CN115362233A

CN115362233A - Interlayer sheet, interlayer sheet with release liner, and optical laminate

Info

Publication number: CN115362233A
Application number: CN202180024127.5A
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: 2022-11-18
Also published as: TW202142396A; KR20220156055A; WO2021193723A1

Abstract

Provided is an interlayer sheet which is disposed between layers of a laminate and used for optical applications. The interlayer sheet has a refractive index n ₁ Is 1.570-25 ℃ storage modulus G' _V1 A viscoelastic layer V of 30kPa to 700kPa ₁ . The interlayer sheet has a total light transmittance of 86% or more and a haze value of 1.0% or less.

Description

Interlayer sheet, interlayer sheet with release liner, and optical laminate

Technical Field

The invention relates to an interlayer sheet, an interlayer sheet with a release liner and an optical laminate.

Priority is claimed for this application based on japanese patent application No. 2020-052408, published 3/24 in 2020, japanese patent application No. 2020-166429, published 9/30 in 2020, and japanese patent application No. 2021-049063, published 3/23 in 2021, the entire contents of which are 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 use of the adhesive include the use of a polarizing film, a retardation film, a cover window member, and other various light-transmitting members bonded 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 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 containing a monomer having a plurality of aromatic rings as a monomer unit, and an adhesive obtained by crosslinking the adhesive composition, but do not disclose a specific adhesive having both a refractive index of 1.570 or more and flexibility. 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) into a resin is also known, but the refractive index of a pressure-sensitive adhesive blended with inorganic particles is in a trade-off relationship with 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. In particular, for adhesives for optical applications, it is necessary to take into consideration the influence on optical characteristics (for example, total light transmittance, haze, and the like) when inorganic particles are compounded. For example, in the optical use, when the improvement of the refractive index of an interlayer sheet to be used by being disposed between layers of a laminate is studied, it is required to achieve a balance between flexibility and high transparency that can exhibit appropriate adhesion and deformation following properties to a member adjacent to the interlayer sheet, and to increase the refractive index.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an interlayer sheet which exhibits flexibility suitable for adhesion to and follow up of adjacent members and which has both a high refractive index and high transparency. Another object of the present invention is to provide an interlayer sheet with a release liner comprising the above interlayer sheet. Another object of the present invention is to provide an optical laminate including the above interlayer sheet as a constituent element.

Means for solving the problems

According to this specification, an interlayer sheet to be used by being disposed between layers of a laminate in optical use is provided. The interlayer sheet has a refractive index n ₁ A viscoelastic layer V of 1.570 or more ₁ . The interlayer sheet has a total light transmittance of 86% or more, a haze value of 1.0% or less, and a storage modulus G 'at 25 ℃' _V1 (hereinafter sometimes referred to as "storage modulus G' _V1 (25) ". ) Is 30kPa to 700kPa. The interlayer sheet contains high refractive index and storage modulus G' _V1 (25) A viscoelastic layer V suppressed to a certain level or less ₁ And is highly transparent, and therefore is useful as an interlayer sheet for optical applications. Further, the interlayer sheet is formed in advance in a sheet shape, and thus can be easily disposed at a desired position.

In some embodiments, the viscoelastic layer has a thickness of 5 μm or more. A viscoelastic layer having such a thickness is preferable because it absorbs irregularities that may be present on the surface of an adjacent member, and thus easily laminates the member with good adhesion.

Some embodiments of the interlayer sheet further comprise a viscoelastic layer V laminated on the above viscoelastic layer ₁ Viscoelastic layer V ₂ . Here, the viscoelastic layer V ₂ Storage modulus G 'at 25℃' _V2 (hereinafter sometimes referred to as "storage modulus G' _V2 (25) ". ) Lower than the above viscoelastic layer V ₁ Storage modulus G 'at 25℃' _V1 . The interlayer sheet thus constituted passes through the viscoelastic layer V ₂ The contribution of (3) can make the flexibility more excellent.

In some embodiments, the viscoelastic layer V ₂ Refractive index n of ₂ Below the viscoelastic layer V ₁ Refractive index n of ₁ . According to having theThe interlayer sheet is formed by using a viscoelastic layer V ₁ 、V ₂ To control the behavior of light transmitted through the interlayer sheet.

Further, according to the specification, there is provided a release liner-equipped interlayer sheet comprising any of the interlayer sheets disclosed herein and a release liner covering at least one surface of the interlayer sheet. The interlayer sheet disclosed herein can be preferably used in the following manner: the release liner-equipped interlayer sheet having at least one surface protected by the release liner is manufactured, stored, distributed, processed, and the like, and the release liner is peeled off before being laminated with an adjacent member.

Further, according to the specification, there is provided an optical laminate comprising any of the interlayer sheets disclosed herein and a resin film laminated on the interlayer sheet. In the optical laminate, the advantages of the interlayer sheet disclosed herein, including high refractive index, high transparency, and flexibility, can be preferably exhibited.

It should be noted that the technical means that the respective elements described in the present specification are appropriately combined may be included in the scope claimed in the present patent application.

Drawings

Fig. 1 is a cross-sectional view schematically showing the structure of an interlayer sheet according to an embodiment.

Fig. 2 is a sectional view schematically showing the constitution of an interlayer sheet of another embodiment.

Fig. 3 is a cross-sectional view schematically illustrating an optical stack including an embodiment of an interlayer sheet.

Detailed Description

Preferred embodiments of the present invention will be described below. 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 given the same reference numerals and description thereof is sometimes omitted or simplified, and redundant description thereof is sometimes omitted. In addition, the embodiments described in the drawings are schematically illustrated for the purpose of clearly explaining the present invention, and do not necessarily accurately show the size and scale of a product 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. When a light-emitting device is referred to in this specification, the light-emitting device may include 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.

According to the specification, an interlayer sheet used by being disposed between layers of a laminate in optical use is provided. The interlayer sheet comprises at least a viscoelastic layer V ₁ . The interlayer sheet may further comprise a viscoelastic layer V laminated on the viscoelastic layer ₁ Viscoelastic layer V ₂ . Viscoelastic layer V ₁ 、V ₂ Typically an adhesive layer comprised of an adhesive. The interlayer sheet of this embodiment can be regarded as an adhesive sheet having an adhesive layer. Hereinafter, the interlayer sheet is referred to as an adhesive sheet, the viscoelastic layer is referred to as an adhesive layer, the viscoelastic material is referred to as an adhesive, and the surface of the viscoelastic layer is referred to as an adhesive surface. In addition, a member in which the viscoelastic layer of the interlayer sheet disclosed herein is laminated may be referred to as an adherend of the interlayer sheet (pressure-sensitive adhesive sheet). In some embodiments, the interlayer sheet preferably has a layer composed of an adhesive V ₁ Forming the adhesive surface.

< example of construction of interlayer sheet >

The interlayer sheet disclosed herein may have an adhesive layer (for example, a viscoelastic layer V) on one side or both sides of a non-releasable substrate (support substrate) ₁ The adhesive layer having a single-layer structure or the adhesive layer containing the viscoelastic layer V ₁ And a viscoelastic layer V ₂ The pressure-sensitive adhesive sheet with a substrate in the form of a pressure-sensitive adhesive sheet with a laminated structure in which two or more pressure-sensitive adhesive layers are directly laminated in contact with each other) may be a substrate-free pressure-sensitive adhesive sheet (i.e., a pressure-sensitive adhesive sheet having no non-releasable substrate) in the form of a release liner holding the pressure-sensitive adhesive layers. Typically an adhesive sheet formed from an adhesive layer). The concept of the adhesive sheet as referred to herein may include objects called adhesive tapes, adhesive labels, adhesive films, etc. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, the pressure-sensitive adhesive sheet may be further processed into various shapes.

Fig. 1 shows an example of the structure of the interlayer sheet disclosed herein. The interlayer sheet (adhesive sheet) 1 is configured as a one-sided adhesive sheet (one-sided adhesive sheet) including: the 1 st surface 10A is a pressure-sensitive adhesive layer 10 serving as a bonding surface (pressure-sensitive adhesive surface) to an adherend, and a support base material 20 laminated on the 2 nd surface 10B of the pressure-sensitive adhesive layer 10. The 2 nd surface 10B of the pressure-sensitive adhesive layer 10 is bonded to the 1 st surface (non-releasable surface) 20A of the support base 20. As the support base 20, for example, a plastic film such as a polyester film can be used. The support substrate 20 may be an optical film such as a polarizing plate. The psa sheet 1 before use (before application to an adherend) may be, for example, as shown in fig. 1, in the form of a release-lined psa sheet 50 having a psa surface 10A protected by a release liner 30 which forms a releasable surface (release surface) at least on the psa layer side. Alternatively, the second surface 20B (the surface opposite to the first surface 20A, also referred to as the back surface) of the support base 20 may be a release surface, and the adhesive surface 10A may be protected by winding or laminating the support base 20 so that the adhesive surface 10A abuts against the second surface 20B. The adhesive layer 10 may be composed of a viscoelastic layer V as shown in FIG. 1 ₁ The single-layer structure may be formed by two or more sub-adhesive layers having different compositions (for example, a viscoelastic layer V constituting the adhesive surface 10A) ₁ And a viscoelastic layer V disposed on the support base 20 side ₂ The two sub-adhesive layers) are in direct contact (i.e., not separated by a layer of non-adhesive material) and laminated.

The interlayer sheet disclosed herein may also be in the form of a substrate-less double-sided adhesive sheet formed of an adhesive layer. As shown in fig. 2, the substrate-less double-sided adhesive sheet 2 may be in the form of: before use, the 1 st surface (1 st adhesive surface) 10A and the 2 nd surface (2 nd adhesive surface) 10B of the adhesive layer 10 are protected by

release liners

31, 32 which become releasable surfaces (release surfaces) at least on the adhesive layer side. Alternatively, the back surface (the surface opposite to the pressure-sensitive adhesive side) of the release liner 31 may be a release surface, and the pressure-

sensitive adhesive surfaces

10A and 10B may be protected by winding or laminating the release liner 31 so that the pressure-sensitive adhesive surface 10B comes into contact with the back surface of the release liner 31. Such a substrate-free double-sided pressure-sensitive adhesive sheet can be used, for example, by bonding a substrate (preferably a light-transmitting substrate, and may be an optical member such as an optical film) to at least one of the 1 st pressure-sensitive adhesive surface and the 2 nd pressure-sensitive adhesive surface.

The pressure-sensitive adhesive layer 10 constituting the substrate-less double-sided pressure-sensitive adhesive sheet 2 shown in fig. 2 has a laminated structure in which two sub-pressure-sensitive adhesive layers having different compositions are directly contacted and laminated. The adhesive layer 10 is specifically composed of a 1 st viscoelastic layer (1 st adhesive layer, viscoelastic layer V) ₁ ) 11 and 2 nd viscoelastic layer (2 nd adhesive layer, viscoelastic layer V) ₂ ) 12 (a double-layer structure). Alternatively, the interlayer sheet disclosed herein may be an adhesive layer (viscoelastic layer V) having a single-layer structure ₁ ) A substrate-free double-sided adhesive sheet is formed. The interlayer sheet in the form of a substrate-less double-sided adhesive sheet of such a laminated structure or a single-layer structure can be used, for example, as a component of an optical laminate in which optical members are laminated on the 1 st adhesive surface and the 2 nd adhesive surface, respectively.

The interlayer sheet disclosed herein may be a component of an optical laminate having an optical member bonded to at least one surface thereof. For example, the interlayer sheet 1 shown in fig. 1 may be a component of an optical laminate 100 in which the optical member 70 is laminated on the 1 st surface 10A of the pressure-sensitive adhesive layer 10 as shown in fig. 3. The optical member may be, for example, a glass plate, a resin film, a metal plate, or the like. The interlayer sheet 1 may be disposed between the optical member 70 and the 2 nd optical member not shown, and may be a component of an optical laminate. In the interlayer sheet 1 shown in fig. 1, when the support base 20 is an optical member such as an optical film, the interlayer sheet 1 can be regarded as an optical laminate in which the optical member is laminated on the 2 nd surface 10B of the pressure-sensitive adhesive layer 10.

Further, although not particularly shown, the interlayer sheet disclosed herein may be in the form of a substrate-attached double-sided adhesive sheet (substrate-attached double-sided adhesive sheet) including a support substrate having non-releasable 1 st and 2 nd surfaces, the 1 st adhesive layer being fixedly laminated on the 1 st surface, and the 2 nd adhesive layer being fixedly laminated on the 2 nd surface. Examples of the configuration of such a double-sided pressure-sensitive adhesive sheet with a substrate include the following: in the single-sided psa sheet 1 shown in fig. 1, the 2 nd surface 20B of the support substrate 20 is a non-releasable surface, and a 2 nd psa layer is provided on the 2 nd surface 20B, the 2 nd surface of the 2 nd psa layer being bonded to the 2 nd surface 20B of the support substrate 20, and the 1 st surface (the surface on the opposite side of the 2 nd surface) of the 2 nd psa layer being the 2 nd psa surface of the double-sided psa sheet with substrate. The composition of the adhesive constituting the 2 nd adhesive layer may be the same as or different from that of the adhesive constituting the 1 st adhesive layer. The interlayer sheet in the form of a double-sided pressure-sensitive adhesive sheet with a substrate can be used, for example, as a component of an optical laminate in which optical members are laminated on the 1 st pressure-sensitive adhesive surface and the 2 nd pressure-sensitive adhesive surface, respectively. As for the double-sided psa sheet with a substrate before use, the 1 st adhesive surface and the 2 nd adhesive surface may be protected by release liners, as in the case of the substrate-less double-sided psa sheet.

< characteristics of interlayer sheet >

(refractive index)

The interlayer sheet disclosed herein has a refractive index n ₁ A viscoelastic layer (adhesive layer) V of 1.570 or more ₁ . Such a viscoelastic layer V ₁ For example, this can be achieved by forming at least one surface (adhesive surface) of the viscoelastic layer with an adhesive (viscoelastic material) having a refractive index of 1.570 or more. According to the technology disclosed herein, an adhesive layer V having a refractive index of 1.570 or more can be provided ₁ And the pressure-sensitive adhesive layer V can be formed ₁ And an adhesive layer V comprising the adhesive composition ₁ The interlayer sheet of (1).

In the present specification, the refractive index of the adhesive (viscoelastic material) refers to the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring 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).

In some forms, the adhesive layer V ₁ The refractive index of (b) is favorably higher than 1.570, and may be preferably 1.580 or more, more preferably 1.585 or more, and still more preferably 1.590 or more (for example, 1.595 or more). According to the adhesive layer V having the refractive index ₁ Using the adhesive layer V ₁ And a layer (which may be another viscoelastic layer contained in the interlayer sheet) adjacent thereto (e.g., an adhesive layer V ₂ ) Alternatively, the pressure-sensitive adhesive layer V may be laminated ₁ The adherend of (1). ) Can effectively control the relative refractive index relationship of the transparent adhesive layer V ₁ The behavior of light. In some versions of the technology disclosed herein, the adhesive layer V ₁ For example, the refractive index of (b) may be 1.600 or more or higher than 1.600, 1.605 or more or higher than 1.605, or 1.610 or more or higher than 1.610. Adhesive layer V ₁ The preferable upper limit of the refractive index of (b) may be different depending on the refractive index of an adjacent layer and the like, and is not limited to a specific range. In some forms, the adhesive layer V is formed in consideration of balance with adhesive property and transparency ₁ The refractive index of (a) may be, for example, 1.700 or less, 1.670 or less, or 1.650 or less.

The interlayer sheet disclosed herein is a double-sided adhesive sheet (including both a substrate-less double-sided adhesive sheet and a substrate-attached double-sided adhesive sheet; as long as there is no interlayer sheet) having one side as a 1 st adhesive side and the other side as a 2 nd adhesive side The same applies to the following, unless otherwise specified. ) And the 1 st adhesive surface is composed of an adhesive layer V ₁ In the case of the above-mentioned structure, the adhesive layer preferably satisfies the above-mentioned arbitrary refractive index at least on the 1 st adhesive surface. The refractive index of the 2 nd adhesive surface is not particularly limited.

In some embodiments, the refractive index n of the 2 nd adhesion surface ₂ Refractive index n of the 1 st adhesive surface ₁ To approximately the same extent. More specifically, | n, which is the absolute value of the difference in refractive index between the two adhesive surfaces ₁ -n ₂ For example, | may be less than 0.05, or less than 0.03, or less than 0.01.| n ₁ -n ₂ The lower limit of |, may be 0.00 or more than 0.00. The relative relationship of the refractive indices of the two adhesive surfaces may be n ₁ >n ₂ May be n ₁ <n ₂ May also be n ₁ ＝n ₂ 。

In other modes, the refractive index n of the 1 st adhesion surface of the interlayer sheet ₁ Refractive index n of 2 nd adhesive surface ₂ The difference, i.e. n ₁ -n ₂ For example, the average particle size may be greater 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. n is ₁ And n ₂ May also be reversed. n is ₁ -n ₂ The upper limit of (b) is not particularly limited. In some embodiments, n is n from the viewpoint of easily balancing both the adhesive property and the transparency ₁ -n ₂ For example, it may be 0.30 or less, may be 0.26 or less, may be 0.21 or less, may be 0.18 or less, or may be 0.16 or less. The interlayer sheet having different refractive indices in the 1 st adhesive face and the 2 nd adhesive face can be realized, for example, by: in the double-sided adhesive sheet with a substrate, 1 st and 2 nd adhesive layers with different refractive indexes are laminated on a non-peeling supporting substrate; the substrate-less double-sided adhesive sheet has a laminated structure of two or more sub adhesive layers, and in the laminated structure, the refractive index of the adhesive constituting the 1 st adhesive surface and the refractive index of the adhesive constituting the 2 nd adhesive surface are made different from each other.

In some modes, the first1 refractive index n of the adhesive surface ₁ Refractive index n of the 2 nd adhesion surface ₂ Ratio of (n) ₁ /n ₂ ) For example, the average particle diameter may be larger 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 modes, the 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.

(storage modulus G')

In the interlayer sheet (adhesive sheet) disclosed herein, the viscoelastic layer (adhesive layer) V ₁ Storage modulus G ' (storage modulus G ' at 25℃ ' _V1 (25) May be appropriately set according to the purpose of use, the mode of use, and the like, and is not limited to a specific range. Storage modulus G' _V1 (25) For example, the pressure may be in the range of about 30kPa to 700 kPa. 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 forms, the adhesive layer V is formed from an adhesive layer at an elevated room temperature region (e.g., 25 deg.C) ₁ Storage modulus G 'from the viewpoint of flexibility of (A) and easy adhesion to an adherend' _V1 (25) Advantageously, the pressure is about 330kPa or less, preferably 300kPa or less. Storage modulus G 'in some embodiments where adhesiveness and flexibility in the room temperature region are more important' _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 thatIn some embodiments, the storage modulus G 'is obtained in consideration of 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 adhesive sheet disclosed herein, the viscoelastic layer (adhesive layer) V ₁ Storage modulus G ' (storage modulus G ' at 50℃ ' _V1 (50) ) 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) Adhesive layer V of ₁ By heating appropriately as needed, the adhesiveness to an adherend can be easily improved, and the adhesiveness to an adherend can be improved. Storage modulus G' _V1 (50) The lower limit of (b) is not particularly limited. In some modes, from the adhesive layer V ₁ Storage modulus G 'from the viewpoint of heat resistance characteristics' _V1 (50) For example, the pressure may be 10kPa or higher, 15kPa or higher, 20kPa or higher, or 23kPa or higher.

In some modes of the interlayer sheet disclosed herein, the viscoelastic layer (adhesive layer) V ₁ Preferably at least one of the following conditions is satisfied:

(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).

An adhesive layer V satisfying at least the above condition (a) ₁ It is preferable from the viewpoint of adhesion to an adherend and flexibility in a room temperature region (e.g., 25 ℃). Has an adhesive layer V satisfying at least the above condition (b) ₁ The interlayer sheet of (3) is preferably heated to a temperature slightly higher than room temperature, because adhesiveness (adhesiveness) to an adherend can be easily improved. For the adhesive layer V which does not satisfy the above condition (a) and satisfies the above condition (b) ₁ The interlayer sheet of (3), adhesion initiation at room temperature region, reworkabilityThe heat-activated interlayer sheet has excellent (re-adhesiveness) properties and can be used as a heat-activated interlayer sheet which can effectively improve the peel strength from an adherend by heating to a temperature slightly higher than room temperature. The heat activation can be performed by heating the interlayer sheet to a temperature slightly higher than room temperature at the time of adhesion 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 interlayer sheet 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) Small adhesive layer V ₁ The interlayer sheet according to (3) is suitable for use as the above-mentioned heat-activated interlayer 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 the heat resistance of the interlayer sheet.

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 apparatus, and for example, ARES manufactured by TA Instruments or its equivalent can be used 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

Viscoelastic layer (adhesive layer) V ₁ Storage modulus G' _V1 (25)、G’ _V1 (50) And the storage modulus ratio can be obtained by constituting the adhesive layer V ₁ The composition of the monomer component of the base polymer (e.g., the selection of the type and content of the monomer (m 1), the selection of whether or not to use and the amount of the crosslinking agent, the selection of whether or not to use, the type and the amount of the plasticizing material, which will be described later), and the like. For example, by using a 1 st monomer as a main component of the monomer (m 1) as the monomer (m 1) and using a 2 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) And G 'is reduced' _V1 (50)/G’ _V1 (25)。

The adhesive sheet disclosed herein is a double-sided adhesive sheet having a 1 st adhesive surface and a 2 nd adhesive surface (for example, having an adhesive layer V on the 1 st surface of a substrate) ₁ A 1 st adhesive layer composed of an adhesive layer V on the 2 nd surface of the substrate ₂ A double-sided adhesive sheet with a substrate constituting the 2 nd adhesive layer; adhesive layer V constituting the 1 st adhesive surface ₁ And an adhesive layer V constituting the 2 nd adhesive surface ₂ A substrate-less double-sided adhesive sheet having a laminated structure in which substrates that are not adhesive are not sandwiched; adhesive layer V ₁ Becomes the 1 st adhesive surface, the adhesive layer V ₁ And a substrate-less double-sided pressure-sensitive adhesive sheet having a single-layer structure in which the other surface of the pressure-sensitive adhesive sheet is the 2 nd pressure-sensitive adhesive surface. The same applies to other similar descriptions. ) In form (1), the storage modulus G' _V1 (25)、G’ _V1 (50) And the storage modulus ratio is applicable to at least the adhesive layer constituting the 1 st adhesive face, preferably to both the adhesive layer constituting the 1 st adhesive face and the adhesive layer constituting the 2 nd adhesive face. The storage modulus G 'of the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface and the storage modulus G' of the pressure-sensitive adhesive layer constituting the 2 nd pressure-sensitive adhesive surface may be the same or different.

(Total light transmittance)

The interlayer sheet disclosed herein comprises the above adhesive layer V having a high refractive index ₁ And the total light transmittance of the interlayer sheet is over 86 percent. Such a highly transparent interlayer sheet having a substrate structure or having no substrate structure can be suitably used in applications requiring high light transmittance (for example, optical applications) and applications requiring good visual recognition of an adherend through the pressure-sensitive adhesive sheet. In some embodiments, the total light transmittance of the interlayer sheet is preferably 88% or more, more preferably 90% or more (e.g., 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 about 98% or less, about 96% or less, or about 95% or less in practical use. In some aspects, the total light transmittance of the interlayer sheet 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 in accordance with jis k7136:2000, measured using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETERHM-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 interlayer sheet can be measured, for example, in accordance with examples described later. The total light transmittance of the interlayer sheet can be adjusted by, for example, selection of the composition and thickness of the viscoelastic layer contained in the interlayer sheet, the type and thickness of the substrate in the composition including the substrate, and the like.

The interlayer sheet disclosed herein is in the form of a double-sided adhesive sheet with a base material in which a 1 st adhesive layer and a 2 nd adhesive layer are fixedly laminated on a support base material, and the 1 st adhesive layer is composed of an adhesive layer V ₁ In the case of the layer, at least the 1 st adhesive layer may satisfy any total light transmittance as described above, and the total light transmittance of the 2 nd adhesive layer is not particularly limited. In the use mode in which light passes through the thickness direction of the adhesive sheet, the total light transmittance of the 2 nd adhesive layer preferably satisfies any of the above-described total light transmittances of the 1 st adhesive layer. The relative relationship between the total light transmittance of the two adhesive layers may be 1 st adhesive layer>The 2 nd adhesive layer may be the second1 adhesive layer<The 2 nd adhesive layer may be the 1 st adhesive layer = the 2 nd adhesive layer.

(haze value)

The interlayer sheet disclosed herein comprises the above adhesive layer V having a high refractive index ₁ And the interlayer sheet has a haze value of 1.0% or less. Such an interlayer sheet having high transparency can be suitably used in applications requiring high light transmittance (for example, optical applications) and applications requiring good visual recognition of an adherend through the interlayer sheet, with or without a substrate. In some embodiments, the haze value of the interlayer sheet may be 0.9% or less, may be 0.8% or less, may be 0.5% or less, and may be 0.3% or less. The lower limit of the haze value of the interlayer sheet 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 interlayer sheet 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 relating to interlayer sheets can also be preferably applied to the haze value of a substrate-free adhesive sheet (typically, an adhesive sheet formed of an adhesive layer) when the technique disclosed herein is carried out in the form of the adhesive sheet.

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 haze value. The haze value can be represented by the following formula.

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 can be adjusted by, for example, selecting the composition, thickness, and the like of the measurement object.

In the form of the interlayer sheet disclosed herein, in which the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer are fixedly laminated on the base-equipped double-sided pressure-sensitive adhesive sheet of the support substrate, the interlayer sheet as a whole may satisfy any haze value as described above, and the haze value of each of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer is not highAnd is particularly limited. The haze values of the two adhesive layers may be in a relative relationship of 1 st adhesive layer>The 2 nd adhesive layer may be the 1 st adhesive layer<The 2 nd adhesive layer may be the 1 st adhesive layer = the 2 nd adhesive layer. That is, the haze value of the 1 st pressure-sensitive adhesive layer may be the same as or different from the haze value of the 2 nd pressure-sensitive adhesive layer. For the interlayer sheet disclosed herein, a plurality of sub-adhesive layers (e.g., adhesive layer V) are included ₁ And an adhesive layer V ₂ ) The same applies to the haze value of each sub-pressure-sensitive adhesive layer in the case of the pressure-sensitive adhesive layer directly laminated.

(surface smoothness of pressure-sensitive adhesive surface)

In some forms of the interlayer sheet disclosed herein, the adhesive surface of the interlayer sheet (e.g., formed by the adhesive layer V) ₁ Structured adhesive surface) 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 interlayer sheet or the like disposed closer to the viewing point side than the self-light emitting element in the light emitting device) in which light is extracted through the adhesive surface, an effect of suppressing 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 the suppression of optical distortion contributes to the improvement of optical homogeneity. When the interlayer adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a 1 st adhesive surface and a 2 nd adhesive surface, 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 imparting high surface smoothness to each pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet, it is possible to preferably realize bonding with excellent optical homogeneity.

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 interlayer sheet having 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 as described above, 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 interlayer sheet disclosed herein is in the form of a double-sided adhesive sheet having a 1 st adhesive surface and a 2 nd adhesive surface, it is preferable that at least the maximum height Rz of the 1 st adhesive surface is limited to a predetermined value or less, and more preferable that the maximum height Rz 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 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 interlayer sheet 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 crest on the upper side from the average line of the roughness curve and the depth Rv of the deepest trough 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 an interlayer sheet including the pressure-sensitive adhesive layer into a size of about 150mm in length and about 50mm in width. When the adhesive surface is protected by the release liner, the release liner is gently peeled off (for example, under conditions of a stretching speed of 300 mm/min and a peeling angle of 180 °) to expose the adhesive surface. 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

DataFill：ON(Max：25)

RemoveSpikes：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, and the like) 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 for protecting the pressure-sensitive adhesive surface, and the like.

(Water absorption)

In some forms, the adhesive layer V ₁ The water absorption is preferably limited to a predetermined value or less. By confining the adhesive layer V ₁ Water absorption rate of (B) due to the adhesive layer V ₁ The viscoelastic layer V caused by the fluctuation of the moisture amount (e.g., the absorption and release of moisture such as moisture in the environment) ₁ Tends to be suppressed. This can suppress the generation of the pressure-sensitive adhesive layer V ₁ And a layer (which may be an adhesive layer V) adjacent thereto ₂ A support base material, a release liner, an adherend, and the like. ) Or a warp of the interlayer sheet or an optical laminate including the interlayer sheet. From the adhesive layer V ₁ From the viewpoint of maintaining flatness, transparency, refractive index, and the like of (b), it is also preferable that the pressure-sensitive adhesive layer V can be suppressed ₁ The amount of water in (2) varies. Further, the adhesive layer V has a low water absorption ₁ The interlayer sheet of (3) is not liable to absorb moisture, and therefore is suitable as an interlayer sheet used for a member or a product containing an element which makes moisture undesirable, such as an organic EL element.

In some modes, the adhesive layer V ₁ The water absorption of (b) is preferably about 1.0% or less, more preferably 0.7% or less, still more preferably 0.5% or less (for example, less than 0.5%), and may be 0.4% or less, 0.3% or less, or 0.2% or less. Adhesive layer V ₁ The lower limit of the water absorption percentage of (b) 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 practical viewpoint of the compatibility with the adhesive property. When the interlayer sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet with a substrate having a 1 st pressure-sensitive adhesive layer and a 2 nd pressure-sensitive adhesive layer, at least the 1 st pressure-sensitive adhesive layer (preferably the pressure-sensitive adhesive layer V) is preferable ₁ ) The water absorption of (2) is limited to a predetermined value or less. From the viewpoint of obtaining higher effects, it is more preferable that the water absorption rates of both the 1 st and 2 nd pressure-sensitive adhesive layers are limited to a predetermined value or less.

The water absorption rate (also referred to as a moisture rate) of the pressure-sensitive adhesive layer was measured by the following method.

[ measurement of Water 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 percentage was measured by karl fischer coulometry under the following conditions using a moisture meter (mitsubishi chemical analytech model-200) equipped with a heat vaporizer (mitsubishi chemical analytech va-200).

Anode liquid: AQUAMICRON AKX (Mitsubishi chemical)

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

Heating and gasifying temperature: 150 ℃ C

(gel fraction)

Viscoelastic layer V ₁ The gel fraction (b) 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, for example, about 99% or less and about 97% or less. 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 satisfying both 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 suitably 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 viscoelastic layer V ₁ Resistance to deformation (prevention factor)Pressure-induced overflow, bubbles caused by the incorporation of foreign matter, etc.), the above-mentioned 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 interlayer sheet (typically, an interlayer sheet in the form of a substrate-free adhesive sheet) is also preferably within 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 predetermined amount of the 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 (5) tightening. As the porous Polytetrafluoroethylene (PTFE) membrane, a product of NITOFLON (registered trademark) NTF1122 (average pore diameter 0.2. Mu.m, porosity 75%, thickness 85 μm) available from Nindon electric Co., ltd., 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 was obtained by substituting each value into the following formula.

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

The interlayer sheet disclosed herein is in the form of a double-sided adhesive sheet having a 1 st adhesive surface and a 2 nd adhesive surface, and the 1 st adhesive surface is composed of an adhesive layer V ₁ The 2 nd adhesive surface is composed of an adhesive layer V ₂ In the composition, the viscoelastic layer V constituting the 1 st adhesive surface ₁ The gel fraction of (2) and the viscoelastic layer V constituting the 2 nd adhesive surface ₂ The gel fraction (c) may be the same or different. In some ways, the viscoelastic layer V may be made ₂ Has a gel fraction lower than that of the viscoelastic layer V ₁ The gel fraction (c) of (d). According to the constitution, the phases are passedFor low gel rate viscoelastic layer V ₂ The flexibility of the interlayer sheet is easily improved. Thereby, it is possible to provide the viscoelastic layer V having both viscoelasticity and suitability ₁ The refractive index of the interlayer sheet is increased and the interlayer sheet has flexibility.

In some forms of the technology disclosed herein, the viscoelastic layer V is constructed ₁ The peak temperature of tan δ of the adhesive of (3) is preferably about-50 ℃ or higher, and further preferably about 50 ℃ or lower. Here, tan δ (loss tangent) of an adhesive means a ratio of loss modulus G ″ of the adhesive to storage modulus G'. That is, 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 viscoelastic testing apparatus, ARES manufactured by TA Instruments, inc. or its equivalent can be used.

In some forms, the viscoelastic layer V ₁ The Tpeak of (A) is advantageously 45 ℃ or less or 35 ℃ or less, preferably 30 ℃ or less (for example, 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 pressure-sensitive adhesive having a high Tpeak may be heated to slightly higher than room temperature as needed for one or both of the pressure-sensitive adhesive and the adherend at the time of adhesion to the adherendA high temperature is preferably used. 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).

When the interlayer sheet disclosed herein is in the form of a double-sided adhesive sheet having a 1 st adhesive surface and a 2 nd adhesive surface, tpeak of the adhesive is preferably applied to at least the adhesive layer constituting the 1 st adhesive surface (preferably the viscoelastic layer V) ₁ ) More preferably, the pressure-sensitive adhesive composition is applied to both the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface and the pressure-sensitive adhesive layer constituting the 2 nd pressure-sensitive adhesive surface. The Tpeak of the adhesive layer constituting the 1 st adhesive surface may be the same as or different from the Tpeak of the adhesive layer constituting the 2 nd adhesive surface.

(base Polymer)

In the technique disclosed herein, the adhesive layer V is constituted ₁ The kind of the binder (2) 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 (e.g., natural rubber, synthetic rubber, a mixture 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, as a pressure-sensitive adhesive polymer (hereinafter, also referred to as "base polymer" as a meaning of a structural polymer to be shaped into a pressure-sensitive adhesive). 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, a binder (acrylic binder) containing an acrylic polymer as a base polymer is preferable. The techniques disclosed herein are preferably implemented using acrylic adhesives.

Hereinafter, mainly for the adhesive layer V ₁ An interlayer sheet comprising an acrylic pressure-sensitive adhesive, that is, an interlayer sheet having an acrylic pressure-sensitive adhesive layer, is described, but the pressure-sensitive adhesive layer in the interlayer sheet disclosed herein is not intended to be limited theretoV ₁ Defined as an acrylic adhesive layer.

In this specification, the term "base polymer" of the pressure-sensitive adhesive means a main component of the rubbery polymer contained in the pressure-sensitive adhesive, and is not to be construed in any way as limiting. 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. Typical examples of the acrylic polymer include polymers 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).

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 interlayer sheet disclosed herein may preferably contain a storage modulus G 'at 25 ℃ having a refractive index of 1.570 or more' _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 700 kPa. Acrylic polymer as a base polymer for the acrylic adhesive layerThe compound 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 adhesive formed from the adhesive composition, and is contained in the adhesive composition in the form of a previously formed polymer (which may be an oligomer) or 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. An 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 an interlayer 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 a decrease in flexibility of the adhesive, it is preferable to use, as the monomer (m 1), a compound (i.e., a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in 1 molecule is 1.

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, and may be 5 or less, 4 or less, 3 or less, or 2 or less, from the viewpoints of ease of production 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 isocyclic rings such as a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a thiophene ring; 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 heteroatoms constituting the above-described heterocyclic ring may be one or both of nitrogen and sulfur. The monomer (m 1) may have a structure in which 1 or 2 or more carbon rings and 1 or 2 or more hetero rings are condensed, such as 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 the 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-), oxyalkylene (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), wherein an alkylene group of the oxyalkylene group, the thiooxyalkylene group and the straight-chain alkylene group is partially halogenated or fully halogenated Groups, and the like. From the viewpoint of flexibility of the adhesive, suitable examples of the linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a linear alkylene group. Specific examples of the monomer having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth) acrylate (e.g., p-phenoxybenzyl (meth) acrylate), thiophenoxybenzyl (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-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 thus 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 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 a 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 having a fused aromatic ring structure 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 structures in which 2 or more non-fused 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; (meth) acrylic esters containing a bromine-substituted aromatic ring such as 2- (4, 6-dibromo-2-sec-butylphenoxy) ethyl (meth) acrylate, 2- (4, 6-dibromo-2-isopropylphenoxy) ethyl (meth) acrylate, 6- (4, 6-dibromo-2-sec-butylphenoxy) hexyl (meth) acrylate, 6- (4, 6-dibromo-2-isopropylphenoxy) hexyl (meth) acrylate, 2, 6-dibromo-4-nonylphenyl acrylate, and 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 a 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 a structure in which an oxyethylene chain is interposed between an ethylenically unsaturated group and an aromatic ring in the above-described various aromatic ring-containing monomers can also 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 containing 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 containing a plurality of aromatic rings in the monomer (m 1) may be, for example, 50 wt% or more, preferably 70 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% 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 having 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 may be carried out so that the content of the monomer having a plurality of aromatic rings in the monomer (m 1) is less than 5% by weight. Monomers 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, 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 monomer containing a plurality of aromatic rings in the monomer component may be 100% by weight, but from the viewpoint of well-balanced balance between the high refractive index and the adhesive property and/or optical property, it is favorably set to less than 100% by weight, preferably to about 99% by weight or less, more preferably to 98% by weight or less, and 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 wt% or less, 50 wt% or less, 25 wt% or less, 15 wt% or less, or 5 wt% or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein may be carried out so 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" means 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 can be used alone in 1 or a combination of 2 or more.

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 substance having a suitable refractive index can be suitably used from among compounds included in the concept of the aromatic ring-containing monomer (m 1) disclosed herein (for example, in the above exemplified compounds and compound groups). Specific examples thereof include m-phenoxybenzyl acrylate (refractive index: 1.566, tg of homopolymer: 35 ℃), 1-naphthylmethyl acrylate (refractive index: 1.595, tg of homopolymer: 31 ℃), 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 ℃), phenoxyethyl acrylate (refractive index (nD 20): 1.517, tg of homopolymer: 2 ℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, tg of homopolymer: -35 ℃), 6-acryloyloxymethyldinaphthothiophene (6 MDNTA, refractive index: 1.75), 6-methacryloyloxymethyldiphenylthiophene (6 MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5 EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene (6 EDA, refractive index: 1.786-vinyldinaphthylthiothiophene, vinyldinaphthylthiothiophene (VDNT: 1.722), 5 VDNT: 3, VDNT: 793, etc., but the refractive index is not limited thereto.

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, 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, 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. 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 view of the balance with the refractive index-increasing effect, 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 some embodiments. 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, phenoxydiethylene glycol acrylate (homopolymer Tg: -35 ℃ C.) is cited.

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 wt% or more, 60 wt% or more, 70 wt% or more, 75 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more, from the viewpoint of easily obtaining a binder having both 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 satisfying both flexibility and high refractive index suitable as a binder in a well-balanced manner, 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 advantageous to be less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, and 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, and 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 may be carried out in such a manner that the content of the monomer L in the monomer component is less than 3% by weight.

In some embodiments, the glass transition temperature Tg based on the composition of the monomer (m 1) is from the viewpoint of flexibility of the adhesive _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, it may be at least-70 deg.C, at least-55 deg.C, or at least-45 deg.C. 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 a 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), the Tg and glass transition temperature Tg of the 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 whose homopolymer has a 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 any of the above glass transition temperatures Tg _m1 The ratio of the amount of the monomer L to the amount of the monomer H used is set as described above.

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 realizing an adhesive that has flexibility, adhesion, and a high refractive index in a well-balanced manner, it is 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 introducing a crosslinking point into the acrylic polymer or imparting appropriate cohesive properties to the pressure-sensitive 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 hydroxyl group-containing monomers 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, 50% by weight or more (e.g., more than 50%, more than 70% by weight, or more than 85% by weight) of the monomer (m 2) may be 4-hydroxybutyl acrylate. The hydroxyl group-containing monomers may be used alone 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 in 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, for example, and from the viewpoint of increasing the content of the monomer (m 1) relatively to facilitate increasing the 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 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, from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index.

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 an 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 methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and isopropyl (meth) acrylate,N-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like, but are not limited thereto.

In some embodiments, it may be preferred to use as at least a portion of monomer (m 3) an alkyl (meth) acrylate whose homopolymer has a Tg of-20 ℃ or less (more preferably-40 ℃ or less, for example-50 ℃ or less). 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 wt% or more, 30 wt% or more, or 45 wt% 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 not be substantially 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 monomer 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 into the acrylic polymer, or contributing to improvement of peel strength and improvement of 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 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 included in the amide group-containing monomers. 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 the like. 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 modes, for constituting the viscoelastic layer V ₁ The base polymer (e.g., acrylic polymer) of (A) to suppress the viscoelastic layer V ₁ From the viewpoint of coloring or discoloration (for example, yellowing), it is preferable to limit the amount of the carboxyl group-containing monomer used. 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 inhibiting possible contact with or access to the viscoelastic layer V ₁ On the other hand, from the viewpoint of corrosion of the disposed metal material (for example, metal wiring, metal film, etc. which may be present on the adherend), it is also advantageous to limit the amount of the carboxyl group-containing monomer used in this way. The interlayer sheet disclosed herein can be preferably implemented in such a manner that the monomer component does not contain a carboxyl group-containing monomer.

For the same reason, in some modes, the viscoelastic layer V is constituted ₁ The monomer component of the base polymer (b) is preferably limited in the amount of the monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, etc. 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 interlayer sheet disclosed herein may preferably be in such a manner that the above monomer component does not contain an acid group-containing monomer (i.e., viscoelasticity)Layer V ₁ The base polymer of (b) 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 glass transition temperature is 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; halogenated alkanes such as 1, 2-dichloroethane; lower alcohols such as isopropyl alcohol (e.g., monohydric alcohols having 1 to 4 carbon atoms); 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 in the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type 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 polymerization, various conventionally known chain transfer agents can be used as needed. For example, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid and α -thioglycerol can be used. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) 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 so on. 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 to be 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 ) The range of (1).

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

[ 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 "TSKguardcolumnSuperHZ-H"1 root + the trade name "TSKgelSuperHZM-H"2 root (manufactured by Tosoh Co., ltd.)

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

A detector: differential Refractometer (RI)

Standard sample: polystyrene

(refractive index improver)

In some versions of the technology disclosed herein, the adhesive layer V ₁ The acrylic pressure-sensitive adhesive layer (for example) 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 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 polymerizable functional group may or may not be present. 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) may be set to an appropriate range by a relative relationship with the refractive index of the base polymer, and thus is not limited to a specific range. The refractive index of the refractive index improver can be selected, 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, the refractive index of the refractive index improver may be advantageously 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 in some embodiments. 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 propertiesIn (1). 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 a base polymer and a 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 set from the viewpoint of compatibility in the pressure-sensitive adhesive layer, transparency of the pressure-sensitive adhesive layer, or 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 forms, the refractive index improver (e.g., 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, 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. Δ n by selecting the composition of the adhesive layer and the refractive index improver _B The refractive index increasing agent tends to be used to increase the refractive index increasing effect. 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 _B For example, it may be 0.70 or less, may be 0.60 or less, may be 0.50 or less, or may beIt may be 0.40 or less or 0.35 or less.

The amount of the refractive index improver used (the total amount of a plurality of refractive index improvers when used) is not particularly limited and may be set according to the purpose, based on 100 parts by weight of the base polymer. 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 that the refractive index improver is not substantially used. Here, substantially unused means at least not intentionally used.

(additive (H) _RO ))

In some modes, as the refractive index improver, an organic material having a higher refractive index than that of the base polymer may be preferably used. Hereinafter, such an organic material may be referred to as "additive (H) _RO ) ". Here, the above "H _RO "denotes an Organic material (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 an additive (H) _RO ) Can achieve a more appropriate balance between refractive index and adhesionAdhesives with properties (peel strength, flexibility, etc.) and/or optical properties (total light transmittance, haze value, etc.). As additive (H) _RO ) The organic material of (b) may be a polymer or a non-polymer. The polymerizable functional group may or may not be present. Additive (H) _RO ) 1 or more species may be used alone or in combination.

Additive (H) _RO ) The refractive index of (2) was measured at a measurement wavelength of 589nm and a measurement temperature of 25 ℃ using an Abbe refractometer 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 may 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, additives (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 (b) 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, or 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, additives (H) _RO ) The molecular weight of (b) may be 130 or more, or 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 ) The molecular weight of (a) is preferably 170 or more, more preferably 200 or more, may be 230 or more, may be 250 or more, may be 270 or more, may be 500 or more, may be 1000 or more, and may be 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 (2) can be calculated from a non-polymer or a polymer having a low degree of polymerization (for example, about 2 to 5-mer) or can be determined by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Additive (H) _RO ) For a polymer having a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When the nominal value of the molecular weight is provided by the manufacturer or the like, the nominal value may be adopted.

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 or nonaromatic). ) 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 modes, 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 useful as the monomer (m 1); an oligomer comprising a compound usable as the monomer (m 1) as a monomer unit; groups having ethylenically unsaturated groups from compounds usable as monomers (m 1)A group (which may be a substituent bonded to a ring-forming atom) or a compound having a structure in which a part of the group constituting an 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); 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 oligomer 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 refractive index increasing effect, an 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. Further, the compound containing a plurality of aromatic rings may be a polyThe compound may be 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; a copolymer of 1 or 2 or more kinds of monomers having a plurality of aromatic rings; 1 or 2 or more aromatic ring-containing monomers and other monomers; and the like. The other monomer may be an aromatic ring-containing monomer other than the 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 a plurality of 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 such as 9, 9-bis (4-hydroxyphenyl) fluorene (refractive index: 1.68), 9-bis (4-aminophenyl) fluorene (refractive index: 1.73), 9-bis (4-hydroxy-3-methylphenyl) fluorene (refractive index: 1.68), and 9, 9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene (refractive index: 1.65) and derivatives thereof, in addition to the monomer having a fluorene structure and the oligomer which is a homopolymer or 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 copolymer of the monomer; hydroxyalkyl dinaphthothiophenes such as 6-hydroxymethyl dinaphthothiophene (refractive index: 1.766); dihydroxydinaphthothiophenes such as 2, 12-dihydroxydinaphthothiophene (refractive index: 1.750); dihydroxyalkyloxydinaphthothiophenes such as 2, 12-dihydroxyethyloxydianaphthothiophene (refractive index: 1.677); diglycidyl oxydianaphthothiophenes such as 2, 12-diglycidyl oxydianaphthothiophene (refractive index 1.723); dinaphthothiophenes having 2 or more ethylenically unsaturated groups, such as 2, 12-diallyloxydinaphthothiophene (abbreviated as 2,12-DAODNT, refractive index of 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 (1) (hereinafter also referred to as 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-epithiopropyl) 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 triazine ring (for example, 3 to 40, preferably 5 to 20) 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 by heat or light (the leveling property is decreased by the progress of gelation or increase in viscosity), and improve the storage stability. From the composition containing the additive (H) _RO ) The pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, a laminate comprising the pressure-sensitive adhesive sheet, and the like, wherein dimensional change, deformation (warpage, waviness, and the like), and optical distortion caused by reaction of ethylenically unsaturated groups are suppressedFrom the viewpoint of generation of (A), (B), and (C), 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. In the case of producing the oligomer 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 components 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, and 2, 3-dimercapto-1-propanol. 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 sticking From the viewpoint of increasing the refractive index of the mixture, 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 preferably 7 parts by weight or more and preferably 10 parts by weight or more, and may be 15 parts by weight or more and preferably 20 parts by weight or more, based on 100 parts by weight of the base polymer. In some modes, the additive (H) _RO ) The amount of the polymer to be used may be, for example, 80 parts by weight or less relative to 100 parts by weight of the base polymer, and is favorably 60 parts by weight or less, preferably 45 parts by weight or less, from the viewpoint of achieving a good balance between the increase in refractive index of the pressure-sensitive adhesive 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 modes of the interlayer sheet disclosed herein, the adhesive layer V ₁ In addition to the base polymer (e.g., acrylic polymer (a)) as described above, a plasticizing material having a lower molecular weight than the base polymer may be included. The adhesive layer V can be improved by using a plasticizing material ₁ Flexibility of the interlayer sheet, improvement of adhesion to an adherend, flexibility of the entire interlayer sheet, and followability to deformation. 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 which can also be used as the above-mentioned refractive index improver (for example, the above-mentioned additive (H) _RO ) Material of).

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 plasticizing material may have a molecular weight of 30000 or less, may have a molecular weight of 25000 or less, may have a molecular weight of less than 10000, preferably less than 5000, more preferably less than 3000 (e.g., less than 1000), may have a molecular weight of less than 800, may have a molecular weight of less than 600, may have a molecular weight of less than 500, or may have a molecular weight of 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 plasticizing material preferably has a molecular weight of 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 easily exerting 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 interlayer sheet 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 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) phenyldiphenyl 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-ethylhexyldiphenyl phosphate (refractive index 1.51), tris (2, 4-di-tert-butylphenyl) 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 suitably 2.50 or less, and advantageously 2.00 or less, and may be 1.90 or less, and 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 may 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 satisfying both the high refractive index of the binder and the 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 ways, for forming the adhesive layer (which may be a viscoelastic layer V) ₁ And/or a viscoelastic layer V ₂ . ) The pressure-sensitive adhesive composition of (1) may contain a leveling agent as needed for the purpose of improving the appearance of the pressure-sensitive adhesive layer formed from the composition (for example, improving the uniformity of thickness), improving the coatability of the pressure-sensitive 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 selected from commercially available leveling agents, for example, as appropriate and used by a conventional method.

In some embodiments, as the leveling agent, a polymer (hereinafter, also referred to as "polymer (B)") that 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 a polymerizable reactive group at one end and having no functional group at the other end, which is capable of causing a crosslinking reaction with a base polymer (the base polymer of the adhesive composition to which the leveling agent is to be compounded, for example, an acrylic polymer), can be preferably used. Examples of commercially available products include single-terminal reactive silicone oils available from shin-Etsu chemical Co., ltd. (for example, trade names such as X-22-174ASX, X-22-2426, X-22-2475 and KF-2012). The monomers 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 equivalent weight of the functional group may be, for example, 20000g/mol or less, less than 10000g/mol, 7000g/mol 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 exhibited.

When two or more monomers having different functional group equivalents are used as the monomer S1, the sum of the product of the functional group equivalent of each monomer and the weight fraction of the monomer can be used as the functional group equivalent of the monomer S1.

Here, "functional group equivalent" means the weight of the main skeleton (e.g., 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 H-NMR (proton NMR) spectrum intensity. 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 structure analysis technique for H-NMR spectroscopy is described in Japanese patent No. 5951153, if necessary. In the functional group equivalent of the monomer S1, the functional group refers to a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth) acryloyl group, a vinyl group, or an 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 for 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, monomer feed B can 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 ester). 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 esters). 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.

As another example of the acrylic monomer, a (meth) acrylate having an alicyclic hydrocarbon group is exemplified. 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 property 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, the use of inorganic particles as the refractive index improver may be allowed within limits that do not greatly impair the application effect of the technology disclosed herein. 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, a product name "EC-400" (manufactured by ja. The amount of the inorganic particles used when the refractive index improver is used is preferably less than 5 parts by weight, more preferably less than 1 part by weight, per 100 parts by weight of the base polymer. In the use of additives (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, for forming the adhesive layer (which may be the viscoelastic layer V) ₁ And/or a viscoelastic layer V ₂ . ) The pressure-sensitive adhesive composition of (3) may contain a crosslinking agent as needed for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive. 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 them, isocyanate-based ones can be preferably usedA crosslinking agent. 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; aromatic isocyanates such as 2, 4-tolylene diisocyanate, 4' -diphenylmethane diisocyanate, and Xylylene Diisocyanate (XDI); 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 so on. Examples of commercially available products include tradenames of Takenate 300S, takenate 500, 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-or more-functional 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 fluorene 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. 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, or may be 0.2 parts by weight or less, relative to 100 parts by weight of the base polymer, from the viewpoint of improving the flexibility of the adhesive. In some embodiments, the amount of 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. Examples of the crosslinking catalyst include tetra-n-butyl titanate, tetra-isopropyl titanate, and iron (II) acetylacetonate

Iron III), butyltin oxide, dioctyltin dilaurate, and other metal-based 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 part by weight or more and 1 part by weight or less, and preferably in the range of 0.001 part by weight or more and 0.5 part 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.), acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably used. The keto-enol tautomerism compounds can be used alone in 1 or a combination of more than 2. 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 (which may be a viscoelastic layer V) in the technology disclosed herein ₁ And/or a viscoelastic layer V ₂ . ) 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 determined by The purpose and use are set so as to exhibit appropriate adhesive performance. 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, for forming the adhesive layer (which may be a viscoelastic layer V) ₁ And/or a viscoelastic layer V ₂ . ) The pressure-sensitive adhesive composition of (1) may contain, as required, known additives that can be used in the pressure-sensitive 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 impair 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.

(peeling Strength)

In some embodiments of the interlayer sheet disclosed herein, the peel strength of the interlayer sheet 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: pressure-bonded to an alkaline glass plate as an adherend, left for 30 minutes in an environment of 23 ℃ and 50% RH, then put into a pressure defoaming apparatus (autoclave), autoclave-treated for 30 minutes under conditions of a temperature of 50 ℃ and a pressure of 0.5MPa, further left for 24 hours in an atmosphere of 23 ℃ and 50% RH, 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 to 50 μm) may be bonded to the interlayer sheet to be measured for reinforcement, if necessary. The peel strength can be measured specifically by the method described in the examples below.

When the interlayer sheet disclosed herein is in the form of a double-sided adhesive sheet having a 1 st adhesive side and a 2 nd adhesive side, in some embodiments, the above peel strength is preferably applied to at least the 1 st adhesive side, more preferably to both the 1 st adhesive side and the 2 nd adhesive side. 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.

In some preferred forms of the interlayer sheet disclosed herein, the interlayer sheet contains the viscoelastic layer V described above ₁ In addition, the adhesive composition may further include a viscoelastic layer V laminated on the viscoelastic layer ₁ Viscoelastic layer (adhesive layer) V ₂ . The above viscoelastic layer V ₂ Preferably storage modulus G 'at 25℃' _V2 Lower than the above viscoelastic layer V ₁ Storage modulus G 'at 25℃' _V1 . That is, G 'is preferred' _V2 (25)<G’ _V1 (25). The interlayer sheet thus constituted passes through the viscoelastic layer V ₂ The contribution of (1) can make the flexibility more excellent. By making the storage modulus G' _V2 (25) Lower than storage modulus G' _V1 (25) In the interlayer sheet, the viscoelastic layer V can be preferably used ₁ Based on a viscoelastic layer V ₂ Flexibility of (3). By applying a viscoelastic layer V ₁ Upper laminated viscoelastic layer V ₂ By providing adhesiveness and flexibility, the step following property and the following property to a curved surface and the like are improved, and an interlayer sheet which can be preferably applied to various device design applications can be realized.

Storage modulus G' _V2 (25) The pressure is not particularly limited, and may be, for example, in the range of 1.0kPa to 500 kPa. From increasing the thickness of the viscoelastic layer V ₂ In some embodiments, the storage modulus G 'is from the viewpoint of the effect of providing flexibility of (2) and improving the following property to deformation' _V2 (25) Preferably 400kPa or less, more preferably 300kPa or less, and still more preferably 200kPa or less (e.g., 180kPa or less, or 150kPa or less), and may be 120kPa or less, 90kPa or less, or 70kPa or less. In addition, the viscoelastic layer V ₂ From the viewpoint of imparting appropriate cohesive properties, the storage modulus G 'may be' _V2 (25) Is preferably 5.0kPa or more, more preferably 10kPa or more, but may be 15kPa or more, 25kPa or more, 35kPa or more, 60kPa or more, or 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 some modes, the viscoelastic layer (adhesive layer) V ₂ Refractive index n of ₂ Lower than the viscoelastic layer (adhesive layer) V ₁ Refractive index n of ₁ . The interlayer sheet having such a structure can utilize the viscoelastic layer V ₁ 、V ₂ To control the behavior of light transmitted through the interlayer sheet. In this mode, the adhesive layer V ₂ Refractive index n of ₂ As long as it is lower than the adhesive layer V ₁ Refractive index n of ₁ The range is not particularly limited, and may be, for example, about 1.35 to 1.55. In some ways, from the enlarged and viscoelastic layer V ₁ Refractive index n of ₁ The viscoelastic layer V is formed so as to easily improve the front luminance improving effect described later due to the refractive index difference of (a) ₂ Refractive index n of 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 addition, from the viewpoint of ease of acquisition of materials and ease of compatibility with adhesive properties, in some embodiments, the viscoelastic layer V ₂ Refractive index n of ₂ For example, the concentration may be 1.36 or more, 1.38 or more, 1.40 or more, or 1.42 or more.

Constituting a viscoelastic layer V ₂ The kind of the binder (c) is not particularly limited. Constituting a viscoelastic layer V ₂ The adhesive may be an acrylic polymer, a rubber polymer (e.g., natural rubber) which can be used in the field of adhesivesSynthetic rubber, mixtures thereof, etc.), 1 or 2 or more of various rubbery polymers such as polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, polyamide-based polymers, fluorine-based polymers, etc. 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 viscoelastic layer V ₁ In the form of an acrylic adhesive layer, from the viscoelastic layer V ₁ With a viscoelastic layer V ₂ From the viewpoint of adhesion, the viscoelastic layer V can be preferably used ₂ The acrylic pressure-sensitive adhesive layer is formed.

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. Alkyl (meth) acrylates can also be present in amounts of more than 55% by weight or more than 60% by weight of the abovementioned monomer composition.

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 carbon atoms may be referred to as "C _1-20 ". ). From storage of adhesivesFrom the viewpoint of modulus, R is preferred ² Is C _1-12 (e.g. C) _2-10 Typically C _4-8 ) The 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. As the copolymerizable monomer, for example, 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 can be used. 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. As a specific example, the viscoelastic layer V can be mentioned ₁ The base polymer of (3) above, but is 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 adhesive layer V ₂ Refractive index n of 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. Viscoelastic layer V with lower refractive index ₂ From the viewpoint of (1), the content of the fluorine-containing 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 moreThe content 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 modes, from the viscoelastic layer V ₂ From the viewpoint of the cohesion and the like, the content of the fluorine-containing monomer is preferably 99.9% by weight or less, more 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. The fluorine-containing monomer 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 (among them, 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; <xnotran> ,1,1,2,2- ,1,2,2,2- ,1,1,2- ,1,2,2- ,2,2,2- ,1,1- ,1,2- ,2,2- ,1- ,2- ; </xnotran> 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, the fluorine atom may be bonded to any carbon atom of the alicyclic hydrocarbon group, and the fluorine atom bonded to 1 carbon atom may be one or more, as in the case of the fluorinated aliphatic hydrocarbon group. 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; a cyclohexyl group having 2 fluorine atoms such as a 2, 4-difluorocyclohexyl group, a 2, 6-difluorocyclohexyl group and the like; cyclohexyl having 3 fluorine atoms such as 2,4,6-trifluorocyclohexyl, and the like.

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 alone in 1 kind or in combination of 2 or more.

The fluorine atom-containing (meth) acrylate [ fluoro (meth) acrylate ] includes, for example: fluorine atom-containing alkyl (meth) acrylate [ (fluoroalkyl (meth) acrylate ], fluorine atom-containing cycloalkyl (meth) acrylate [ (fluorocycloalkyl (meth) acrylate ], fluorine atom-containing aryl (meth) acrylate [ (fluoroaryl (meth) acrylate ], and the like.

The fluorine atom-containing (meth) acrylate is preferably a fluoroalkyl (meth) acrylate (particularly, a fluoroalkyl acrylate). As the fluoroalkyl (meth) acrylate, there may be mentioned, examples thereof include 2,2,2-trifluoroethyl acrylate (for example, a trade name "Viscoat3F" manufactured by Osaka organic chemical Co., ltd.), 2,2,3,3-tetrafluoropropyl acrylate (for example, a trade name "Viscoat 4F" manufactured by Osaka organic chemical Co., ltd.), 1H, 5H-octafluoropentyl acrylate (for example, a trade name "Viscoat 8F" manufactured by Osaka organic chemical Co., ltd.), 1H, 5H-octafluoropentyl methacrylate (for example, a trade name "Viscoat 8FM" manufactured by Osaka organic chemical Co., ltd.), 2- (heptadecafluorononyl) ethyl acrylate (for example, a trade name "FA-108" manufactured by Kyowa chemical Co., ltd.), 1H, 2H-tridecafluorooctyl acrylate (for example, a trade name "Viscoat F13" manufactured by Osaka organic chemical 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 forms of the interlayer sheet disclosed herein, the viscoelastic layer V ₂ The acrylic polymer as a base polymer of the adhesive may be a polymer of a monomer raw material containing at least the above-mentioned fluorine-containing acrylic monomer (e.g., fluoroalkyl (meth) acrylate) and further containing another monomer (copolymerizable monomer) copolymerizable with the fluorine-containing acrylic monomer, for example, an acrylic adhesive layer. 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. Viscoelastic layer V with lower refractive index ₂ From the viewpoint of (1), the content of the fluorine-containing acrylic monomer is preferably 40% by weight or more, and more preferablyPreferably 45% by weight or more, 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, 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 forms, from the viscoelastic layer V ₂ From the viewpoint of the cohesion and the like, the content of the fluorine-containing acrylic monomer is preferably 99.9% by weight or less, more 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. The fluorine-containing acrylic monomer may be used alone in 1 kind or in combination of 2 or more kinds.

For producing the viscoelastic layer V ₂ The monomer raw material of the base polymer (b) may be a composition containing a copolymerizable monomer in addition to the fluorine-containing acrylic monomer (e.g., 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, cycloalkyl (meth) acrylates, nonaromatic ring-containing (meth) acrylates such as isobornyl (meth) acrylate, and alkoxy group-containing monomers; and so on. As a specific example, the viscoelastic layer V can be mentioned ₁ The base polymer of (3) above, but is 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, for the preparation of the viscoelastic layer V ₂ The monomer raw material of the base polymer (b) 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. ComprisesThe hydroxyl 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, or may be less than 1.5% by weight, from the viewpoint of reducing the refractive index.

In some ways, from the inhibition of the viscoelastic layer V ₂ For the preparation of the viscoelastic layer V from the viewpoint of coloring or discoloration (e.g., yellowing) ₂ The monomer raw material of the base polymer of (1) is preferably limited in the content of the carboxyl group-containing monomer. 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). From inhibiting possible contact with or access to the viscoelastic layer V ₂ On the other hand, from the viewpoint of corrosion of the disposed metal material (for example, metal wiring, metal film, etc. which may be present on the adherend), it is also advantageous to limit the content of the carboxyl group-containing monomer in this way. The interlayer sheet 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 ways, for the preparation of the viscoelastic layer V ₂ The monomer raw material of the base polymer of (2) is preferably limited in the content of a monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, etc. in addition to a carboxyl group). As monomers of this modeThe content of the acid functional group-containing monomer in the component (B) may be the preferred content of the above carboxyl group-containing monomer. The interlayer sheet disclosed herein may preferably be in such a manner that the above monomer raw material does not contain an acidic group-containing monomer (i.e., the viscoelastic layer V) ₂ The base polymer of (b) is acid-free).

Adhesive layer V ₂ With the base polymer and the adhesive layer V ₁ The base polymer of (3) can also be suitably prepared by a known polymerization method. 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 The range of (1). In some modes, the adhesive layer V ₁ From the viewpoint of adhesiveness and the like, the pressure-sensitive adhesive layer V ₂ Has an Mw of 150X 10 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 addition, in some modes, from the adhesive layer V ₂ From the viewpoint of the cohesion, etc., the Mw of the base polymer may be, for example, 30X 10 ⁴ Above, it may be 40 × 10 ⁴ Above, it may be 50 × 10 ⁴ As described above. For the preparation of Mw, conventionally known chain transfer agents can be used as needed.

Although not particularly limited, the pressure-sensitive adhesive layer V is a pressure-sensitive adhesive layer V from the viewpoint of adhesiveness ₂ The base polymer (e.g., acrylic polymer) of (a) is advantageously at a Tg of about 0 ℃ or less, preferably about-5 ℃ or less (e.g., about-15 ℃ or less, or-25 ℃ or less). In addition, the pressure-sensitive adhesive layer V is from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer ₂ The Tg of the base polymer (b) is about-75 ℃ or higher, preferably about-70 ℃ or higher (for example, -50 ℃ or higher, further, -30 ℃ or higher). The Tg of the base polymer can be adjusted by appropriately changing the monomer composition (i.e., the kind of the monomer used in the synthesis of the polymer, and the amount ratio used).

Adhesive layer V ₂ In (b), a known crosslinking agent may be used as necessary. In addition, an adhesive layerV ₂ In the above step (b), other additives such as a thickener may be contained as necessary. The crosslinking agent and the tackifier can be mixed with the adhesive layer V ₁ The same substances are appropriately selected and used in appropriate amounts.

In the process for forming the adhesive layer V ₂ In the embodiment in which the pressure-sensitive adhesive composition of (1) includes a crosslinking agent, an isocyanate-based crosslinking agent can be preferably used as the crosslinking agent. In some modes, the adhesive layer V ₁ 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, based on 100 parts by weight of the base polymer in the pressure-sensitive adhesive composition, from the viewpoint of adhesion and 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 interlayer sheet disclosed herein, the viscoelastic layer V is constituted ₁ 、V ₂ The respective viscoelastic materials may be adhesives obtained by curing adhesive compositions 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, cured products of the adhesive compositions. 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. In the active energy ray-curable adhesive composition, typically, an adhesive is formed by performing a polymerization reaction and/or a crosslinking reaction by irradiation with active energy rays. When the active energy ray-curable adhesive composition needs to be dried, it is preferable to irradiate active energy rays after drying.

Interlayer sheet disclosed hereinViscoelastic layer V ₁ 、V ₂ Can be formed by imparting (e.g., coating) the 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.

In the interlayer sheet disclosed herein, the viscoelastic layer V ₁ 、V ₂ Either or both of them may be an adhesive layer having post-curing property, or may be an adhesive layer having no post-curing property. 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 the 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 not having post-curing property does not cause dimensional change accompanying the subsequent curing reaction (i.e., dimensional stability is good), and therefore warpage of the pressure-sensitive adhesive sheet or the adherend to which the pressure-sensitive adhesive sheet 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.

Viscoelastic layer V ₁ The thickness of (b) is not particularly limited, and may be, for example, 3 μm or more, preferably 5 μm or more. According to the thickness of the viscoelastic layer V of more than 5 mu m ₁ And good adhesive properties are easily obtained. In addition, a viscoelastic layer V of this thickness ₁ The adhesive sheet can easily absorb irregularities that may be present on the surface of an adherend and can be bonded to the adherend with good adhesion. The viscoelastic layer V is also preferable from the viewpoint of preventing coloring and color unevenness due to light interference ₁ The thickness of (2) is 5 μm or more. In some forms, the viscoelastic layer V ₁ The thickness of (A) may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 85 μm or more. Additionally, in some aspects, viscoelasticSex layer V ₁ The thickness of (b) 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. Viscoelastic layer V ₁ If the thickness of (b) is not too large, it may be advantageous from the viewpoint of thinning of the interlayer sheet. The techniques disclosed herein may be preferred, for example, with a viscoelastic layer V ₁ The thickness of (b) is in the range of 3 to 200 μm (more preferably 5 to 100 μm). Having a viscoelastic layer V ₁ And a viscoelastic layer V ₂ In the case of the interlayer sheet of (3), the viscoelastic layer V ₂ The thickness of (D) may be selected from the same viscoelastic layers V as those exemplified above ₁ In the same range as in (c). Viscoelastic layer V ₁ And a viscoelastic layer V ₂ The thickness of (a) may be the same or different. In the case of an interlayer sheet in the form of a substrate-less double-sided adhesive sheet formed of an adhesive layer, the thickness of the adhesive layer is the thickness of the interlayer sheet.

Adhesive layer V ₁ With an adhesive layer V ₂ The pressure-sensitive adhesive layer having a laminated structure may be formed by, for example: the pressure-sensitive adhesive layers V are respectively formed on a releasable surface (for example, the release surface of a release liner) ₁ 、V ₂ And bonding the adhesive surfaces thereof to each other; will be used to form the adhesive layer V ₂ Is applied to the adhesive layer V ₁ A method of curing the same; and vice versa will be used to form the adhesive layer V ₁ Is applied to the adhesive layer V ₂ A method of curing the same; and the like, but are not limited thereto. A preformed adhesive layer V ₁ 、V ₂ When the adhesive surfaces of (a) are bonded to each other, a treatment for promoting adhesion of the two adhesive 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 interlayer sheet (pressure-sensitive adhesive sheet) of some embodiments may be in the form of a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a support substrate. The material of the support substrate is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the adhesive sheet. 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 a single or blended fiber of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semisynthetic fibers such as acetate); 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 resin film having a non-porous structure, typically a (non-porous) resin film substantially free of 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 kind of such resin alone, or may be formed using a resin material obtained by blending 2 or more kinds of such resins. 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.

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 in accordance with jis k7136:2000, measured using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETERHM-150" manufactured by the color technology research on village 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 of the interlayer sheet. 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 properties and processability of the interlayer sheet. 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 (viscoelastic layer) is laminated may be subjected to conventionally known surface treatments 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), and 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. Examples of other treatments that can be applied to the base material as needed include an antistatic layer formation treatment, a coloring layer formation treatment, and a printing treatment. These treatments may be applied alone or in combination.

When the interlayer sheet disclosed herein is in the form of a substrate-attached pressure-sensitive adhesive sheet, the thickness of the interlayer 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. From the viewpoint of handling properties and the like, the thickness of the interlayer sheet may be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

The thickness of the interlayer sheet is the thickness of the portion to be adhered to the adherend. For example, the interlayer sheet 1 having the structure shown in fig. 1 has a thickness from the 1 st surface (pressure-sensitive adhesive surface) 10A of the pressure-sensitive adhesive layer to the 2 nd surface 20B of the support base, and does not include the thickness of the release liner 30.

< interlayer sheet with Release liner >

The interlayer sheet (pressure-sensitive adhesive sheet) disclosed herein may be in the form of a pressure-sensitive adhesive product in which the surface (pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layer is brought into contact with the release surface of the release liner. Thus, according to this specification, there is provided an interlayer sheet (adhesive article) with a release liner, comprising: any of the interlayer sheets disclosed herein, and a release liner having a release surface that comes into contact with the adhesive surface of the interlayer sheet.

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 employed. 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. Various plastic films can be used as the release film substrate. 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, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, cyclic polyolefin resins such as norbornene resins, (meth) acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyarylate resins, 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, a preferable release film substrate is a polyester resin film (for example, 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, the respective additives may be blended in all the sub-layers, or may be blended in 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 may 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 release surface arithmetic average roughness Ra and a low maximum height Rz. 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.

The release liner-equipped interlayer sheet having the form of a release liner on each of the 1 st adhesive surface and the 2 nd adhesive surface may have the same material and composition as 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), 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 interlayer 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 aspects, it is preferred that one release liner has a different thickness from another release liner from the viewpoint of release workability or the like, for example, it is preferred that the thicker release liner has a thickness of about 1.1 times or more (e.g., about 1.25 times or more) the thickness of the thinner release liner.

(arithmetic average roughness Ra of adhesive surface side surface)

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 adhesive-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 interlayer sheet having the release liner disposed on each of the 1 st adhesive surface and the 2 nd adhesive surface, the adhesive surface side surfaces of both the release liners preferably satisfy the above-mentioned arbitrary arithmetic average roughness Ra. The arithmetic average roughness Ra of the adhesive-side surfaces of the two release liners may be the same or different.

(maximum height of adhesive surface side surface Rz)

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 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-equipped interlayer sheet in which release liners are disposed on the 1 st adhesive surface and the 2 nd adhesive surface, the adhesive surface side surfaces of both release liners preferably satisfy the above-mentioned arbitrary maximum height Rz. The maximum heights Rz of the adhesive-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, 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 "NewView7300", manufactured by ZYGO) or a product equivalent thereof can be used. For example, a glass plate (soda lime glass plate manufactured by MATSUNAMI; 1.3mm in thickness) was bonded and fixed to the surface of the release liner opposite to the surface to be measured, and the surface shape was measured using a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) at 23 ℃ and 50% RH.

< use >

The interlayer sheet disclosed herein can be used by being attached to various adherends. The constituent material of the adherend (adherend material) is not particularly limited, and examples thereof include: examples of the metal material include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, and alloys containing 2 or more of these metals, 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), and various resin materials such as alumina, zirconia, titanium oxide, siO ₂ Metal oxides such as ITO (indium tin oxide) and ATO (antimony doped tin oxide), mixtures thereof, aluminum nitride, and nitrogenAnd nitrides such as 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, and sapphire glass. The interlayer sheet disclosed herein may be used by being bonded to a member (for example, an optical member) at least the surface of which is made of the above-described material.

The interlayer sheet disclosed herein can be used in an adhesive form without being heated 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 constituent material of the interlayer sheet (for example, the material of the base material) and the type of the adherend, the heat treatment may be performed at least at any time after the lamination to the adherend, at the time of the lamination, and before the lamination, if allowable. The heat treatment may be performed for the purpose of improving the adhesion of the pressure-sensitive adhesive to an 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, for example, about 100 ℃ or less, 80 ℃ or less, 60 ℃ or less, or 50 ℃ or less, depending on the constituent material of the interlayer sheet and the kind of the adherend.

The member or material to which the interlayer sheet is to be attached or laminated (at least one adherend in the interlayer sheet in the form of a double-sided pressure-sensitive adhesive sheet) may have light permeability. In such an adherend, the advantage of high transparency of the interlayer sheet disclosed herein is readily 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 interlayer sheet disclosed herein can be preferably used by being stuck to or laminated on an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The above total light transmittance is in accordance with JISK7136:2000, measured using a commercially available transmittance meter. As the transmittance meter, the product name "HAZEMETERHM-150" manufactured by the color technology research on village or the equivalent thereof was used.

Refractive index of adherend and adhesive articleConfigured viscoelastic layer (e.g. viscoelastic layer V) ₁ In the presence of a viscoelastic layer V ₂ In the form of (1), the viscoelastic layer V may be ₂ . ) May be of the same or different refractive indices. For example, by relatively increasing the refractive index of the viscoelastic layer (typically, 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 increased. In this case, the refractive index of the adherend may be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, 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 have any of the total light transmittances described above. In the form of being attached to or laminated on such an adherend, the effects brought by the technology disclosed herein can be particularly preferably exhibited.

As an example of preferable applications, optical applications are cited. More specifically, the interlayer sheet disclosed herein can be preferably used, for example, as an optical pressure-sensitive adhesive sheet for use in applications of bonding optical members (for bonding optical members), production of products using the optical members (optical products), and the like.

The optical member is a member having optical characteristics (e.g., polarization, light refraction, light scattering, light reflection, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.). The optical member is not particularly limited as long as it is a member having optical characteristics, and examples thereof include a member constituting a device (optical device) such as a display device (image display device) or an input device, and a member used in such a device, and examples thereof include a polarizing plate, a wavelength plate, a retardation plate, an optical compensation film, a luminance improving film, a light guide plate, a reflection film, an antireflection film, a Hard Coat (HC) film, an impact absorption film, an antifouling film, a photochromic film, a light control film, a transparent conductive film (ITO film), an appearance film, a decorative film, a surface protection plate, a prism, a lens, a color filter, a transparent substrate, and a member further laminated with these (these may be collectively referred to as a "functional film"). 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 (for example, sheet-shaped, film-shaped, and plate-shaped members) formed of glass, acrylic resin, polycarbonate, polyethylene terephthalate, a metal film, and the like. 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 interlayer sheet disclosed herein can be used, for example, as a sheet disposed between an optical film having 1 or 2 or more functions such as transmission, reflection, diffusion, waveguide, light collection, diffraction, and the like of light, a fluorescent film, and another optical member (which may be another optical film)It is preferably used for bonding the optical film to the other optical member. Among them, in the bonding of optical thin films having at least 1 function of light waveguide, light collection, and diffraction, the entire bonding layer is desirably high in refractive index, and can be a preferable application object of the technology disclosed herein. For example, a viscoelastic layer (adhesive layer) V can be preferably used ₁ As the bonding layer.

The viscoelastic layer (preferably an adhesive layer) of the interlayer sheet disclosed herein is, for example, a viscoelastic layer V ₁ The adhesive layer of the single-layer structure formed, or the adhesive layer containing the viscoelastic layer V ₁ And a viscoelastic layer V ₂ The pressure-sensitive adhesive layer having a laminated structure in which two or more pressure-sensitive adhesive layers are directly in contact with each other) 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, there is a demand for a thinner optical member and an improvement in light extraction efficiency. As the viscoelastic layer (e.g., adhesive layer) that can cope with this demand, the viscoelastic layer of the interlayer sheet 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. When the fluorescent film is bonded, 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 adhesive. 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 interlayer sheet disclosed herein is preferably used by being stuck to an adherend having a high refractive index (which may be a layer, a member, or the like having a high refractive index), and can suppress interface reflection with the adherend. Interlayer sheet used in this mannerAs described above, it is preferable that an adherend having a high refractive index and a pressure-sensitive adhesive layer (typically, viscoelastic layer V) attached to the adherend are high ₁ ) Has a small refractive index difference and has high adhesion to an adherend at the interface. 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, a 1 st retardation layer and a 2 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.

Further, the interlayer sheet disclosed herein has a viscoelastic layer V having a high refractive index ₁ Therefore, it is preferable to use the light-emitting layer (for example, a highly refractive light-emitting layer mainly composed of an inorganic material) attached to a light-emitting layer such as an optical semiconductor. By reducing the luminescent layer and the viscoelastic layer V ₁ The refractive index difference of (2) can suppress reflection at the interface between them, and improve the light extraction efficiency. The interlayer sheet used in this embodiment preferably has a pressure-sensitive adhesive layer having a high refractive index as the viscoelastic layer V ₁ . In addition, from the viewpoint of preventing deterioration of the self-light emitting element due to moisture in advance, the viscoelastic layer V is preferable ₁ Has low water absorption. From the viewpoint of improvement in brightness, the interlayer sheet is preferably low colored. This may also be advantageous from the viewpoint of suppressing unintentional coloring due to the interlayer sheet.

Viscoelastic layer V of the interlayer sheet disclosed herein ₁ The coating layer covering the lens surface, the bonding layer of a member facing the lens surface (e.g., a member having a surface shape corresponding to the lens surface), the bonding layer, the coating layer, and the like can be preferably used for microlenses and other lens members (e.g., lens members such as microlenses constituting a microlens array film and microlenses for cameras) used as constituent members of cameras, light-emitting devices, and the like, A filling layer filled between the lens surface and the member. Viscoelastic layer V as disclosed herein ₁ Since this is suitable for increasing the refractive index, even if the lens is placed in contact 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), the refractive index difference from the lens can be reduced. 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 viscoelastic layer V is constituted ₁ The viscoelastic material of (a) can also use itself as a lens resin, for example, in a form filled in a recess or a void of an appropriate transparent member.

The method of bonding the optical member using the interlayer sheet disclosed herein is not particularly limited, and may be, for example, (1) a method of bonding the optical members to each other via the interlayer sheet disclosed herein, (2) a method of bonding the optical member to a member other than the optical member via the interlayer sheet disclosed herein, or (3) a method of bonding the interlayer sheet disclosed herein to the optical member or a member other than the optical member in a form including the optical member. In the aspect (3), the interlayer sheet including the optical member may be an interlayer sheet in which the optical member (for example, an optical film) is used as a support. Such an interlayer 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 interlayer sheet disclosed herein is a type of pressure-sensitive adhesive sheet having a support and the functional film is used as the support, the interlayer sheet disclosed herein can be also regarded as an "adhesive type 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 interlayer sheet disclosed herein and a member (for example, a resin film such as an optical film) to which the interlayer sheet is bonded. The member to which the interlayer sheet is attached may have a refractive index of the adherend material. In addition, the adhesion of the constituent interlayer sheetsLayer of face (e.g. viscoelastic layer V) ₁ ) The difference (refractive index difference) between the refractive index of (b) 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 the same as those described above as the members, materials, and adherends, and therefore, the description thereof will not be repeated.

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) to a glass plate of 3N/25mm or more.

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 in the form of a laminate comprising the pressure-sensitive adhesive layer and a light-transmitting substrate.

The adhesive sheet according to [ 6 ] above, 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 from the pressure-sensitive adhesive layer.

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

the pressure-sensitive 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 a compound having 2 or more aromatic rings in 1 molecule.

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

(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.

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

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

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 pressure-sensitive 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 ] above.

[ 21 ] an adhesive comprising the adhesive composition according to any one of [ 11 ] to [ 20 ] above, wherein the adhesive has a refractive index of 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 over 86 percent;

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 primary polymer and a plasticising material having a lower molecular weight than the primary 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 Below the 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 Below the 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.

Examples

The following examples are illustrative of the present invention, but are not intended to limit the invention to the scope of the specific examples. In the following description, "part(s)" and "%" indicating 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 stirring blade, ase:Sub>A thermometer, ase:Sub>A nitrogen gas introduction tube and ase:Sub>A condenser, 95 parts of m-phenoxybenzyl ACRYLATE (trade name "LIGHT ACYLATE POB-A", manufactured by Kyoeishase:Sub>A chemical Co., ltd., refractive index: 1.566, tg of homopolymer: -35 ℃ C. Hereinafter abbreviated as "POB-A") and 5 parts of 4-hydroxybutyl ACRYLATE (4 HBA), 0.2 part 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, and ase:Sub>A polymerization reaction was carried out for 6 hours while slowly stirring to keep the liquid temperature in the flask at 60 ℃ to prepare ase:Sub>A solution (50%) of the acrylic polymer A1. 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%, 334 parts (100 parts of nonvolatile matter) of the solution were added 10 parts (0.1 part of nonvolatile matter) of A1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX" manufactured by Tosoh corporation, 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and iron acetylacetonate (iron (II) (A) as a crosslinking catalyst

Iron III) in 1 part (non-volatile matter 0.01 part) of a 1% ethyl acetate solution and stirred to prepare an acrylic adhesive composition C1.

< preparation of acrylic adhesive composition C2 >

Into a four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas inlet and a condenser were placed 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"; 5 parts of 4 HBA), 0.2 parts of AIBN as a polymerization initiator, and 100 parts of toluene as a polymerization solvent, and while gradually stirring, nitrogen gas was introduced, and polymerization was carried out for 6 hours 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.

A solution (50%) of the acrylic polymer A2 was diluted with ethyl acetate to 30%, and 334 parts (100 parts of nonvolatile matter) of the solution were added 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 Tosoh Corp., 3-functional isocyanate Compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and iron acetylacetonate (iron (II) (0.1 part of a crosslinking catalyst)

Iron III) was added to 1 part (0.01 part of nonvolatile matter) of a 1% ethyl acetate solution 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 charged 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 4HBA2 parts of AIBN0.2 part as a polymerization initiator, and 200 parts of ethyl acetate as a polymerization solvent, and a solution (33%) of acrylic polymer A3 was prepared by conducting polymerization for 9 hours while keeping the liquid temperature in the flask at about 60 ℃. 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 content) of a 1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (product name "Coronate HX" manufactured by tokyo co., ltd., and A3-functional isocyanate compound) as a crosslinking agent (0.1 part of nonvolatile content) was added to 100 parts of nonvolatile content (solid content) and mixed under stirring to prepare an acrylic pressure-sensitive adhesive composition C3.

< preparation of interlayer 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. The silicone-treated surface of the PET film R2 (38 μm thick) having been silicone-treated on one side was bonded to the surface of the pressure-sensitive adhesive layer. In this manner, an adhesive layer (adhesive layer V) having both surfaces protected by PET films (release liners) R1 and R2 was obtained ₁ ). The release liner R2 is relatively light in weight compared to the release liner R1.

Further, 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 V having a thickness of 10 μm ₂ . 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. By doing so, obtainPressure-sensitive adhesive layer (pressure-sensitive adhesive layer V) of a type protected on both sides by PET films (release liners) R1, R2 ₂ )。

From the adhesive layer V ₁ 、V ₂ The release liner R2 was peeled off, and the adhesive surfaces were bonded to each other, and pressure-bonded by a manual roller. The laminate was autoclaved at 50 ℃ and 0.60MPa for 30 minutes and then cured at 50 ℃ for 48 hours. By doing so, an adhesive layer V is obtained ₁ /V ₂ An interlayer sheet (substrate-free double-sided adhesive sheet) having a two-layer structure of (1). The surface of the interlayer sheet was protected by 2 release liners R1.

(example 2)

Will be used to form the adhesive layer V ₁ 、V ₂ The pressure-sensitive adhesive layer V was obtained in the same manner as in example 1, except that the kind of the pressure-sensitive adhesive composition and the thickness of each pressure-sensitive adhesive layer were changed as shown in table 1 ₁ /V ₂ An interlayer sheet (substrate-free double-sided adhesive sheet) having a two-layer structure of (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 interlayer sheets of examples 3 to 5 in the same manner as in example 1.

The obtained interlayer sheet was 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 pressure-sensitive adhesive layers of the examples 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 of the test pieces obtained by bonding the interlayer sheets of each example to alkali-free glass (thickness of 0.8 to 1.0mm, total light transmittance of 92%, haze of 0.4%) were measured at 23 ℃ in a measurement environment using a haze meter (trade name "hazeme hm-150" manufactured by color technical research in village). 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 interlayer sheet. The results are shown in Table 1.

(peeling Strength to glass plate)

The release liner was peeled from one surface of the interlayer sheet of each example (the surface of the pressure-sensitive adhesive layer formed of the pressure-sensitive 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 then the liner was 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 mixture 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 universal tensile compression testing machine in accordance with JIS Z0237:2000, the peel strength (adhesive force) [ N/25mm ] was measured under the conditions of 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 interlayer sheets of examples 1 to 4 contained a refractive index n ₁ Is 1.570 or more and has a storage modulus G' _V1 (25) An adhesive layer V of 700kPa or less ₁ And exhibits high transparency in the interlayer sheet. These interlayer sheets exhibit practical peel strength suitable for interlayer bonding of optical members.

< evaluation of front luminance improving Effect >

The interlayer sheets of each example were attached to a white LED light source, and after the light source was turned on and stabilized in a dark room environment for 30 minutes or more, the front luminance of the portion to which the interlayer sheet was attached was measured using a spectroradiometer SR-UL1R (manufactured by topcechnohous corporation). Using the average of the luminance measured 3 times, the case where the luminance improvement effect was 10% or more with respect to the luminance of the light source without the interlayer sheet attached was evaluated as G (Good), and the case where the luminance improvement was less than 10% was evaluated as P (Poor).

[ 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, the adhesive layer (adhesive layer V) according to example 5 having a combined low refractive index ₂ ) With the adhesive layers (adhesive layers V) of examples 3 and 4 having high refractive indices ₁ ) The interlayer sheets of examples 1 and 2, which are pressure-sensitive adhesive layers having a laminated structure, were found to have a front luminance improving effect of 10% or more, compared with the case where the interlayer sheet was not used. The interlayer sheets of examples 3 to 5, in which the pressure-sensitive adhesive layer of the interlayer sheet had a single-layer structure, were not confirmed to have the effect of improving the front luminance by the interlayer sheet alone. The interlayer sheets of examples 3 and 4 can exhibit the effect of improving the front luminance in a laminate with a member having a lower refractive index (for example, a resin film). The interlayer sheet of example 5 can exhibit an effect of improving the front luminance in a laminate with a member having a higher refractive index (for example, a resin film).

< preparation of acrylic adhesive composition C4 >

In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen introduction tube and a condenser, 79 parts of POB-a, 20 parts of n-Butyl Acrylate (BA), 1 part of 4HBA, 0.2 part of AIBN as a polymerization initiator and 100 parts of toluene as a polymerization solvent were charged as monomer components, nitrogen was introduced while slowly stirring, and polymerization was carried out for 6 hours while maintaining the liquid temperature in the flask at about 60 ℃ to prepare 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 to 30% with ethyl acetate, to whichTo 334 parts of the solution (100 parts of non-volatile matter) were added 10 parts of a 1% ethyl acetate solution of Coronate HX as a crosslinking agent (0.1 part of non-volatile matter), 2 parts of acetylacetone as a crosslinking retarder, and iron acetylacetonate (a crosslinking catalyst) ((C))

Ironiii) in 1% ethyl acetate solution (non-volatile matter 0.01 part) and mixed with stirring 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 a 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. The "P2H-A" in the composition of the monomer component represents phenoxy diethylene glycol ACRYLATE (trade name "LIGHT ACRYLATE P2H-A", product of Kyoeisha chemical Co., ltd., refractive index: 1.510, tg of homopolymer: -35 ℃ C.). The acrylic polymer A6 had an Mw of 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]20 parts of thiophene (6-acryloyloxyethyldinaphthothiophene manufactured by Sugai Chemical IND.CO., LTD., no. 6EDNTA, refractive index: 1.722), 10 parts of a 1% ethyl acetate solution of Coronate HX as a crosslinking agent (nonvolatile matter 0.1 part), and extension of crosslinking2 parts of acetylacetone as retarder, iron acetylacetonate as crosslinking catalyst: (

Iron III) in 1 part (non-volatile matter 0.01 part) of a 1% ethyl acetate solution and stirred to prepare an acrylic adhesive composition C6.

< preparation of acrylic adhesive composition C7 >

A solution (50%) of an acrylic polymer A1 was diluted with ethyl acetate to 30%, and to 334 parts (100 parts of nonvolatile matter) of the solution were added 10 parts of POB-A as an additive (plasticizing agent), 10 parts of A1% 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 iron (II) acetylacetonate (a crosslinking catalyst)

Iron III) was added to 1 part (0.01 part of nonvolatile matter) of a 1% ethyl acetate solution and mixed with stirring to prepare an acrylic adhesive composition C7.

< preparation of acrylic adhesive composition C8 >

An acrylic adhesive composition C8 was prepared in the same manner as in the preparation of the acrylic adhesive composition C7 except that 10 parts of POB-A was changed to 10 parts of 3-phenoxybenzyl alcohol (having a refractive index of 1.59, manufactured by Tokyo chemical Co., ltd.).

< preparation of acrylic adhesive composition C9 >

A solution (50%) of acrylic polymer A9 was prepared in the same manner as the preparation of the solution of acrylic polymer A3, except that the composition (weight ratio) of the monomer components was changed to 2EHA/Viscoat 13F/4hba = 49/50/1. "Viscoat13F" in the composition of the monomer component means acrylic acid 1H, 2H-tridecafluorooctyl ester (product name "Viscoat13F" manufactured by Osaka organic chemical Co., ltd.). The Mw of the acrylic polymer A9 was 55 ten thousand. An acrylic adhesive composition C9 was prepared in the same manner as in the preparation of the acrylic adhesive composition C3, except that a solution of the acrylic polymer A9 was used instead of the solution of the acrylic polymer A3.

< preparation of interlayer sheet >

Examples 6 to 10

Will be used to form the adhesive layer V ₁ 、V ₂ The pressure-sensitive adhesive layer V was obtained in the same manner as in example 1, except that the kind of the pressure-sensitive adhesive composition and the thickness of each pressure-sensitive adhesive layer were as shown in table 3 ₁ Adhesive layer V ₂ An interlayer sheet (substrate-free double-sided adhesive sheet) having a two-layer structure of (1).

The interlayer sheets obtained in examples 6 to 10 were subjected to sufficient adaptation in an environment of 23 ℃ and 50% RH, and then the measurement and evaluation of each item were carried out in the same manner as in the above-mentioned "measurement and evaluation (1)". 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) 1C0 parts +6EDNTA 20 parts

C7: POB-A/4HBA (95/5) 100 parts and POB-A10 parts

C8: POB-A/4HBA (95/5) 100 parts + 3-phenoxybenzyl alcohol 10 parts

C9：2EHA/Viscoat13F/4HBA(49/50/1)

As shown in Table 3, the interlayer sheets of examples 6 to 10 had a refractive index n ₁ Is 1.570 or more and has a storage modulus G' _V1 (25) An adhesive layer V of 700kPa or less ₁ And exhibits high transparency in the interlayer sheet. These interlayer sheets exhibit practical peel strength suitable for interlayer bonding of optical members.

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 scope of the claims include various modifications and changes made to the specific examples illustrated above.

Description of the reference numerals

1. 2 interlayer sheet (adhesive sheet)

10. Viscoelastic layer (adhesive layer, viscoelastic layer V) ₁ )

10A No. 1 surface (adhesive surface)

10B No. 2 surface

11. No. 1 viscoelastic layer (No. 1 adhesive layer, viscoelastic layer V) ₁ )

12. No. 2 viscoelastic layer (No. 2 adhesive layer, viscoelastic layer V) ₂ )

20. Supporting substrate

20A No. 1 surface

20B No. 2 (Back)

30. 31, 32 Release liner

50. Release liner-equipped adhesive sheet (release liner-equipped interlayer sheet)

70. Optical member

100. Optical laminate

Claims

1. An interlayer sheet used by being disposed between layers of a laminate in optical use,

comprising a refractive index n ₁ Is 1.570 or more and has a storage modulus G 'at 25℃' _V1 A viscoelastic layer V of 30kPa to 700kPa ₁ ，

The interlayer sheet has a total light transmittance of 86% or more and a haze value of 1.0% or less.

2. The interlayer sheet according to claim 1, which has a thickness of 5 μm or more.

3. The interlayer sheet of claim 1 or 2, further comprising a viscoelastic layer V laminated to the viscoelastic layer ₁ Viscoelastic layer V ₂ ，

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

4. The interlayer sheet of claim 3, wherein said viscoelastic layer V ₂ Refractive index n of ₂ Below the viscoelastic layer V ₁ Refractive index n of ₁ 。

5. An interlayer sheet with a release liner, comprising:

the interlayer sheet as claimed in any one of claims 1 to 4, and

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

6. An optical stack, comprising:

the interlayer sheet as claimed in any one of claims 1 to 4, and

and a resin film laminated on the interlayer sheet.