethyl (meth) acrylate, and carboxypentyl (meth) acrylate, and itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Examples of the carboxyl group-containing monomer that can be preferably used include acrylic acid and methacrylic acid. The carboxyl group-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds. A combination of a hydroxyl group-containing monomer and a carboxyl group-containing monomer may also be used.

The content of the monomer (m 2) in the monomer components constituting the acrylic polymer is not particularly limited and may be set according to the purpose. In some embodiments, the content of the monomer (m 2) may be, for example, 0.01 wt% or more, 0.1 wt% or more, or 0.5 wt% or more. From the viewpoint of obtaining a higher effect of use, the content of the monomer (A2) may be preferably 1% by weight or more, 2% by weight or more, or 4% by weight or more in some embodiments. The upper limit of the content of the monomer (m 2) in the monomer component is set so that the total content thereof with the content of other monomers does not exceed 100% by weight. In some embodiments, the content of the monomer (m 2) is preferably 30% by weight or less or 25% by weight or less, and from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index, the content 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.

In the embodiment using a hydroxyl group-containing monomer as the monomer (m 2), the content of the hydroxyl group-containing monomer in the monomer component is not particularly limited, and may be, for example, 0.01 wt% or more (preferably 0.1 wt% or more, more preferably 0.5 wt% or more). In some embodiments, the content of the hydroxyl group-containing monomer is preferably 1% by weight or more, may be 2% by weight or more, and may be 4% by weight or more of the monomer component. The upper limit of the content of the hydroxyl group-containing monomer in the monomer component is set so that the total content of the hydroxyl group-containing monomer and the content of the other monomer does not exceed 100% by weight, and is preferably 30% by weight or less or 25% by weight or less, for example, and from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index, the content 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, or may be less than 7% by weight.

In the embodiment using a carboxyl group-containing monomer as the monomer (m 2), the content of the carboxyl group-containing monomer in the monomer component is not particularly limited, and may be, for example, 0.01 wt% or more (preferably 0.1 wt% or more, more preferably 0.3 wt% 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 amount thereof and the amount of other monomers used does not exceed 100% by weight, and is preferably 30% by weight or less or 25% by weight or less, for example, and 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 from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index. In some embodiments, the content of the carboxyl group-containing monomer is favorably less than 7% by weight, preferably 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, from the viewpoint of improving the flexibility of the binder. The technique disclosed herein can be preferably carried out, for example, in such a manner that only a hydroxyl group-containing monomer is used as the monomer (m 2), that is, in such a manner that a carboxyl group-containing monomer is not used.

The total content of the monomer (m 1) and the monomer (m 2) in the monomer components constituting the acrylic polymer may be, for example, 31 wt% or more, preferably 51 wt% or more, 61 wt% or more, or 71 wt% or more. In some embodiments, from the viewpoint of easily and suitably exhibiting the effects of these monomers, the total content of the monomer (m 1) and the monomer (m 2) in the monomer components constituting the acrylic polymer may be, for example, 76% by weight or more, preferably 81% by weight or more, may be 86% by weight or more, may be 91% by weight or more, may be 96% by weight or more, may be 99% by weight or more, or may be substantially 100% by weight.

(monomer m 3)

The monomer component constituting the acrylic polymer may contain a monomer other than the monomer (m 1) and the monomer (m 2) as required. An example of such an optional component is alkyl (meth) acrylate (hereinafter also referred to as "monomer (m 3)"). The monomer (m 3) can contribute to adjustment of flexibility of the adhesive and improvement of compatibility in the adhesive.

As the monomer (m 3), one having 1 to 20 carbon atoms at the ester terminal (i.e., C) _1-20 Of (b) a linear or branched alkyl (meth) acrylate. As (meth) acrylic acid C _1-20 Specific examples of the alkyl ester include, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (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, and eicosyl (meth) acrylate.

In some embodiments, it may be preferable to use, as at least a part of monomer (m 3), an alkyl (meth) acrylate whose homopolymer has a Tg of-20 ℃ or lower (more preferably-40 ℃ or lower, for example-50 ℃ or lower). Such low Tg alkyl (meth) acrylates can help to improve the flexibility of the adhesive. The lower limit of Tg of the above-mentioned alkyl (meth) acrylate is not particularly limited, and may be, for example, not less than-85 ℃, not less than-75 ℃, not less than-65 ℃ or not less than-60 ℃. Specific examples of the low Tg alkyl (meth) acrylate include n-Butyl Acrylate (BA), 2-ethylhexyl acrylate (2 EHA), isononyl acrylate (iNA), and the like.

In some embodiments using the monomer (m 3), it is preferable that at least a part of the monomer (m 3) is an alkyl acrylate from the viewpoint of flexibility, adhesiveness, and the like. For example, it is preferable that 50% by weight or more (more preferably 75% by weight or more, and still more preferably 90% by weight or more) of the monomer (m 3) is an alkyl acrylate. The method may be one in which only 1 or 2 or more alkyl acrylates are used as the monomer (m 3) and alkyl methacrylates are not used.

In the embodiment where the monomer component contains an alkyl (meth) acrylate, the content of the alkyl (meth) acrylate in the monomer component may be set so as to exhibit its use effect appropriately. In some embodiments, the content of the alkyl (meth) acrylate may be, for example, 1 wt% or more, 3 wt% or more, 5 wt% or more, or 8 wt% or more. In some embodiments, the content of the 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 the monomer (m 3) in the monomer component is set so that the total content thereof with the content of other monomers does not exceed 100% by weight, and may be, for example, less than 50% by weight. In some embodiments, the content of the above monomer (m 3) may be, for example, less than 35% by weight. Since the refractive index of the alkyl (meth) acrylate is generally low, it is advantageous to relatively increase the content of the monomer (m 1) by limiting the content of the monomer (m 3) in the monomer component in order to increase the refractive index. From this viewpoint, the content of the monomer (m 3) is favorably 24% by weight or less, 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, and may be less than 1% by weight of the monomer component. The monomer (m 3) may be substantially not used.

(other monomers)

The monomer component constituting the acrylic polymer may contain a monomer other than the monomers (m 1), (m 2), and (m 3) (hereinafter referred to as "other monomer") as necessary. The other monomers may be used for the purpose of, for example, adjusting Tg of the acrylic polymer, adjusting adhesive properties, improving compatibility in the adhesive layer, and the like. The other monomers can be used alone in 1 or a combination of 2 or more.

Examples of the other monomer include monomers having a functional group other than a hydroxyl group and a carboxyl group (functional group-containing monomers). Examples of the other monomers capable of improving the cohesive force and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, and cyano group-containing monomers. Examples of the monomer capable of introducing a functional group capable of serving as a crosslinking base point into the acrylic polymer, or contributing to an improvement in peel strength and an improvement in compatibility in the pressure-sensitive adhesive layer include an amide group-containing monomer (e.g., (meth) acrylamide, N-methylol (meth) acrylamide, etc.), an amino group-containing monomer (e.g., (meth) aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, etc.), a monomer having a ring containing a nitrogen atom (e.g., N-vinyl-2-pyrrolidone, N- (meth) acryloylmorpholine, etc.), an imide group-containing monomer, an epoxy group-containing monomer, a ketone group-containing monomer, an isocyanate group-containing monomer, an alkoxysilyl group-containing monomer, and the like. Among the monomers having a nitrogen atom-containing ring, for example, N-vinyl-2-pyrrolidone is also a monomer belonging to an amide group-containing monomer. The same applies to the relationship between the monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Examples of the other monomers that can be used in addition to the functional group-containing monomer include vinyl ester monomers such as vinyl acetate; non-aromatic ring-containing (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; olefin 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 monomers such as methyl vinyl ether; and so on. As a suitable example of the other monomer which can be used for the purpose of improving the flexibility of the adhesive, etc., ethoxyethoxyethoxyethyl acrylate (also known as ethylcarbitol acrylate, homopolymer Tg: -67 ℃ C.) can be mentioned.

When the above-mentioned other monomers are used, the amount thereof to be used is not particularly limited, and may be appropriately set within a range that the total amount of the monomer components does not exceed 100% by weight. In some embodiments, the content of the other monomer in the monomer component may be, for example, about 35% by weight or less, preferably about 25% by weight or less (for example, 0 to 25% by weight), or may be about 20% by weight or less (for example, 0 to 20% by weight), or may be about 10% by weight or less, or may be about 5% by weight or less, or may be, for example, about 1% by weight, from the viewpoint of easily exerting the refractive index improving effect by the use of the monomer (m 1). The techniques disclosed herein can be preferably carried out in such a manner that the monomer component does not substantially contain the other monomers described above.

In some embodiments, the monomer component constituting the acrylic polymer may 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 in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. From the viewpoint of achieving a pressure-sensitive adhesive that has flexibility, adhesiveness, and a high refractive index in a well-balanced manner, it may be advantageous to limit the amount of the methacryloyl group-containing monomer used in this manner. The monomer component constituting the acrylic polymer may be a composition containing no methacryloyl group-containing monomer (for example, a composition containing only an acryloyl group-containing monomer).

In some embodiments, the amount of the carboxyl group-containing monomer used is preferably limited in view of suppressing coloring or discoloration (e.g., yellowing) of the pressure-sensitive adhesive layer with respect to the monomer component of the base polymer (e.g., acrylic polymer) constituting the high-refractive-index pressure-sensitive adhesive layer. The amount of the carboxyl 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. From the viewpoint of suppressing corrosion of a metal material (for example, a metal wiring, a metal film, or the like that may be present on an adherend) that may be disposed in contact with or in proximity to the high refractive index pressure-sensitive adhesive layer, it is also advantageous to limit the amount of the carboxyl group-containing monomer used in this way. The technique disclosed herein can be preferably carried out in such a manner that the monomer component does not contain a carboxyl group-containing monomer.

For the same reason, in some aspects, the monomer component of the base polymer constituting the high refractive index adhesive layer is preferably limited in the amount of the monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, and the like in addition to a carboxyl group). As the amount of the acidic functional group-containing monomer used in the monomer component of this embodiment, the preferable amount of the carboxyl group-containing monomer can be used. The technique disclosed herein can be preferably carried out in such a manner that the monomer component does not contain an acid group-containing monomer (i.e., in such a manner that the base polymer of the high-refractive-index adhesive layer is acid-free).

(glass transition temperature Tg of base Polymer _T )

In some aspects, the glass transition temperature Tg of the base polymer (e.g., acrylic polymer) of the adhesive layer based on the composition of the monomer components that make up the polymer _T Suitably at a temperature of about 20 ℃ or lower, preferably at a temperature of about 10 ℃ or lower, more preferably at a temperature of 0 ℃ or lower, and may be at a temperature of-10 ℃ or lower, may be at a temperature of-20 ℃ or lower, may be at a temperature of-25 ℃ or lower, may be at a temperature of-28 ℃ or lower, or may be at a temperature of-30 ℃ or lower. Glass transition temperature Tg _T When the content is low, it may be advantageous from the viewpoint of improving the flexibility of the adhesive. In addition, the glass transition temperature Tg _T For example, it may be-60 ℃ or higher, and from the viewpoint of facilitating the increase in refractive index of the adhesive, it is preferably-50 ℃ or higher, more preferably higher than-45 ℃, and may be higher than-40 ℃, may be higher than-35 ℃, may be higher than-25 ℃, may be-15 ℃ or higher, and may be-5 ℃ or higher.

Here, the glass transition temperature Tg of the polymer _T Unless otherwise specified, the term "glass transition temperature" refers to the glass transition temperature determined by the Fox equation based on the composition of the monomer components constituting the polymer. The Fox formula is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing monomers constituting the copolymer, as shown below.

1/Tg＝Σ(Wi/Tgi)

In the Fox formula, tg represents the glass transition temperature (unit: K) of the copolymer, wi represents the weight fraction (copolymerization ratio on the weight basis) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of the homopolymer of the monomer i.

As the glass transition temperature of the homopolymer used for calculating Tg, a value described in publicly known data such as "Polymer Handbook" (3 rd edition, john Wiley & Sons, inc., 1989) was used. The highest value was used for the monomers with various values described in the above Polymer Handbook. In the case where the Tg of a homopolymer is not described in the publicly known documents, a value obtained by the measurement method described in Japanese patent application laid-open No. 2007-51271 is used.

(method for producing base Polymer)

In the technique disclosed herein, the method for obtaining the base polymer of the pressure-sensitive adhesive layer (for example, the acrylic polymer (a) composed of the monomer components described above) is not particularly limited, and known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately employed. In some embodiments, solution polymerization may be preferred. The polymerization temperature in the solution polymerization may be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and may be, for example, about 20 to 170 ℃ (typically about 40 to 140 ℃).

The solvent (polymerization solvent) used for the solution polymerization may be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) selected from toluene and the like; acetic acid esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane and other halogenated alkanes; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as t-butyl methyl ether; ketones such as methyl ethyl ketone; etc. or a mixed solvent of 2 or more.

The initiator used for the polymerization may be appropriately selected from conventionally known polymerization initiators depending on the kind of the polymerization method. For example, 1 or 2 or more azo polymerization initiators such as 2,2' -Azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; an aromatic carbonyl compound; and the like. As still another example of the polymerization initiator, a redox-type initiator based on a combination of a peroxide and a reducing agent can be cited. The polymerization initiators may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the polymerization initiator to be used may be a usual amount, and may be selected from a range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer component.

In 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, and α -thioglycerol can be used. Alternatively, a chain transfer agent (non-sulfur chain transfer agent) containing no sulfur atom may be used. Examples of the non-sulfur chain transfer agent include anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenes such as α -pinene and terpinolene; styrenes such as α -methylstyrene and α -methylstyrene dimer; and the like. The chain transfer agent may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the chain transfer agent used may be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer raw material.

The weight average molecular weight (Mw) of the base polymer is not particularly limited, and may be, for example, about 10X 10 ⁴ ～500×10 ⁴ The range of (1). From the viewpoint of adhesive properties, the Mw of the base polymer is preferably at about 20X 10 ⁴ ～400×10 ⁴ (more preferably about 30X 10) ⁴ ～150×10 ⁴ E.g. about 50X 10 ⁴ ～130×10 ⁴ ) In (c) is used.

Here, the Mw of the polymer can be determined in terms of polystyrene by Gel Permeation Chromatography (GPC). Specifically, the measurement was carried out under the following conditions using a GPC measurement apparatus having the trade name "HLC-8220GPC" (manufactured by Tosoh corporation).

[ measurement conditions of GPC ]

Sample concentration: 0.2 wt% (tetrahydrofuran solution)

Sample injection amount: 10 μ L

Eluent: tetrahydrofuran (THF)

Flow rate (flow velocity): 0.6 mL/min

Column temperature (measurement temperature): 40 deg.C

Column:

sample column: the trade name "TSKguardcolumn SuperHZ-H"1 root + the trade name "TSKgel SuperHZM-H"2 roots (manufactured by Tosoh Corp.)

Reference column: trade name "TSKgel SuperH-RC"1 root (manufactured by Tosoh corporation)

A detector: differential Refractometer (RI)

Standard sample: polystyrene

(refractive index improver)

In some aspects of the technology disclosed herein, a high refractive index adhesive layer (e.g., an acrylic adhesive layer) may contain a refractive index improver, if necessary, in addition to the base polymer. Here, in the present specification, the refractive index improver means a material capable of improving the refractive index of the adhesive layer by using the same. As the refractive index improver, a material having a refractive index higher than that of the adhesive layer containing the refractive index improver can be preferably used. In addition, as the refractive index improver, a material having a refractive index higher than that of the base polymer (for example, acrylic polymer (a)) of the pressure-sensitive adhesive layer containing the refractive index improver can be preferably used. By appropriately using the refractive index improver, both a higher refractive index and practical adhesion performance can be appropriately achieved. In some embodiments, 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. The functional group may or may not have a polymerizable functional group. The refractive index improver may be used alone in 1 kind or in combination of 2 or more kinds.

Refractive index improver (e.g., additive (H) described later) _RO ) The refractive index of the base polymer is not limited to a specific range because the refractive index can be set to an appropriate range by a relative relationship with the refractive index of the base polymer. The refractive index of the refractive index improver can be selected, for example, from a range of higher than 1.55, higher than 1.56, or higher than 1.57, and higher than the refractive index of the base polymer. From the viewpoint of increasing the refractive index of the binder, there are some methodsAmong them, the refractive index improver advantageously has a refractive index of 1.58 or more, preferably 1.60 or more, more preferably 1.63 or more, and may be 1.65 or more, may be 1.70 or more, and may be 1.75 or more. With a higher refractive index improver, the target refractive index can be achieved through the use of a smaller amount of the refractive index improver. This is preferable from the viewpoint of suppressing the decrease in adhesive properties and optical properties. The upper limit of the refractive index improver is not particularly limited, and from the viewpoint of compatibility in the binder, an increase in refractive index, and easiness of compatibility with flexibility suitable as a binder, for example, the refractive index improver may be 3.000 or less, 2.500 or less, 2.000 or less, 1.950 or less, 1.900 or less, or 1.850 or less.

In some forms, the refractive index improver (e.g., additive (H) described later) _RO ) Refractive index n of) _b Refractive index n with base polymer _a A difference of (i.e. n) _b -n _a (hereinafter also referred to as "Δ n _A ". ) Is set to be greater than 0. In some modes, Δ n _A For example, the content is 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, and may be 0.20 or more, or 0.25 or more. Making Δ n by selecting base polymer and refractive index improver _A The refractive index improving agent tends to be more effective in improving the refractive index. In some embodiments, Δ n is calculated from the viewpoint of compatibility in the pressure-sensitive adhesive layer, transparency of the pressure-sensitive adhesive layer, and the like _A For example, it may be 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35 or less.

In some modes, a refractive index improver (e.g., an additive (H) described later) _RO ) Refractive index n of) _b Refractive index n of adhesive layer containing the refractive index improver _T The difference, i.e. n _b -n _T (hereinafter also referred to as "Δ n _B ". ) Is set to be greater than 0. In some modes, Δ n _B For example, 0.02 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or moreThe above. Δ n by selecting the composition of the adhesive layer and the refractive index improver _B The refractive index improving agent tends to be more effective in improving the refractive index. In some embodiments, Δ n is set from the viewpoint of compatibility in the pressure-sensitive adhesive layer, transparency of the pressure-sensitive adhesive layer, or the like _B For example, it may be 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35 or less.

The amount of the refractive index improver used relative to 100 parts by weight of the base polymer (the total amount of a plurality of refractive index improvers when used) is not particularly limited and may be set according to the purpose. From the viewpoint of increasing the refractive index of the binder, the amount of the refractive index improver used may be, for example, 1 part by weight or more and advantageously 3 parts by weight or more, preferably 5 parts by weight or more and preferably 7 parts by weight or more, and may be 10 parts by weight or more, and may be 15 parts by weight or more, and may be 20 parts by weight or more, based on 100 parts by weight of the base polymer. In some embodiments, the amount of the refractive index improver used may be, for example, 80 parts by weight or less based on 100 parts by weight of the base polymer, and is preferably 60 parts by weight or less, more preferably 45 parts by weight or less, from the viewpoint of achieving a good balance between the increase in refractive index of the adhesive and the suppression of the decrease in adhesive properties and optical properties. In some embodiments where the adhesion property and the optical property are more important, the refractive index improver 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, 10 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the base polymer. The technique disclosed herein can also be preferably carried out in such a manner that the amount of the refractive index improver used is less than 1 part by weight relative to 100 parts by weight of the base polymer in the adhesive layer, or the refractive index improver is not substantially used. Here, substantially unused means at least not intentionally used.

(additive (H) _RO ))

In some embodiments, as the refractive index improver, an organic material having a refractive index higher than that of the base polymer can be preferably usedAnd (5) feeding. Hereinafter, such an organic material may be referred to as "additive (H) _RO ) ". Here, the above "H _RO "indicates an Organic material having a High Refractive index (High Refractive index). By using a base polymer (e.g., an acrylic polymer, preferably the acrylic polymer (A)) in combination with the additive (H) _RO ) An adhesive having a refractive index and adhesive properties (peel strength, flexibility, etc.) and/or optical properties (total light transmittance, haze value, etc.) can be obtained at the same time. As additive (H) _RO ) The organic material of (a) may be a polymer or a non-polymer. The functional group may or may not have a polymerizable functional group. Additive (H) _RO ) 1 or more species may be used alone or in combination.

Additive (H) _RO ) The refractive index of (B) was measured using an Abbe refractometer under the conditions of a measurement wavelength of 589nm and a measurement temperature of 25 ℃ in the same manner as the refractive index of the monomer. When a nominal value of the refractive index at 25 ℃ is provided by a manufacturer or the like, the nominal value can be adopted.

As additive (H) _RO ) The molecular weight of the organic material to be used is not particularly limited and may be selected according to the purpose. Additive (H) _RO ) The molecular weight of (b) can be selected from the range of 30000 or less, for example. In addition, an additive (H) _RO ) 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 (e.g., optical properties suitable for the adhesive such as flexibility and haze), the additive (H) is used in some embodiments _RO ) Suitably, the molecular weight of (a) is less than about 10000, preferably less than 5000, more preferably less than 3000 (e.g. less than 1000), and may be less than 800, may be less than 600, may be less than 500, and may be less than 400. Additive (H) _RO ) When the molecular weight of (b) is not too large, it may be advantageous from the viewpoint of improving compatibility in the adhesive layer. In addition, an additive (H) _RO ) The molecular weight of (b) may be 130 or more, or may be 150 or more, for example. In some forms, from the additive (H) _RO ) From the viewpoint of increasing the refractive index of (C), an additive (H) _RO ) Preferably has a molecular weight of 170 or more, more preferably 200 or more, 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 (e.g., 1000 or more and less than 5000) may be used as the additive (H) _RO )。

As additive (H) _RO ) The molecular weight of (b) is calculated from the chemical structure of a non-polymer or a polymer having a low degree of polymerization (for example, about 2 to 5 mer). Additive (H) _RO ) In the case of a polymer having a higher polymerization degree, a weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. The nominal value of the molecular weight may be used when it is provided by a manufacturer or the like.

Can be used as additive (H) _RO ) Examples of the organic material of (4) include organic compounds having an aromatic ring and heterocyclic rings (which may be aromatic rings or non-aromatic heterocyclic rings). ) The organic compound of (4) and the like, but is not limited thereto.

As additive (H) _RO ) The above-mentioned organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") is used. ) The aromatic ring to be included may be selected from the same aromatic rings as those included in the compound used as the monomer (m 1).

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

As useful as additives (H) _RO ) Examples of the aromatic ring-containing compound of (2) include: a compound usable as the monomer (m 1); an oligomer comprising a compound usable as the monomer (m 1) 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 a ring-forming atom) or a part of the group constituting the ethylenically unsaturated group is removed and replaced with a hydrogen atom or a group having no ethylenically unsaturated group (for example, a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, or the like) from among compounds usable as the monomer (m 1); and the like, but are not limited thereto. Can be used as additive (H) _RO ) Non-limiting examples of the aromatic ring-containing compound of (a) may 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 above-mentioned monomer having a fluorene structure, the monomer having a dinaphthothiophene structure, and the monomer having a dibenzothiophene structure; an aromatic ring-containing compound having no ethylenically unsaturated group, such as 3-phenoxybenzyl alcohol, dinaphthothiophene, and derivatives thereof (for example, compounds having a structure in which 1 or 2 or more substituents selected from a hydroxyl group, a carbinol group, a diethanol group, a glycidyl group, and the like are bonded to the dinaphthothiophene ring); and the like. 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, an oligomer of about 2 to 5-mer) containing such an aromatic ring-containing monomer as a monomer unit. The above oligomers may be, for example: homopolymers of aromatic ring-containing monomers; a copolymer of 1 or 2 or more aromatic ring-containing monomers; copolymers of 1 or 2 or more aromatic ring-containing monomers with other monomers; and the like. As the other monomer, 1 or 2 or more kinds of monomers having no aromatic ring can be used.

In some forms, as an additive (H) _RO ) From the viewpoint of easily obtaining a high effect of increasing the refractive indexAn organic compound having 2 or more aromatic rings in 1 molecule (hereinafter also referred to as "a compound containing a plurality of aromatic rings") can be preferably used. The compound containing a plurality of aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. The compound containing a plurality of aromatic rings may be a polymer or a non-polymer. The polymer may be an oligomer containing a monomer having a plurality of aromatic rings as a monomer unit (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less, for example, an oligomer having about 2 to 5 mers). The above oligomer may be, for example: homopolymers of monomers containing multiple aromatic rings; 1 or 2 or more aromatic ring-containing monomers; 1 or 2 or more aromatic ring-containing monomers and other monomers; and so on. The other monomer may be an aromatic ring-containing monomer that is not a monomer containing a plurality of aromatic rings, may be a monomer having no aromatic ring, or may be a combination thereof.

Non-limiting examples of compounds containing multiple aromatic rings include: a compound having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group, a compound having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded (i.e., without via other atoms), a compound having a condensed aromatic ring structure, a compound having a fluorene structure, a compound having a dinaphthothiophene structure, a compound having a dibenzothiophene structure, and the like. The compounds containing a plurality of aromatic rings may be used alone in 1 kind or in combination of 2 or more kinds.

Specific examples of the compound having a fluorene structure include 9,9-bisphenylfluorene and derivatives thereof, such as 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), in addition to the monomer having a fluorene structure and an oligomer which is a homopolymer or a copolymer of the monomer.

Specific examples of the compound having a dinaphthothiophene structure include dinaphthothiophene (refractive index: 1.808) in addition to the monomer having a dinaphthothiophene structure and an oligomer which is a homopolymer or a copolymer of the monomer; hydroxyalkyl dinaphthothiophenes such as 6-hydroxymethyl dinaphthothiophene (refractive index: 1.766); 2,12-dihydroxydinaphthothiophene (refractive index: 1.750) or dihydroxydinaphthothiophene; 2,12-dihydroxyethyloxydianhthiophene (refractive index: 1.677), dihydroxyalkyloxydinaphthothiophene; diglycidyl oxydianaphthothiophenes such as 2,12-diglycidyl oxydianaphthothiophene (refractive index: 1.723); 5363 a dinaphthothiophene having 2 or more ethylenically unsaturated groups, such as 2,12-diallyloxydinaphthothiophene (2,12-DAODNT, refractive index 1.729); and the like dinaphthothiophenes and derivatives thereof.

Specific examples of the compound having a dibenzothiophene structure include dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), and the like, in addition to the monomer having a dibenzothiophene structure and an oligomer which is a homopolymer or a copolymer of the monomer.

As an additive (H) _RO ) The organic compound having a heterocycle of (c) of (a) (hereinafter also referred to as a heterocycle-containing organic compound. ) Examples of (3) include thioepoxy compounds, compounds having a triazine ring, and the like. Examples of the thioepoxy compound include bis (2,3-thiocyclopropyl) disulfide and a polymer thereof (refractive index: 1.74) described in japanese patent No. 3712653. Examples of the compound having a triazine ring include compounds having at least 1 (for example, 3 to 40, preferably 5 to 20) triazine ring in 1 molecule. Since the triazine ring is aromatic, a compound having a triazine ring is also included in the concept of the aromatic ring-containing compound, and a compound having a plurality of triazine rings is also included in the concept of the aromatic ring-containing compound.

In some forms, as an additive (H) _RO ) Compounds having no ethylenically unsaturated group can be preferably used. This can suppress the adhesive composition from being deteriorated (coagulated) by heat or lightGelling proceeds, leveling property decreases due to increase in viscosity), and storage stability is improved. From the inclusion of the additive (H) _RO ) From the viewpoint of suppressing dimensional change, deformation (warpage, waviness, etc.), generation of optical distortion, etc. due to the reaction of the ethylenically unsaturated group in the pressure-sensitive adhesive layer of (a), a laminate (for example, a laminate sheet) containing the pressure-sensitive adhesive layer, etc., it is also preferable to use an additive (H) having no ethylenically unsaturated group _RO )。

In the use of oligomers as additives (H) _RO ) In the embodiment (1), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method. When the oligomer is produced by radical polymerization, a polymerization initiator, a chain transfer agent, an emulsifier, and the like for radical polymerization may be appropriately added to the monomer component to carry out polymerization. The polymerization initiator, chain transfer agent, emulsifier, and the like used for the radical polymerization are not particularly limited, and may be appropriately selected and used. The weight average molecular weight of the oligomer can be controlled by the amount of the polymerization initiator, the amount of the chain transfer agent used, and the reaction conditions, and the amount of the oligomer used is appropriately adjusted depending on the kind of the oligomer.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, thioglycolic 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 in 1 kind, or may be used in combination of 2 or more kinds. The amount of the chain transfer agent to be used may be set so that an oligomer having a desired weight average molecular weight can be obtained, depending on the composition of the monomer component used for synthesizing the oligomer, the kind of the chain transfer agent, and the like. In some embodiments, the amount of the chain transfer agent used is suitably about 15 parts by weight or less, and may be 10 parts by weight or less, or about 5 parts by weight or less, based on 100 parts by weight of the total amount of the monomers used for oligomer synthesis. The lower limit of the amount of the chain transfer agent used is not particularly limited, and may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more, based on 100 parts by weight of the total amount of the monomers used for synthesizing the oligomer.

In the presence of an additive (H) _RO ) As a refractive index improver, an additive (H) _RO ) The amount of the base polymer to be used (the total amount of the plurality of compounds when used) is not particularly limited and may be set according to the purpose. From the viewpoint of increasing the refractive index of the binder, the additive (H) _RO ) The amount of the polymer to be used may be, for example, 1 part by weight or more, and preferably 3 parts by weight or more, and preferably 5 parts by weight or more, and may be 7 parts by weight or more, and may be 10 parts by weight or more, and may be 15 parts by weight or more, and may be 20 parts by weight or more, relative to 100 parts by weight of the base polymer. In some modes, the additive (H) _RO ) The amount of the binder to be used may be, for example, 80 parts by weight or less based on 100 parts by weight of the base polymer, and is preferably 60 parts by weight or less, more preferably 45 parts by weight or less, from the viewpoint of achieving a good balance between the increase in refractive index of the binder and the suppression of the decrease in adhesive properties and optical properties. In some of the ways in which the adhesive property and the optical property are more important, the additive (H) _RO ) The amount of the polymer to be used may be, 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 based on 100 parts by weight of the base polymer.

(plasticizing Material)

In some approaches, the high refractive index adhesive layer may comprise 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 pressure-sensitive adhesive layer, the adhesion to an adherend, the overall flexibility, the ability to follow deformation, and the like can be improved. As the plasticizing material, an organic material can be preferably used from the viewpoint of compatibility and transparency in the pressure-sensitive adhesive layer. The plasticizing material may be one that can also be used as the above-mentioned refractive index improver (e.g., the above-mentioned additive (H) _RO ) ) of a material.

The molecular weight of the plasticizing material is not particularly limited as long as it is lower than that of the base polymer. In some embodiments, from the viewpoint of easily exhibiting the plasticizing effect, the molecular weight of the plasticizing material may be 30000 or less, may be 25000 or less, may be less than 10000, preferably less than 5000, more preferably less than 3000 (e.g., less than 1000), may be less than 800, may be less than 600, may be less than 500, or may be less than 400. When the molecular weight of the plasticizing material is not excessively large, it may be advantageous from the viewpoint of improvement in compatibility in the pressure-sensitive adhesive layer, or the like. In some embodiments, the molecular weight of the plasticizing material is preferably 130 or more, preferably 150 or more, and may be 170 or more, 200 or more, 250 or more, or 300 or more, from the viewpoint of facilitating the exertion of a sufficient plasticizing effect. In some embodiments, the plasticizing material may have a molecular weight of 500 or more, 1000 or more, or 2000 or more. When the molecular weight of the plasticizing material is not too low, it is also preferable from the viewpoint of heat resistance of the pressure-sensitive adhesive layer and suppression of contamination of an adherend.

Non-limiting examples of compounds that may be options for plasticizing materials include: compounds useful as the monomer (m 1) (e.g., (meth) acrylate having an aromatic ring such as benzyl, phenoxy, or naphthyl, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, or the like); an oligomer comprising a compound usable as the monomer (m 1) as a monomer unit; a compound having a structure in which a portion having an ethylenically unsaturated group is removed from the compounds usable as the monomer (m 1) and replaced with a hydrogen atom or a group having no ethylenically unsaturated group (for example, 3-phenoxybenzyl alcohol); and the like. The oligomer containing a compound usable as the monomer (m 1) as a monomer unit may be copolymerized with a low Tg monomer such as n-butyl acrylate or 2-ethylhexyl acrylate, for example, from the viewpoint of improving flexibility. As the plasticizing material, 1 or 2 or more kinds of known plasticizers (for example, phthalate ester, terephthalate ester, adipate ester, adipic acid polyester, and glycol benzoate) can be used.

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 options for plasticizing materials 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), butylbenzyl phthalate (refractive index 1.54), rosin methyl ester (refractive index 1.53), alkylbenzylphthalate (refractive index 1.53), butyl (benzenesulfonyl) amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2-ethylhexyl diphenyl phosphate (refractive index 1.51), tris (2,4-di-butyl phenyl phosphite), and the like, but not limited thereto. From the viewpoint of refractive index and compatibility, for example, diethylene glycol dibenzoate can be preferably used. The upper limit of the refractive index of the plasticizing material is not particularly limited, and may be, for example, 3.00 or less. In some embodiments, the refractive index of the plasticizing material is preferably 2.50 or less, and is advantageously 2.00 or less, and may be 1.90 or less, may be 1.80 or less, and may be 1.70 or less, from the viewpoints of ease of preparation of the adhesive composition, compatibility within the adhesive, and the like.

The refractive index of the plasticized material was measured using an Abbe refractometer at a measurement wavelength of 589nm and a measurement temperature of 25 ℃ in the same manner as the refractive index of the monomer. When a nominal value of the refractive index at 25 ℃ is provided by a manufacturer or the like, the nominal value can be adopted.

In the embodiment using the plasticizing material, the amount of the plasticizing material to be used is not particularly limited, and may be set according to the purpose. 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, or 0.5 part by weight or more, from the viewpoint of enhancing the plasticizing effect, and is preferably 1 part by weight or more, more preferably 3 parts by weight or more, or 5 parts by weight or more, or 7 parts by weight or more, or 10 parts by weight or more, or 15 parts by weight or more, or 20 parts by weight or more, from the viewpoint of obtaining a higher plasticizing effect. From the viewpoint of achieving both high refractive index of the pressure-sensitive adhesive and transparency and plasticizing effect in a well-balanced manner, the amount of the plasticizing material to be used is preferably about 100 parts by weight or less, more preferably 80 parts by weight or less, even more preferably 60 parts by weight or less, and may be 45 parts by weight or less, and may be 35 parts by weight or less, and may be 25 parts by weight or less, based on 100 parts by weight of the base polymer. In some embodiments where the adhesion property and the optical property are more important, the plasticizing material may be used in an amount of 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less, based on 100 parts by weight of the base polymer.

(leveling agent)

In some embodiments, the adhesive composition for forming the adhesive layer may contain a leveling agent as needed for the purpose of improving the appearance (e.g., improving the uniformity of thickness) of the adhesive layer formed from the composition, improving the coatability of the adhesive composition, and the like. Examples of the leveling agent include, but are not limited to, acrylic leveling agents, fluorine leveling agents, and silicone leveling agents. The leveling agent may be used by a conventional method by selecting an appropriate substance from commercially available leveling agents, for example.

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

The monomer S1 is not particularly limited, and any monomer having a polyorganosiloxane skeleton can be used. As the monomer S1, a monomer having a structure having a polymerizable reactive group at one end can be preferably used. Among them, the monomer S1 having the following structure can be preferably used: having a polymerizablly reactive group at one end and having no functional group at the other end that would undergo a crosslinking reaction with a base polymer (e.g., an acrylic polymer) of an adhesive composition to which the leveling agent is to be compounded. Examples of commercially available products include single-terminal reactive silicone oils manufactured by shin-Etsu chemical Co., ltd. (for example, trade names X-22-174ASX, X-22-2426, X-22-2475, KF-2012 and the like). The monomer S1 may be used singly or in combination of two or more.

The functional group equivalent of the monomer S1 may be, for example, about 100g/mol to about 30000 g/mol. In some preferred embodiments, the functional group equivalent weight is, for example, 500g/mol or more, 800g/mol or more, 1500g/mol or more, or 2000g/mol or more. The functional group equivalent may be, for example, 20000g/mol or less, less than 10000g/mol, 7000g/mol or less, or 5500g/mol or less. When the functional group equivalent of the monomer S1 is within the above range, a good leveling effect can be easily exerted.

When two or more monomers having different functional group equivalents are used as the monomer S1, the functional group equivalent of the monomer S1 may be the sum of the products of the functional group equivalents of the respective monomers and the weight fractions of the monomers.

Here, "functional group equivalent" means the weight of the main skeleton (for example, polydimethylsiloxane) bonded per 1 functional group. The labeling unit g/mol was converted to 1mol of the functional group. The functional equivalent of the monomer S1 can be determined, for example, by Nuclear Magnetic Resonance (NMR) ¹ The spectral intensity of H-NMR (proton NMR) was calculated. Based on ¹ The functional group equivalent (g/mol) of the monomer S1 of the spectral intensity of H-NMR can be calculated based on ¹ A general structural analysis method in H-NMR spectroscopy is described in JP 5951153A, as necessary. In the functional group equivalent of the monomer S1, the functional group means a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth) acryloyl group, vinyl group, or allyl group).

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

The monomer raw material B contains an acrylic monomer copolymerizable with the monomer S1 in addition to the monomer S1. This improves the compatibility of the polymer (B) in the adhesive layer. Examples of the acrylic monomer that can be used as the monomer raw material B include alkyl acrylates. The "alkyl" as used herein means a chain (including straight-chain and branched-chain) alkyl (group), and does not include the alicyclic hydrocarbon group described later. In some embodiments, the monomer feedstock B may comprise (meth) acrylic acid C _4-12 Alkyl esters (preferably (meth) acrylic acid C) _4-10 Alkyl esters, e.g. C (meth) acrylate _6-10 Alkyl esters). In other embodiments, the monomer feed B may comprise methacrylic acid C _1-18 Alkyl esters (preferably methacrylic acid C) _1-14 Alkyl esters, e.g. methacrylic acid C _1-10 Alkyl ester). The monomer raw material B may contain, for example, one or two or more selected from Methyl Methacrylate (MMA), n-Butyl Methacrylate (BMA), and 2-ethylhexyl methacrylate (2 EHMA) as an acrylic monomer.

Other examples of the acrylic monomer include (meth) acrylates having an alicyclic hydrocarbon group. For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate, and the like can be used. The (meth) acrylate having an alicyclic hydrocarbon group may not be used.

The content of the alkyl (meth) acrylate and the (meth) acrylate having an alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10 wt% or more and 95 wt% or less, 20 wt% or more and 95 wt% or less, 30 wt% or more and 90 wt% or less, 40 wt% or more and 90 wt% or less, or 50 wt% or more and 85 wt% or less.

Other examples of the monomer which can be contained in the monomer raw material B together with the monomer S1 include: examples of the monomer that can be used in the acrylic polymer include the above-mentioned carboxyl group-containing monomer, acid anhydride group-containing monomer, hydroxyl group-containing monomer, epoxy group-containing monomer, cyano group-containing monomer, isocyanate group-containing monomer, amide group-containing monomer, nitrogen atom-containing ring-containing monomer, aminoalkyl (meth) acrylate, vinyl ester, vinyl ether, olefin, (meth) acrylate having an aromatic hydrocarbon group, halogen atom-containing (meth) acrylate, and the like.

The Mw of the polymer (B) may be, for example, 5000 or more, preferably 10000 or more, or 15000 or more. The Mw of the polymer (B) may be, for example, 200000 or less, preferably 100000 or less, 50000 or less, or 30000 or less. By setting the Mw of the polymer (B) in an appropriate range, appropriate compatibility and leveling properties can be exhibited.

The polymer (B) can be produced by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization, for example.

In order to adjust the molecular weight of the polymer (B), a chain transfer agent may be used as necessary. Examples of the chain transfer agent to be used include compounds having a mercapto group such as n-dodecylmercaptan, mercaptoethanol, and α -thioglycerol; thioglycolates such as thioglycolic acid and methyl thioglycolate; alpha-methylstyrene dimer; and the like. The amount of the chain transfer agent to be used is not particularly limited, and may be appropriately set so as to obtain the polymer (B) having a desired molecular weight. In some embodiments, the chain transfer agent may be used in an amount of, for example, 0.1 to 5 parts by weight, 0.2 to 3 parts by weight, or 0.5 to 2 parts by weight, based on 100 parts by weight of the monomer.

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

(inorganic particles)

The techniques disclosed herein may preferably be implemented in a manner that does not substantially use inorganic particles as refractive index improvers. Of course, in some embodiments, the use of inorganic particles as the refractive index improver may be allowed within limits that satisfy desired optical characteristics (total light transmittance, haze value) without greatly impairing the characteristics as the binder. Examples of the inorganic particles usable as the refractive index improver include titanium oxide (titanium oxide, tiO) ₂ ) Zirconium oxide (zirconium oxide, zrO) ₂ ) Aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide (Nb) ₂ O ₅ Etc.) and the like, and inorganic particles composed of an inorganic oxide (specifically, a metal oxide). The average particle diameter of the inorganic particles (which means 50% volume average particle diameter by laser scattering/diffraction method) may be selected from a range of about 10nm to 100nm, for example. The refractive index of the inorganic particles was measured using a commercially available spectroscopic ellipsometer at a measurement wavelength of 589nm and a measurement temperature of 23 ℃. As the spectroscopic ellipsometer, for example, product name "EC-400" (product of ja. The amount of the inorganic particles used in the case of using the inorganic particles as the refractive index improver 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 presence of an additive (H) _RO ) In the embodiment (b), the amount of the inorganic particles used is preferably the additive (H) on a weight basis _RO ) Is 2 times or less, more preferably 1 time or less or 0.5 time or less.

(crosslinking agent)

In the technique disclosed herein, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer may contain a crosslinking agent as needed for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive or the like. As the crosslinking agent, crosslinking agents known in the field of adhesives, such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based resins, and metal chelate-based crosslinking agents, can be used. Among these, isocyanate-based crosslinking agents can be preferably used. Other examples of the crosslinking agent include a polyfunctional monomer having 2 or more ethylenically unsaturated groups in 1 molecule. The crosslinking agent can be used alone in 1 or a combination of more than 2.

The isocyanate-based crosslinking agent may be a 2-or more-functional isocyanate compound, and examples thereof include aliphatic polyisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene Diisocyanate (HDI), and dimer acid diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis (isocyanatomethyl) cyclohexane, and the like; 2,4-tolylene diisocyanate, 4,4' -diphenylmethane diisocyanate, xylylene Diisocyanate (XDI), and other aromatic isocyanates; modified polyisocyanates obtained by modifying the above isocyanate compounds with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds or the like; and the like. Examples of commercially available products include tradenames Takenate 300S, takenate, takenate 600, takenate D165N, takenate D178N (see above, manufactured by Takara chemical industries, ltd.), sumidur T80, sumidur L, desmodur N3400 (see above, manufactured by Sumika Bayer Urethane Co., ltd.), millionate MR, millionate MT, cornate L, cornate HL, and Cornate HX (see above, manufactured by Tosoh Co., ltd.). The isocyanate compound may be used alone in 1 kind or in combination of 2 or more kinds. It is also possible to use a 2-functional isocyanate compound and a 3-functional or higher isocyanate compound in combination.

Examples of the epoxy crosslinking agent include bisphenol a, epichlorohydrin type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidyl amine, N' -tetraglycidyl m-xylylenediamine, and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane. These may be used alone in 1 kind or in combination of 2 or more kinds.

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 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, bisphenoxyethanolfluorene di (meth) acrylate, bisphenol a di (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyl glycol (meth) acrylate, and hexyldiol di (meth) acrylate. The polyfunctional monomers may be used alone in 1 kind or in combination of 2 or more kinds.

The amount of the crosslinking agent (which may be a polyfunctional monomer) used is not particularly limited, and may be, for example, about 0.001 to 5.0 parts by weight per 100 parts by weight of the base polymer. From the viewpoint of improving the flexibility of the adhesive, in some embodiments, the amount of the crosslinking agent used is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and may be 1.0 part by weight or less, may be 0.5 parts by weight or less, and may be 0.2 parts by weight or less, with respect to 100 parts by weight of the base polymer. In some embodiments, the amount of the crosslinking agent used may be, for example, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.08 parts by weight or more, relative to 100 parts by weight of the base polymer, from the viewpoint of appropriately exhibiting the effect of the crosslinking agent used.

In order to more efficiently perform the crosslinking reaction, a crosslinking catalyst may also be used. As examples of crosslinking catalysts, mention may be made ofExamples thereof include tetra-n-butyl titanate, tetra-isopropyl titanate, iron acetylacetonate (

Iron (III)), butyltin oxide, dioctyltin dilaurate, and other metal crosslinking catalysts. Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferable. The amount of the crosslinking catalyst used is not particularly limited. In view of the balance between the rate of crosslinking reaction and the length of pot life of the adhesive composition, the amount of the crosslinking catalyst used per 100 parts by weight of the base polymer may be, for example, in the range of about 0.0001 parts by weight or more and 1 part by weight or less, and preferably in the range of 0.001 parts by weight or more and 0.5 parts by weight or less.

The adhesive composition may contain a compound that undergoes keto-enol tautomerism as a crosslinking retarder. This can achieve the effect of extending the pot life of the adhesive composition. For example, in the adhesive composition containing an isocyanate-based crosslinking agent, a compound that undergoes keto-enol tautomerism can be preferably used. As the compound which causes keto-enol tautomerism, various β -dicarbonyl compounds can be used. For example, β -diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably used. The keto-enol tautomerism-inducing compounds may be used in 1 species alone or in combination of 2 or more. The amount of the compound that causes keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, 0.5 to 10 parts by weight, or 1 to 5 parts by weight, based on 100 parts by weight of the base polymer.

(tackifier)

The adhesive layer in the technology disclosed herein may contain a tackifier. As the tackifier, known tackifier resins such as rosin-based tackifier resin, terpene-based tackifier resin, phenol-based tackifier resin, hydrocarbon-based tackifier resin, ketone-based tackifier resin, polyamide-based tackifier resin, epoxy-based tackifier resin, and elastic-based tackifier resin can be used. These may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the tackifier resin used is not particularly limited, and may be set so as to exhibit an appropriate adhesive performance according to the purpose and use. In some embodiments, the amount of the tackifier used is preferably 30 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less, based on 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer, from the viewpoint of refractive index and transparency. The techniques disclosed herein may preferably be practiced without the use of a tackifier.

(other additives)

In the technique disclosed herein, the adhesive composition for forming the adhesive layer may contain, as necessary, known additives that can be used in the adhesive composition, such as plasticizers, softeners, colorants, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, and preservatives, within a range that does not significantly interfere with the effects of the present invention. The various additives can be conventionally known additives, and the present invention is not particularly characterized, and therefore, detailed description thereof is omitted.

(Peel Strength)

In some embodiments, the peel strength of the adhesive layer disclosed herein to a glass plate is suitably about 1.0N/25mm or more (e.g., 1.5N/25mm or more), preferably 2N/25mm or more, more preferably 3N/25mm or more, may be 4N/25mm or more, may be 6N/25mm or more, may be 8N/25mm or more, may be 10N/25mm or more, and may be 12N/25mm or more. The upper limit of the peel strength is not particularly limited, and may be, for example, 30N/25mm or less, 25N/25mm or less, or 20N/25mm or less.

Here, the peel strength can be grasped as follows: an alkali glass plate as an adherend was pressure-bonded thereto, and left to stand in an atmosphere of 23 ℃ and 50% RH for 30 minutes, then put into a pressure defoaming apparatus (autoclave), and autoclave-treated at 50 ℃ and 0.5MPa for 30 minutes, and further left to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, and then the 180 DEG peel adhesion was measured under conditions of a peel angle of 180 DEG and a tensile rate of 300 mm/min. In the measurement, an appropriate backing material (for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm to about 50 μm) may be bonded to the measurement object for reinforcement, if necessary. The peel strength can be measured specifically by the method described in the examples below.

In the case of the laminate sheet disclosed herein, which is a form of a double-sided adhesive sheet having a1 st adhesive surface and a2 nd adhesive surface, in which a high-refractive-index adhesive layer and a low-refractive-index adhesive layer are laminated, the peel strength is preferably applied to at least the 1 st adhesive surface (adhesive surface formed of a high-refractive-index adhesive layer), and more preferably to both the 1 st adhesive surface and the 2 nd adhesive surface. The peel strength of the 1 st adhesive surface to the glass plate may be the same as or different from the peel strength of the 2 nd adhesive surface to the glass plate.

< Low refractive index layer >

In the technique disclosed herein, the refractive index n of the low refractive index layer (preferably, the low refractive index adhesive layer) ₂ Preferably lower than the refractive index n of the high refractive index adhesive layer ₁ . This makes it possible to control the behavior of light transmitted through the laminate sheet including the high-refractive-index adhesive layer and the low-refractive-index layer by the difference in refractive index between these layers. Refractive index n of low refractive index layer ₂ For example, it may be in the range of about 1.35 to 1.55. In some ways, the refractive index n of the adhesive layer with high refractive index is increased ₁ The refractive index n of the low refractive index layer is set so as to easily improve the front luminance improvement effect described later ₂ For example, it is preferably 1.49 or less, more preferably 1.47 or less (for example, 1.46 or less, or 1.45 or less), and may be 1.43 or less, 1.41 or less, or 1.40 or less. In some embodiments, the refractive index n of the low refractive index layer is set to be equal to or greater than the refractive index n of the low refractive index layer in order to obtain a material easily and to achieve both adhesion properties easily ₂ For example, the concentration may be 1.36 or more, 1.38 or more, 1.40 or more, or 1.42 or more.

In some modes, the refractive index n of the high refractive index adhesive layer ₁ With refractive index n of the low-refractive-index layer ₂ Ratio of (n) ₁ /n ₂ ) For example, the average particle size may be greater than 1.00, may be about 1.01 or more, is preferably about 1.02 or more, and may be about 1.03 or more. In some waysMiddle to middle ratio (n) ₁ /n ₂ ) Advantageously, it is about 1.05 or more, preferably about 1.07 or more, more preferably about 1.10 or more, and may be about 1.11 or more. Ratio (n) ₁ /n ₂ ) The upper limit of (b) is not particularly limited. In some embodiments, the ratio (n) is from the viewpoint of adhesive properties, transparency, and the like ₁ /n ₂ ) For example, the concentration may be about 1.20 or less, about 1.18 or less, about 1.16 or less, about 1.14 or less, or about 1.12 or less.

In some forms, the refractive index n of the high refractive index adhesive layer ₁ With refractive index n of the low-refractive-index layer ₂ The difference, i.e. the difference in refractive index (n) ₁ -n ₂ ) For example, the average molecular weight may be more than 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, and may be 0.25 or more. Difference in refractive index (n) ₁ -n ₂ ) The upper limit of (b) is not particularly limited. In some embodiments, the difference in refractive index (n) is from the viewpoint of adhesive properties, transparency, and the like ₁ -n ₂ ) For example, it may be 0.30 or less, 0.26 or less, 0.21 or less, 0.18 or less, or 0.16 or less.

In some preferred embodiments, the storage modulus G '(hereinafter sometimes referred to as "storage modulus G ″) at 25 ℃ of the low refractive index layer' _V2 (25) ". ) Preferably lower than the storage modulus G ' (storage modulus G ' at 25 ℃ C.) of the high refractive index adhesive layer ' _V1 (25)). That is, G 'is preferred' _V2 (25)<G’ _V1 (25). According to this configuration, by laminating the low refractive index layer on the high refractive index pressure-sensitive adhesive layer to provide adhesiveness and flexibility, the step height conformability and conformability to a curved surface and the like are improved, and a laminated sheet (pressure-sensitive adhesive sheet) that can be preferably applied to various device design applications can be realized.

Storage modulus G' _V2 (25) The pressure is not particularly limited, but may be, for example, in the range of 1.0kPa to 500 kPa. In some embodiments, the storage modulus G 'is from the viewpoint of improving the effect of imparting flexibility to the low refractive index layer and improving the followability to deformation' _V2 (25) At 400kPaThe pressure is preferably 300kPa or less, more preferably 200kPa or less (for example, 180kPa or less, or 150kPa or less), and may be 120kPa or less, or may be 90kPa or less, or may be 70kPa or less. In some embodiments, the storage modulus G 'is from the viewpoint of providing a proper cohesive property to the low refractive index layer' _V2 (25) Preferably, the pressure is 5.0kPa or more, more preferably 10kPa or more, further preferably 15kPa or more, further preferably 25kPa or more, further preferably 35kPa or more, further preferably 60kPa or more, further preferably 80kPa or more. In some embodiments, the storage modulus G 'is from the viewpoint of easily achieving higher cohesive force and adhesive properties' _V2 (25) May be 95kPa or more, may be 110kPa or more, or may be 140kPa or more.

In the embodiment where the low refractive index layer is a pressure-sensitive adhesive layer, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive constituting the low refractive index pressure-sensitive adhesive layer may be a pressure-sensitive adhesive containing 1 or 2 or more of various rubbery 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., which are used in the field of pressure-sensitive adhesives. From the viewpoint of adhesive performance, cost, and the like, an adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably used. Among them, an adhesive (acrylic adhesive) containing an acrylic polymer as a base polymer is preferable. In the embodiment in which the high refractive index pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, a configuration in which the low refractive index pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer can be preferably employed from the viewpoint of adhesion between the high refractive index pressure-sensitive adhesive layer and the low refractive index pressure-sensitive adhesive layer.

In some embodiments, the acrylic polymer is preferably a polymer of a monomer raw material containing, for example, an alkyl (meth) acrylate and may further contain another monomer (copolymerizable monomer) copolymerizable with the alkyl (meth) acrylate. 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 acrylic polymer may be a polymer containing an alkyl (meth) acrylate as a main monomer and further containing the copolymerizable monomer as a monomer component of a sub-monomer. Here, the main monomer means a component occupying more than 50% by weight of the monomer composition in the above monomer raw materials. It is also possible for more than 55% by weight or more than 60% by weight of the abovementioned monomer composition to be alkyl (meth) acrylates.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.

CH ₂ ＝C(R ¹ )COOR ² (1)

Here, R in the above formula (1) ¹ Is a hydrogen atom or a methyl group. In addition, R ² Is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of the number of carbon atoms may be referred to as "C _1-20 ". ). From the viewpoint of storage modulus of the binder, R is preferred ² Is C _1-12 (e.g. C) _2-10 Typically C _4-8 ) An alkyl (meth) acrylate having a chain alkyl group of (1). R is as defined above ² Is C _1-20 The alkyl (meth) acrylate of the chain alkyl group(s) may be used singly in 1 kind or in combination in 2 or more kinds. As preferred alkyl (meth) acrylates, n-butyl acrylate and 2-ethylhexyl acrylate may be mentioned.

The copolymerizable monomer can be used to introduce a crosslinking point into the acrylic polymer or to increase the cohesive force of the acrylic polymer. Examples of the copolymerizable monomer include 1 or 2 or more kinds of functional group-containing monomers such as a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a monomer having a nitrogen atom-containing ring, a sulfonic acid group-containing monomer, and a phosphoric acid group-containing monomer. Other examples of the copolymerizable monomer include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, nonaromatic ring-containing (meth) acrylates, and alkoxy group-containing monomers. Specific examples thereof include the monomers described above as the base polymer usable as the high refractive index pressure-sensitive adhesive layer, but are not limited thereto. For example, from the viewpoint of improving the cohesive force, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer as the copolymerizable monomer is preferable. Suitable examples of the carboxyl group-containing monomer include acrylic acid and methacrylic acid. Suitable examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

In some ways, to reduce the refractive index n of the low refractive index layer ₂ As the copolymerizable monomer, a fluorine-containing monomer may be used. The content of the fluorine-containing monomer in the monomer raw material may be, for example, 10% by weight or more, 25% by weight or more, or 35% by weight or more. From the viewpoint of easily realizing a low refractive index layer having 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, and still more preferably 55% by weight or more, and 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, and 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, the content of the fluorine-containing monomer is suitably 99.9% by weight or less, preferably 99.5% by weight or less, and may be 99% by weight or less, 97% by weight or less, or 92% by weight or less, from the viewpoint of the cohesiveness of the low refractive index layer and the like. The fluorine-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds.

As the fluorine-containing monomer, a fluorine-containing acrylic monomer can be suitably used. The fluorine-containing acrylic monomer is not particularly limited as long as it is an acrylic monomer having at least 1 fluorine atom in the molecule. For example, a fluorine-containing (meth) acrylate can be suitably used. Suitable examples of the fluorine-containing (meth) acrylate include those having a fluorinated hydrocarbon group at an 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. The fluorinated hydrocarbon group is suitably a fluoroaliphatic hydrocarbon group. Examples of the fluoroaliphatic hydrocarbon group include fluoroalkyl groups. In the fluoroaliphatic hydrocarbon group, the aliphatic hydrocarbon moiety may be linear or branched. In the fluoroaliphatic hydrocarbon group, the fluorine atom may be bonded to any carbon atom of the aliphatic hydrocarbon group site. The fluorine atom bonded to 1 carbon atom may be single or plural. The number of carbon atoms to which fluorine atoms are bonded is not particularly limited.

In the fluoroaliphatic hydrocarbon group (particularly, fluoroalkyl group), the number of carbon atoms in the hydrocarbon group site is not particularly limited. In some embodiments, in view of compatibility with other copolymerizable monomers, a fluoroaliphatic hydrocarbon group having, for example, about 1 to 18 (preferably about 1 to 12) carbon atoms is preferred. Specific examples of the fluoroaliphatic hydrocarbon group include a fluoromethyl group such as a trifluoromethyl group, a difluoromethyl group, and a monofluoromethyl group; fluoroethyl groups such as pentafluoroethyl, 1,1,2,2-tetrafluoroethyl, 1,2,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl, 1,2,2-trifluoroethyl, 2,2,2-trifluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, 2,2-difluoroethyl, 1-monofluoroethyl, and 2-monofluoroethyl; and the like. Examples of the fluoroalkyl group having 3 or more carbon atoms include various fluoroalkyl groups in which one or more fluorine atoms are bonded to any 1 or more carbon atoms among the carbon atoms in the alkyl group, similarly to the above-exemplified fluoromethyl group and fluoroethyl group.

Examples of the fluorinated alicyclic hydrocarbon group include a fluorinated cycloalkyl group and the like. In the fluorinated alicyclic hydrocarbon group, as in the fluorinated aliphatic hydrocarbon group, a fluorine atom may be bonded to any carbon atom of the alicyclic hydrocarbon group, and the number of fluorine atoms bonded to 1 carbon atom may be one or more. Further, the number of carbon atoms to which fluorine atoms are bonded is not particularly limited. Fluorinated alicyclic hydrocarbon groups include, for example: cyclohexyl having 1 fluorine atom such as 2-fluorocyclohexyl, 3-fluorocyclohexyl and 4-fluorocyclohexyl; 2,4-difluorocyclohexyl group, 2,6-difluorocyclohexyl group, and cyclohexyl group having 2 fluorine atoms; and a cyclohexyl group having 3 fluorine atoms such as 2,4,6-trifluorocyclohexyl group.

The fluorinated hydrocarbon group may have no substituent or may have a substituent. Such a substituent is not particularly limited, and examples thereof include a hydrocarbon group such as an alkyl group, an alkoxy group, a hydroxyl group, a carboxyl group, an amino group, a nitro group, a cyano group, a halogen atom, and the like. The substituents may be used singly or in combination of 1 or more.

The fluorine atom-containing (meth) acrylate [ fluoro (meth) acrylate ] includes, for example: examples of the fluorinated alkyl (meth) acrylate include a fluorinated alkyl (meth) acrylate, a fluorinated cycloalkyl (meth) acrylate, and a fluorinated aryl (meth) acrylate.

The fluorine atom-containing (meth) acrylate is preferably a fluoroalkyl (meth) acrylate (particularly, a fluoroalkyl acrylate). Examples of the fluoroalkyl (meth) acrylate include 2,2,2-trifluoroethyl acrylate (trade name "Viscoat 3F" manufactured by osaka organic chemical industry co., ltd.), 2,2,3,3-tetrafluoropropyl acrylate (trade name "Viscoat 4F" manufactured by osaka organic chemical industry co., ltd.), 1h, 5h-octafluoropentyl acrylate (trade name "Viscoat 8F" manufactured by osaka organic chemical industry co., ltd.), 1h, 5h-octafluoropentyl methacrylate (trade name "Viscoat 8FM" manufactured by osaka organic chemical industry co., ltd.), 2- (heptadecafluorononyl) ethyl acrylate (trade name "FA-108" manufactured by cooka organic chemical industry co., ltd.), acrylic acid 1h,2h, and tridecafluorooctyl acrylate (trade name "Viscoat 13F manufactured by osaka organic chemical industry co., ltd.).

From the viewpoint of the effect of reducing the refractive index, flexibility, and the like, the fluoroalkyl group in the fluoroalkyl (meth) acrylate has a carbon number of 3 or more, preferably 4 or more, more preferably 5 or more, further preferably 6 or more, or 7 or more, and particularly preferably 8 or more. From the viewpoint of adhesion performance and the like, the fluoroalkyl group has 18 or less carbon atoms, preferably 14 or less, more preferably 12 or less, and may be 10 or less, or may be 9 or less. In some embodiments, the fluoroalkyl group may have 7 or less carbon atoms, or may have 5 or less carbon atoms. In some embodiments, the fluorine atom-containing (meth) acrylate is preferably a fluoroalkyl (meth) acrylate in which fluorine is not bonded to the carbon at the 1-position of the alkyl group, and for example, a fluoroalkyl (meth) acrylate in which fluorine is not bonded to both the carbon at the 1-position and the carbon at the 2-position of the alkyl group, such as 1h, 2h-tridecafluorooctyl acrylate, can be preferably used.

In some embodiments, the low refractive index layer is an acrylic adhesive layer, and the acrylic polymer as a base polymer of the adhesive may be a polymer of a monomer raw material containing at least the fluorine-containing acrylic monomer (for example, fluoroalkyl (meth) acrylate) described above and further containing another monomer (copolymerizable monomer) copolymerizable with the fluorine-containing acrylic monomer. The monomer raw material may or may not contain an alkyl (meth) acrylate. The content of the fluorine-containing acrylic monomer in the monomer raw material may be, for example, 10 wt% or more, 25 wt% or more, or 35 wt% or more. From the viewpoint of easily realizing a low refractive index layer having a lower refractive index, the content of the fluorinated acrylic monomer is preferably 40% by weight or more, more preferably 45% by weight or more, further preferably 55% by weight or more, and 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, the content of the fluorinated acrylic monomer is suitably 99.9% by weight or less, preferably 99.5% by weight or less, and may be 99% by weight or less, 97% by weight or less, or 92% by weight or less, from the viewpoint of the cohesion of the low refractive index layer, or the like. The fluorine-containing acrylic monomer may be used alone in 1 kind or in combination of 2 or more kinds.

The monomer raw material for the base polymer for producing the low refractive index layer may be a composition containing a copolymerizable monomer in addition to a fluorine-containing acrylic monomer such as fluoroalkyl (meth) acrylate. Examples of the copolymerizable monomer include 1 or 2 or more species of functional group-containing monomers such as a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a monomer having a nitrogen atom-containing ring (e.g., an N-vinyl cyclic amide such as N-vinyl-2-pyrrolidone), a sulfonic acid group-containing monomer, and a phosphoric acid group-containing monomer. Other examples of the copolymerizable monomer include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, (meth) acrylic acid cycloalkyl esters, (meth) acrylic acid isobornyl ester and other nonaromatic ring-containing (meth) acrylic acid esters, alkoxy group-containing monomers; and so on. Specific examples thereof include the monomers described above as the base polymer usable as the high refractive index pressure-sensitive adhesive layer, but are not limited thereto. For example, from the viewpoint of improving the cohesive force, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer as the copolymerizable monomer is preferable.

In some preferred modes, the monomer raw material for the base polymer for producing the low refractive index layer may be a composition containing a fluorine-containing monomer (for example, a fluorine-containing acrylic monomer such as fluoroalkyl (meth) acrylate) and further containing a hydroxyl group-containing monomer. The hydroxyl group-containing monomer can contribute to improvement of cohesive force, introduction of crosslinking points, and the like. Suitable 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 region, 4-hydroxybutyl acrylate may be more preferably used. The content of the hydroxyl group-containing monomer in the monomer raw material is not particularly limited, and may be, for example, 0.01 wt% or more (preferably 0.1 wt% or more, more preferably 0.5 wt% or more). In some embodiments, the content of the 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 monomer raw material. The upper limit of the content of the hydroxyl group-containing monomer is not particularly limited, and may be, for example, 15 wt% or less or 10 wt% or less. In some embodiments, the content of the hydroxyl group-containing monomer in the monomer raw material is suitably 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, and may be less than 1.5% by weight, from the viewpoint of reducing the refractive index.

In some modes, the monomer raw material for the base polymer used for preparing the low refractive index layer is preferably limited in the content of the carboxyl group-containing monomer 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 still more preferably less than 0.1% by weight (e.g., less than 0.05% by weight). Such a limitation of the content of the carboxyl group-containing monomer is also advantageous from the viewpoint of suppressing corrosion of a metal material (for example, a metal wiring, a metal film, or the like that may be present on an adherend) that may be disposed in contact with or in proximity to the low refractive index layer. The technique disclosed herein can be preferably carried out in such a manner that the monomer raw material does not contain a carboxyl group-containing monomer.

For the same reason, in some modes, the monomer raw material for preparing the base polymer of the low refractive index layer is preferably limited in the content of the monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, and the like in addition to a carboxyl group). As the content of the acidic functional group-containing monomer in the monomer raw material of this embodiment, the preferable content of the carboxyl group-containing monomer can be applied. The technique disclosed herein can be preferably carried out in such a manner that the above-mentioned monomer raw materials do not contain an acid group-containing monomer (i.e., in such a manner that the base polymer of the low refractive index layer is acid-free).

The base polymer of the low refractive index layer can be suitably prepared by a known polymerization method, as in the case of 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, about 10X 10 ⁴ ～500×10 ⁴ May be in the range of about 20X 10 ⁴ ～200×10 ⁴ In (c) is used. In some embodiments, the Mw of the base polymer of the low refractive index adhesive layer is 150 × 10 from the viewpoint of adhesion to the high refractive index adhesive layer and the like ⁴ The following are suitable, preferably 120X 10 ⁴ The following (e.g., 95X 10) ⁴ Below), may be 75 × 10 ⁴ Hereinafter, it may be 68 × 10 ⁴ Hereinafter, the value may be 60 × 10 ⁴ The following. In some embodiments, the Mw of the base polymer may be, for example, 30 × 10 from the viewpoint of the cohesiveness of the low refractive index adhesive layer and the like ⁴ Above, can be 40 × 10 ⁴ Above, it may be 50 × 10 ⁴ The above. To prepare the Mw, as requiredConventionally known chain transfer agents can be used.

Although not particularly limited, the Tg of the base polymer (e.g., acrylic polymer) of the low refractive index layer is favorably about 0 ℃ or lower, and preferably about-5 ℃ or lower (e.g., about-15 ℃ or lower, or-25 ℃ or lower), from the viewpoint of adhesiveness. From the viewpoint of the cohesive force of the adhesive layer, the Tg of the base polymer of the low refractive index layer is about-75 ℃ or higher, preferably about-70 ℃ or higher (for example, -50 ℃ or higher, further, -30 ℃ or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the kind and the amount ratio of the monomers used for synthesizing the polymer).

A known crosslinking agent may be used for the low refractive index layer. The low refractive index layer may contain other additives such as a tackifier. The crosslinking agent and the tackifier may be appropriately selected from the same substances as those usable for the high refractive index adhesive layer and used in appropriate amounts.

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

< preparation of adhesive layer >

In the technique disclosed herein, the adhesive constituting the adhesive layer (which may be a high refractive index adhesive layer and/or a low refractive index layer, the same applies hereinafter) may be an adhesive obtained by curing an adhesive composition in the form of a solvent type, an active energy ray-curable type, a water dispersion type, a hot melt type or the like by drying, crosslinking, polymerization, cooling or the like, that is, a cured product of the adhesive composition. The curing means (for example, drying, crosslinking, polymerization, cooling, etc.) of the adhesive composition may be applied in only 1 kind, or may be applied in 2 or more kinds simultaneously or in a plurality of stages. For solvent-based adhesive compositions, the composition typically can be dried (preferably further crosslinked) to form an adhesive. The active energy ray-curable adhesive composition is typically formed by irradiation with an active energy ray to cause a polymerization reaction and/or a crosslinking reaction. When the active energy ray-curable adhesive composition needs to be dried, it is preferable to irradiate the active energy ray after drying.

The adhesive layer in the technology disclosed herein may be formed by imparting (e.g., coating) an adhesive composition to an appropriate surface and then curing the composition. The adhesive composition can be applied using a conventional coater such as a gravure roll coater, a reverse roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

The adhesive layer in the technique disclosed herein may be an adhesive layer having post-curing properties or may be an adhesive layer having no post-curing properties. Here, the adhesive layer having post-curing properties 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 pressure-sensitive adhesive layer having post-curing properties include a pressure-sensitive adhesive layer having an unreacted ethylenically unsaturated group in a side chain of a base polymer and a pressure-sensitive adhesive layer containing an unreacted polyfunctional monomer. In some embodiments, the adhesive layer preferably has no post-curability. The pressure-sensitive adhesive layer having no post-curing property does not undergo dimensional change accompanying a subsequent curing reaction (i.e., dimensional stability is good), and therefore warpage of the pressure-sensitive adhesive layer or an adherend to which the pressure-sensitive adhesive layer is attached is easily suppressed. When dimensional change (for example, cure shrinkage) due to post-curing does not occur, it may also be advantageous from the viewpoint of suppressing optical distortion of the pressure-sensitive adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 3 μm or more, preferably 5 μm or more. Good adhesive properties are easily obtained with an adhesive layer having a thickness of 5 μm or more. In addition, the pressure-sensitive adhesive layer having such a thickness easily absorbs irregularities that may be present on the surface of the adherend, and is bonded to the adherend with good adhesion. From the viewpoint of preventing coloring and color unevenness due to light interference, the thickness of the pressure-sensitive adhesive layer (for example, the thickness of the high-refractive-index pressure-sensitive adhesive layer) is preferably 5 μm or more. In some embodiments, the thickness of the adhesive layer may be 10 μm or more, may be 20 μm or more, may be 30 μm or more, may be 50 μm or more, may be 70 μm or more, or 85 μm or more. In some embodiments, the thickness of the pressure-sensitive 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. When the thickness of the pressure-sensitive adhesive layer is not excessively large, it may be advantageous from the viewpoint of thinning of a laminate sheet including the pressure-sensitive adhesive layer, a light-emitting device, and the like. The technique disclosed herein can be preferably carried out such that the thickness of the pressure-sensitive adhesive layer is in the range of 3 to 200 μm (more preferably 5 to 100 μm), for example.

In some embodiments, the thickness of the adhesive layer may be at least applied to the thickness T of the high refractive index adhesive layer ₁ . Thickness T of low refractive index adhesive layer ₂ And may be selected from the same range. The thickness of the adhesive layer described above may also be applied to the thickness T of the low refractive index layer ₂ Whether or not an adhesive layer. Thickness T of high refractive index adhesive layer ₁ Thickness T of low refractive index layer ₂ May be the same or different. Thickness T of high refractive index adhesive layer ₁ Thickness T of low refractive index layer ₂ Ratio of (T) ₁ /T ₂ ) For example, the content may be 0.1 or more, 0.3 or more, 0.5 or more, 0.8 or more, 1.2 or more, and 1.5 or more. In addition, the above ratio (T) ₁ /T ₂ ) For example, it may be 20 or less, 10 or less, 5 or less, or 3 or less. In some forms, the ratio (T) is ₁ /T ₂ ) May be lower than 2, may be lower than 1.5, or may be lower than 1.

As a method for obtaining a structure (laminate 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, there can be adopted: a method of forming a high refractive index adhesive layer and a low refractive index layer on a releasable surface (for example, a release surface of a release liner) and bonding them together; a method of coating the composition for forming a low refractive index layer on the high refractive index adhesive layer and curing it; on the contrary, the present invention is not limited to the method of coating the adhesive composition for forming the high refractive index adhesive layer on the low refractive index layer and curing the same. When the high refractive index pressure-sensitive adhesive layer and the low refractive index layer formed in advance are bonded, treatment for promoting adhesion of these layers may be performed as necessary. For example, autoclave treatment, roll treatment, etc. may be performed, but the present invention is not limited thereto.

< supporting 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. Such a structure in which the high refractive index pressure-sensitive adhesive layer and the low refractive index layer are laminated on the support substrate can also be known as a pressure-sensitive adhesive sheet with a substrate. Thus, according to the specification, there is provided an adhesive sheet (adhesive article) with a substrate, comprising: a laminate formed of a high refractive index adhesive layer and a low refractive index layer (preferably a low refractive index adhesive layer), and a support base for supporting the laminate.

The material of the support base is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like. Examples of usable substrates include, but are not limited to, plastic films such as 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), and polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets formed of foams such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; woven and nonwoven fabrics based on various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semisynthetic fibers such as acetate) alone or in a blend; paper such as japanese paper, fine paper, kraft paper, crepe paper, and the like; metal foils such as aluminum foil and copper foil; and the like. The substrate may be a composite of these. Examples of such composite substrates include substrates having a structure in which a metal foil and the plastic film are laminated, and plastic substrates reinforced with inorganic fibers such as glass cloth.

In some embodiments, various film substrates may be preferred. The film substrate may be a porous substrate such as a foamed film or a nonwoven 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 film substrate, a substrate including a resin film (self-supporting or independent) capable of independently maintaining a shape as a base film can be preferably used. Here, the "resin film" refers to a (non-porous) resin film having a non-porous structure, typically containing substantially no air bubbles. Therefore, the resin film is a concept different from a foamed film and a nonwoven fabric. As the resin film, a film (self-supporting type or independent type) capable of independently maintaining the shape can be preferably used. The resin film may have a single-layer structure or a multilayer structure having 2 or more layers (for example, a 3-layer structure).

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 copolymers, and ethylene-butene copolymers, cellulose resins such as triacetyl cellulose, cellulose resins such as acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide (PA) resins such as nylon 6, nylon 66, and partially aromatic polyamides, polyimide (PI) resins, transparent polyimide resins, polyamideimide (PAI), polyether ether ketone (PEEK), polyether Sulfone (PEs), and 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, polyvinyl sulfide resins, polyphenylene Sulfide (PPs), polyethylene Urethane (PU), ethylene-vinyl acetate copolymers (EVA), and fluorinated polyimides.

The resin film may be formed using a resin material containing 1 type of such resin alone, or may be formed using a resin material obtained by blending 2 or more types of resin. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, a PET film, a PBT film, a PEN film, a non-stretched polypropylene (CPP) film, a biaxially stretched polypropylene (OPP) film, a Low Density Polyethylene (LDPE) film, a Linear Low Density Polyethylene (LLDPE) film, a PP/PE blend film, and the like can be preferably used. From the viewpoint of strength and dimensional stability, preferable examples of the resin film include a PET film, a PEN film, a PPS film, and a PEEK film. From the viewpoint of easy acquisition, etc., a PET film and a PPS film are particularly preferable, and among them, a PET film is preferable.

The resin film may contain, as necessary, known additives such as a light stabilizer, an antioxidant, an antistatic agent, a colorant (dye, pigment, etc.), a filler, a lubricant, and an antiblocking agent, within a range not significantly impairing the effects of the present invention. The amount of the additive to be blended is not particularly limited, and may be appropriately set according to the use of the pressure-sensitive adhesive sheet and the like.

The method for producing 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, calender roll molding and the like can be suitably used.

The substrate may be substantially composed of such a base film. Alternatively, the base film may further include an auxiliary layer. Examples of the auxiliary layer include optical property adjusting layers (for example, a colored layer and an antireflection layer), printing layers for giving a desired appearance to a substrate, lamination layers, antistatic layers, undercoating layers, release layers, and other surface treatment layers.

In some embodiments, a substrate having light-transmitting properties (hereinafter also referred to as a light-transmitting substrate) can be preferably used as the supporting substrate. This makes it possible to form a pressure-sensitive adhesive sheet with a substrate having light-transmitting properties. The total light transmittance of the light-transmitting substrate may be, for example, higher than 50% or 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 (e.g., 95 to 100%). The above total light transmittance is measured according to JIS K7136: 2000, measured using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETER HM-150" manufactured by the color technology research on villages or a product equivalent thereof was used. A preferable example of the light-transmitting substrate is a resin film having light-transmitting properties. The light-transmitting substrate may be an optical film.

The thickness of the base material is not particularly limited, and may be selected according to the purpose of use, the mode of use, and the like. The thickness of the base material may be, for example, 500 μm or less, and is preferably 300 μm or less, may be 150 μm or less, may be 100 μm or less, may be 50 μm or less, may be 25 μm or less, and may be 10 μm or less from the viewpoint of handling property and processability. When the thickness of the base material is reduced, the following property to the surface shape of the adherend tends to be improved. From the viewpoint of handling properties, processability, and the like, the thickness of the base material may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

The surface of the substrate on the side on which the pressure-sensitive adhesive layer is laminated may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, formation of a primer layer by coating with a primer (primer), or the like, as necessary. Such a surface treatment may be a treatment for improving the anchoring property of the adhesive layer to the substrate. The composition of the primer used for forming the undercoat layer is not particularly limited, and may be appropriately selected from known compositions. The thickness of the undercoat layer is not particularly limited, and is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. As other treatments that can be performed on the base material as needed, antistatic layer formation treatment, coloring layer formation treatment, printing treatment, and the like can be cited. These treatments may be applied alone or in combination.

In the technique disclosed herein, in the case of a psa sheet with a substrate composed of a high refractive index psa layer and a low refractive index layer, the thickness of the psa 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. The thickness of the 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 from the viewpoint of handling property and the like.

The thickness of the pressure-sensitive adhesive sheet is a thickness of a portion to be adhered to an adherend. For example, the substrate-less double-sided pressure-sensitive adhesive sheet 2 having the structure shown in fig. 2 has a thickness from the 1 st surface (1 st pressure-sensitive adhesive surface) 10A to the 2 nd surface (2 nd pressure-sensitive adhesive surface) 10B of the pressure-sensitive adhesive layer, and does not include the thickness of the

release liners

31 and 32.

< laminated sheet with Release liner >

The high refractive index adhesive layer and the low refractive index layer disclosed herein may be in the form of an adhesive article (release-lined laminate sheet) in which the adhesive surface of the laminate sheet including the high refractive index adhesive layer and the low refractive index layer is brought into contact with the release surface of the release liner before being assembled to the light-emitting device. Thus, according to this specification, there is provided a release liner-bearing laminate (adhesive article) comprising: a laminate of a high refractive index pressure-sensitive adhesive layer and a low refractive index layer, and a release liner having a release surface that comes into contact with the pressure-sensitive adhesive surface of the laminate.

The release liner is not particularly limited, and examples thereof include a release liner having a release treatment layer on a release liner base material such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), and a release liner comprising a resin film made of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene or the like). The release-treated layer may be a layer formed by surface-treating a release liner substrate with a release treatment agent. The release agent may be a known release agent such as a silicone release agent, a long chain alkyl release agent, a fluorine release agent, or molybdenum (IV) sulfide. In some modes, a release liner having a release treatment layer based on a silicone-based release treatment agent may be preferably used. The thickness and the forming method of the release treatment layer are not particularly limited, and may be set so as to exhibit appropriate releasability on the pressure-sensitive adhesive surface side of the release liner.

In some embodiments, a release liner (hereinafter, also referred to as a release film) having a release treatment layer on a resin film (hereinafter, also referred to as a release film base) as a release liner base may be preferably used from the viewpoint of smoothness of the pressure-sensitive adhesive surface and the like. As the release film substrate, various plastic films can be used. In this specification, the plastic film is typically a non-porous sheet, and is a concept distinguished from, for example, a nonwoven fabric (i.e., excluding a nonwoven fabric).

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 copolymers and ethylene-butene copolymers, cellulose resins such as triacetyl cellulose, acetate resins, polysulfone resins, polyether sulfone 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 and polyphenylene sulfide resins. A release film substrate formed of a mixture of 1 or 2 or more of any of these resins may be used. Among them, preferable examples of the release film substrate include a polyester resin film (for example, a PET film) made of a polyester resin.

The plastic film used as the base material of the release film may be an unstretched film, a uniaxially stretched film or a biaxially stretched film. The plastic film may have a single-layer structure or a multilayer structure including 2 or more sublayers. The plastic film may contain known additives that can be used in a release film base material of a pressure-sensitive adhesive sheet, such as an antioxidant, an anti-aging agent, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant such as a pigment or a dye, a lubricant, a filler, an antistatic agent, and a nucleating agent. In the plastic film having a multilayer structure, each additive may be blended in all the sub-layers or only a part of the sub-layers.

In some preferred embodiments, as the release film substrate (typically, a plastic film), a substrate in which the content of particles such as inorganic particles (for example, a pigment, a lubricant, a filler, and the like) is limited in a layer on the release surface side thereof, or a substrate substantially not containing such particles can be preferably used. Substantially free means herein that the amount of particles (e.g., inorganic particles) in the layer is less than 1 wt%, preferably less than 0.1 wt% (e.g., 0 to 0.01 wt%). The release film provided with such a release film substrate is likely to have a low arithmetic mean roughness Ra and a low maximum height Rz of the release surface. When the release film substrate (typically, a plastic film) has a multilayer structure, the content of particles in the layer on the release surface side may be 1/10 or less (for example, 1/50 or less) of the content of particles in the layers other than the release surface side layer.

In the release-liner-provided laminate sheet having the release liner on each of the 1 st adhesive surface and the 2 nd 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 material and composition or may have different materials and compositions.

The thickness of the release liner (preferably, release film) is not particularly limited, and may be, for example, about 10 μm to 500 μm. The thickness of the release liner is suitably 20 μm or more, preferably 30 μm or more, and may be 35 μm or more, and may be 40 μm or more, and may be 45 μm or more, from the viewpoint of the strength and dimensional stability of the release liner. The thickness of the release liner is suitably 300 μm or less, preferably 250 μm or less, and may be 200 μm or less, 150 μm or less, and 130 μm or less from the viewpoint of handling properties (e.g., ease of winding) of the release liner. In some preferred embodiments, the release liner has a thickness of about 125 μm or less, may be about 115 μm or less, may be about 105 μm or less, may be about 90 μm or less, and may be about 70 μm or less. When the thickness of the release liner is set to a predetermined value or less, a winding mark is not easily formed when the release liner is rolled, removal from the adhesive sheet becomes smooth, and high surface smoothness is easily obtained on the adhesive surface after removal of the release liner.

In the release liner-equipped laminate sheet of the type having one release liner and the other release liner, the thicknesses of these release liners may be the same or different. In some embodiments, it is preferable that one release liner has a different thickness from another release liner from the viewpoint of peeling workability or the like, and for example, the thickness of a thicker release liner is preferably about 1.1 times or more (e.g., about 1.25 times or more) the thickness of a thinner release liner.

(arithmetic average roughness Ra of surface of adhesive side)

In some embodiments, from the viewpoint of realizing an adhesive surface having high surface smoothness, it is preferable that the arithmetic average roughness Ra of the surface of the release liner (preferably, release film) on the adhesive surface side is limited to a predetermined value or less (for example, about 100nm or less, and further less than 50 nm). In some embodiments, the arithmetic average roughness Ra of the pressure-sensitive adhesive surface side surface of the release liner is, for example, preferably about 30nm or less, more preferably about 25nm or less, and may be about 20nm or less, or may be about 18nm or less. In some embodiments, the arithmetic average roughness Ra may be, for example, about 5nm or more, about 10nm or more, or about 15nm or more, from the viewpoint of ease of production of the release liner, handleability, and the like. In the release-lined laminate sheet in which the release liner is disposed on each of the 1 st adhesive surface and the 2 nd adhesive surface, it is preferable that the adhesive surface side surfaces of both the release liners satisfy any one of the above arithmetic average roughness Ra. The arithmetic average roughness Ra of the pressure-sensitive adhesive surface side surfaces of the two release liners may be the same or different.

(maximum height Rz of the adhesive surface side surface)

In some embodiments, from the viewpoint of realizing an adhesive surface having high surface smoothness, the release liner (preferably a release film) preferably has a maximum height Rz of the adhesive surface side surface of 700nm or less. In some embodiments, the maximum height Rz of the pressure-sensitive adhesive surface side surface of the release liner is preferably about 600nm or less, may be about 500nm or less, may be about 400nm or less, and may be about 300nm or less. In some embodiments, the maximum height Rz may be, for example, about 50nm or more, about 80nm or more, about 100nm or more, about 200nm or more, or about 300nm or more, from the viewpoint of ease of production of the release liner, handleability, and the like. In the release-liner-provided laminate sheet in which the release liner is disposed on each of the 1 st adhesive surface and the 2 nd adhesive surface, it is preferable that the adhesive surface side surfaces of both the release liners satisfy any of the maximum heights Rz. The maximum heights Rz of the adhesive surface side surfaces of the two release liners may be the same or different.

(surface Property of the Back surface)

The arithmetic average roughness Ra and the maximum height Rz of the back surface (the surface opposite to the pressure-sensitive adhesive layer side) of the release liner (preferably, release film) are not particularly limited. From the viewpoint of productivity and the like, the arithmetic average roughness Ra of the back surface of the release liner may be, for example, higher than 30nm (for example, higher than 35nm, and further, about 50nm or more). From the viewpoint of productivity and the like, the maximum height Rz of the back surface of the release liner may be, for example, higher than 400nm (for example, about 500nm or more) or higher than 800nm (for example, 1000nm or more).

The arithmetic average roughness Ra and the maximum height Rz of the surface of the release film can be adjusted by selecting a film material, a forming method, a surface treatment such as a release treatment, and the like. Examples thereof include: adjustment of smoothness of layers (anti-blocking layer, hard coat layer, oligomer prevention layer, etc.) constituting the releasable surface; reduction and nonuse (non-granulation) of filler particles in the surface layer and the release film substrate; adjustment of other stretching conditions, and the like.

The arithmetic average roughness Ra and the maximum height Rz of the surface of the release liner (preferably, release film) were measured using a noncontact surface roughness measuring apparatus. As the noncontact surface roughness measuring device, a surface roughness measuring device using an optical interference system, for example, a three-dimensional optical profiler (trade name "new view7300", manufactured by ZYGO) or a product equivalent thereof can be used. For example, a glass plate (a soda-lime glass plate manufactured by MATSUNAMI, thickness 1.3 mm) was bonded and fixed to the surface opposite to the surface of the release liner to be measured, and the surface shape was measured using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO) at 23 ℃ and 50% RH.

< use >

In the technique disclosed herein, the high refractive index pressure-sensitive adhesive layer can be used by being bonded to various adherends constituting the light-emitting device. The constituent material of the adherend (adherend material) is not particularly limited, and examples thereof include: examples of the metal material include metal materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, and alloys containing 2 or more of these metals, and examples of the metal material include polyimide-based resins, acrylic-based resins, polyether nitrile-based resins, polyether sulfone-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate-based resins, and the like), polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyether ether ketone-based resins, polyamide-based resins (so-called aramid resins, and the like), polyarylate-based resins, fluorine-based resins, polycarbonate-based resins, cellulose-based polymers such as diacetylcellulose and triacetylcellulose, vinyl butyral-based polymers, liquid crystal polymers, and carbon materials such as graphene (typically, plastic materials), alumina, zirconia, titanium oxide, siO, and the like ₂ Metal oxides such as ITO (indium tin oxide) and ATO (antimony doped tin oxide) and mixtures thereof, nitrides such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride and indium nitride and composites thereof, and inorganic materials such as alkali glass, alkali-free glass, quartz glass, borosilicate glass, sapphire glassy carbon and the like. The high refractive index adhesive layer disclosed herein may be adhered to a member (for example, a member whose surface is made of the above-mentioned material) at leastOptical members). In addition, the low refractive index layer (preferably, the low refractive index pressure-sensitive adhesive layer) in the technology disclosed herein can be used by being laminated (for example, bonded) on the various adherends described above.

The high refractive index pressure-sensitive adhesive layer disclosed herein can be used in a bonding manner without performing a treatment of heating to a temperature higher than a temperature range of room temperature (for example, 20 to 35 ℃) after being bonded to an adherend. In addition, depending on the kind of the adherend, and the like, if allowable, the heat treatment may be performed at least at any time after the adherend is attached to the adherend, at the time of the attachment, and before the attachment. The heat treatment may be performed for the purpose of improving the adhesion of the pressure-sensitive adhesive to the adherend, promoting adhesion, or the like. The heat treatment temperature may be appropriately set within an allowable range in consideration of the surface state of the adherend to obtain a desired effect, depending on the constituent material of the pressure-sensitive adhesive sheet and the kind of the adherend, and may be, for example, about 100 ℃ or less, 80 ℃ or less, 60 ℃ or less, or 50 ℃ or less.

The member or material to be attached to the pressure-sensitive adhesive layer may have light-transmitting properties. In such an adherend, the advantage that the high refractive index pressure-sensitive adhesive layer disclosed herein has high transparency can be easily obtained. The total light transmittance of the adherend may be, for example, higher than 50% or 70% or more. In some preferred embodiments, the total light transmittance of the adherend is 80% or more. More preferably 90% or more, and still more preferably 95% or more (for example, 95 to 100%). The high refractive index pressure-sensitive adhesive layer disclosed herein can be preferably used by being attached to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The above total light transmittance is measured according to JIS K7136: 2000, measured using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETER HM-150" manufactured by the color technology research on villages or a product equivalent thereof was used.

The refractive index of the adherend may be the same as or different from the refractive index of the pressure-sensitive adhesive layer (high refractive index pressure-sensitive adhesive layer or low refractive index layer) disposed in contact with the adherend. For example, by relatively increasing the refractive index of the pressure-sensitive adhesive layer compared to the refractive index of the adherend, light incident on the pressure-sensitive adhesive layer at an angle equal to or less than the critical angle from the adherend side can be refracted toward the front side, and the front luminance can be improved. 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, or less than 1.45, or, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. In addition, the adherend having a relatively higher refractive index than the pressure-sensitive adhesive layer can refract light incident on the adherend from the pressure-sensitive adhesive layer side toward the front side, thereby improving front luminance. 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, or 2.50 or less, or 2.00 or less. On the other hand, by reducing the difference in refractive index between the pressure-sensitive adhesive layer and the adherend, reflection of light at the interface can be suppressed. In this case, the refractive index of the adherend may be about 1.55 to 1.80, about 1.55 to 1.75, or about 1.60 to 1.70. The refractive index of the adherend can be measured by the same method as the refractive index of the pressure-sensitive adhesive.

In some preferred embodiments, the 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 which a high refractive index pressure-sensitive adhesive layer and/or a low refractive index layer are/is adhered or laminated on such an adherend, the effects of the technology disclosed herein can be particularly preferably exhibited.

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 laminate including them. As an example of preferable applications, optical applications are cited. More specifically, the laminate sheet disclosed herein can be preferably used as an optical pressure-sensitive adhesive sheet for use in, for example, applications of bonding optical members (for bonding optical members), and applications of manufacturing products (optical products) using the optical members. The laminate sheet used in this manner can be regarded as an interlayer sheet disposed between layers of the optical laminate.

The optical member is a member having optical characteristics (for example, polarization, light refraction, light scattering, light reflection, light transmittance, light absorption, light diffraction, optical rotation, visibility, and the like). The optical member is not particularly limited as long as it has optical properties, and examples thereof include members constituting devices (optical devices) such as display devices (image display devices) and input devices, and members used in these devices, such as polarizing plates, wavelength plates, phase difference plates, optical compensation films, brightness enhancement films, light guide plates, reflection films, reflection prevention films, hard Coat (HC) films, impact absorption films, stain-proofing films, photochromic films, light control films, transparent conductive films (ITO films), appearance films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and members further laminated with these (these may be collectively referred to as "functional films"). The "plate" and the "film" each include a plate-like, film-like, sheet-like form, and the like, and for example, "polarizing film" includes "polarizing plate", "polarizer", and the like, and "light guide plate" includes "light guide film", "light guide sheet", and the like. In addition, the "polarizing plate" includes a circular polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a micro LED (μ LED), a mini LED (miniLED), a PDP (plasma display panel), and electronic paper. The input device may be a touch panel.

The optical member is not particularly limited, and examples thereof include members (e.g., sheet-like, film-like, and plate-like members) formed of glass, acrylic resin, polycarbonate, polyethylene terephthalate, and a metal film. The term "optical member" as used herein includes a member (e.g., an appearance film, a decorative film, and a surface protective film) that retains the visibility of the display device and the input device and plays a role of decoration and protection.

The high refractive index adhesive layer disclosed herein (which may be in the form of a laminate with a low refractive index layer) may be used, for example, in a manner to be disposed between an optical film such as a film having 1 or 2 or more functions of light transmission, reflection, diffusion, wave guide, light collection, diffraction, or the like, a fluorescent film, and another optical member (which may be another optical film), and may be preferably used for bonding the optical film and the other optical member. Among these, in the bonding of optical thin films having at least 1 function of light waveguide, light collection, and diffraction, the entire volume of the bonding layer is preferably high in refractive index, and this can be a preferable application target of the technology disclosed herein.

The high refractive index pressure-sensitive 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 control film, a prism sheet, a lenticular film, and a microlens array film. In these applications, from the viewpoint of the tendency toward miniaturization and high performance of optical members, thinning and improvement of light extraction efficiency are required. As an adhesive layer that can cope with this demand, the high refractive index adhesive layer disclosed herein can be preferably utilized. More specifically, for example, in bonding a light guide film and a diffusion film, the refractive index of the pressure-sensitive adhesive layer serving as a bonding layer is adjusted (for example, the refractive index is increased), thereby contributing to the reduction in thickness. In the bonding of the fluorescent film, the light extraction efficiency (which can also be grasped as the light emission efficiency) can be improved by appropriately adjusting the refractive index difference between the fluorescent light-emitting body and the binder. In the joining of the color matching film, the refractive index of the binder is appropriately adjusted so that the difference in refractive index with the color matching pigment is small, whereby the scattering component can be reduced and the improvement in light transmittance can be contributed. In the joining of a prism sheet, a lenticular film, a microlens array film, or the like, by appropriately adjusting the refractive index of the adhesive, it is possible to control the diffraction of light and contribute to the improvement of the luminance and/or the viewing angle.

The high refractive index pressure-sensitive adhesive layer disclosed herein (which may be in the form of a laminate with a low refractive index layer) is preferably used to be attached to an adherend having a high refractive index (which may be a high refractive index layer, member, or the like), and can suppress interface reflection with the adherend. As described above, the high refractive index pressure-sensitive adhesive layer used in this manner preferably has a small refractive index difference with an adherend having a high refractive index and high adhesion at the interface with the adherend. From the viewpoint of improving the uniformity of appearance, the thickness of the pressure-sensitive adhesive layer is preferably highly uniform, and for example, the surface smoothness of the pressure-sensitive adhesive surface is preferably high. In the case where the thickness of the adherend having a high refractive index is small (for example, 5 μm or less, 4 μm or less, or 2 μm or less), it is particularly significant to suppress reflection at the interface from the viewpoint of suppressing coloring and color unevenness caused by interference of reflected light. Examples of such a use mode include: in the polarizing plate with a retardation layer, which comprises a polarizer, a1 st retardation layer and a2 nd retardation layer in this order, the method is used for bonding the polarizer and the 1 st retardation layer and/or bonding the 1 st retardation layer and the 2 nd retardation layer.

The high refractive index pressure-sensitive adhesive layer disclosed herein can be preferably used by being bonded to a light-emitting layer (for example, a high refractive light-emitting layer mainly composed of an inorganic material) of an optical semiconductor or the like. By reducing the difference in refractive index between the light-emitting layer and the high-refractive-index binder layer, reflection at the interface between them can be suppressed, and light extraction efficiency can be improved. In addition, from the viewpoint of preventing deterioration of the self-light emitting element due to moisture in advance, the high refractive index pressure-sensitive adhesive layer preferably has a low water absorption rate. From the viewpoint of improvement in brightness, the high refractive index adhesive layer is preferably low colored. This may also be advantageous from the viewpoint of suppressing unintentional coloring due to the high refractive index adhesive layer.

The high refractive index adhesive layer disclosed herein can be preferably used as a coating layer for covering a lens surface, a bonding layer for a member (for example, a member having a surface shape corresponding to the lens surface) facing the lens surface, a filling layer for filling between the lens surface and the member, and the like, in a microlens and other lens members (for example, a lens member such as a microlens constituting a microlens array film or a microlens for a camera) used as a constituent member of a camera, a light-emitting device, and the like. The high refractive index adhesive layer disclosed herein can reduce the refractive index difference with a lens having a high refractive index (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 the high refractive index adhesive layer is disposed in contact with the lens. This is advantageous from the viewpoint of reducing the thickness of the lens and a product including the lens, and contributes to the suppression of aberrations and the improvement of abbe number. In the technique disclosed herein, the adhesive (viscoelastic material) constituting the high refractive index adhesive layer can also be used by itself as a lens resin, for example, in a form filled in a concave portion or a void of an appropriate transparent member.

The method of bonding the optical member using the pressure-sensitive adhesive layer disclosed herein (which may be a high refractive index pressure-sensitive adhesive layer and/or a low refractive index pressure-sensitive adhesive layer, and preferably a high refractive index pressure-sensitive adhesive layer optionally laminated on a low refractive index layer) is not particularly limited, and may be, for example, (1) a method of bonding the optical members to each other via the pressure-sensitive adhesive layer disclosed herein, (2) a method of bonding the optical member to a member other than the optical member via the pressure-sensitive adhesive layer disclosed herein, or (3) a method of bonding the pressure-sensitive adhesive layer disclosed herein in the form of a pressure-sensitive adhesive sheet including an optical member to the optical member or a member other than the optical member. In the aspect (3), the pressure-sensitive adhesive sheet including the optical member may be, for example, a pressure-sensitive adhesive sheet in which the support is an optical member (for example, an optical film). Such an adhesive sheet containing an optical member as a support can also be regarded as an adhesive optical member (e.g., an adhesive optical film). In addition, when the pressure-sensitive adhesive layer disclosed herein constitutes a pressure-sensitive adhesive sheet of the type having a support and the functional film is used as the support, the pressure-sensitive adhesive sheet can also be regarded as an "adhesive functional film" having the pressure-sensitive adhesive layer disclosed herein on at least one side of the functional film.

As described above, according to the technology disclosed herein, there is provided an optical laminate including the pressure-sensitive adhesive layer disclosed herein and a member (for example, a resin film such as an optical film) in which the pressure-sensitive adhesive layer is laminated by adhesion or the like. The member on which the pressure-sensitive adhesive layer is laminated by being stuck or the like may have a refractive index of the adherend material. The difference (refractive index difference) between the refractive index of the pressure-sensitive adhesive layer and the refractive index of the member may be the refractive index difference between the adherend and the pressure-sensitive adhesive layer. The members constituting the laminate are not described again, since the description has been given as the above members, materials, and adherends.

As can be understood from the above description and the following examples, the matters disclosed in the specification include the following.

[ 1] an adhesive sheet comprising an adhesive layer,

which has an adhesive surface comprising the adhesive layer,

the adhesive layer has a refractive index of higher than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

The pressure-sensitive adhesive sheet according to item [ 1] above, wherein the thickness of the pressure-sensitive adhesive layer is 5 μm or more.

[ 3] the adhesive sheet according to the above [ 1] or [ 2], which has a peel strength (adhesive force) of 3N/25mm or more with respect to a glass plate.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 3] above, wherein the arithmetic average roughness Ra of the pressure-sensitive adhesive surface is 100nm or less.

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

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 5 ] above, which is configured as a laminate comprising the pressure-sensitive adhesive layer and a light-transmissive substrate.

[ 7 ] the adhesive sheet according to [ 6 ], wherein the light-transmissive substrate is a resin film.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 5 ] above, which is a double-sided adhesive pressure-sensitive adhesive sheet formed of the pressure-sensitive adhesive layer.

[ 9 ] A release liner-attached adhesive sheet comprising:

the adhesive sheet according to any one of [ 1] to [ 8 ] above, and

a release liner disposed on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet.

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

[ 11 ] an adhesive composition comprising:

an acrylic polymer (A) containing an aromatic ring-containing monomer (m 1) as a monomer unit; and

additive (H) _RO ) And an organic material having a higher refractive index than the acrylic polymer (A).

[ 12 ] the adhesive composition according to [ 11 ] above, wherein the additive (H) is _RO ) Has a refractive index of 1.60 or more.

[ 13 ] the adhesive composition according to the above [ 11 ] or [ 12 ], wherein the additive (H) is added to 100 parts by weight of the acrylic polymer (A) _RO ) Is more than 0 part by weight and 60 parts by weight or less.

[ 14 ] the adhesive composition according to any one of [ 11 ] to [ 13 ] above, wherein the additive (H) _RO ) Comprising at least 1 compound selected from the group consisting of aromatic ring-containing compounds and heterocyclic ring-containing compounds.

[ 15 ] the adhesive composition according to any one of [ 11 ] to [ 14 ] above, wherein the additive (H) _RO ) Contains 1 compound having 2 or more aromatic rings in the molecule.

[ 16 ] the adhesive composition according to [ 15 ] above, wherein the additive (H) is _RO ) A compound having 2 or more aromatic rings in the 1 molecule, which satisfies at least one of the following conditions:

(i) A structure in which 2 non-fused aromatic rings are directly chemically bonded; and

(ii) Comprises a structure obtained by fusing 2 aromatic rings.

[ 17 ] the adhesive composition according to any one of [ 11 ] to [ 16 ], wherein a content of the aromatic ring-containing monomer (m 1) in monomer components constituting the acrylic polymer (A) is 50% by weight or more.

The adhesive composition according to any one of [ 11 ] to [ 17 ] above, wherein the content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (A) is more than 70% by weight and less than 100% by weight,

50% by weight or more of the aromatic ring-containing monomer (m 1) is a monomer having a homopolymer glass transition temperature of 10 ℃ or lower.

The adhesive composition according to any one of [ 11 ] to [ 18 ] above, wherein the monomer component constituting the acrylic polymer (A) further contains a monomer (m 2) having at least one of a hydroxyl group and a carboxyl group.

The adhesive composition according to any one of [ 11 ] to [ 18 ] above, which is used for forming an adhesive layer of the adhesive sheet according to any one of [ 1] to [ 8 ].

An adhesive comprising the adhesive composition according to any one of [ 11 ] to [ 20 ] above, wherein the refractive index of the adhesive is higher than 1.570.

[ 22 ] an adhesive sheet comprising an adhesive layer composed of an adhesive agent formed from the adhesive composition according to any one of [ 11 ] to [ 20 ] above.

The pressure-sensitive adhesive sheet according to [ 22 ] above, wherein the haze value of the pressure-sensitive adhesive layer is 1.0% or less.

[ 24 ] an interlayer sheet which is used by being disposed between layers of a laminate in optical use,

comprising a refractive index n ₁ A viscoelastic layer V of 1.570 or more ₁ And is and

the interlayer sheet satisfies: the total light transmittance is more than 86%;

a haze value of 1.0% or less; and,

The storage modulus G' at 25 ℃ is 30 to 700kPa.

[ 25 ] the interlayer sheet according to [ 24 ] above, which has a thickness of 5 μm or more.

[ 26 ] the interlayer sheet according to the above [ 24 ] or [ 25 ], wherein the viscoelastic layer V ₁ Comprising a main polymer and a plasticising material having a lower molecular weight than the main polymer.

[ 27 ] the interlayer sheet according to [ 26 ], wherein the weight average molecular weight of the plasticizing material is 30000 or less.

The interlayer sheet according to any one of [ 24 ] to [ 27 ] above, further comprising a viscoelastic layer V laminated on the viscoelastic layer ₁ Viscoelastic layer V ₂ ，

The above viscoelastic layer V ₂ Storage modulus G 'at 25℃' _V2 Lower than the above viscoelastic layer V ₁ Storage modulus G 'at 25℃' _V1 。

[ 29 ] the interlayer sheet according to [ 28 ], wherein the viscoelastic layer V ₂ Refractive index n of ₂ Lower than the above viscoelastic layer V ₁ Refractive index n of ₁ 。

[ 30 ] the interlayer sheet according to any one of [ 24 ] to [ 29 ], wherein the viscoelastic layer V ₁ Is a layer formed from the adhesive composition according to any one of [ 11 ] to [ 18 ] above.

[ 31 ] the interlayer sheet according to any one of [ 24 ] to [ 29 ], wherein the viscoelastic layer V ₁ Is the adhesive layer in the adhesive sheet according to any one of [ 1] to [ 5 ] above.

[ 32 ] an optical laminate comprising:

the interlayer sheet according to any one of [ 24 ] to [ 31 ] above, and

and a resin film laminated on the interlayer sheet.

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

the interlayer sheet according to any one of [ 24 ] to [ 31 ] above, and

and a release liner covering at least one surface of the interlayer sheet.

[ 34 ] A light-emitting device, comprising:

a self-luminous element,

A low refractive index layer disposed on the side of the self-luminous element which is visually recognized, and

a high refractive index adhesive layer laminated in direct contact with the low refractive index layer,

refractive index n of the high refractive index adhesive layer ₁ Higher than 1.570, total light transmittance of 86% or more, and haze value of 3.0% or less.

[ 35 ] the light-emitting device according to [ 34 ] above, wherein the refractive index n of the high refractive index adhesive layer ₁ Refractive index n of the low refractive index layer ₂ Ratio of (n) ₁ /n ₂ ) Is 1.05 or more.

The light-emitting device according to the above [ 35 ] or [ 36 ], wherein an arithmetic average roughness Ra of a surface of the high refractive index pressure-sensitive adhesive layer is 100nm or less.

[ 37 ] the light-emitting device according to any one of [ 34 ] to [ 36 ] above, wherein a thickness T of the high refractive index adhesive layer ₁ Thickness T of the low refractive index layer ₂ Ratio of (T) ₁ /T ₂ ) Is 0.5 to 5.

[ 38 ] the light-emitting device according to any one of [ 34 ] to [ 37 ] above, wherein a thickness T of the high refractive index adhesive layer ₁ Is 5 μm or more.

The light-emitting device according to any one of [ 34 ] to [ 38 ], wherein a total light transmittance of a laminate sheet comprising the high-refractive-index pressure-sensitive adhesive layer and the low-refractive-index layer is 86% or more and a haze value is 3.0% or less.

The light-emitting device according to any one of [ 34 ] to [ 39 ] above, wherein the high-refractive-index pressure-sensitive adhesive layer is a layer formed from the pressure-sensitive adhesive composition according to any one of [ 11 ] to [ 18 ].

The light-emitting device according to any one of [ 34 ] to [ 40 ] above, wherein the high-refractive-index pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to any one of [ 1] to [ 5 ].

[ 101 ] an adhesive comprising an acrylic polymer (F) containing a fluorine-containing acrylic monomer (M1) as a monomer unit,

the adhesive has a refractive index of 1.46 or less, and

the storage modulus G' at 25 ℃ is 1.0kPa or more and 400kPa or less.

[ 102 ] the adhesive according to [ 101 ] above, wherein a content of the fluorine-containing acrylic monomer (M1) in monomer components constituting the acrylic polymer (F) is 25% by weight or more.

The adhesive according to [ 101 ] or [ 102 ] above, wherein the fluorine-containing acrylic monomer (M1) contains a fluorine atom-containing alkyl (meth) acrylate.

The adhesive according to any one of [ 101 ] to [ 103 ] above, wherein the acrylic polymer (F) contains a hydroxyl group-containing monomer as a monomer unit.

[ 105 ] A laminate comprising

A low refractive index adhesive layer comprising the adhesive according to any one of [ 101 ] to [ 104 ] above, and

and a high refractive index pressure-sensitive adhesive layer laminated on the low refractive index pressure-sensitive adhesive layer.

[ 106 ] the laminate sheet according to [ 105 ] above, wherein the refractive index n of the high refractive index adhesive layer ₁ A refractive index n of the low refractive index adhesive layer ₂ Ratio of (n) ₁ /n ₂ ) Is 1.02 or more.

[ 107 ] the laminate sheet according to the above [ 105 ] or [ 106 ], wherein the refractive index n of the high refractive index adhesive layer ₁ Above 1.570.

The laminate sheet according to any one of [ 105 ] to [ 107 ] above, wherein the high refractive index adhesive layer has a storage modulus G' at 25 ℃ of 700kPa or less.

The laminate sheet according to any one of [ 105 ] to [ 108 ] above, wherein the total light transmittance is 86% or more and the haze value is 3.0% or less.

[ 110 ] A light-emitting device, comprising:

self-luminous element and

the laminate sheet according to any one of [ 105 ] to [ 109 ] above,

the laminated sheet is disposed on the side of the self-luminous element which is visually recognized.

[ 111 ] the adhesive according to any one of [ 101 ] to [ 104 ] above, which is used for forming the viscoelastic layer V in the interlayer sheet according to any one of [ 28 ] to [ 31 ] above ₂ 。

[ 112 ] the adhesive according to any one of [ 101 ] to [ 104 ] above, which is used for forming the low refractive index layer in the light-emitting device according to any one of [ 34 ] to [ 41 ].

Examples

Some experiments related to the present invention are described below. In the following description, "part" and "%" representing the amount and content of the compound are based on weight unless otherwise specified.

< preparation of acrylic adhesive composition C1 >

Into ase:Sub>A four-necked flask equipped with ase:Sub>A stirrer blade, ase:Sub>A thermometer, ase:Sub>A nitrogen gas inlet tube and ase:Sub>A condenser, 95 parts of m-phenoxybenzyl acrylate (product name: LIGHT ACRYLATE POB-ase:Sub>A, manufactured by Kyoritsu chemical Co., ltd.; refractive index: 1.566, tg of homopolymer: -35 ℃. Hereinafter, abbreviated as "POB-ase:Sub>A"), 5 parts of 4-hydroxybutyl acrylate (4 hbase:Sub>A), 0.2 parts of 2,2' -Azobisisobutyronitrile (AIBN) as ase:Sub>A polymerization initiator, and 100 parts of toluene as ase:Sub>A polymerization solvent were charged as monomer components, nitrogen gas was introduced while slowly stirring, and polymerization was carried out for 6 hours while keeping the liquid temperature in the flask at about 60 ℃ to prepare ase:Sub>A solution (50%) of the acrylic polymer ase:Sub>A 1. The weight average molecular weight (Mw) of the acrylic polymer A1 was 50 ten thousand. Tg (i.e., tg) of the acrylic polymer A1 based on the composition of the monomer components _T ) At-35 ℃ and a Tg (i.e., tg) based on the composition of the aromatic ring-containing monomer _m1 ) Is-35 ℃.

The solution (50%) of the acrylic polymer A1 was diluted with ethyl acetate to 30%, and to 334 parts (100 parts of nonvolatile components) of the solution, 10 parts (0.1 part of nonvolatile components) of A1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX" manufactured by tokyo co., ltd., 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part (0.01 part of nonvolatile components) of A1% ethyl acetate solution of iron acetylacetonate as a crosslinking catalyst were added and mixed with stirring to prepare an acrylic adhesive composition C1.

< preparation of acrylic adhesive composition C2 >

A four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a condenser was charged with 72 parts of POB-A, 23 parts of 1-naphthylmethyl acrylate (trade name "LIGHT ACRYLATE NMT-A", manufactured by Kyoeisha chemical Co., ltd., refractive index: 1.595, tg of homopolymer: 31 ℃ C., hereinafter abbreviated as "NMT-A"), 4 parts of HBA5, 0.2 part of AIBN as a polymerization initiator, and 100 parts of toluene as a polymerization solvent, and polymerization was carried out for 6 hours while slowly stirring while maintaining the liquid temperature in the flask at about 60 ℃ to prepare a solution (50%) of an acrylic polymer A2. The weight average molecular weight (Mw) of the acrylic polymer A2 was 50 ten thousand.

In a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet, 20 parts of POB-A, 80 parts of NMT-A, 0.2 parts 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 as monomer components, and nitrogen gas was introduced and nitrogen substitution was performed for about 1 hour while stirring. Then, the flask was heated to 70 ℃ to carry out a reaction for 12 hours, thereby obtaining an acrylic oligomer (oligomer B) having a weight average molecular weight (Mw) 4000 and a refractive index of 1.63.

The solution (50%) of the acrylic polymer A2 was diluted with ethyl acetate to 30%, and to 334 parts (100 parts of nonvolatile matter) of the solution, 20 parts of the oligomer B prepared above, 10 parts (0.1 part of nonvolatile matter) of a 1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (product name "Coronate HX" manufactured by tokyo co., ltd., 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part (0.01 part of nonvolatile matter) of a 1% ethyl acetate solution of iron acetylacetonate as a crosslinking catalyst were added and mixed with stirring to prepare an acrylic adhesive composition C2.

< preparation of acrylic adhesive composition C3 >

Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube and a condenser were introduced 65 parts of 2-ethylhexyl acrylate, 1h, 5h-octafluoropentyl acrylate (product name: viscoat 8F, manufactured by osaka organic chemical industries, inc.), 30 parts of N-vinyl-2-pyrrolidone (NVP, manufactured by japan catalyst), 3 parts and 4hba 2 parts, 0.2 part of AIBN as a polymerization initiator, and 200 parts of ethyl acetate as a polymerization solvent, as monomer components, and while gradually stirring, nitrogen gas was introduced, and a polymerization reaction was carried out for 9 hours while keeping the liquid temperature in the flask at about 60 ℃ to prepare a solution (33%) of acrylic polymer A3. The weight average molecular weight (Mw) of the acrylic polymer A3 was 55 ten thousand.

The solution (33%) of the acrylic polymer A3 was diluted with ethyl acetate to 30% and 10 parts (0.1 part of nonvolatile matter) of a 1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (product name "Coronate HX" manufactured by tokyo co., ltd., 3-functional isocyanate compound) as a crosslinking agent was added to 100 parts of nonvolatile matter (solid matter) and mixed with stirring to prepare an acrylic pressure-sensitive adhesive composition C3.

< preparation of pressure-sensitive adhesive sheet >

(example 1)

The acrylic pressure-sensitive adhesive composition C1 prepared above was coated on a silicone-treated surface of a polyethylene terephthalate (PET) film R1 (thickness 50 μm) having silicone-treated one surface, and heated at 130 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 25 μm. A silicone-treated surface of the PET film R2 (38 μm thick) having silicone-treated one surface was bonded to the surface of the pressure-sensitive adhesive layer. In this manner, a pressure-sensitive adhesive layer (high refractive index pressure-sensitive adhesive layer) having both surfaces protected by PET films (release liners) R1 and R2 was obtained. The release liner R2 is relatively light in weight compared to the release liner R1.

The acrylic pressure-sensitive adhesive composition C3 prepared above was applied to the silicone-treated surface of the PET film R1 (thickness 50 μm) having silicone-treated one surface, and heated at 130 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 10 μm. A silicone-treated surface of the PET film R2 (38 μm thick) having silicone-treated one surface was bonded to the surface of the pressure-sensitive adhesive layer. In this manner, a pressure-sensitive adhesive layer (low refractive index pressure-sensitive adhesive layer) having both surfaces protected by PET films (release liners) R1 and R2 was obtained.

The release liner R2 was peeled off from the high refractive index adhesive layer and the low refractive index adhesive layer, and the adhesive surfaces were bonded to each other, and pressure-bonded by a manual roll. The laminate was autoclaved at 50 ℃ and 0.60MPa for 30 minutes and then cured at 50 ℃ for 48 hours. In this manner, a laminate sheet (substrate-less double-sided adhesive sheet) having a two-layer structure of a high refractive index adhesive layer/a low refractive index adhesive layer was obtained. The surface of the adhesive sheet was protected by 2 release liners R1.

(example 2)

A laminate sheet (substrate-less double-sided adhesive sheet) having a two-layer structure of a high refractive index adhesive layer/a 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 changed as shown in table 1.

Examples 3 to 5

Adhesive layers having a single-layer structure and each having a thickness shown in table 1, each formed from acrylic adhesive compositions C1 to C3, were prepared as the adhesive sheets of examples 3 to 5 in the same manner as in example 1.

The obtained adhesive sheets were subjected to the following measurement and evaluation in an environment of 23 ℃ and 50% RH after being sufficiently adapted.

< measurement and evaluation (1) >

(refractive index)

The refractive index of each pressure-sensitive adhesive layer was measured using an Abbe refractometer (model "DR-M4" manufactured by ATAGO) under conditions of a measurement wavelength of 589nm and a measurement temperature of 25 ℃. The results are shown in Table 1.

(storage modulus G')

The adhesive layers were stacked to a thickness of about 1.5mm, and the resultant was used as a sample for measurement. Dynamic viscoelasticity was measured under the following conditions using ARES manufactured by TA Instruments. The storage modulus G' at 25 ℃ was read from the measurement results. The results are shown in Table 1.

[ measurement conditions ]

Deformation mode: torsion

Measuring frequency: 1Hz

Temperature rise rate: 5 ℃ per minute

Shape: parallel plates

(Total light transmittance and haze value)

The total light transmittance and haze of each test piece obtained by bonding the adhesive sheet of each example to alkali-free glass (thickness of 0.8 to 1.0mm, total light transmittance of 92%, haze of 0.4%) was measured using a haze meter (trade name "HAZEMETER HM-150", manufactured by color technology research in village) under a measurement environment of 23 ℃. The total light transmittance and haze of the alkali-free glass were subtracted from the measured values to obtain values as the total light transmittance and haze value of the adhesive sheet. The results are shown in Table 1.

(peeling Strength to glass plate)

The release liner was peeled from one surface of each adhesive sheet (the surface of the adhesive layer formed of the adhesive composition C3 in examples 1 and 2) in a measuring environment of 23 ℃ and 50% rh, and a PET film having a thickness of 50 μm was attached to the release liner and lined with the liner, and then cut into a size of 25mm in width and 100mm in length to prepare a test piece. The release liner on the other side was peeled from the test piece, and a 2kg roller was reciprocated 1 time and pressure-bonded to the surface of an alkali glass plate (a product having a thickness of 1.35mm and a green plate edge, manufactured by Songlanzui industries) as an adherend. The resultant was allowed to stand in this atmosphere for 30 minutes, then charged into a pressure defoaming apparatus (autoclave), and subjected to autoclave treatment at a temperature of 50 ℃ and a pressure of 0.5MPa for 30 minutes, and further allowed to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, and then subjected to a tensile compression testing machine in accordance with JIS Z0237: the peel strength (adhesive force) [ N/25mm ] was measured at a tensile rate of 300 mm/min and a peel angle of 180 degrees. As a universal tensile compression tester, "tensile compression tester, TG-1kN", manufactured by Minebea corporation, was used.

[ Table 1]

TABLE 1

C1：POB-A/4HBA(95/5)

C2: POB-A/NMT-A/4HBA (72/23/5) 100 parts + oligomer B20 parts

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

As shown in Table 1, the adhesive sheets of examples 1 to 4 contained a refractive index n _V1 An adhesive layer V1 (high refractive index adhesive layer) of more than 1.570, and high transparency is exhibited in the adhesive sheet. These adhesive sheets exhibit practical peel strength suitable for bonding of optical members.

< evaluation of front Brightness improving Effect >

The adhesive sheets of the examples were attached to a white LED light source, and after the light source was turned on and stabilized for 30 minutes or more in a dark room environment, the front luminance of the portion to which the adhesive sheet was attached was measured using a spectroradiometer SR-UL1R (manufactured by TOPCON TECHNOLOGOUSE CORPORATION). Using the average of the luminances measured 3 times, the case where the luminance improvement effect was 10% or more with respect to the luminance of the light source to which no adhesive sheet was attached was evaluated as G (Good), and the case where the luminance improvement was less than 10% was evaluated as P (Poor).

The results are shown in Table 2

[ Table 2]

TABLE 2

Example (B)	1	2	3	4	5
						Front side brightness enhancement effect	G	G	P	P	P

As shown in table 2, it was confirmed that the pressure-sensitive adhesive sheets (laminated sheets) of examples 1 and 2 having a pressure-sensitive adhesive layer having a laminated structure in which the pressure-sensitive adhesive layer of example 5 having a low refractive index and the pressure-sensitive adhesive layers of examples 3 and 4 having a high refractive index were combined exhibited a front luminance improvement effect of 10% or more with respect to the case where the pressure-sensitive adhesive sheet was not used. The interlayer sheets of examples 3 to 5, in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet had a single-layer structure, were not confirmed to have the effect of improving the front luminance by the pressure-sensitive adhesive sheet alone.

< preparation of acrylic adhesive composition C4 >

Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen introduction tube and a condenser were charged 79 parts of POB-a, 20 parts of n-butyl acrylate, 4hba 1 parts, 0.2 part of AIBN as a polymerization initiator and 100 parts of toluene as a polymerization solvent, and nitrogen was introduced while slowly stirring, and the liquid temperature in the flask was maintained at about 60 ℃ to conduct a polymerization reaction for 6 hours, thereby preparing a solution (50%) of an acrylic polymer A4. The Mw of the acrylic polymer A4 was 52 ten thousand.

The solution (50%) of the acrylic polymer A4 was diluted with ethyl acetate to 30%, and to 334 parts of the solution (100 parts of nonvolatile matter) were added 10 parts of a 1% ethyl acetate solution of Coronate HX as a crosslinking agent (0.1 part of nonvolatile matter), 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of iron acetylacetonate as a crosslinking catalyst (0.01 part of nonvolatile matter), and the mixture was stirred and mixed to prepare an acrylic adhesive composition C4.

< preparation of acrylic adhesive composition C5 >

ase:Sub>A solution (50%) of acrylic polymer ase:Sub>A 5 was prepared in the same manner as the preparation of the solution of acrylic polymer ase:Sub>A 4, except that the composition (weight ratio) of the monomer components was changed to POB-ase:Sub>A/ethyl carbitol acrylate (cbase:Sub>A)/4 hbase:Sub>A = 79/20/1. The Mw of the acrylic polymer A5 was 46 ten thousand. An acrylic adhesive composition C5 was prepared in the same manner as in the preparation of the acrylic adhesive composition C4, except that a solution of the acrylic polymer A5 was used instead of the solution of the acrylic polymer A4.

< preparation of acrylic adhesive composition C6 >

A solution (50%) of the acrylic polymer A6 was prepared in the same manner as the preparation of the solution of the acrylic polymer A4, except that the composition (weight ratio) of the monomer component was changed to P2H-a/4hba = -99/1. In the composition of the monomer components, "P2H-A" represents phenoxy diethylene glycol acrylate (trade name "LIGHT ACRYLATE P H-A" manufactured by Kyoeisha chemical Co., ltd., refractive index: 1.510, tg of homopolymer: -35 ℃ C.). The Mw of the acrylic polymer A6 was 100 ten thousand.

A solution (50%) of the acrylic polymer A6 was diluted with ethyl acetate to 30% and 334 parts (100 parts of nonvolatile matter) of the solution was added as an additive (H) _RO ) 6-Ethylacrylate-dinaphtho [2,1-b:1',2' -d]Thiophene (6-acryloyloxyethyldinaphthothiophene manufactured by Sugai Chemical IND. CO., LTD., no. 6EDNTA, refractive index: 1.722) 20 parts, a 1% ethyl acetate solution of Coronate HX as a crosslinking agent 10 parts (non-volatile content 0.1 part), acetylacetone as a crosslinking retarder 2 parts, and a 1% ethyl acetate solution of iron acetylacetonate as a crosslinking catalyst 1 part (non-volatile content 0.01 part) were mixed with stirring to prepare an acrylic adhesive composition C6.

< preparation of acrylic adhesive composition C7 >

A solution (50%) of the acrylic polymer A7 was prepared in the same manner as the preparation of the solution of the acrylic polymer A3, except that the composition (weight ratio) of the monomer components was changed to 2EHA/Viscoat 13F/4hba = 49/50/1. "Viscoat 13F" in the composition of the above monomer component means acrylic acid 1H, 2H-tridecafluorooctyl ester (product name "Viscoat 13F" manufactured by Osaka organic chemical Co., ltd.). The Mw of the acrylic polymer A7 was 55 ten thousand. An acrylic adhesive composition C7 was prepared in the same manner as in the preparation of the acrylic adhesive composition C3, except that a solution of the acrylic polymer A7 was used instead of the solution of the acrylic polymer A3.

< preparation of pressure-sensitive adhesive sheet >

Examples 6 to 8

A laminated sheet (substrate-less double-sided adhesive sheet) having a two-layer structure of a high refractive index adhesive layer/a low refractive index adhesive layer was obtained in the same manner as in example 1, except that the kind of the adhesive composition for forming each adhesive layer and the thickness of each adhesive layer were set as shown in table 3.

The adhesive sheets obtained in examples 6 to 8 were subjected to the measurement and evaluation in the same manner as in the above-mentioned "measurement and evaluation (1)" after they were sufficiently adapted to the environment of 23 ℃ and 50% RH. The results are shown in Table 3.

[ Table 3]

TABLE 3

C4：POB-A/BA/4HBA(79/20/1)

C5：POB-A/CBA/4HBA(79/20/1)

C6: P2H-A/4HBA (99/1) 100 parts +6EDNTA20 parts

C7：2EHA/Viscoat13F/4HBA(49/50/1)

As shown in Table 3, the adhesive sheets of examples 6 to 8 had a refractive index n ₁ The laminated structure of the adhesive layer (high refractive index adhesive layer) higher than 1.570 and the low refractive index layer shows high transparency. These adhesive sheets show a suitable bond for optical membersPractical peel strength.

Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The embodiments described in the claims include various modifications and changes made to the specific examples illustrated above.

Description of the reference numerals

2. Substrate-less double-sided adhesive sheet

10. Laminate sheet (adhesive sheet)

10A No. 1 surface (No. 1 adhesive surface)

10B No. 2 surface (No. 2 adhesive surface)

11. High refractive index adhesive layer

12. Low refractive index adhesive layer (Low refractive index layer)

70. Self-luminous element

80. Covering window component

100. Light emitting device

Claims

1. A light emitting device, comprising:

a self-luminous element,

A low refractive index layer disposed on a side of the self-luminous element which is visually recognized, and

2. The light-emitting device according to claim 1, wherein a refractive index n of the high-refractive-index adhesive layer ₁ And a refractive index n of the low refractive index layer ₂ Ratio of (n) ₁ /n ₂ ) Is 1.05 or more.

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

4. The light-emitting device according to any one of claims 1 to 3, wherein the thickness T of the high-refractive-index adhesive layer ₁ And the thickness T of the low refractive index layer ₂ Ratio of (T) ₁ /T ₂ ) 0.5 to 5.

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

6. The light-emitting device according to any one of claims 1 to 5, wherein a laminate sheet comprising 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.