KR20230141560A - Light emitting apparatus - Google Patents

Abstract

A light-emitting device is provided in which an adhesive layer having a high refractive index and capable of withstanding large deformation is disposed on a viewing side of a self-luminous element.
The light emitting device includes a self-luminous element, a low refractive index layer disposed on a viewing side of the self-luminous element, and a high refractive index adhesive layer laminated in direct contact with the low refractive index layer. The high refractive index adhesive layer has a refractive index of more than 1.560, and a deformation amount in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min is 350% or more.

Description

Light emitting device {LIGHT EMITTING APPARATUS}

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

In general, adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) are in a flexible solid (viscoelastic) state in the temperature range around room temperature and have the property of easily adhering to an adherend by applying pressure. Taking advantage of these properties, adhesives are widely used for purposes such as bonding, fixation, and protection in various industrial fields such as home appliances, automobiles, various machines, electrical devices, and electronic devices. An example of the use of the adhesive is to bond polarizing films, retardation films, cover window members, and various other light-transmitting members to other members in display devices such as liquid crystal displays and organic EL displays. . Technical literature on adhesives for optical members includes Patent Documents 1 and 2. Patent Document 3 is a technical document regarding a light-emitting device having an adhesive layer.

Japanese Patent Publication No. 2014-169382 Japanese Patent Publication No. 2017-128732 Japanese Patent Publication No. 2022-8015

Patent Documents 1 and 2 disclose a pressure-sensitive adhesive composition containing as a main component a (meth)acrylic acid ester polymer containing a monomer having a plurality of aromatic rings as a monomer unit, and an adhesive obtained by crosslinking the pressure-sensitive adhesive composition, which contains a plurality of aromatic rings. It is proposed that the refractive index of the adhesive is set to 1.50 or higher, particularly preferably 1.51 or higher, by using a monomer having the same. Additionally, a technique for increasing the refractive index by mixing particles made of an inorganic material with a high refractive index (for example, inorganic particles such as zirconium oxide particles or titanium oxide particles) into a resin is also known. However, adhesives containing inorganic particles have a trade-off relationship between refractive index and adhesive properties (e.g., peel strength, flexibility, etc.), making application to the adhesive field difficult. For example, in order to increase the refractive index of the adhesive layer disposed on the viewing side of the self-luminous element in a light-emitting device, it is necessary to consider the effect on optical properties (e.g. total light transmittance, haze, etc.) when mixing inorganic particles. There is. Against this background, the present inventors, in Patent Document 3, propose a light-emitting device in which an adhesive layer with high refractive index and optical quality is disposed on the viewing side of the self-light-emitting element.

However, in recent years, foldable displays and rollable displays have been put into practical use as displays such as organic EL displays used in electronic devices such as smartphones, and the adhesives used for these applications have the ability to follow the adherend that is repeatedly bent. There is a need to have the flexibility to do so. Adhesives with excellent flexibility are easy to follow and adhere to curved surfaces such as three-dimensional shapes, and are also suitable for use in electronic devices having curved shapes. Even for adhesives with a high refractive index, if flexibility can be increased, application to applications that are repeatedly bent, such as the foldable display, can be expected. However, adhesive polymers with a high refractive index tend to have a high glass transition temperature, such as having an aromatic ring, and adhesives formed using high refractive index materials tend to have reduced flexibility. In the design of adhesives, high refractive index and flexibility have a trade-off relationship. If an adhesive can be realized that has a high refractive index and is flexible enough to withstand use in applications involving large deformation, the adhesive layer disposed on the viewing side of the self-luminous element can be made to have a high refractive index in the foldable display, etc. It's possible, it's useful.

The present invention was created in consideration of the above circumstances, and its purpose is to provide a light-emitting device in which an adhesive layer that has a high refractive index and can withstand large deformation is disposed on the viewing side of a self-light-emitting element.

The light-emitting device provided by this specification includes a self-luminous element, a low refractive index layer disposed on a viewing side compared to the self-luminous element, and a high refractive index adhesive layer laminated in direct contact with the low refractive index layer. The high refractive index adhesive layer has a refractive index of more than 1.560, and a deformation amount in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min is 350% or more. The high refractive index adhesive layer has a high refractive index and can deform by more than 350% in a low-temperature and high-speed deformation test, so it can sufficiently deform at high speed even in a low-temperature environment and can withstand large deformations. A laminate composed of a high-refractive-index adhesive layer that satisfies the above characteristics in combination with a low-refractive-index layer can be applied to applications involving large deformation, such as foldable displays, and can improve frontal brightness using a high refractive index. A light emitting device can be built.

In some embodiments, the high refractive index adhesive layer preferably has a stress of 5.0 N/mm 2 or less at a deformation amount of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. An adhesive that satisfies the above characteristics has a high refractive index and can be sufficiently deformed at high speed while maintaining a certain level of flexibility even in a low temperature environment. Therefore, it is suitable as a high refractive index adhesive layer for applications involving large deformation.

In some embodiments, the ratio (n ₁ /n ₂ ) between the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer is preferably approximately 1.05 or more. Thereby, the front luminance improvement effect is easy to obtain.

In addition, appropriate combinations of the elements described in this specification may also be included in the scope of inventions requiring patent protection through this patent application.

1 is a cross-sectional view schematically showing the configuration of a light-emitting device according to an embodiment.
FIG. 2 is a cross-sectional view schematically showing the structure of a laminated sheet used in a light-emitting device according to one embodiment.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and matters necessary for practicing the present invention can be understood by those skilled in the art based on the teachings for implementing the invention described in this specification and the technical common sense at the time of filing the application. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

In addition, in the drawings below, members and parts that exert the same function may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are modeled to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actually provided product.

In this specification, a self-luminous device refers to a light-emitting device whose luminance can be controlled by the flowing current value. The self-luminous element may be composed of a single entity or an aggregate. Specific examples of self-luminous devices include, but are not limited to, light emitting diodes (LEDs) and organic ELs. The light-emitting device disclosed herein includes such self-luminous elements as constituent elements. Examples of the light-emitting device include, but are not limited to, a light source module device (for example, a planar light-emitting body module) used as lighting and a display device in which pixels are formed.

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

<Configuration example of light emitting device>

An example of a configuration of a light emitting device provided by this specification is shown in FIG. 1. The light emitting device 100 shown in FIG. 1 is in direct contact with the self-luminous element 70, the low refractive index layer 12 disposed on the viewing side of the self-luminous element 70, and the low refractive index layer 12. It includes a laminated high refractive index adhesive layer (11). The light emitting device 100 may further include a cover window member 80 disposed on the viewing side of the high refractive index adhesive layer 11. In the light emitting device 100 shown in FIG. 1, a laminated sheet 10 made of a high refractive index adhesive layer 11 and a low refractive index layer 12 is provided between the self-luminous element 70 and the cover window member 80. It is placed. Between the self-luminous element 70 and the low refractive index layer 12, between the high refractive index adhesive layer 11 and the cover window member 80, and on the viewing side of the cover window member 80, each independently, a layer not shown 1 or 2 or more of these may be inserted, or they may not be inserted. Additionally, contrary to FIG. 1, the high refractive index adhesive layer 11 may be disposed on the self-luminous element side, and the low refractive index layer 12 may be disposed on the cover window member side.

In the technology disclosed herein, the low refractive index layer may have adhesiveness or may be non-adhesive. In some embodiments, the low refractive index layer is preferably a layer having adhesive properties, that is, a low refractive index adhesive layer. As a result, the laminated sheet (adhesive sheet) of the low-refractive-index adhesive layer and the high-refractive-index adhesive layer becomes double-sided adhesive, improving assembly and mountability in the manufacture of a light-emitting device. For example, as shown in FIG. 2, before being incorporated into a light emitting device, such a laminated sheet is a laminated sheet 10 (baseless double-sided adhesive) made of a high refractive index adhesive layer 11 and a low refractive index adhesive layer 12. sheet 2), and the surface (first surface) 10A on the high refractive index adhesive layer 11 side of the laminated sheet 10 is the first adhesive surface and the surface on the low refractive index adhesive layer 12 side (first surface) 2 surface) 10B is the second adhesive surface, and each of those adhesive surfaces is protected by the release liners 31 and 32, and may be in the form of a laminated sheet with a release liner.

<High refractive index adhesive layer>

The light emitting device disclosed herein includes a high refractive index adhesive layer laminated in direct contact with a low refractive index layer included in the light emitting device. This high refractive index adhesive layer is a layer with a relatively higher refractive index than the low refractive index layer. The high refractive index adhesive layer preferably has a refractive index of more than 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. In this way, a high refractive index adhesive layer that has a high refractive index and is capable of deformation of 350% or more in a low-temperature, high-speed deformation test can sufficiently deform at high speed even in a low-temperature environment and can withstand large deformations. A laminate composed of a high refractive index adhesive layer that satisfies the above characteristics in combination with a low refractive index layer can be applied to applications involving large deformation, such as foldable displays, using the high refractive index of the high refractive index adhesive layer. A light emitting device capable of improving frontal luminance can be constructed.

(refractive index)

The light emitting device disclosed herein has a high refractive index adhesive layer with a refractive index n ₁ of more than 1.560. Such a high refractive index adhesive layer can be realized by configuring at least one surface (adhesive surface) of the high refractive index adhesive layer with an adhesive (viscoelastic material) with a refractive index of more than 1.560.

In addition, in this specification, the refractive index of the adhesive refers to the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As an Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO or its equivalent is used. As a measurement sample, an adhesive layer made of the adhesive to be evaluated can be used. Specifically, the refractive index of the adhesive can be measured by the method described in the test example described later. The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive (for example, the composition of the monomer component constituting the base polymer, additives that can be used as needed, etc.).

The technical details provided by this specification include a pressure-sensitive adhesive layer having a refractive index greater than 1.560 (high-refractive-index pressure-sensitive adhesive layer), a pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive layer, and a laminated sheet including the high-refractive-index pressure-sensitive adhesive layer. The laminated sheet may be, for example, a laminated adhesive layer consisting of the high refractive index adhesive layer and the low refractive index layer (typically a low refractive index adhesive layer), and the high refractive index adhesive layer and the low refractive index layer on one side of the support substrate. The structure may be stacked in this order or in reverse order.

In some embodiments, the refractive index of the high refractive index adhesive layer is, for example, 1.563 or more, suitably 1.565 or more, and preferably more than 1.570. In some preferred embodiments, the refractive index of the high refractive index adhesive layer may be 1.575 or more, 1.580 or more, 1.585 or more, 1.590 or more, or 1.595 or more. According to the high refractive index adhesive layer having such a refractive index, the high refractive index adhesive layer is transmitted by using the relative refractive index relationship between the high refractive index adhesive layer and the low refractive index layer (typically a low refractive index adhesive layer) directly adjacent to the high refractive index adhesive layer. The behavior of light can be effectively controlled. The preferable upper limit of the refractive index of the high refractive index adhesive layer may vary depending on the refractive index of the adjacent layer, etc., and is therefore not limited to a specific range. In some embodiments, taking into account the balance of flexibility, adhesive properties, transparency, etc., the refractive index of the high refractive index adhesive layer may be, for example, 1.700 or less, 1.670 or less, 1.650 or less, or 1.620 or less. , may be less than 1.600.

(Deformation characteristics)

In some embodiments, the high refractive index adhesive layer preferably has a refractive index of more than 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. Since the high refractive index adhesive layer has a high refractive index and satisfies the above characteristics, it can be sufficiently deformed at high speed even in a low temperature environment and can withstand large deformations. A high refractive index adhesive layer that satisfies the above characteristics preferably has a high refractive index and can withstand use in applications involving large deformation, such as foldable display applications. In addition, the high refractive index adhesive layer disclosed in the present specification includes an embodiment in which there is no limitation in the above characteristics (the amount of deformation is 350% or more in a deformation test conducted under the conditions of a temperature of -20 ° C. and a speed of 300 mm / min). , in such an aspect, the high refractive index adhesive layer is not limited to satisfying the above characteristics.

In addition, in some embodiments, the high refractive index adhesive layer preferably has a stress of 5.0 N/mm2 or less at a deformation of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. . A high refractive index adhesive layer that satisfies the above characteristics has a high refractive index and can be sufficiently deformed at high speed while maintaining a certain level of flexibility even in a low temperature environment. Therefore, it is suitable for use in applications involving large deformation. In some preferred embodiments, the stress at a strain of 350% may be 4.9 N/mm 2 or less, 4.8 N/mm 2 or less, 4.7 N/mm 2 or less, or 4.6 N/mm 2 or less, or 4.5 N/mm 2 or less, 4.4 N or less. /㎟ or less, 4.3N/㎟ or less, 4.2N/㎟ or less, 4.1N/㎟ or less, 4.0N/㎟ or less, 3.9N/㎟ or less, 3.8N/㎟ or less, 3.7N/㎟ or less, 3.6N/㎟ or less or less, 3.5N/mm2 or less, 3.4N/mm2 or less, 3.3N/mm2 or less, 3.2N/mm2 or less, 3.1N/mm2 or less, 3.0N/mm2 or less, 2.9N/mm2 or less, 2.8N/mm2 or less, It may be 2.7N/mm2 or less, 2.6N/mm2 or less, 2.5N/mm2 or less, 2.4N/mm2 or less, 2.3N/mm2 or less, or 2.2N/mm2 or less. The lower limit of the stress at the above-described strain of 350% is theoretically 0.0 N/mm 2 or more, and in some preferred embodiments, 0.1 N/mm 2 or more, 0.2 N/mm 2 or more, 0.3 N/mm 2 or more, and 0.4 N/mm 2 or more, 0.5N/mm2 or more, 0.6N/mm2 or more, 0.7N/mm2 or more, 0.8N/mm2 or more, 0.9N/mm2 or more, 1.0N/mm2 or more, 1.1N/mm2 or more, 1.2N/mm2 or more, 1.3N/mm2 or more, 1.4N/mm2 or more, 1.5N/mm2 or more, 1.6N/mm2 or more, 1.7N/mm2 or more, 1.8N/mm2 or more, 1.9N/mm2 or more, 2.0N/mm2 or more, 2.1N /mm2 or more or 2.2N/mm2 or more, 2.3N/mm2 or more, 2.4N/mm2 or more, 2.5N/mm2 or more, 2.6N/mm2 or more, 2.7N/mm2 or more, 2.8N/mm2 or more, 2.9N /mm2 or more, 3.0N/mm2 or more, 3.1N/mm2 or more, 3.2N/mm2 or more, 3.3N/mm2 or more, 3.4N/mm2 or more, 3.5N/mm2 or more, 3.6N/mm2 or more, 3.7N/mm2 or more, 3.8N/mm2 or more, 3.9N/mm2 or more, 4.0N/mm2 or more, 4.1N/mm2 or more, 4.2N/mm2 or more, 4.3N/mm2 or more, 4.4N/mm2 or more, 4.5N/mm2 or more It may be 4.6N/㎟ or more. The high refractive index adhesive layer having stress at the above-mentioned strain amount of 350% can be flexible and have appropriate cohesive force.

In some embodiments, the high refractive index adhesive layer has stress S (-20°C) at a strain of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min, and a temperature of 25°C. , it is preferable that the ratio of stress S(25°C) (S(-20°C)/S(25°C)) at a deformation amount of 350% in a deformation test conducted at a speed of 300 mm/min is 50 or less. According to a high refractive index adhesive layer that satisfies the above characteristics, stable performance can be achieved in a wide temperature range, including a low temperature range. In some preferred embodiments, the ratio (S(-20°C)/S(25°C)) is 49 or less, 48 or less, 47 or less, 46 or less, 45 or less, 44 or less, 43 or less, 42 or less, 41 or less, 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, 34 or less, 33 or less, 32 or less, or 31 or less, 30 or less, 29 or less, 28 or less, 27 or less, 26 or less, It may be 25 or less, 24 or less, 23 or less, 22 or less, 21 or less, 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, or 15 or less. The lower limit of the ratio (S(-20°C)/S(25°C)) is usually 0 or more, and in some preferred embodiments, it is 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more. 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, or 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or more. or more, 23 or more, 24 or more, 25 or more, 26 or more, 27 or more, 28 or more, 29 or more, 30 or more, or 31 or more.

The deformation test conducted under the above conditions of temperature -20°C and speed of 300 mm/min is more specifically conducted by the method described in the test example described later. The deformation test conducted under the above conditions of temperature 25°C and speed 300 mm/min was conducted in the same manner as the deformation test at -20°C except that the temperature was changed to 25°C, and the deformation test was performed at 350% deformation. The stress [N/mm2] was measured, and from the results obtained, the stress S (-20°C) at a deformation amount of 350% in the deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min, and a temperature of 25 The ratio of stress S(25°C) (S(-20°C)/S(25°C)) at a deformation amount of 350% in a deformation test conducted under conditions of ℃ and speed 300 mm/min can be obtained.

The 350% deformability of the high refractive index adhesive layer at a temperature of -20°C and a speed of 300 mm/min, and the stress and ratio (S(-20°C)/S(25°C)) at a deformation amount of 350% are based on the base polymer. Selection of the composition of the constituting monomer components, setting of the weight average molecular weight (Mw) of the base polymer, selection of plasticizer type and amount used, selection of the presence, type and amount of crosslinking agent used, selection of the use or absence of additives, type and amount used, etc. It can be adjusted by

(Storage modulus G')

Although not particularly limited, in some embodiments, the high refractive index adhesive layer has a storage modulus G' (0°C) at 0°C within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. According to the high refractive index adhesive layer, although it has a high refractive index, the range of storage elastic modulus G' (0°C) is suppressed to a low range, so it can achieve both high refractive index and flexibility. A high refractive index adhesive layer having a storage modulus G' (0°C) in the above range can achieve both high refractive index and flexibility and have flexibility that can withstand repeated bending operations. The storage modulus G' (0°C) is preferably 5.0×10 ⁵ Pa or less, may be 2.0×10 ⁵ Pa or less, may be 1.0×10 ⁵ Pa or less, may be 7.0×10 ⁴ Pa or less, and may be 5.0 It may be ×10 ⁴ Pa or less, and may be 3.0 × 10 ⁴ Pa or less. In addition, the storage modulus G' (0°C) is preferably 2.0×10 ⁴ Pa or more, more preferably 4.0×10 ⁴ Pa or more, and may be 6.0×10 ⁴ Pa or more, or 1.0×10 ⁵ Pa or more. You can continue.

The storage modulus G' (-20°C) at -20°C of the high refractive index adhesive layer disclosed herein is not particularly limited, and may be, for example, less than 1.0×10 ¹⁰ Pa or less than 1.0×10 ⁹ Pa. It is suitable to be 5.0×10 ⁸ Pa or less, may be 1.0×10 ⁸ Pa or less, may be 5.0×10 ⁷ Pa or less, may be 1.0×10 ⁷ Pa or less, may be 5.0×10 ⁶ Pa or less, or 1.0× It may be 10 ⁶ Pa or less, and may be 5.0×10 ⁵ Pa or less. A high refractive index adhesive layer with a limited storage modulus G' (-20°C) as described above can have excellent flexibility. For example, it can have good flexibility in a lower temperature range and can have flexibility to withstand repeated bending operations in a wide temperature range including the low temperature range. The lower limit of the storage modulus G' (-20°C) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, suitably 1.0×10 ³ Pa or more, preferably 1.0×10 ⁴ Pa or more, More preferably, it is 1.0×10 ⁵ Pa or more, and may be 5.0×10 ⁵ Pa or more, or may be 1.0×10 ⁶ Pa or more. The high refractive index adhesive layer having the storage elastic modulus G' (-20°C) can be flexible and have appropriate cohesive force. In addition, according to the high refractive index adhesive layer having the storage elastic modulus G' (-20°C), there is a tendency to achieve both high refractive index and flexibility even in a low temperature region.

The storage modulus G' (25°C) at 25°C of the high refractive index adhesive layer disclosed herein is appropriately set depending on the purpose of use, usage mode, etc., and is not limited to a specific range, and is determined by factors such as ease of attachment to the adherend, etc. In terms of, for example, it is suitable to be less than 1.0×10 ⁶ Pa, preferably less than 5.0×10 ⁵ Pa, more preferably less than 3.0×10 ⁵ Pa, and may be less than 1.0×10 5 Pa, or less than 5.0×10 ⁵ Pa. It may be less than 10 ⁴ Pa. The high refractive index adhesive layer with a limited storage modulus G' (25°C) as described above has good flexibility at normal use temperatures, such as a room temperature environment. The lower limit of the storage elastic modulus G' (25°C) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, from the viewpoint of processability, handling, etc., and also considering a high refractive index, and 5.0×10 It is appropriate that it is ² Pa or more, preferably 1.0×10 ³ Pa or more, more preferably 3.0×10 ³ Pa or more, and may be 5.0×10 ³ Pa or more. A high refractive index pressure-sensitive adhesive layer having the storage elastic modulus G' (25°C) is preferable because it tends to have appropriate cohesion even in a high temperature range and has excellent heat resistance.

In some embodiments, the storage elastic modulus G'(25°C) of the high refractive index adhesive layer at 25°C is preferably lower than the storage elastic modulus G'(25°C) of the low refractive index layer described later at 25°C. According to this configuration, adhesion and flexibility are imparted to the laminate of the high-refractive-index adhesive layer and the low-refractive-index layer, thereby improving the ability to follow steps or curved surfaces, etc., making it a laminated sheet (adhesive sheet) that can be suitably applied to a variety of device designs. can be realized.

(Storage modulus ratio)

In some embodiments, as the high refractive index adhesive layer, the ratio of the storage modulus G'(0°C) at 0°C to the storage modulus G'(25°C) at 25°C (G'(0°C)/G An adhesive having '(25°C)) in the range of 1 to 1000 is used. According to a high refractive index adhesive layer that satisfies the above characteristics, the change in elastic modulus is suppressed over a wide temperature range from 0°C to room temperature, so it is easy to exhibit stable characteristics (flexibility, etc.) with respect to temperature changes. The ratio (G'(0°C)/G'(25°C)) is suitably 300 or less, preferably 100 or less, more preferably 50 or less, may be 25 or less, may be 10 or less, and may be 5 or less. The following may be acceptable. The lower limit of the ratio (G'(0°C)/G'(25°C)) may be, for example, 2 or more, or 3 or more.

In some embodiments, as the high refractive index adhesive layer, the ratio of the storage modulus G'(-20°C) at -20°C to the storage modulus G'(25°C) at 25°C (G'(-20°C) )/G' (25°C)) is used. According to a high refractive index adhesive layer that satisfies the above characteristics, the change in elastic modulus is suppressed in a wide temperature range from a lower temperature range to the room temperature range, and thus stable characteristics (flexibility, etc.) can be exhibited with respect to temperature changes. The ratio (G'(-20°C)/G'(25°C)) may be 500 or less, 300 or less, 150 or less, 100 or less, 50 or less, or 30 or less. The lower limit of the ratio (G'(-20°C)/G'(25°C)) may be, for example, 5 or more, 50 or more, 100 or more, or 200 or more.

(Glass transition temperature)

The glass transition temperature (Tg) of the high refractive index adhesive layer is not particularly limited and can be set considering flexibility in a low temperature range and cohesion (heat resistance, etc.) in a high temperature range. In some embodiments, the Tg of the high refractive index adhesive layer may be, for example, 30°C or lower, 15°C or lower, or 5°C or lower. In some preferred embodiments, the Tg of the high refractive index adhesive layer is 0°C or lower from the viewpoint of flexibility, more preferably -5°C or lower, further preferably -10°C or lower, and -15°C or lower (e.g. For example, it may be -20℃ or lower). The lower the Tg of the high refractive index adhesive layer, the better the adhesive properties, such as adhesion to the adherend, tend to be excellent. Additionally, by setting the Tg of the high refractive index adhesive layer low, the change in elastic modulus in a temperature range higher than Tg can be suppressed. The lower limit of Tg of the high refractive index adhesive layer is, for example, -50°C or higher, preferably -40°C or higher, -30°C or higher, or -25°C or higher. According to the high refractive index adhesive layer having the above Tg, appropriate cohesion tends to be easily obtained. In addition, there is a tendency to easily form an adhesive that combines high refractive index and large-diameter properties.

The storage modulus G' of the adhesive layer at each of the above temperatures and the glass transition temperature of the adhesive layer can be measured by the dynamic viscoelasticity measurement method described in the test examples described later, and each storage modulus ratio can be calculated from the results. . Each storage elastic modulus G', each storage elastic modulus ratio, and glass transition temperature of the adhesive layer (for example, a high refractive index adhesive layer) are determined by, for example, selection of the composition of the monomer component constituting the base polymer, setting of Mw of the base polymer, It can be adjusted by selection of plasticizer type or amount used, selection of crosslinking agent, type and amount used, use of additives, type and amount used, etc.

(Change in elastic modulus after maintaining 130℃ for 1 hour)

Although not particularly limited, in some embodiments, the storage modulus G'1 at -20°C after the adhesive is held in an environment at 130°C for 1 hour, and the storage modulus at -20°C before being held in an environment at 130°C for 1 hour. It is preferable to use an adhesive having a storage elastic modulus G'0 ratio (G'1/G'0) of 50 or less (specifically, 1 to 50) as the high refractive index adhesive layer. A high refractive index adhesive layer that satisfies this characteristic has the change in elastic modulus limited to a predetermined range even when exposed to high temperatures, and can exhibit stable characteristics. The ratio (G'1/G'0) is preferably 30 or less, more preferably 10 or less, and still more preferably 3 or less, and may be 2 or less, and may be less than 1.5.

The change in elastic modulus after holding at 130°C for 1 hour is measured by the following method. That is, the adhesive composition is applied to the silicone-treated side of PET film R1, one side of which has been silicone-treated, and heated at 130°C for 3 minutes to form an adhesive layer with a thickness of 20 μm. Next, the silicone-treated side of PET film R2, one side of which was silicone-treated, is bonded to the surface of the adhesive layer. One release liner is peeled from the adhesive layer (release liner/adhesive layer/release liner) provided with the obtained release liner, and kept in an oven at 130°C for 1 hour. As an oven, one that has sufficient capacity for the measurement sample and can be heated while exhausting the sample is used. For example, an oven made by espec can be used. The adhesive (layers) maintained at 130°C for 1 hour are laminated to a thickness of about 1.5 mm, and then autoclaved (0.5 MPa, 50°C, 15 minutes) to bring each layer into close contact. For the sample for measurement obtained in this way, the storage elastic modulus G'(G'1) [Pa Find ]. And, the ratio (G'1/G'0) of the obtained storage elastic modulus G'1 [Pa] and the storage elastic modulus G'0 [Pa] at -20°C before being held for 1 hour in an environment of 130°C measured in advance. Find .

(total light transmittance)

In some embodiments, the total light transmittance of the high refractive index adhesive layer is preferably 85.0% or more (for example, 86.0% or more, 88.0% or more, 90.0% or more, or more than 90.0%). The upper limit of the total light transmittance is theoretically 100% minus the light loss (Fresnel loss) due to reflection occurring at the air interface, and in practice, for example, it may be approximately 98% or less, and approximately 96%. It may be less than or equal to about 95%. In some embodiments, taking the refractive index and adhesive properties into consideration, the total light transmittance of the high refractive index adhesive layer may be approximately 94% or less, approximately 93% or less, or approximately 92% or less. These total light transmittances for the high refractive index adhesive layer can also be suitably applied to the total light transmittance of a laminated sheet consisting of the high refractive index adhesive layer and the low refractive index layer (typically a low refractive index adhesive layer) described later.

The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used. The total light transmittance can be measured according to the method described in the test example described later. The total light transmittance of the high refractive index adhesive layer can be adjusted, for example, by selecting the composition or thickness of the adhesive layer. In addition, the total light transmittance may be referred to as the initial total light transmittance for the purpose of distinguishing it from the total light transmittance after the bending test described later.

In addition, in some embodiments, the high refractive index adhesive layer is a bending test obtained by repeating 10 times a bending test in which each side of the sheet-like adhesive is bent in a U shape with a radius of 2 mm at 25°C. It is preferable that the negative total light transmittance (total light transmittance after the bending test) is maintained at 85% or more of the total light transmittance before the bending test. A high refractive index adhesive layer that satisfies the above characteristics has little change in optical properties (for example, whitening) even when repeatedly bent, and is therefore suitable for optical applications that require bending, such as foldable display applications. The total light transmittance after the bending test is more preferably 90% or more of the total light transmittance before the bending test, further preferably 95% or more, and particularly preferably 98% or more (for example, 99% or more). The total light transmittance after the bending test is determined by selection of the composition of the monomer component constituting the base polymer, setting of the weight average molecular weight (Mw) of the base polymer, selection of plasticizer species and amount used, selection of the presence, type and amount of crosslinking agent used, It can be adjusted by selecting the presence, type, and amount of additives used.

More specifically, the total light transmittance before and after the bending test is measured by the following method. That is, the adhesive layer is cut into a rectangle of 2 cm x 10 cm to obtain a test piece for measurement. A 4 mm cylindrical bar is fixed horizontally at a height sufficient for measurement, the test piece obtained above is hung on the bar, one side is bent into a U shape with a radius of 2 mm, and held for 1 minute. Specifically, the above-described test piece is hung at the center portion in the longitudinal direction on a bar to form an inverted U shape. Then, both ends located below the test piece are fixed with clips (13g), a weight of 60g is hung and fixed to the clip through a 1 cm long thread, and a load is applied to the bent portion of the test piece. In this state, the test piece is held in a predetermined temperature environment (25°C) for 1 minute, and after 1 minute, the test piece is removed from the bar. Next, under the same temperature environment, the other side of the test piece (the side opposite to the one side) is bent into a U-shape with a radius of 2 mm on the opposite side of the bend of the one side, in the same manner as the one side. Hold for 1 minute. After repeating the bending test using this as one set 10 times on the bent portion of the same test piece, the total light transmittance [%] after bending was measured for the bent portion by the same method as the measurement method for the initial total light transmittance. Measure.

(Haze value)

In some embodiments, the haze value of the high refractive index adhesive layer may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, and 0.9% or less. It may be less than 0.8%, less than 0.5%, or less than 0.3%. Such highly transparent adhesives are advantageous in applications that require high light transparency (for example, optical applications) or applications that require good visibility of the adherend through the adhesive. The lower limit of the haze value of the high refractive index adhesive layer is not particularly limited, and from the viewpoint of improving transparency, a smaller haze value is more preferable. On the other hand, in some embodiments, taking the refractive index and adhesive properties into consideration, the haze value of the high refractive index adhesive layer may be, for example, 0.05% or more, or 0.10% or more. These haze values for the high refractive index adhesive layer can also be suitably applied to the haze value of a laminated sheet consisting of the high refractive index adhesive layer and the low refractive index layer (typically a low refractive index adhesive layer) described later.

Here, “haze value” refers to the ratio of diffuse transmitted light to the total transmitted light when visible light is irradiated to the measurement object. Also called cloudiness. The haze value can be expressed by the following equation.

Th(%)=Td/Tt×100

In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total light transmittance. Haze value can be measured according to the method described in the test example described later. The haze value of the adhesive layer can be adjusted, for example, by selecting the composition or thickness of the adhesive layer.

(Surface smoothness of adhesive surface)

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

For example, it is preferable that the arithmetic mean roughness Ra of the adhesive surface is limited to a predetermined value or less. A configuration including an adhesive surface designed to lower the arithmetic mean roughness Ra is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic mean illuminance Ra, for example, in a usage mode in which light is extracted through the adhesive surface (adhesive sheet disposed on the viewpoint side rather than the self-luminous element in a light-emitting device, etc.), this is due to the surface condition of the adhesive layer. It can exert the effect of suppressing the occurrence of luminance unevenness. The low arithmetic mean roughness Ra of the adhesive surface is advantageous for suppressing optical distortion, and suppressing optical distortion also contributes to improving optical homogeneity. When the laminated sheet (adhesive sheet) disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface (for example, in the form of a laminated sheet consisting of a high refractive index adhesive layer and a low refractive index adhesive layer) It is preferable that at least the arithmetic mean roughness Ra of the first adhesive surface is limited to a predetermined value or less, and it is more preferable that the arithmetic average roughness Ra of both adhesive surfaces are limited to a predetermined value or less. When each adhesive surface of the double-sided adhesive sheet has high surface smoothness, adhesion with excellent optical homogeneity can be preferably achieved.

In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is preferably approximately 70 nm or less, more preferably approximately 65 nm or less, further preferably approximately 55 nm or less, and may be less than 50 nm. , may be less than 45 nm, or may be less than 40 nm. From the viewpoint of production efficiency, etc., in some embodiments, the arithmetic mean roughness Ra of the adhesive surface may be, for example, approximately 10 nm or more, may be approximately 20 nm or more, or may be approximately 30 nm or more (e.g., approximately 40 nm or more) ㎚ or more) may be sufficient. In an embodiment in which the laminated sheet has a first adhesive surface and a second adhesive surface, the arithmetic mean roughness Ra of the first adhesive surface and the arithmetic mean roughness Ra of the second adhesive surface may be the same or different.

In addition, for example, it is preferable that the maximum height Rz of the adhesive surface is limited to a predetermined value or less. A configuration including an adhesive surface designed to have a lower maximum height Rz is preferable from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example, in a usage mode in which light is extracted through the adhesive surface as described above, the effect of suppressing the occurrence of luminance unevenness due to the surface condition of the adhesive layer can be exerted. A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion. When the laminated sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that the maximum height Rz of at least the first adhesive surface is limited to a predetermined value or less, and both adhesive surfaces are It is more preferable that the maximum height Rz of the surface is all limited to a predetermined value or less. When each adhesive surface of the double-sided adhesive sheet has 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 approximately 600 nm or less, more preferably approximately 500 nm or less, further preferably approximately 450 nm or less, and particularly preferably approximately 400 nm or less. It may be less than nm, less than 350 nm, less than 300 nm, or less than 250 nm. From the viewpoint of production efficiency, etc., in some embodiments, the maximum height Rz of the adhesive surface may be, for example, approximately 10 nm or more, approximately 50 nm or more, approximately 100 nm or more, or approximately 200 nm or more. You can continue. In an embodiment having a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be about the same or different.

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

That is, in an environment of 23°C and 50%RH, the surface shape of the sample for measurement is measured using a three-dimensional optical profiler (brand name “NewView7300”, manufactured by ZYGO) under the following conditions. From the measured data, the arithmetic surface roughness Ra is calculated according to JIS B 0601-2001. The maximum height Rz is obtained as the sum of the height Rp of the highest peak above the average line of the roughness curve and the depth Rv of the deepest valley below the average line with respect to the data (illuminance curve) obtained by the above measurement. Measurements are performed 5 times (i.e. N=5), and the average value is used.

The sample for measurement can be prepared, for example, by cutting the adhesive layer to be measured or an adhesive sheet containing the adhesive layer into a size of about 150 mm in length and 50 mm in width. When the adhesive surface is protected with a release liner, the release liner is peeled off slowly (for example, under conditions of a tensile speed of 300 mm/min and a peel angle of 180°) to expose the adhesive surface. It is preferable to measure after exposing the adhesive surface and allowing it to stand for about 30 minutes.

[Measuring conditions]

Measurement area: 5.62㎜×4.22㎜

(Objective lens: 2.5x, internal lens: 0.5x)

Interpretation mode:

Remove: Cylinder

Data Fill: ON (Max: 25)

Remove Spikes: ON (xRMS: 1)

Filter: OFF

The arithmetic mean roughness Ra and maximum height Rz of the adhesive surface are determined by the composition and properties (viscosity, leveling properties, etc.) of the adhesive composition used to form the adhesive layer, and the properties of the surface (release surface) of the release liner that protects the adhesive surface. can be adjusted by

(base polymer)

In the technology disclosed herein, the type of adhesive constituting the high refractive index adhesive layer is not particularly limited. The adhesives include acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, and polyamide polymers that can be used in the field of adhesives. , may contain one or two or more types of various rubber-like polymers such as fluorine-based polymers as an adhesive polymer (hereinafter also referred to as a “base polymer” in the sense of a structural polymer that forms an adhesive). From the viewpoint of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably used. Among them, an adhesive containing an acrylic polymer as a base polymer (acrylic adhesive) is preferable. The technology disclosed herein is preferably implemented using an acrylic adhesive.

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

In addition, in this specification, the “base polymer” of the adhesive refers to the main component of the rubber-like polymer contained in the adhesive, and other than this, it is not interpreted in any limited way. The rubber-like polymer refers to a polymer that exhibits rubbery elasticity in a temperature range around room temperature. In addition, in this specification, the “main component” refers to a component contained in excess of 50% by weight, unless otherwise specified.

In addition, in this specification, “acrylic polymer” refers to a polymer containing a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an “acrylic monomer.” Therefore, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of an acrylic polymer is a polymer in which the proportion of acrylic monomers out of all monomers used in the synthesis of the acrylic polymer is more than 50% by weight (preferably more than 70% by weight, for example, more than 90% by weight). .

In addition, in this specification, “(meth)acryloyl” refers comprehensively to acryloyl and methacryloyl. Likewise, “(meth)acrylate” refers comprehensively to acrylate and methacrylate, and “(meth)acrylic” refers to acrylic and methacrylic, respectively. Therefore, the concept of acrylic monomer as used herein may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

(Acrylic polymer)

As the high refractive index adhesive layer disclosed herein, an acrylic adhesive layer (high refractive index acrylic adhesive layer) can be preferably employed. The acrylic polymer, which is the base polymer of the acrylic adhesive, preferably contains an aromatic ring-containing monomer (A1) as a monomer component constituting the acrylic polymer. That is, an acrylic polymer containing an aromatic ring-containing monomer (A1) as a monomer unit is preferable. Here, in this specification, the “monomer component constituting the acrylic polymer” refers to whether it is included in the adhesive composition in the form of a pre-formed polymer (which may be an oligomer) or in the form of an unpolymerized monomer. , refers to a monomer that constitutes a repeating unit of an acrylic polymer in an adhesive formed from the adhesive composition. That is, the monomer component constituting the acrylic polymer may be contained in the pressure-sensitive adhesive composition in any of the forms of a polymerized product, unpolymerized product, or partially polymerized product. From the viewpoint of ease of preparation of the adhesive composition, etc., in some embodiments, the adhesive composition contains substantially all of the monomer components (for example, 95% by weight or more, preferably 99% by weight or more) in the form of a polymer. desirable.

(Monomer (A1))

As the monomer (A1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule is used. As the monomer (A1), one type of such compound can be used individually or in combination of two or more types.

Examples of the ethylenically unsaturated group include (meth)acryloyl group, vinyl group, and (meth)allyl group. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryloyl group is more preferable from the viewpoint of flexibility and adhesiveness. From the viewpoint of suppressing a decrease in the flexibility of the high refractive index adhesive layer, a compound (i.e., a monofunctional monomer) having 1 ethylenically unsaturated group per molecule is preferably used as the monomer (A1).

The number of aromatic rings contained in one molecule of the compound used as the monomer (A1) may be 1 or 2 or more. The upper limit of the number of aromatic rings is not particularly limited, and may be, for example, 16 or less. In some embodiments, from the viewpoint of ease of preparation of the acrylic polymer, transparency of the adhesive, etc., the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, and 5 or less. It may be 2 or less, it may be 4 or less, it may be 3 or less, and it may be 2 or less.

The aromatic ring possessed by the compound used as the monomer (A1) includes a benzene ring (may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); Condensed rings of naphthalene ring, indene ring, azulene ring, anthracene ring, and phenanthrene ring; It may be a carbon ring such as pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, thiophene ring. ; It may be a heterocycle (heterocycle) such as: In the above heterocycle, the heteroatoms included as ring constituent atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur. The monomer (A1) may have a structure in which 1 or 2 or more carbocyclic rings and 1 or 2 or more heterocycles are condensed, such as a dinaphthothiophene structure.

The aromatic ring (preferably a carbocyclic ring) may have one or two or more substituents on the ring constituent atoms, and does not need to have any substituent. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In a substituent containing a carbon atom, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the aromatic ring is an aromatic ring that has no substituents on ring constituent atoms or has one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). You can. In addition, that the aromatic ring of the monomer (A1) has a substituent on its ring constituent atoms means that the aromatic ring has a substituent other than the substituent having an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be directly bonded or may be bonded through a linking group. The linking group is, for example, an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, and a group in which one or two or more hydrogen atoms in these groups are substituted with hydroxyl groups (e.g. , hydroxyalkylene group), oxy group (-O- group), thioxy group (-S- group), etc. may be a group containing one or two or more structures selected from the group. In some embodiments, an aromatic ring is contained in a structure in which an aromatic ring and an ethylenically unsaturated group are bonded directly or bonded through a linking group selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly(oxyalkylene) group. A monomer can be preferably employed. 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, for example, 1 or 2. The repeating number of the oxyalkylene unit in the poly(oxyalkylene) group may be, for example, 2 to 3.

Examples of compounds that can be preferably employed as the monomer (A1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylate and aromatic ring-containing vinyl compound can be used individually or in combination of two or more types. You may use a combination of 1 type or 2 or more types of aromatic ring-containing (meth)acrylates and 1 type or 2 or more types of aromatic ring-containing vinyl compounds.

In some preferred embodiments, a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule is used as the monomer (A1) because it is easy to obtain a high refractive index effect. Examples of monomers having two or more aromatic rings in one molecule (monomers containing multiple aromatic rings) include monomers having a structure in which two or more non-fused aromatic rings are bonded through a linking group, and two or more non-fused aromatic rings are formed directly (i.e., without passing through other atoms). ) Monomers having a chemically bonded structure, monomers having a condensed aromatic ring structure, monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc. Among them, a monomer having a structure in which two or more non-fused aromatic rings are bonded through a linking group (for example, phenoxybenzyl (meth)acrylate described later) is preferably used. The monomer containing multiple aromatic rings can be used individually or in combination of two or more types.

The linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (for example -O-(CH ₂ ) _n -group, where n is 1 to 3, Preferably 1), a thiooxyalkylene group (e.g. -S-(CH ₂ ) _n -group, where n is 1 to 3, preferably 1), a straight chain alkylene group (e.g. -(CH ₂ ) _n -group, where n is 1 to 6, preferably 1 to 3), the alkylene group in the oxyalkylene group, the thiooxyalkylene group and the straight chain alkylene group may be a partially halogenated or fully halogenated group, etc. . From the viewpoint of flexibility of the high refractive index adhesive layer, etc., suitable examples of the linking group include an oxy group, a thioxy group, an oxyalkylene group, and a straight chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded through a linking group include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl ( Meth)acrylate, benzylbenzyl (meth)acrylate, etc. are mentioned.

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

Examples of the monomer having the condensed aromatic ring structure include (meth)acrylate containing a naphthalene ring, (meth)acrylate containing an anthracene ring, naphthalene containing a vinyl group, and anthracene containing a vinyl group. Specific examples include 1-naphthylmethyl (meth)acrylate (alias: 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2- Naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, etc. are mentioned.

Specific examples of monomers having the above fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluor Orene (meth)acrylate, etc. can be mentioned. In addition, since the monomer having a fluorene structure includes a structural portion in which two benzene rings are directly chemically bonded, it is included in the concept of a monomer having a structure in which two or more non-fused aromatic rings are directly chemically bonded.

Examples of monomers having the dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. As a specific example, (meth)acryloyloxymethyldinaphthothiophene (for example, a compound having a structure in which CH ₂ CH(R ¹ )C(O)OCH ₂ - is bonded to the 5th or 6th position of the dinaphthothiophene ring Here, R ¹ is a hydrogen atom or a methyl group), (meth)acryloyloxyethyldinaphthothiophene (for example, at the 5th or 6th position of the dinaphthothiophene ring, CH ₂ CH(R ¹ )C (O)OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - A compound having a structure where R ¹ is a hydrogen atom or a methyl group), vinyldinaphthothiophene ( For example, compounds having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, etc. In addition, the monomer having a dinaphthothiophene structure is included in the concept of the monomer having the above condensed aromatic ring structure by including a naphthalene structure and having a structure in which a thiophene ring and two naphthalene structures are condensed.

Examples of the monomer having the dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene, vinyl group-containing dibenzothiophene, and the like. In addition, a monomer having a dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings are condensed, and is therefore included in the concept of a monomer having the above-mentioned condensed aromatic ring structure.

In addition, neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly chemically bonded.

In some preferred embodiments, a monomer having one aromatic ring (preferably a carbocyclic ring) per molecule is used as the monomer (A1). A monomer having one aromatic ring per molecule (monomer containing a single aromatic ring) can be helpful, for example, in improving the flexibility of a high refractive index adhesive layer, adjusting adhesive properties, and improving transparency. Single aromatic ring-containing monomers can be used individually or in combination of two or more types. In some embodiments, a monomer having one aromatic ring per molecule may be used in combination with a monomer containing multiple aromatic rings from the viewpoint of improving the refractive index of the high refractive index adhesive layer.

Examples of monomers having one aromatic ring per molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, and phenoxypropyl (meth)acrylate. ) Acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, chlorobenzyl (meth)acrylate, etc., carbon aromatic rings containing (meth)acrylates; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl(meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl(meth)acrylate , 6-(4,6-dibromo-2-s-butylphenoxy)hexyl(meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl(meth)acrylate bromine-substituted aromatic ring-containing (meth)acrylates such as late, 2,6-dibromo-4-nonylphenylacrylate, and 2,6-dibromo-4-dodecylphenylacrylate; Vinyl compounds containing aromatic carbon rings, such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; Compounds having a vinyl substituent on the heteroaromatic ring, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; etc. can be mentioned.

As the monomer (A1), a monomer having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in the various aromatic ring-containing monomers described above may be used. In this way, the monomer in which the oxyethylene chain is sandwiched between the ethylenically unsaturated group and the aromatic ring can be understood as an ethoxylated product of the original monomer. The repeating number of the oxyethylene unit (-CH ₂ CH ₂ O-) in the oxyethylene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, for example It is 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, and phenoxyethyl (meth)acrylate. , phenoxydiethylene glycol di(meth)acrylate, etc.

The content of the monomer containing multiple aromatic rings in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, and 40% by weight or more. In some embodiments, the content of the monomer containing multiple aromatic rings in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of making it easier to obtain a higher refractive index, It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a monomer containing multiple aromatic rings. That is, as the monomer (A1), only one or two or more types of aromatic ring-containing monomers may be used. In addition, in some other embodiments, for example, considering the balance between high refractive index and large-diameter formation, the content of the aromatic ring-containing monomer in the monomer (A1) may be less than 100% by weight, and may be 98% by weight. It may be less than 90% by weight, less than 80% by weight, less than 70% by weight, less than 65% by weight, less than 50% by weight, less than 25% by weight, or less than 10% by weight. It's okay. The technology disclosed here can also be implemented in an embodiment in which the content of the monomer containing multiple aromatic rings in the monomer (A1) is less than 5% by weight. It is not necessary to use a monomer containing multiple aromatic rings.

The content of the monomer containing multiple aromatic rings in the monomer component constituting the acrylic polymer is not particularly limited, and can be set so as to realize a high refractive index adhesive layer that achieves both the desired refractive index and large-diameter formation. The content of the monomer containing multiple 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, from the viewpoint of making it easier to realize a high refractive index adhesive layer with a higher refractive index, the content of the aromatic ring plurality-containing monomer in the monomer component may be, for example, more than 35% by weight, and may be 50% by weight. It is advantageous to be more than 70% by weight, preferably more than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, 91% by weight or more, 92% by weight or more, 93% by weight or more. It may be % or more, 94% by weight or more, 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of the aromatic ring-containing monomer in the monomer component is advantageously set to approximately 99% by weight or less, and may be 98% by weight or less, or 96% by weight or less, in consideration of the balance between high refractive index and large-diameter formation. , 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 several other embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (for example, transparency), the content of the aromatic ring-containing monomer in the monomer component is 70% by weight or less. It may be 60% by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, and 5% by weight or less. The technology disclosed here can also be implemented in an embodiment in which the content of the monomer containing multiple aromatic rings in the monomer component is less than 3% by weight.

The content of the monomer containing a single aromatic ring in the monomer (A1) 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 single aromatic ring in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of making it easier to obtain a higher refractive index, It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a monomer containing a single aromatic ring. That is, as the monomer (A1), only one or two or more types of monomers containing single aromatic rings may be used. Additionally, in some embodiments, for example, considering the balance between high refractive index and large-diameter formation, the content of the aromatic ring single-containing monomer in monomer (A1) may be less than 100% by weight, and may be 98% by weight or less. It may be 90% by weight or less, 80% by weight or less, 70% by weight or less, 65% by weight or less, 50% by weight or less, 25% by weight or less, and 10% by weight or less. do. The technology disclosed here can also be carried out in an embodiment in which the content of the monomer containing a single aromatic ring in the monomer (A1) is less than 5% by weight. It is not necessary to use a monomer containing a single aromatic ring.

The content of the monomer containing a single aromatic ring in the monomer component constituting the acrylic polymer is not particularly limited and can be set so as to realize a high refractive index adhesive layer that achieves both the desired refractive index and large-diameter formation. The content of the aromatic ring single-containing monomer 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, from the viewpoint of making it easier to realize a high refractive index adhesive layer with a higher refractive index, the content of the aromatic ring single-containing monomer in the monomer component may be, for example, more than 35% by weight, and may be 50% by weight. It is advantageous that it is more than 60% by weight, more preferably more than 70% by weight, and may be 75% by weight or more, 85% by weight or more, 90% by weight or more, and 95% by weight. It may be more than 98% by weight or more. The content of the aromatic ring single-containing monomer in the monomer component may be approximately 99% by weight or less, preferably 98% by weight or less, and 96% by weight or less, considering the balance between high refractive index and large-diameter formation. It is more preferable, and may be 93 weight% or less, 90 weight% or less, 85 weight% or less, 80 weight% or less, and 75 weight% or less. In some embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (e.g. transparency), the content of the aromatic ring single-containing monomer in the monomer component may be 70% by weight or less. It may be 60% by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, and 5% by weight or less. The technique disclosed herein can also be carried out in an embodiment in which the content of the monomer containing a single aromatic ring in the monomer component is less than 3% by weight.

In some preferred embodiments, a high refractive index monomer can be preferably employed as at least part of the monomer (A1). Here, “high refractive index monomer” refers to a monomer whose refractive index is, for example, approximately 1.510 or higher, preferably approximately 1.530 or higher, and more preferably approximately 1.550 or higher. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but from the viewpoint of ease of preparation of acrylic polymer and compatibility with flexibility suitable as an adhesive, it may be, for example, 3.000 or less, 2.500 or less, or 2.000 or less. It may be less than 1.900, less than 1.800, or less than 1.700. High refractive index monomers can be used individually or in combination of two or more types.

In addition, the refractive index of the monomer is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As an Abbe refractometer, model “DR-M4” manufactured by ATAGO or its equivalent can be used. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

As the high refractive index monomer, those having the corresponding refractive index can be appropriately adopted from among the compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed herein (for example, the compounds and compound groups exemplified above). there is. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o- Phenylphenol acrylate (number of repetitions of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6°C), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35℃), 6-acryloyloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75) , 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene Examples include, but are not limited to, ophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), and 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793). does not

The content of the high refractive index monomer (i.e., an aromatic ring-containing monomer with a refractive index of approximately 1.510 or more, preferably approximately 1.530 or more, more preferably approximately 1.550 or more) in the monomer (A1) is not particularly limited, and is, for example, For example, it may be 5% by weight or more, 25% by weight or more, 35% by weight or more, and 40% by weight or more. In some embodiments, from the viewpoint of making it easier to obtain a higher refractive index, the content of the high refractive index monomer in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more, 85 It may be % by weight or more, may be 90 % by weight or more, and may be 95 % by weight or more. Substantially 100% by weight of the monomer (A1) may be a high refractive index monomer. In addition, in some embodiments, for example, from the viewpoint of achieving both high refractive index and large-diameter formation in a good balance, the content of the high refractive index monomer in monomer (A1) may be less than 100% by weight, and may be 98% by weight or less. It may be 90% by weight or less, 80% by weight or less, or 65% by weight or less. In several other embodiments, taking adhesion properties and/or optical properties into consideration, the content of the high refractive index monomer in monomer (A1) may be 50% by weight or less, 25% by weight or less, or 15% by weight. It may be less than or equal to 10% by weight. The technology disclosed here can also be carried out in an embodiment where the content of the high refractive index monomer in the monomer (A1) is less than 5% by weight. There is no need to use a high refractive index monomer.

The content of the high refractive index monomer in the monomer component constituting the acrylic polymer is not particularly limited and can be set so as to realize a high refractive index adhesive layer that achieves both the desired refractive index and large-diameter formation. Additionally, if necessary, it can be set taking into account compatibility with adhesive properties (e.g., adhesive force, 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% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer component constituting the acrylic polymer may be, for example, more than 35% by weight, and from the viewpoint of making it easier to obtain a higher refractive index, it is advantageous to be more than 50% by weight. It is preferably more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The content of the high refractive index monomer in the monomer component is advantageously set to 99% by weight or less, preferably 98% by weight or less, and 96% by weight or less from the viewpoint of achieving both high refractive index and large-diameter formation in a good balance. It is more preferable to set it as 93 weight% or less, 90 weight% or less, 85 weight% or less, 80 weight% or less, and 75 weight% or less. In several other embodiments, taking adhesion properties and/or optical properties into consideration, the content of the high refractive index monomer in the monomer component may be 70% by weight or less, 50% by weight or less, and 25% by weight or less. It may be 15% by weight or less, and may be 5% by weight or less. The technique disclosed herein can also be carried out in an embodiment in which the content of the high refractive index monomer in the monomer component is less than 3% by weight.

In some preferred embodiments, at least part of the monomer (A1) is an aromatic ring-containing monomer (hereinafter sometimes referred to as “monomer L”) having a homopolymer Tg of 10°C or lower. Increase the content of the aromatic ring-containing monomer (A1) (in particular, the aromatic ring-containing monomer (A1) corresponding to at least one of the above-mentioned multiple aromatic ring-containing monomers, single aromatic ring-containing monomers, and high refractive index monomers) in the monomer component. Since the flexibility of the bottom adhesive generally tends to decrease, the decrease in flexibility can be suppressed by employing monomer L as part or all of the monomer (A1). Thereby, the refractive index can be improved while better maintaining the large-scale formation. The Tg of monomer L may be, for example, 5°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, and -25°C or lower. The lower limit of Tg of monomer L is not particularly limited. Considering the balance with the refractive index improvement effect, in some embodiments, the Tg of monomer L may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. In several other embodiments, the Tg of monomer L may be, for example, -30°C or higher, -10°C or higher, 0°C or higher, or 3°C or higher. Monomer L can be used individually or in combination of two or more types.

As the monomer L, one having the corresponding Tg can be appropriately adopted from among the compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed herein (for example, the compounds and compound groups exemplified above). Suitable examples of aromatic ring-containing monomers that can be used as monomer L include m-phenoxybenzyl acrylate (homopolymer Tg: -35°C), benzyl acrylate (homopolymer Tg: 6°C), and phenoxyethyl acrylate. Rate (Tg of homopolymer: 2°C) and phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C).

The content of monomer L in the monomer (A1) 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, from the viewpoint of making it easier to obtain a high refractive index adhesive layer that achieves both high refractive index and flat form at a higher level, the content of monomer L in the monomer (A1) may be, for example, 50% by weight or more. From the viewpoint of improving stool formation, it is preferable to be 60% by weight or more, may be 70% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. . Substantially 100% by weight of monomer (A1) may be monomer L. In addition, in some other embodiments, for example, from the viewpoint of achieving both high refractive index and large-diameter formation in a good balance, the content of monomer L in monomer (A1) may be less than 100% by weight, and may be 98% by weight or less. It may be 90% by weight or less, 80% by weight or less, or 65% by weight or less.

The content of monomer L in the monomer component constituting the acrylic polymer may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of making it easier to obtain a high refractive index adhesive layer that achieves both high refractive index and flat form at a higher level, the content of monomer L in the monomer component may be, for example, more than 35% by weight, From the viewpoint of improving the refractive index, it is advantageous to exceed 50% by weight, preferably to exceed 70% by weight, and may be 75% by weight or more, 85% by weight or more, 90% by weight or more, and 95% by weight or more. . The content of monomer L in the monomer component is advantageously set to approximately 99% by weight or less, preferably 98% by weight or less, and preferably 96% by weight or less from the viewpoint of achieving both high refractive index and large-diameter formation in a good balance. It is more preferable to set it as 93 weight% or less, 90 weight% or less, 85 weight% or less, 80 weight% or less, and 75 weight% or less.

In some embodiments, as the aromatic ring-containing monomer (A1), monomer L (i.e., aromatic ring-containing monomer with a homopolymer Tg of 10°C or lower) and monomer H with a Tg higher than 10°C may be used in combination. . The Tg of monomer H may be, for example, greater than 10°C, greater than 15°C, or greater than 20°C. By using monomer L and monomer H in combination, in a high refractive index adhesive layer containing a large content of aromatic ring-containing monomer (A1) in the monomer component, the high refractive index adhesive layer is increased in refractive index and adheres to the adherend. Flexibility suitable for this can be achieved at a higher level. The usage ratio of monomer L and monomer H can be set to appropriately produce these effects, and is not particularly limited.

In some embodiments, the aromatic ring-containing monomer (A1) can be preferably selected from compounds that do not contain a structure in which two or more non-fused aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, it is composed of a monomer component with a composition in which the content of a compound containing a structure in which two or more non-fused 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). Acrylic polymers are preferred. In this way, limiting the amount of use of a compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded can be advantageous from the viewpoint of realizing a high refractive index adhesive layer that achieves both high refractive index and large-diameter formation in a better balance.

The content of monomer (A1) in the monomer component constituting the acrylic polymer is not particularly limited, and includes the desired refractive index and large polarity, as well as adhesive properties (e.g., adhesive force, etc.) and/or optical properties (e.g., full-light It can be set to realize a high refractive index adhesive layer that achieves both transmittance, haze value, etc.). In some embodiments, the content of monomer (A1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. , may be 70% by weight or more. In some preferred embodiments, the content of monomer (A1) in the monomer component constituting the acrylic polymer may be, for example, more than 70% by weight, and is preferably 75% by weight or more, so that a higher refractive index can be easily obtained. From this point of view, it is preferable that it is 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, 91% by weight or more, 92% by weight or more, 93% by weight or more, 94% by weight or more, 95% by weight or more, It may be 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of monomer (A1) in the monomer component is typically less than 100% by weight, and from the viewpoint of achieving both high refractive index and large-diameter formation in a good balance, it is advantageous to be approximately 99% by weight or less, and may be 98% by weight or less. It may be 96% by weight or less, 93% by weight or less, or 90% by weight or less. In some embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (e.g. transparency), the content of monomer (A1) in the monomer component may be less than 90% by weight. , may be less than 85% by weight, or may be less than 80% by weight.

(Monomer (A2))

In some preferred embodiments, the monomer component constituting the acrylic polymer may further contain a monomer (A2) in addition to the monomer (A1). The monomer (A2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxylic group-containing monomer). The hydroxyl group-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The carboxyl group-containing monomer is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer (A2) can be helpful for introducing crosslinking points into the acrylic polymer or providing appropriate cohesiveness to the high refractive index adhesive layer. Monomer (A2) can be used individually or in combination of two or more types. The monomer (A2) may contain an aromatic ring or may not contain an aromatic ring. As the monomer (A2), a monomer containing no aromatic ring is preferably used. In addition, the monomer (A2) is defined as a monomer different from the monomer (A1) described above. For example, the monomer (A1) described above may be defined as a monomer that does not have a hydroxyl group or a carboxyl group.

Examples of the ethylenically unsaturated group contained in the monomer (A2) include (meth)acryloyl group, vinyl group, and (meth)allyl group. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryloyl group is more preferable from the viewpoint of improved flexibility and adhesiveness. From the viewpoint of improving the flexibility of the high refractive index adhesive layer, a compound (i.e., a monofunctional monomer) having 1 ethylenically unsaturated group per molecule is preferably used as the monomer (A2).

In some embodiments, as the monomer (A2), a monomer having a relatively long distance between an ethylenically unsaturated group (for example, a (meth)acryloyl group) and a hydroxyl group and/or a carboxyl group can be used. As a result, in the embodiment in which the hydroxyl group and/or carboxyl group is used in the crosslinking reaction, a highly flexible crosslinked structure can be easily obtained. For example, the number of atoms (typically carbon atoms or oxygen atoms) constituting the chain (connected chain) connecting the ethylenically unsaturated group and the hydroxyl group and/or carboxyl group is 3 or more (for example, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, or 19 or more) as monomer (A2). You can use it. The upper limit of the number of atoms in the linking chain is, for example, 45 or less, and 20 or less (e.g., 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, It may be 10 or less, 9 or less, or 8 or less). In addition, the number of atoms forming the connecting chain connecting the ethylenically unsaturated group and the hydroxyl group and/or the carboxyl group refers to the minimum number of atoms required to reach the hydroxyl group or the carboxyl group from the ethylenically unsaturated group. For example, when the linking chain consists of a straight chain alkylene group (i.e. -(CH ₂ ) _n -group), the number of n becomes the number of atoms constituting the linking chain. Also, for example, when the linking chain is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of 3 and n, which is the sum of the number of carbon atoms 2 and the number of oxygen atoms 1 constituting the oxyethylene group, is (3n) is the number of atoms constituting the linking chain. Although not particularly limited, such monomer (A2) includes, for example, an alkylene unit represented by -(CH ₂ ) _n - or -( C _m H _2m O) - An oxyalkylene unit (e.g., an oxyethylene unit where m is 2 in the above formula, an oxypropylene unit where m is 3 in the above formula, and oxybutyl where m is 4 in the above formula) Those having at least one ren unit) can be used. The number of the alkylene units or oxyalkylene units is not particularly limited and may be 1 or more (for example, 1 to 15, 1 to 10, 2 to 6, or 2 to 4). In addition, n in the formula representing the alkylene unit is, for example, an integer of 1 to 10, and may be 2 or more, 3 or more, 4 or more, 6 or less, or 5 or less. In the formula representing the oxyalkylene unit, m is an integer of 2 or more, for example, an integer of 2 to 4. In addition to the ethylenically unsaturated group, hydroxyl group and/or carboxyl group, alkylene unit and/or oxyalkylene unit, the monomer (A2) contains an ester bond, an ether bond, a thioether bond, an aromatic ring, an aliphatic ring, and a hetero ring ( For example, it may contain a ring containing a nitrogen atom (N), an oxygen atom (O), or a sulfur atom (S). Additionally, the alkylene unit or oxyalkylene unit may have a substituent.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 4-hydroxybutyl (meth)acrylic acid, 6-hydroxyhexyl (meth)acrylic acid, and (meth)acrylic acid. Hydroxy (meth)acrylate such as 8-hydroxyoctyl, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. alkyl; Polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polybutylene glycol mono(meth)acrylate; These may be mentioned, but are not limited to these. Examples of hydroxyl group-containing monomers that can be preferably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is more preferable. In addition, in an embodiment in which hydroxyalkyl (meth)acrylate is used as a hydroxyl group-containing monomer and the hydroxyl group is used in a crosslinking reaction, from the viewpoint of obtaining a highly flexible crosslinked structure, the hydroxyalkyl (meth)acrylate in the hydroxyalkyl (meth)acrylate is used. Monomers with a large number of carbon atoms in the alkyl group, for example, hydroxyalkyl (meth)acrylate (for example, 4-hydroxy acrylic acid) whose carbon number in the hydroxyalkyl group is 3 or more (for example, 3 to 12, preferably 4 to 10) Roxybutyl) is preferred. In some preferred embodiments, at least 50 weight percent (e.g., greater than 50 weight percent, greater than 70 weight percent, or greater than 85 weight percent) of monomer (A2) may be 4-hydroxybutyl acrylate. Hydroxyl group-containing monomers can be used individually or in combination of two or more types.

In some embodiments of using a hydroxyl group-containing monomer as the monomer (A2), the hydroxyl group-containing monomer may be one or two or more types selected from compounds without a methacryloyl group. Suitable examples of hydroxyl group-containing monomers that do not have a methacryloyl group include the various hydroxyalkyl acrylates described above. For example, it is preferable that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (A2) is hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, a hydroxy group that is helpful in providing crosslinking points and providing appropriate cohesion can be introduced into the acrylic polymer, and also in the room temperature range compared to the case of using only the corresponding hydroxyalkyl methacrylate. It is easy to obtain an adhesive with good flexibility and adhesion.

Examples of carboxylic acid-containing monomers include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. It is not limited to these. Examples of carboxyl group-containing monomers that can be preferably used include acrylic acid and methacrylic acid. Additionally, in some embodiments, from the viewpoint of improving the flexibility of the high refractive index adhesive layer, it is preferable to use, for example, a compound represented by the following formula (1) as the carboxyl group-containing monomer.

CH ₂ =CR ¹ -COO-R ² -OCO-R ³ -COOH (1)

Here, R ¹ in the formula (1) is hydrogen or a methyl group. R ² and R ³ are divalent linking groups (specifically, organic groups having 1 to 20 carbon atoms (for example, 2 to 10, preferably 2 to 5)), and may be the same or different from each other. R ² and R ³ in the above formula (1) may be, for example, a divalent aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group. For example, R ² and R ³ may be alkylene having 2 to 5 carbon atoms. Specific examples of the carboxyl group-containing monomer represented by the formula (1) include, for example, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl-phthalic acid, and 2-(meth) Acryloyloxyethyl-2-hydroxyethyl-phthalic acid, 2-(meth)acryloyloxyethyl-succinic acid, 2-(meth)acryloyloxypropylhexahydrohydrogenphthalate, 2-(meth)acrylo One oxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, etc. can be mentioned. Carboxyl group-containing monomers can be used individually or in combination of two or more types. A hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used together.

The content of monomer (A2) in the monomer component constituting the acrylic polymer is not particularly limited and can be set depending on the purpose. In some embodiments, the content of the monomer (A2) is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, and preferably 0.5% by weight or more. From the viewpoint of obtaining higher usage effects, in some embodiments, the content of the monomer (A2) 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 monomer (A2) in the monomer component is set so that the total of the content of the monomer (A1) does not exceed 100% by weight. In some embodiments, it is appropriate that the content of the monomer (A2) is, for example, 30% by weight or less or 25% by weight or less, and by increasing the content of the monomer (A1) relatively, it is easy to achieve a high refractive index. From the viewpoint of doing so, it is preferable to set it to 20% by weight or less, more preferably to 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 some preferred embodiments, from the viewpoint of improving the large-diameter formation of the high refractive index adhesive layer, the content of the monomer (A2) is less than 5% by weight, more preferably less than 3% by weight, and 1.5% by weight or less. It's okay.

(Monomer A3)

In some embodiments, the monomer component constituting the acrylic polymer may further contain an alkyl (meth)acrylate (hereinafter also referred to as “monomer (A3)”) in addition to the monomer (A1). Monomer (A3) can help improve the flexibility of the high refractive index adhesive layer. In addition, it can be helpful in improving adhesive properties such as compatibility of additives in the adhesive and adhesive strength. Monomer (A3) can be used individually or in combination of two or more types.

As the monomer (A3), an alkyl (meth)acrylate having a straight-chain or branched alkyl group of 1 to 20 carbon atoms (i.e., C _1-20 ) at the ester terminal can be preferably used. Specific examples of C _1-20 alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth) _acrylate . Isobutyl acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate , dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, Examples include isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate, but are not limited to these.

In some embodiments, at least a portion of the monomer (A3) is an alkyl (meth)acrylate whose Tg of the homopolymer is -20°C or lower (more preferably -40°C or lower, for example -50°C or lower). can be preferably employed. Such low Tg alkyl (meth)acrylate can help improve the flexibility of the high refractive index adhesive layer. In addition, it can be helpful in improving adhesive properties such as adhesion. The lower limit of Tg of the alkyl (meth)acrylate is not particularly limited, and may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the low Tg alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), heptyl acrylate, octyl acrylate, and isononyl acrylate (iNA). . In several other embodiments, an alkyl (meth)acrylate whose homopolymer Tg is more than -20°C (for example, -10°C or more) can be employed as at least a part of the monomer (A3). The upper limit of Tg of the alkyl (meth)acrylate is, for example, 10°C or less, may be 5°C or less, or may be 0°C or less. An alkyl (meth)acrylate having a Tg in this range can be helpful in adjusting the flexibility of the high refractive index adhesive layer. Although there is no particular limitation, it is preferable to use the alkyl (meth)acrylate having the above Tg in combination with the above low Tg alkyl (meth)acrylate. Specific examples of the alkyl (meth)acrylate having the above Tg include lauryl acrylate (LA).

In some embodiments of using monomer (A3), it is preferable to use C _4-8 alkyl (meth)acrylate as monomer (A3). Among them, use of C _4-8 alkyl acrylate is more preferable. C _4-8 alkyl (meth)acrylate can be used individually or in combination of two _or more types. By using C _{4 -8} alkyl (meth)acrylate, it is easy to improve the flexibility of the high refractive index adhesive layer, and it is also easy to obtain good adhesive properties (adhesion, etc.). In the embodiment of using C _4-8 alkyl (meth)acrylate as the monomer (A3), the ratio of C _4-8 alkyl (meth)acrylate in the alkyl (meth)acrylate contained in the monomer component is 30 weight. It is appropriate that it is % or more, preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, and may be substantially 100% by weight.

In some embodiments using monomer (A3), C _1-6 alkyl (meth)acrylate may be used as monomer (A3). By using C _1-6 alkyl (meth)acrylate, the storage modulus of each temperature _range can be adjusted. For example, the storage elastic modulus in the high temperature range can be set to be relatively high, or the difference in storage elastic modulus between the low temperature range and the high temperature range can be suppressed from increasing. Additionally, C _1-6 alkyl (meth)acrylate tends to have excellent copolymerization with monomer (A1). C _1-6 alkyl (meth)acrylate can be used individually or in combination of two or _more types. As C _1-6 alkyl (meth)acrylate, C _1-6 alkyl acrylate is preferable, C _2-6 alkyl acrylate is more preferable, and C _4-6 alkyl acrylate is still more preferable _. In several other embodiments, the C _1-6 alkyl (meth)acrylate is preferably C _1-4 alkyl (meth)acrylate, more preferably C _2-4 alkyl (meth)acrylate, More preferably, it is C _2-4 alkyl acrylate. A _suitable example of C _1-6 alkyl (meth)acrylate includes BA.

The content of C _1-6 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It may be % or more. In some embodiments, the content of the C _1-6 alkyl (meth)acrylate may be 10% by weight or more, 15% by weight or more, or 20% by weight or more from the viewpoint of improved flexibility, adhesive strength, etc. It may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _1-6 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _1-6 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and less than 17% by weight. It is more preferable, and may be less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced without substantially using C _1-6 alkyl (meth)acrylate.

In several other embodiments of using monomer (A3), C _7-12 alkyl (meth)acrylate can be preferably used as monomer (A3). The storage modulus can be preferably reduced by using C _{7 -12} alkyl (meth)acrylate. C _{7 -12} Alkyl (meth)acrylate can be used individually or in combination of two or more types. As C _7-12 alkyl (meth)acrylate, C _7-10 alkyl acrylate is preferable, C _7-9 alkyl acrylate is more preferable, and C ₈ alkyl acrylate is still more preferable _. Examples of C _{7 -12} alkyl (meth)acrylate include 2EHA, iNA, and LA, and a suitable example includes 2EHA.

The content of C _7-12 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It may be % or more. In some embodiments, the content of the C _7-12 alkyl (meth)acrylate may be 10% by weight or more, 15% by weight or more, or 20% by weight or more from the viewpoint of improved flexibility, adhesive strength, etc. It may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _7-12 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _7-12 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and less than 17% by weight. It is more preferable, and may be less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced without substantially using C _7-12 alkyl (meth)acrylate.

In some embodiments of using the monomer (A3), it is preferable that at least a part of the monomer (A3) is an alkyl acrylate from the viewpoint of improving flexibility. The use of alkyl acrylate is also advantageous in terms of adhesive properties such as adhesive strength. For example, it is preferable that 50% by weight or more of monomer (A3) is alkyl acrylate, and the proportion of alkyl acrylate in monomer (A3) is more preferably 75% by weight or more, and even more preferably 90% by weight. It is % by weight or more, and substantially 100 % by weight of the monomer (A3) may be an alkyl acrylate. As the monomer (A3), only one or two or more types of alkyl acrylate may be used, and alkyl methacrylate may not be used.

In an embodiment in which the monomer component contains alkyl (meth)acrylate, the content of the alkyl (meth)acrylate in the monomer component can be set so that the use effect is appropriately exhibited. In some embodiments, the content of the alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. The upper limit of the content of monomer (A3) in the monomer component is set so that the total of the contents of monomer (A1) and (A2) does not exceed 100% by weight, for example, less than 50% by weight, and 35% by weight. It may be less than %. In some embodiments, the content of the monomer (A3) may be, for example, 24% by weight or less. Generally, the refractive index of alkyl (meth)acrylate is relatively low, so in order to increase the refractive index, it is advantageous to limit the content of monomer (A3) in the monomer component and increase the content of monomer (A1) relatively. . From this viewpoint, the content of monomer (A3) is suitably less than 23% by weight of the monomer component, preferably less than 20% by weight, more preferably less than 17% by weight, less than 12% by weight, and may be 7% by weight. It may be less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be preferably implemented in an embodiment in which monomer (A3) is not substantially used.

(Other monomers)

The monomer component constituting the acrylic polymer may, if necessary, contain monomers other than the above monomers (A1), (A2), and (A3) (hereinafter referred to as “other monomers”). The other monomers mentioned above can be used for purposes such as adjusting the Tg of the acrylic polymer, adjusting adhesive performance, and improving compatibility in the adhesive layer. The other monomers mentioned above can be used individually or in combination of two or more types.

Examples of the other monomers include monomers (functional group-containing monomers) having functional groups other than hydroxyl groups and carboxyl groups. For example, other monomers that can improve the cohesion and heat resistance of the adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and a cyano group-containing monomer. In addition, as a monomer that can introduce a functional group that can serve as a crosslinking origin into an acrylic polymer, or can contribute to improving adhesion to an adherend or improving compatibility in an adhesive, an amide group-containing monomer (e.g., (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (e.g., aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), nitrogen Monomers having atom-containing rings (e.g., N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide group-containing monomers, epoxy group-containing monomers, keto group-containing monomers, isocyanate groups Containing monomers, alkoxysilyl group-containing monomers, etc. can be mentioned. In addition, among the monomers having a nitrogen atom-containing ring, there are also monomers containing an amide group, such as N-vinyl-2-pyrrolidone. The same applies to the relationship between the monomer having the nitrogen atom-containing ring and the monomer containing an amino group.

Other monomers that can be used other than the functional group-containing monomers include vinyl ester monomers such as vinyl acetate; Non-aromatic ring-containing (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; Olefin-based monomers such as ethylene, butadiene, and isobutylene; Chlorine-containing monomers such as vinyl chloride; Alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate; Vinyl ether-based monomers such as methyl vinyl ether; etc. can be mentioned. A suitable example of another monomer that can be used for purposes such as improving the flexibility of the adhesive includes ethoxyethoxyethyl acrylate (alias: ethylcarbitol acrylate, homopolymer Tg: -67°C).

When using the other monomers mentioned above, the amount used is not particularly limited and can be appropriately set within the range where the total amount of monomer components does not exceed 100% by weight. From the viewpoint of facilitating the effect of improving the refractive index by using the monomer (A1), the content of the other monomers in the monomer component can be, for example, approximately 35% by weight or less, and approximately 25% by weight or less. It is appropriate to set it to (for example, 0 to 25% by weight), approximately 20% by weight or less (for example, 0 to 20% by weight) may be sufficient, and approximately 10% by weight or less (for example, 0 to 10% by weight). It is advantageous, and preferably approximately 5% by weight or less, for example approximately 1% by weight or less. The technology disclosed herein can be preferably implemented in a manner in which 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 methacryloyl group-containing monomer used is suppressed to a predetermined level or less. The usage 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. Limiting the amount of methacryloyl group-containing monomer used in this way can be advantageous from the viewpoint of realizing an adhesive that has both flexibility and adhesiveness and a high refractive index in a good balance. The monomer component constituting the acrylic polymer may be a composition that does not contain a methacryloyl group-containing monomer (for example, a composition consisting only of an acryloyl group-containing monomer).

In some embodiments, the monomer component constituting the base polymer (e.g., acrylic polymer) of the high refractive index adhesive layer contains a carboxyl group from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the high refractive index adhesive layer. The amount of monomer used is limited. The amount of the carboxyl group-containing monomer used in the monomer component may be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. The reason why the amount of carboxyl group-containing monomer is limited in this way is that metal materials that can be placed in contact with or close to the high refractive index adhesive layer disclosed herein (for example, metal wiring or metal films that can be present on the adherend, etc.) ) is also advantageous from the viewpoint of suppressing corrosion. The technology disclosed herein can be practiced in an embodiment in which the monomer component does not contain a carboxyl group-containing monomer.

For the same reason, in some embodiments, the monomer component constituting the base polymer of the high refractive index adhesive layer may be a monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, etc. in addition to a carboxyl group), even if the usage amount is limited. do. As the usage amount of the acidic functional group-containing monomer in the monomer component of this aspect, the above-mentioned preferable usage amount of the carboxyl group-containing monomer can be applied. The technology disclosed herein can be implemented in an embodiment in which the monomer component does not contain an acidic group-containing monomer (that is, an embodiment in which the base polymer of the high refractive index adhesive layer is acid-free).

(Glass transition temperature)

The monomer component constituting the base polymer (for example, an acrylic polymer) of the high refractive index adhesive layer preferably has a composition such that the glass transition temperature (Tg) based on the composition of the monomer component is approximately 15°C or lower. In some embodiments, the Tg is preferably 10°C or lower, more preferably 5°C or lower, further preferably 1°C or lower, and may be 0°C or lower. In several other embodiments, the Tg may be -10°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, and -35°C or lower. A low Tg can be advantageous from the viewpoint of improving the flexibility of the high refractive index adhesive layer. In addition, the Tg may be, for example, -60°C or higher, and from the viewpoint of facilitating high refractive index of the adhesive, it is preferably -50°C or higher, more preferably -45°C or higher, and exceeds -40°C. It's okay. In some embodiments, the Tg may be greater than -30°C, greater than -20°C, greater than -10°C, or greater than -5°C. A high-refractive-index adhesive layer that achieves both high refractive index and large-diameter formation can be suitably formed by using a base polymer with a composition having a Tg in the above range.

Here, Tg, which is based on the composition of the monomer component constituting the base polymer (for example, an acrylic polymer), unless otherwise specified, refers to the glass transition temperature determined by Fox's equation based on the composition of the monomer component. . As described below, the Fox equation is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by independently polymerizing each of the monomers constituting the copolymer.

1/Tg=Σ(Wi/Tgi)

In the Fox equation, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio by weight), and Tgi is the homopolymer of monomer i. Indicates the glass transition temperature (unit: K).

As the glass transition temperature of the homopolymer used to calculate Tg, the value described in known materials such as “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) is used. For monomers for which multiple types of values are described in the Polymer Handbook, the highest value is adopted. If the Tg of the homopolymer is not described in the known data, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 is used.

(Method for preparing base polymer)

In the technology disclosed herein, the method of obtaining a base polymer (for example, an acrylic polymer) composed of such a monomer component is not particularly limited, and includes solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, Known polymerization methods such as photopolymerization can be appropriately employed. For example, a solution polymerization method can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., for example, about 20°C to 170°C (typically about 40°C to 140°C). can do.

The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) such as toluene; 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 (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butylmethyl ether; Ketones such as methyl ethyl ketone; Any one type of solvent selected from the like, or a mixed solvent of two or more types can be used.

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, one or two or more types of azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; Peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; etc. can be mentioned. Another example of a polymerization initiator is a redox initiator made by combining a peroxide and a reducing agent. The polymerization initiator can be used individually or in combination of two or more types. The amount of the polymerization initiator used may be a normal amount, and can be selected from the range of approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) per 100 parts by weight of the monomer component.

In the above polymerization, various conventionally known chain transfer agents can be used as 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 that does not contain a sulfur atom (non-sulfur-based chain transfer agent) may be used. Examples of non-sulfur-based chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; Terpenoids such as α-pinene and terpinolene; Styrenes such as α-methylstyrene and α-methylstyrene dimer; etc. can be mentioned. Chain transfer agents can be used individually or in combination of two or more types. When using a chain transfer agent, the amount used can be, for example, approximately 0.01 to 1 part by weight based on 100 parts by weight of the monomer component.

The weight average molecular weight (Mw) of the base polymer (for example, an acrylic polymer) is not particularly limited, and is suitably, for example, approximately 30×10 ⁴ or greater, approximately 50×10 ⁴ or greater, and approximately 70×10 ⁴ It may be more than or approximately 80×10 ⁴ or more. By using a base polymer whose Mw is a predetermined value or more, it is easy to obtain an appropriate cohesive force that can exhibit the desired adhesive properties. Additionally, it is possible to contain a larger amount of additives such as plasticizers, which tends to make it easier to achieve the desired flexibility. In addition, the upper limit of the Mw of the base polymer is, for example, approximately 500 × 10 ⁴ or less, and from the viewpoint of adhesion performance, approximately 400 × 10 ⁴ or less (more preferably approximately 150 × 10 ⁴ or less, for example, approximately 130 It is preferable that it is in the range of (×10 ⁴ or less). In some embodiments, the Mw may be less than 100×10 ⁴ , 80×10 ⁴ or less, or 60×10 ⁴ or less. The effects achieved by the technology disclosed herein can be suitably realized in an embodiment using an acrylic polymer having Mw in the above range.

Here, the Mw of the polymer can be calculated by converting it to polystyrene using gel permeation chromatography (GPC). Specifically, it can be obtained by measuring under the following conditions using the product name "HLC-8220GPC" (manufactured by Tosoh Corporation) as a GPC measuring device.

[GPC measurement conditions]

Sample concentration: 0.2% by weight (tetrahydrofuran solution)

Sample injection volume: 10μL

Eluent: Tetrahydrofuran (THF)

Flow rate (flow rate): 0.6mL/min

Column temperature (measurement temperature): 40℃

column:

Sample column: 1 unit of product name “TSKguardcolumn SuperHZ-H” + 2 units of product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)

Reference column: 1 product name “TSKgel SuperH-RC” (manufactured by Tosoh Corporation)

Detector: Differential refractometer (RI)

Standard sample: polystyrene

(plasticizer)

In some embodiments, the above-mentioned high refractive index adhesive layer (for example, high refractive index acrylic adhesive layer) contains a plasticizer in addition to the base polymer. By using a plasticizer, the flexibility of the high refractive index pressure-sensitive adhesive layer can be improved, and further large-diameter formation can be achieved. As a plasticizer, it is preferable to select and use one or two or more types of plasticizers that have a refractive index of 1.55 or more and can achieve both the above-mentioned 350% deformation characteristics from among the plasticizers described below.

Suitable examples of the plasticizer disclosed herein include cyclic unsaturated organic compounds having two or more double bond-containing rings. In other words, the plasticizer as a suitable example is a compound having two or more double bond-containing rings in one molecule. Accordingly, the plasticizer has at least a first double bond-containing ring and a second double bond-containing ring. By having two or more double bond-containing rings, it is possible to improve the flexibility of the high refractive index adhesive layer and, by extension, to form a large stool, without damaging the refractive index of the high refractive index adhesive layer or maintaining the refractive index. From the viewpoint of exerting a plasticizing effect, the number of double bond-containing rings in the plasticizer is preferably 6 or less, may be 4 or less, and may be 3 or less.

Additionally, the plasticizer used in the technology disclosed herein is preferably a liquid compound at 30°C. In addition, in this specification, “liquid phase” means showing fluidity, and refers to a liquid state as a state of a substance. These compounds include compounds with a melting point of 30°C or lower. Since the plasticizer is in a liquid state at 30°C, the plasticizing effect is appropriately exhibited, and the flexibility of the high refractive index adhesive layer can be improved, and further, stool formation can be appropriately realized. The plasticizer is preferably a liquid compound at 25°C, and more preferably a liquid compound at 20°C. For example, by using a liquid compound at 30°C that has two or more double bond-containing rings as a plasticizer, a high refractive index adhesive layer that achieves both high refractive index and large stool formation can be suitably formed.

The molecular weight of the plasticizer is not particularly limited, but usually one with a molecular weight smaller than that of the base polymer (for example, an acrylic polymer) is used. From the viewpoint of facilitating the plasticization effect, the molecular weight of the plasticizer is suitably 30,000 or less, advantageously 25,000 or less, may be less than 10,000 (for example, less than 5,000), or less than 3,000. In some embodiments, the molecular weight of the plasticizer is preferably 2000 or less, more preferably 1200 or less, even more preferably 900 or less, may be 600 or less, may be 500 or less, may be 400 or less, and may be 300 or less. It may be 250 or less (for example, 220 or less). The fact that the molecular weight of the plasticizer is not too large can be advantageous from the viewpoint of improving compatibility within the adhesive layer. In addition, from the viewpoint of making it easy to achieve sufficient plasticizing effect, the molecular weight of the plasticizer is suitably 100 or more, preferably 130 or more, more preferably 150 or more, may be 170 or more, may be 200 or more, and may be 220 or more. It can be 250 or more. It is desirable that the molecular weight of the plasticizer is not too low from the viewpoint of heat resistance performance of the adhesive and suppression of contamination of the adherend. In some embodiments, the molecular weight of the plasticizer is, for example, 300 or more, suitably 315 or more, and may be 350 or more. Since plasticizers with a large molecular weight are difficult to vaporize, it is easy to obtain an adhesive that can exhibit stable properties by using a plasticizer with a large molecular weight in the adhesive. Additionally, plasticizers with large molecular weight have difficulty moving within the adhesive. Therefore, for example, it is difficult for the plasticizer to migrate to the surface of the adhesive, causing events that affect the adhesive properties. The molecular weight of the plasticizer is more preferably 400 or more, further preferably 450 or more, particularly preferably 500 or more, and may be 530 or more.

Additionally, as the molecular weight of the plasticizer, the molecular weight calculated based on the chemical structure is used. If a nominal value of molecular weight is provided by a manufacturer, etc., that nominal value can be adopted.

Although not particularly limited, in some embodiments, the plasticizer has a transition amount to a gas phase at 130°C (130°C vaporization amount) of 10% or less by weight (specifically, 0 to 10% by weight). can be used. By using a plasticizer that satisfies these properties, the high refractive index adhesive layer containing the plasticizer is suppressed from changing properties due to the plasticizer with respect to temperature or humidity changes. For example, it can be an adhesive that exhibits stable properties even when used in an environment exposed to high temperature or high humidity or when used for a long period of time. The 130°C vaporization amount of the plasticizer may be less than 10% by weight, less than 5% by weight, less than 3% by weight, or less than 1% by weight.

The amount of plasticizer transferred to the gas phase at 130°C can be determined from the weight change before and after maintaining the plasticizer at 130°C for 1 hour. More specifically, it can be measured by the following method.

[Amount of transfer of plasticizer to vapor phase]

Approximately 1 g of plasticizer (measurement sample) is dropped into an aluminum cup and weighed to the nearest 0.01 mg with an electronic balance in an environment of 23°C and 45%RH (W0g). Next, the cup containing the measurement sample is kept in an oven at 130°C for 1 hour. As an oven, one that has sufficient capacity for the measurement sample and can be heated while exhausting the sample is used. For example, an oven made by espec can be used. After holding at 130°C for 1 hour, the cup containing the measurement sample is taken out from the oven, returned to room temperature, and weighed (W1g). Substitute the weight W0 [g] of the measurement sample before heating in the oven and the weight W1 [g] of the measurement sample after heating in the oven into the equation: 1-W1/W0 to obtain the gas phase of the measurement sample at 130°C. Find the transition amount [%]. Measurements are performed on 3 samples (n=3), and the average value is adopted.

Although not particularly limited, in some embodiments, the high refractive index adhesive layer has a weight loss of 5% or less (specifically, 0%) of the plasticizer in the high refractive index adhesive layer after being maintained in an environment at 130°C for 1 hour. to 5% by weight). In a high refractive index adhesive layer that satisfies this characteristic, even when heated under predetermined conditions, most of the plasticizer in the high refractive index adhesive layer remains in the high refractive index adhesive layer, and its effect (mainly the plasticizing effect) can be maintained. Therefore, the high refractive index adhesive layer is suppressed from changing properties due to the plasticizer, and can exhibit stable properties regardless of the use environment and even when used for a long period of time. The loss of plasticizer in the high refractive index adhesive layer after holding at 130°C for 1 hour is preferably less than 3% by weight, more preferably less than 1% by weight, still more preferably less than 0.5% by weight, and may be less than 0.3% by weight. , may be 0.1% by weight or less. The weight loss of the plasticizer in the high refractive index adhesive layer after holding at 130°C for 1 hour can be determined from the change in weight of the plasticizer in the high refractive index adhesive layer before and after holding for 1 hour in an environment at 130°C.

The amount of plasticizer in the high refractive index adhesive layer can be quantified, for example, by liquid chromatography measurement. More specifically, it can be measured by the following method.

[Heating loss of plasticizer in adhesive]

The adhesive composition is applied to the silicone-treated side of PET film R1, one side of which has been silicone-treated, and heated at 130°C for 3 minutes to form an adhesive layer with a thickness of 20 μm. Next, the silicone-treated side of PET film R2, one side of which was silicone-treated, is bonded to the surface of the adhesive layer. One release liner is peeled from the adhesive layer (release liner/adhesive layer/release liner) provided with the obtained release liner, and kept in an oven at 130°C for 1 hour. As an oven, one that has sufficient capacity for the measurement sample and can be heated while exhausting the sample is used. For example, an oven made by espec can be used. Liquid chromatography (LC) measurement is performed on the adhesive before and after heating in an oven under the following conditions. From the results of the LC, the amount of plasticizer contained in the adhesive before and after heating is determined, and from the weight ratio, the loss [%] of the plasticizer in the adhesive after holding for 1 hour in an environment at 130°C is determined. Measurements are performed on 3 samples (n=3), and the average value is adopted. In addition, prior to the LC measurement of the adhesive, it is preferable to perform an LC measurement on the plasticizer alone, prepare a calibration curve, and quantify the plasticizer in the adhesive based on this calibration curve.

[LC measurement conditions]

Take about 0.01 g of adhesive, add 2 mL of chloroform, and shake overnight. 8 mL of acetonitrile was added to this solution to reprecipitate the polymer component, and the supernatant was filtered through a 0.45㎛ membrane filter. The obtained filtrate is appropriately diluted and measured by injecting it into an analysis device (HPLC Prominence, manufactured by Shimadzu Corporation).

Column: GL Sciences, Inertsil ODS-3 (4.6㎜ϕ×250㎜, 5㎛)

Column temperature: 40℃

Column flow rate: 1.0mL/min

Eluent: gradient conditions of ultrapure water/acetonitrile

Injection volume: 1μL

Detector: DAD (190 nm to 400 nm, 272 nm extraction)

In an aspect in which a plasticizer having a double bond-containing ring is used, the double bond-containing ring of the plasticizer may be either a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer may have at least one ring selected from aromatic rings and heterocycles (heterocycles) as a double bond-containing ring. In addition, the heterocycle may have a structure contained in an aromatic ring, or may have a double bond-containing heterocycle structure different from the aromatic ring. Examples of the double bond-containing ring (typically an aromatic ring) that the plasticizer may have include a benzene ring (which may be a benzene ring forming part of a biphenyl structure or a fluorene structure); Condensed rings of naphthalene ring, indene ring, azulene ring, anthracene ring, and phenanthrene ring; It may be a carbon ring such as pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, thiophene ring. ; It may be a complex ring such as In the above heterocycle, the heteroatoms included as ring constituent atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur. The plasticizer may have a structure in which 1 or 2 or more carbon rings and 1 or 2 or more heterocycles are condensed, such as a dinaphthothiophene structure.

The double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have one or two or more substituents on the ring constituent atoms, and may not have a substituent. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In a substituent containing a carbon atom, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the double bond-containing ring has no substituents on ring constituent atoms, or has an alkyl group, an alkoxy group, an ethylenically unsaturated group (e.g., (meth)acryloxy group), a hydroxy group, and a hydroxyalkyl group. It may be an aromatic ring having one or two or more substituents selected from the group consisting of As the substituent, an alkyl group, an alkoxy group, or a hydroxyalkyl group is preferably used.

In some embodiments, a compound without an ethylenically unsaturated group can be preferably used as the plasticizer. As a result, deterioration of the adhesive composition due to heat or light (deterioration of leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adopting a plasticizer that does not have an ethylenically unsaturated group prevents changes in elastic modulus, dimensional changes and deformations (bending, waviness, etc.), and optical distortions due to the reaction of the ethylenically unsaturated group in the adhesive layer containing the plasticizer. It is also desirable from the viewpoint of suppressing outbreaks, etc.

As the plasticizer, a high refractive index plasticizer with a refractive index of approximately 1.50 or more can be preferably used. By using a high refractive index plasticizer, it is easy to achieve both high refractive index and large stool formation. The refractive index of the plasticizer is preferably approximately 1.51 or greater, more preferably approximately 1.53 or greater, further preferably approximately 1.55 or greater, from the viewpoint of maintaining and improving the refractive index of the high refractive index adhesive layer while obtaining flexibility, and approximately 1.56. It may be greater than or equal to approximately 1.58, approximately 1.60 or greater, or approximately 1.62 or greater. In some embodiments, from the viewpoint of ease of preparation of the adhesive composition and compatibility in the adhesive, the refractive index of the plasticizer is suitably 2.50 or less, advantageously 2.00 or less, may be 1.90 or less, and may be 1.80 or less. It can be 1.70 or less.

In addition, the refractive index of the plasticizer, like the refractive index of the monomer, is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

In some embodiments, the plasticizer is a compound having a structure in which two or more non-fused double bond-containing rings (typically aromatic rings) are bonded through a linking group, and two or more non-fused double bond-containing rings (typically aromatic rings). Compounds having this structure chemically bonded directly (i.e., without passing through other atoms), compounds having a condensed double bond-containing ring (typically aromatic ring) structure, compounds having a fluorene structure, and compounds having a dinaphthothiophene structure. , compounds having a dibenzothiophene structure, etc. may be used.

In some preferred embodiments, Compound A, which has a structure in which two or more non-fused double bond-containing rings are bonded through a linking group, is used as the plasticizer. The linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (for example -O-(CH ₂ ) _n -group, where n is 1 to 3, Preferably 1), a thiooxyalkylene group (e.g. -S-(CH ₂ ) _n -group, where n is 1 to 3, preferably 1), a straight chain alkylene group (e.g. -(CH ₂ ) _n -group, where n is 1 to 6, preferably 1 to 3), the alkylene group in the oxyalkylene group, the thiooxyalkylene group and the straight chain alkylene group may be a partially halogenated or fully halogenated group, etc. . The linking group may have an ester bond. In the plasticizer, the linking group connecting the first double bond-containing ring (non-condensed ring) and the second double bond-containing ring (non-condensed ring) may be selected from the same group as above. From the viewpoint of large-scale formation of the high refractive index adhesive layer, suitable examples of the linking group include an oxy group, a thioxy group, an oxyalkylene group, and a straight chain alkylene group. The number of atoms of the linking group is not particularly limited, and in some embodiments, for example, it is 1 to 30, may be 1 to 25, may be 1 to 20, and is suitably 1 to 18, Preferably it is 1 to 12, more preferably 1 to 10, further preferably 1 to 8, especially preferably 1 to 5, and may be 1 to 3, or may be 1 or 2. In addition, in several other preferred embodiments, the number of atoms of the linking group is, for example, 10 or more, preferably 15 or more, more preferably 20 or more, and even more preferably 22 or more (e.g. 25 or more or 30 or more). In addition, the upper limit of the number of atoms of the linking group is, for example, 50 or less, preferably 40 or less, and may be 35 or less. In the aspect of using a plasticizer having an oxyalkylene group as the linking group, the number of atoms of the linking group is preferably applied. In addition, the number of atoms of the linking group refers to the minimum number of atoms required to reach from one non-fused double bond-containing ring to the other non-fused double bond-containing ring. For example, when the linking group consists of a straight chain alkylene group (i.e. -(CH ₂ ) _n -group), the number of n becomes the number of atoms of the linking group. Also, for example, if the linking group is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of 3 and n, which is the sum of the number of carbon atoms 2 and the number of oxygen atoms 1 constituting the oxyethylene group (3n ) is the number of atoms of the linking group. Suitable examples of the above compounds include compounds having a phenoxybenzyl group. Examples of the above compounds include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), phenoxybenzyl alcohol, oxybis[(alkoxyalkyl)benzene] (e.g., 4 , 4'-oxybis[(methoxymethyl)benzene]), polyethylene glycol benzoic acid ester, etc.

In the aspect of using Compound A as a plasticizer, which has a structure in which two or more non-fused double bond-containing rings are bonded through a linking group, the amount of Compound A used is not particularly limited, and the adhesive properties and effects disclosed herein are achieved. It is set to do so. From the viewpoint of stool formation, in some preferred embodiments, the amount of compound A used relative to 100 parts by weight of the base polymer is greater than 30 parts by weight, more preferably 35 parts by weight or more, and even more preferably 40 parts by weight. or more, particularly preferably 45 parts by weight or more, more particularly preferably 50 parts by weight or more, and may be 55 parts by weight or more, and may be 60 parts by weight or more. In addition, from the viewpoint of achieving a good balance between increasing the refractive index of the high refractive index adhesive layer and forming large pieces, it is appropriate that the amount of the compound A used per 100 parts by weight of the base polymer is approximately 200 parts by weight or less, and 150 parts by weight or less. It is preferable to set it as 120 parts by weight or less, and it may be 100 parts by weight or less, 80 parts by weight or less, and 70 parts by weight or less.

In addition, in an embodiment of using Compound A as a plasticizer, which has a structure in which two or more non-fused double bond-containing rings are bonded through a linking group, the high refractive index adhesive layer optionally contains one or two or more types of plasticizers other than Compound A. You may or may not include it. Plasticizers other than Compound A can be used in appropriate amounts as long as they do not impair the effects of the technology disclosed herein. In this embodiment, the amount of plasticizer other than the compound A used is suitably less than 50% by weight of the total plasticizer used in the high refractive index adhesive layer, preferably less than 30% by weight, more preferably 10% by weight. Less than 3% by weight, more preferably less than 3% by weight, particularly preferably less than 1% by weight. The technology disclosed herein can be preferably implemented using a high refractive index adhesive layer that substantially does not contain a plasticizer other than the compound A.

In some preferred embodiments, an ethylene glycol-based compound having two or more double bond-containing rings in one molecule can be used as the plasticizer. The number of oxyethylene units (i.e. -(C ₂ H ₄ O)- units) of the ethylene glycol-based compound is, for example, 1 or more, suitably 2 or more, preferably 3 or more, more preferably 3 or more. It is 4 or more (for example, 5 or more). In addition, the upper limit of the number of oxyethylene units is, for example, 10 or less, may be 8 or less, and may be 6 or less. The ethylene glycol-based compound may be a compound having a structure in which two or more non-fused double bond-containing rings are bonded through the oxyethylene unit as a linking group. These compounds may have one or two or more ester groups. Examples of the ethylene glycol-based compound include compounds having a structure in which two or more benzoic acids are linked to triethylene glycol or polyethylene glycol by an ester bond.

In the aspect of using an ethylene glycol-based compound having two or more double bond-containing rings in one molecule as a plasticizer, the amount of the ethylene glycol-based compound used is not particularly limited, and the adhesive properties and effects disclosed herein can be achieved. It is set to do so. From the viewpoint of stool formation, in some preferred embodiments, the amount of the ethylene glycol-based compound used relative to 100 parts by weight of the base polymer is greater than 30 parts by weight, more preferably 35 parts by weight or more, and even more preferably 40 parts by weight. It is more than 55 parts by weight, particularly preferably 45 parts by weight or more, and more particularly preferably 50 parts by weight or more. It may be 55 parts by weight or more, and may be 60 parts by weight or more. In addition, from the viewpoint of achieving a good balance between increasing the refractive index of the high refractive index adhesive layer and forming a large stool, it is appropriate that the amount of the ethylene glycol-based compound used per 100 parts by weight of the base polymer is approximately 200 parts by weight or less, and 150 parts by weight. It is preferably 120 parts by weight or less, more preferably 120 parts by weight or less, 100 parts by weight or less, 80 parts by weight or less, and 70 parts by weight or less.

In addition, in the embodiment of using an ethylene glycol-based compound having two or more double bond-containing rings in one molecule as a plasticizer, the high refractive index adhesive layer optionally contains one or two or more types of plasticizers other than the ethylene glycol-based compound. You may or may not include it. Plasticizers other than the ethylene glycol-based compounds can be used in appropriate amounts as long as they do not impair the effects of the technology disclosed herein. In this embodiment, the amount of plasticizer other than the ethylene glycol-based compound used is suitably less than 50% by weight of the total plasticizer used in the high refractive index adhesive layer, preferably less than 30% by weight, more preferably 10% by weight. It is less than % by weight, more preferably less than 3% by weight, especially preferably less than 1% by weight. The technology disclosed herein can be preferably implemented using a high refractive index adhesive layer that substantially does not contain plasticizers other than the ethylene glycol-based compounds.

In several other embodiments, liquid rosins such as liquid rosin ester and liquid camphene phenol can be used as the plasticizer. The liquid rosins (for example, liquid rosin ester) may correspond to compounds having the condensed double bond-containing ring structure.

In addition, as a plasticizer, one or two or more types of known plasticizers (for example, phthalic acid ester series, terephthalic acid ester series, adipic acid ester series, adipic acid polyester, benzoic acid glycol ester, etc.) may be used.

The amount of plasticizer used is not particularly limited and can be set depending on the purpose. From the viewpoint of stool formation, in some preferred embodiments, the amount of plasticizer used per 100 parts by weight of the base polymer is greater than 30 parts by weight, more preferably 35 parts by weight or more, further preferably 40 parts by weight or more, Particularly preferably, it is 45 parts by weight or more, and more particularly preferably, it is 50 parts by weight or more. It may be 55 parts by weight or more, and may be 60 parts by weight or more. In addition, from the viewpoint of achieving a good balance between increasing the refractive index of the high refractive index adhesive layer and forming large pieces, it is appropriate that the amount of plasticizer used per 100 parts by weight of the base polymer is approximately 200 parts by weight or less, and 150 parts by weight or less. It is preferable, and it is more preferable to set it to 120 parts by weight or less, and may be 100 parts by weight or less, may be 80 parts by weight or less, and may be 70 parts by weight or less. In some embodiments that place greater emphasis on adhesive properties, the amount of plasticizer used may be 45 parts by weight or less, or 35 parts by weight or less, per 100 parts by weight of the base polymer.

(Additive (H _RO ))

The high refractive index adhesive layer disclosed herein may contain an organic material with a higher refractive index than the base polymer (for example, an acrylic polymer) as an additive used as desired. Hereinafter, such organic materials may be referred to as “additive (H _RO ).” Here, “H _RO ” indicates that it is an organic material with a high refractive index. By using an additive (H _RO ), a high refractive index adhesive layer that more appropriately achieves both refractive index and adhesive properties (peel strength, flexibility, etc.) can be realized. The organic material used as the additive ( _HRO ) may be a polymer or a non-polymer. Additionally, it may or may not have a polymerizable functional group. In addition, in this specification, the additive (H _RO ) is defined as being different from the compound used as the above-mentioned plasticizer. For example, the additive (H _RO ) may not be liquid at 30°C (eg, 25°C or 20°C). Additives (H _RO ) can be used individually or in combination of two or more types.

The refractive index of the additive (H _RO ) can be set in an appropriate range in relation to the refractive index of the base polymer (for example, acrylic polymer), and is therefore not limited to a specific range. The refractive index of the additive (H _RO ) is, for example, greater than 1.55, greater than 1.56, or greater than 1.57, and can be selected from a range higher than the refractive index of the base polymer. From the viewpoint of increasing the refractive index of the high refractive index adhesive layer, in some embodiments, the refractive index of the additive ( _HRO ) is advantageously 1.58 or more, preferably 1.60 or more, more preferably 1.63 or more, and may be 1.65 or more. It can be 1.70 or more, and it can be 1.75 or more. By using an additive (H _RO ) with a higher refractive index, the target refractive index can be achieved even by using a smaller amount of the additive (H _RO ). This is desirable from the viewpoint of suppressing deterioration of adhesive properties and optical properties. The upper limit of the refractive index of the additive ( _HRO ) is not particularly limited, but is, for example, 3.000 or less, and may be 2.500 or less, from the viewpoint of compatibility in the adhesive and ease of coexistence of high refractive index and flexibility suitable as an adhesive. It may be 2.000 or less, 1.950 or less, 1.900 or less, and 1.850 or less.

In addition, the refractive index of the additive (H _RO ), like the refractive index of the monomer, is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

The molecular weight of the organic material used as the additive ( _HRO ) is not particularly limited and can be selected depending on the purpose. From the viewpoint of achieving a good balance between the effect of increasing the refractive index and other properties (e.g., optical properties such as flexibility and haze suitable for an adhesive), in some embodiments, the molecular weight of the additive ( _HRO ) is approximately 10000. It is suitable to be less than 5000, more preferably less than 3000 (for example, less than 1000), less than 800, less than 600, less than 500, and less than 400. The fact that the molecular weight of the additive ( _HRO ) is not too large can be advantageous from the viewpoint of improving compatibility in the adhesive. In addition, the molecular weight of the additive ( _HRO ) may be, for example, 130 or more, or 150 or more. In some embodiments, the molecular weight of the additive ( _HRO ) is preferably 170 or more, more preferably 200 or more, may be 230 or more, or 250 or more from the viewpoint of increasing the refractive index of the additive ( _HRO ). It may be 270 or more, 300 or more, 500 or more, 1000 or more, or 2000 or more. In some embodiments, a polymer having a molecular weight of about 1,000 to 10,000 (for example, 1,000 to 5,000) can be used as the additive (H _RO ).

As the molecular weight of the additive ( _HRO ), for non-polymers or polymers with a low degree of polymerization (for example, about 2 to 5 polymers), the molecular weight calculated based on the chemical structure or matrix-assisted laser desorption ionization time-of-flight mass spectrometry ( Measurements using MALDI-TOF-MS) can be used. When the additive (H _RO ) is a polymer with a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC conducted under appropriate conditions can be used. If a nominal value of molecular weight is provided by a manufacturer, etc., that nominal value can be adopted.

Examples of organic materials that can be selected as an additive (H _RO ) include organic compounds having an aromatic ring, organic compounds having a heterocycle (may be an aromatic ring, or may be a non-aromatic heterocycle), etc. It is not limited to.

The aromatic ring possessed by the organic compound having the aromatic ring (hereinafter also referred to as “aromatic ring-containing compound”) used as the additive (H _RO ) may be selected from the same group as the aromatic ring possessed by the compound used as the monomer (A1). You can.

The aromatic ring may have one or two or more substituents on the ring constituent atoms, and may not have any substituents. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In the substituent containing a carbon atom, 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 10. 3, and may be 1 or 2, for example. In some embodiments, the aromatic ring is an aromatic ring that has no substituents on ring constituent atoms or has one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). You can.

Examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include: compounds that can be used as monomers (A1); An oligomer containing a compound that can be used as a monomer (A1) as a monomer unit; From the compounds that can be used as monomer (A1), a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring-forming atom) or a hydrogen atom or an ethylenically unsaturated group, excluding the portion constituting the ethylenically unsaturated group in the group, Compounds with a structure substituted with a group that it does not have (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, etc.); etc., and those that do not correspond to the plasticizers disclosed herein may be mentioned, but are not limited to these.

In some embodiments, the additive ( _HRO ) is an organic compound having two or more aromatic rings in one molecule (hereinafter also referred to as a “compound containing multiple aromatic rings”) because a high refractive index effect can easily be obtained. ) can be preferably employed. The compound containing multiple aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. In addition, the compound containing multiple aromatic rings may be a polymer or a non-polymer. In addition, the polymer is an oligomer containing a plurality of aromatic ring-containing monomers as monomer units (preferably an oligomer with a molecular weight of approximately 5000 or less, more preferably approximately 1000 or less. For example, a low polymer of about 2 to 5 polymers). You can. The oligomers include, for example: homopolymers of monomers containing multiple aromatic rings; A copolymer of two or more types of aromatic ring-containing monomers; copolymers of one or more types of aromatic ring-containing monomers and other monomers; It may be, etc. The other monomer may be an aromatic ring-containing monomer that does not correspond to a monomer containing multiple aromatic rings, may be a monomer that does not have an aromatic ring, or may be a combination thereof. In the aspect of using an oligomer as an additive ( _HRO ), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method.

Non-limiting examples of compounds containing multiple aromatic rings include compounds having a structure in which two or more non-fused aromatic rings are bonded through a linking group, compounds having a structure in which two or more non-fused aromatic rings are chemically bonded directly (i.e., without passing through 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, etc. can be mentioned. A compound containing multiple aromatic rings can be used individually or in combination of two or more types.

Examples of organic compounds having a heterocycle (hereinafter also referred to as heterocycle-containing organic compounds) that can be an option for the additive (H _RO ) include thioepoxy compounds and compounds having a triazine ring. Examples of thioepoxy compounds include bis(2,3-epithiopropyl)disulfide and its polymer (refractive index 1.74) described in Japanese Patent No. 3712653. Examples of compounds having a triazine ring include compounds having at least one triazine ring (for example, 3 to 40, preferably 5 to 20) in one molecule. In addition, since the triazine ring has aromaticity, 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 compound containing a plurality of aromatic rings.

In some embodiments, a compound that does not have an ethylenically unsaturated group can be preferably used as the additive (H _RO ). As a result, deterioration of the adhesive composition due to heat or light (deterioration of leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adoption of an additive (H _RO ) that does not have an ethylenically unsaturated group prevents dimensional changes or deformations (bending, waviness, etc.) due to the reaction of the ethylenically unsaturated group in the adhesive layer containing the additive (H _RO ). , it is also desirable from the viewpoint of suppressing the occurrence of optical distortion, etc.

The additive (H _RO ) may be used in an appropriate amount within the range in which the effect of the technology disclosed herein is not significantly impaired. In some embodiments, the amount of additive (H _RO ) used (if multiple types of compounds are used, their total amount) per 100 parts by weight of the base polymer (for example, an acrylic polymer) exceeds 0 parts by weight. It is not particularly limited and can be set depending on the purpose. In some embodiments, the amount of additive ( _HRO ) used per 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and the high refractive index of the high refractive index adhesive layer is increased and the adhesive properties and optical properties are improved. From the viewpoint of suppressing degradation in a well-balanced manner, it is advantageous to set it to 60 parts by weight or less, and preferably to set it to 45 parts by weight or less. In some embodiments that place more emphasis on adhesive properties or optical properties, the amount of additive ( _HRO ) used per 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, 10 parts by weight or less, or 3. It may be less than 1 part by weight or less than 1 part by weight. The technology disclosed herein can be preferably implemented using a high refractive index adhesive layer that does not contain an additive (H _RO ). In addition, from the viewpoint of increasing the refractive index of the high refractive index adhesive layer, the amount of additive (H _RO ) used per 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, and it is advantageous to use 3 parts by weight or more. It is preferably 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, and may be 20 parts by weight or more.

(Cross-linking agent)

In the technology disclosed herein, the adhesive composition used for forming the high refractive index adhesive layer may contain a crosslinking agent as needed for purposes such as adjusting the cohesive force of the adhesive. As the crosslinking agent, crosslinking agents known in the adhesive field can be used, 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. Among them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents can be preferably employed. Other examples of crosslinking agents include monomers having two or more ethylenically unsaturated groups in one molecule, that is, polyfunctional monomers. The crosslinking agent can be used individually or in combination of two or more types.

As the isocyanate-based crosslinking agent, bifunctional or higher isocyanate compounds can be used, for example, aliphatic polys such as trimethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and dimer acid diisocyanate. isocyanates; Alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and 1,3-bis(isocyanatomethyl)cyclohexane; Aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate (XDI); Polyisocyanate modified product ( For example, isocyanurate form of HDI, allophanate form of HDI, etc.); etc. can be mentioned. Examples of commercial products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N, Takenate D178NL (manufactured by Mitsui Chemicals), Sumidur T80, Sumidur L, and Desmodur N3400 ( (above, manufactured by Sumika Bayer Urethane Corporation), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX, Coronate 2770 (above, manufactured by Tosoh Corporation), brand name Duranate A201H (above, Asahi Kasei Corporation) j), etc. Isocyanate compounds can be used individually or in combination of two or more types. You may use a bifunctional isocyanate compound and a trifunctional or more isocyanate compound together.

As an epoxy-based crosslinking agent, for example, bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6 -hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N', N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. are mentioned. These can be used individually or in combination of two or more types.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and neopentyl glycol di( Meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexane Dioldi(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, hexyldiol di(meth)acrylate, etc. I can hear it. Polyfunctional monomers can be used individually or in combination of two or more types.

In some embodiments, at least part of the crosslinking agent is a bifunctional crosslinking agent having two crosslinking reactive groups (for example, isocyanate groups) per molecule. By using a bifunctional crosslinking agent, it is easy to form a flexible crosslinked structure. Bifunctional crosslinking agents can be used individually or in combination of two or more types. In addition, the bifunctional crosslinking agent may be used in combination with a trifunctional or higher crosslinking agent.

In some embodiments, an acyclic crosslinking agent (also referred to as a chain crosslinking agent) that does not have a ring structure such as an aromatic ring or an aliphatic ring is preferably used as the crosslinking agent. For example, among the above-mentioned isocyanate-based crosslinking agents, it is preferable to use isocyanate-based compounds that do not have ring structures such as aromatic rings and isocyanurate rings. By using an acyclic isocyanate-based compound as a crosslinking agent, it is easy to form a crosslinking agent with high flexibility. Specific examples of the acyclic isocyanate include aliphatic isocyanate compounds (e.g., PDI and HDI) and modified forms of aliphatic isocyanate compounds (e.g., allophanate linkage, biuret linkage, urea linkage, and carbodiyl compound of PDI and HDI). and polyisocyanate modified products modified by mead bonds. Acyclic crosslinking agents can be used individually or in combination of two or more types. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent.

In some embodiments, a crosslinking agent in which the distance between one crosslinking reactive group (for example, an isocyanate group) and the other crosslinking reactive group in one molecule is relatively long can be used. As a result, a flexible crosslinked structure having a length of a predetermined length or more is formed. For example, in one molecule of the crosslinking agent, a compound in which the number of atoms constituting the linking chain connecting one crosslinking reactive group to another crosslinking reactive group is 10 or more (for example, 12 or more or 14 or more) can be used as the crosslinking agent. The upper limit of the number of atoms forming the linking chain is not particularly limited because it can be prepared by polymerization or the like depending on the purpose, and is, for example, 2000 or less, may be 1000 or less, may be 500 or less, may be 100 or less, and may be 50 or less. It may be 20 or less, or it may be 30 or less, or it may be 20 or less. In addition, the number of atoms in the linking chain connecting the crosslinking reactive groups refers to the number of atoms from one crosslinking reactive group to another crosslinking reactive group in one molecule of the crosslinking agent (when having 3 or more crosslinking reactive groups, the crosslinking reactive group closest to the one crosslinking reactive group refers to the minimum number of atoms required to reach a reactive group. The crosslinking agent having the above linking chain can be used individually or in combination of two or more types. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent. Examples of commercial products of the crosslinking agent include Coronate 2770 (manufactured by Tosoh Corporation), Takenate D178NL (manufactured by Mitsui Chemicals), Duranate A201H (Asahi Kasei Corporation), and the like.

When using a crosslinking agent, the amount used is not particularly limited, and can be, for example, in the range of 0.001 parts by weight to 5.0 parts by weight based on 100 parts by weight of the base polymer. From the viewpoint of improving the flexibility of the high refractive index adhesive layer and adhesion to the adherend, in some embodiments, the amount of crosslinking agent used per 100 parts by weight of the base polymer is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight. part or less, may be 1.0 part by weight or less, and may be 0.5 part by weight or less. In some preferred embodiments, the amount of crosslinking agent used per 100 parts by weight of the base polymer may be less than 0.5 parts by weight, less than 0.4 parts by weight, less than 0.3 parts by weight, or less than 0.2 parts by weight. In addition, from the viewpoint of appropriately demonstrating the effect of using the crosslinking agent, in some embodiments, the amount of the crosslinking agent used per 100 parts by weight of the base polymer may be, for example, 0.005 parts by weight or more, or 0.01 parts by weight or more, It may be 0.05 part by weight or more, 0.08 part by weight or more, or 0.1 part by weight or more. In some preferred embodiments, the amount of crosslinking agent used per 100 parts by weight of the base polymer may be greater than 0.1 part by weight, may be 0.2 part by weight or more, may be 0.3 part by weight or more, or may be 0.4 part by weight or more. According to the technology disclosed herein, a high refractive index adhesive layer that can withstand large deformation can be suitably formed by using an appropriate amount of a crosslinking agent in the above range.

In order to advance the crosslinking reaction more effectively, a crosslinking catalyst may be used. Examples of crosslinking catalysts include metal crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, zirconium tetraacetylacetonate, ferric nasem, butyltin oxide, and dioctyltin dilaurate. . Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferable. The amount of crosslinking catalyst used is not particularly limited. The amount of crosslinking catalyst used per 100 parts by weight of the base polymer can be, for example, in the range of approximately 0.0001 part by weight to 1 part by weight, taking into account the balance between the speed of the crosslinking reaction rate and the length of the pot life of the adhesive composition. , it is desirable to set it in the range of 0.001 parts by weight or more and 0.5 parts by weight or less.

The adhesive composition may contain a compound that generates keto-enol tautomerism as a crosslinking retardant. Thereby, the effect of extending the pot life of the adhesive composition can be realized. For example, in an adhesive composition containing an isocyanate-based crosslinking agent, a compound that generates keto-enol tautomerism can be preferably used. As a compound that generates keto-enol tautomerism, various β-dicarbonyl compounds can be used. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) or acetoacetate esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably used. Compounds that generate keto-enol tautomerism can be used individually or in combination of two or more types. The amount of the compound that generates keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, 0.5 to 10 parts by weight, or 100 parts by weight of the base polymer. It may be more than 5 parts by weight and less than 5 parts by weight.

(Tackifier)

The high refractive index adhesive layer disclosed herein may contain a tackifier. As a tackifier, rosin-based tackifying resin, terpene-based tackifying resin, phenol-based tackifying resin, hydrocarbon-based tackifying resin, ketone-based tackifying resin, polyamide-based tackifying resin, epoxy-based tackifying resin, and elastomer-based tackifier. Known tackifying resins such as tackifying resin can be used. These can be used individually or in combination of two or more types. The amount of tackifying resin used is not particularly limited and can be set to achieve appropriate adhesive performance depending on the purpose or use. In some embodiments, from the viewpoint of refractive index and transparency, the amount of tackifier used per 100 parts by weight of the base polymer is appropriately 30 parts by weight or less, preferably 10 parts by weight or less, and 5 parts by weight or less. It is more preferable to set it to 10 or less. The technology disclosed herein can be preferably implemented without using a tackifier.

(High refractive index particles)

The high refractive index adhesive layer disclosed herein may contain high refractive index particles as an optional component. Here, high refractive index particles mean particles that can increase the refractive index of the adhesive by including them in the adhesive. Hereinafter, high refractive index particles may be expressed as “particle P _HRI ”. HRI stands for high refractive index. The type of particle P _HRI is not particularly limited, and one or two or more types of materials that can improve the refractive index of the adhesive are selected from metal particles, metal compound particles, organic particles, and organic-inorganic composite particles. , can be used. As the particles P _HRI , those that can improve the refractive index of the adhesive from inorganic oxides (for example, metal oxides) can be preferably used. Suitable examples of materials constituting particle P _HRI include titania (titanium oxide, TiO ₂ ), zirconia (zirconium oxide, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide (Nb _{2 )} . O ₅ , etc.) and inorganic oxides (specifically, metal oxides) can be mentioned. Particles made of these inorganic oxides (for example, metal oxides) can be used individually or in combination of two or more types. The average particle diameter (referring to the 50% volume average particle diameter based on laser scattering/diffraction method) of the particles P _HRI is not particularly limited and can be selected from the range of approximately 1 nm to 1000 nm, for example.

The content of particles P _HRI in the high refractive index adhesive layer can be used in an appropriate amount within a range that does not impair the effect of the technology disclosed here. Additionally, the content of the particles P _HRI may vary depending on the target refractive index. For example, the content of the particles P _HRI can be appropriately set to have a refractive index of a predetermined or higher level, taking into account required adhesive properties, etc. In some embodiments, the content of particles P _HRI in the high refractive index adhesive layer may be, for example, less than 10% by weight, less than 1% by weight, or less than 0.1% by weight. The technology disclosed herein can be practiced in an aspect in which the high refractive index adhesive layer does not substantially contain particles P _HRI .

(Leveling system)

In some embodiments, the adhesive composition used to form the high refractive index adhesive layer includes improving the appearance of the high refractive index adhesive layer formed from the composition (for example, improving uniformity of thickness) or improving the coatability of the adhesive composition. For purposes such as these, a leveling agent may be contained as needed. Non-limiting examples of the leveling agent include an acrylic leveling agent, a fluorine-based leveling agent, and a silicone-based leveling agent. The leveling agent can be used, for example, by selecting an appropriate leveling agent from commercially available leveling agents and using a conventional method.

(Other additives)

In the technology disclosed herein, the adhesive composition used to form the high refractive index adhesive layer includes softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, and aging agents, to the extent that the effects of the present invention are not significantly impaired. Known additives that can be used in the adhesive composition, such as inhibitors, ultraviolet absorbers, antioxidants, light stabilizers, and preservatives, may be included as needed. Regarding these various additives, conventionally known ones can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

Although not particularly limited, the effects achieved by the technology disclosed herein can be preferably achieved by using a high refractive index adhesive layer containing the above-described base polymer (typically an acrylic polymer) and a plasticizer. The technology disclosed herein can be preferably implemented in an aspect that uses a high refractive index adhesive layer mainly composed of the base polymer and the plasticizer. Therefore, in some preferred embodiments, a composition with a limited content of components other than the base polymer and the plasticizer (other components) may be adopted as the high refractive index adhesive layer. For example, the total amount of the base polymer and the plasticizer in the high refractive index adhesive layer is 75% by weight or more (for example, 75% by weight or more and 100% by weight or less or less than 100% by weight). It may be 85% by weight or more, 90% by weight or more, 95% by weight or more, 98% by weight or more, or 99% by weight or more (for example, more than 99% by weight). Limiting the use of components other than the base polymer and the plasticizer can be advantageous in realizing large-scale formation of the high refractive index adhesive layer.

<Low refractive index layer>

In the technology disclosed herein, the refractive index n ₂ of the low refractive index layer (preferably the low refractive index adhesive layer) is preferably lower than the refractive index n ₁ of the high refractive index adhesive layer. As a result, the behavior of light passing through the laminated sheet containing these layers can be controlled using the difference in refractive index between the high refractive index adhesive layer and the low refractive index layer. The refractive index n ₂ of the low refractive index layer may be, for example, in the range of 1.35 to 1.55. In some embodiments, from the viewpoint of increasing the refractive index difference with the refractive index n ₁ of the high refractive index adhesive layer to facilitate the enhancement of the front brightness improvement effect described later, the refractive index n ₂ of the low refractive index layer is, for example, 1.49 or less. It is preferable, and it is more preferable that it is 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 availability of the material and compatibility with adhesive properties, in some embodiments, the refractive index n ₂ of the low refractive index layer may be, for example, 1.36 or more, 1.38 or more, or 1.40 or more. , may be 1.42 or more, and may be 1.45 or more. Additionally, in an embodiment where the low refractive index layer is a low refractive index adhesive layer, the relative relationship between the adhesive forces on each surface of the laminate (laminated sheet) of the high refractive index adhesive layer and the low refractive index adhesive layer can be adjusted.

In some embodiments, the ratio (n ₁ /n ₂ ) of the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer may be, for example, greater than 1.00, approximately 1.01 or more, or approximately 1.02. A value greater than or equal to 1.03 is appropriate, and approximately 1.03 or greater may also be used. In some embodiments, the ratio (n ₁ /n ₂ ) is advantageously approximately 1.05 or greater, preferably approximately 1.06 or greater, more preferably approximately 1.07 or greater, and may be approximately 1.08 or greater. The upper limit of the ratio (n ₁ /n ₂ ) is not particularly limited. In some embodiments, from the viewpoint of adhesive properties, transparency, etc., the ratio (n ₁ /n ₂ ) may be, for example, approximately 1.20 or less, approximately 1.18 or less, approximately 1.16 or less, or approximately 1.14 or less. It may be 1.12 or less.

In some embodiments, the difference between the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer, that is, the refractive index difference (n ₁ -n ₂ ), may be, for example, greater than 0.00 or 0.01 or more. , it is preferably 0.02 or more, may be 0.03 or more, may be 0.05 or more, may be 0.07 or more, may be 0.09 or more, may be 0.10 or more, and may be 0.12 or more. The upper limit of the refractive index difference (n ₁ -n ₂ ) is not particularly limited. In some embodiments, from the viewpoint of adhesive properties, transparency, etc., the refractive index difference (n ₁ -n ₂ ) may be, for example, 0.30 or less, 0.26 or less, 0.21 or less, or 0.18 or less; It may be 0.16 or less.

In some embodiments, the low refractive index layer preferably has a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. In addition to the high refractive index adhesive layer, the low refractive index layer also satisfies the above characteristics, so that the laminated sheet (adhesive sheet) containing the high refractive index adhesive layer and the low refractive index layer can be sufficiently deformed at high speed even in a low temperature environment and withstand large deformation. You can. The deformation test conducted under the above conditions of temperature -20°C and speed of 300 mm/min is more specifically conducted by the method described in the test example described later.

In addition, in some embodiments, the low refractive index layer preferably has a stress of 5.0 N/mm 2 or less at a strain of 350% in a strain test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. A low refractive index layer that satisfies the above characteristics has a high refractive index and can be sufficiently deformed at high speed while maintaining a certain level of flexibility even in a low temperature environment. Therefore, it is suitable for use in applications involving large deformation. In some preferred embodiments, the stress at a deformation of 350% may be 4 N/mm 2 or less, 3 N/mm 2 or less, 2 N/mm 2 or less, 1 N/mm 2 or less, or 0.5 N/mm 2 or less. It may be 0.3N/㎟ or less. The lower limit of the stress at the above-described strain of 350% is theoretically 0.0 N/mm 2 or more, and in some preferred embodiments, may be 0.1 N/mm 2 or more.

The storage modulus G' (25°C) of the low refractive index layer is not particularly limited and may range from 1.0 kPa to 500 kPa, for example. From the viewpoint of enhancing the effect of providing flexibility by the low refractive index layer or improving the ability to follow deformation, in some embodiments, the storage modulus G' (25°C) of the low refractive index layer is suitably 400 kPa or less, and 300 kPa or less. It is preferable, and it is more preferable that it is 200 kPa or less (for example, 180 kPa or less or 150 kPa or less), and may be 120 kPa or less, 90 kPa or less, and 70 kPa or less. Furthermore, from the viewpoint of providing appropriate cohesion to the low refractive index layer, in some embodiments, the storage modulus G' (25°C) of the low refractive index layer is suitably 5.0 kPa or more, preferably 10 kPa or more, and 15 kPa or more. It may be 25 kPa or more, 35 kPa or more, 60 kPa or more, or 80 kPa or more. From the viewpoint of making it easier to realize higher cohesion and adhesive properties, in some embodiments, the storage elastic modulus G' (25°C) of the low refractive index layer may be 95 kPa or more, 110 kPa or more, or 140 kPa or more.

In an embodiment in which the low refractive index layer is an adhesive layer, the type of adhesive constituting the adhesive layer is not particularly limited. The adhesives constituting the low refractive index adhesive layer include acrylic polymers, rubber polymers (e.g. natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, and polyether polymers that can be used in the field of adhesives. It may contain one or two or more types of various rubber-like polymers such as polymers, silicone-based polymers, polyamide-based polymers, and fluorine-based polymers as the base polymer. From the viewpoint of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably used. Among them, an adhesive containing an acrylic polymer as a base polymer (acrylic adhesive) is preferable. In an embodiment in which the high refractive index adhesive layer is an acrylic adhesive layer, a configuration in which the low refractive index adhesive layer is an acrylic adhesive layer can be preferably adopted from the viewpoint of adhesion between the high refractive index adhesive layer and the low refractive index adhesive layer.

In some embodiments, the acrylic polymer includes, for example, alkyl (meth)acrylate and may further include another monomer (copolymerizable monomer) that is copolymerizable with the alkyl (meth)acrylate. Polymers of monomer raw materials are preferred. The content of the alkyl (meth)acrylate in the monomer raw material may be, for example, 10% by weight or more, 25% by weight or more, 35% by weight or more, or 45% by weight or more. The acrylic polymer may be a polymer of a monomer component that contains alkyl (meth)acrylate as a main monomer and may further contain the copolymerizable monomer as a parent monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomer raw material. More than 55% by weight or more than 60% by weight of the monomer composition may be alkyl (meth)acrylate. In some embodiments, the proportion of alkyl (meth)acrylate in the monomer raw material of the acrylic polymer can be, for example, 70% by weight or more, 85% by weight or more, or 90% by weight or more. It may be 95% by weight or more, or 98% by weight or more. The upper limit of the proportion of the alkyl (meth)acrylate is not particularly limited, but is preferably 99.5% by weight or less (e.g., 99% by weight or less), or the property based on the parentomer (e.g., cohesion) ), it may be 98% by weight or less (for example, less than 97% by weight).

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 ¹ in the formula (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 expressed as “C _1-20 ”). From the viewpoint of the storage modulus of the adhesive, etc., alkyl ( _meth )acrylates where R ² is a C _1-12 (for example, C _2-10 , typically C _4-8 ) chain alkyl group are preferred. The alkyl (meth)acrylate wherein R ² is a C _1-20 chain alkyl group can be used individually or in combination of two or more. Preferred alkyl (meth)acrylates include n-butylacrylate and 2-ethylhexyl acrylate.

The copolymerizable monomer may be helpful for introducing crosslinking points into the acrylic polymer or increasing the cohesion of the acrylic polymer. Examples of the copolymerizable monomer include carboxyl group-containing monomers, hydroxyl group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a nitrogen atom-containing ring, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers. One or two or more types of functional group-containing monomers can be used. Other examples of copolymerizable monomers include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, non-aromatic ring-containing (meth)acrylates, and alkoxy group-containing monomers. Specific examples include those mentioned above as monomers that can be used in the base polymer of the high refractive index adhesive layer, but are not limited to them. For example, from the viewpoint of improving cohesion, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer is preferred as the copolymerizable monomer. Suitable examples of carboxyl group-containing monomers include acrylic acid and methacrylic acid. Suitable examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

In some embodiments, a fluorine-containing monomer can be used as the copolymerizable monomer in order to lower the refractive index n ₂ of the low refractive index layer. The content of the fluorine-containing monomer in the monomer raw material may be, for example, 10% by weight or more, 25% by weight or more, or 35% by weight or more. From the viewpoint of making it easier to realize a low refractive index layer with a lower refractive index, the content of the fluorine-containing monomer is preferably 40% by weight or more, more preferably 45% by weight or more, even more preferably 55% by weight or more, and 60% by weight or more. It may be more than weight%, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The upper limit of the content of fluorine-containing monomer in the monomer raw material is not particularly limited, and may be 100% by weight. In some embodiments, from the viewpoint of cohesiveness of the low refractive index layer, etc., the content of the fluorine-containing monomer is suitably 99.9% by weight or less, preferably 99.5 or less, may be 99% by weight or less, and may be 97% by weight or less. It may be 92% by weight or less. Fluorine-containing monomers can be used individually or in combination of two or more types.

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 that has at least one fluorine atom in the molecule. For example, fluorine-containing (meth)acrylic acid ester can be suitably used. Suitable examples of fluorine-containing (meth)acrylic acid esters include those having a fluorinated hydrocarbon group at the ester terminal. Examples of the fluorinated hydrocarbon group include a fluorinated aliphatic hydrocarbon group, a fluorinated alicyclic hydrocarbon group, and a fluorinated aromatic hydrocarbon group. As the fluorinated hydrocarbon group, a fluorinated aliphatic hydrocarbon group is suitable. Examples of the fluorinated aliphatic hydrocarbon group include a fluorinated alkyl group. In the fluorinated aliphatic hydrocarbon group, the aliphatic hydrocarbon moiety may be linear or branched. Additionally, in the fluorinated aliphatic hydrocarbon group, the fluorine atom may be bonded to any carbon atom in the aliphatic hydrocarbon group site. The fluorine atom bonded to one carbon atom may be singular or plural. The number of carbon atoms to which the fluorine atom is bonded is not particularly limited.

In fluorinated aliphatic hydrocarbon groups (especially fluorinated alkyl groups), the number of carbon atoms in the hydrocarbon group portion is not particularly limited. In some embodiments, considering compatibility with other copolymerizable monomers, a fluorinated aliphatic hydrocarbon group having a carbon atom number of, for example, 1 to 18 (preferably 1 to 12) is preferred. Specific examples of the fluorinated aliphatic hydrocarbon group include fluorinated methyl groups such as trifluoromethyl group, difluoromethyl group, and monofluoromethyl group; Pentafluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoro Roethyl group, 2,2,2-trifluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1-monofluoroethyl group, 2- Fluorinated ethyl groups such as monofluoroethyl groups; etc. can be mentioned. As a fluorinated alkyl group having 3 or more carbon atoms, similar to the above example fluorinated methyl group or fluorinated ethyl group, various fluorinated alkyl groups in which one or more fluorine atoms are bonded to any one or more carbon atoms of the alkyl group moiety can be exemplified. .

Examples of the fluorinated alicyclic hydrocarbon group include fluorinated cycloalkyl groups. Similarly to the above fluorinated aliphatic hydrocarbon group, in the fluorinated alicyclic hydrocarbon group, the fluorine atom may be bonded to any carbon atom of the alicyclic hydrocarbon group, and the fluorine atom bonded to one carbon atom may be singular or plural. do. Additionally, the number of carbon atoms to which the fluorine atom is bonded is not particularly limited. Examples of the fluorinated alicyclic hydrocarbon group include cyclohexyl groups having one fluorine atom such as 2-fluorocyclohexyl group, 3-fluorocyclohexyl group, and 4-fluorocyclohexyl group; Cyclohexyl groups having two fluorine atoms, such as 2,4-difluorocyclohexyl group and 2,6-difluorocyclohexyl group; Cyclohexyl groups having three fluorine atoms, such as 2,4,6-trifluorocyclohexyl groups, are included.

The fluorinated hydrocarbon group does not need to have a substituent, and may have one. Such substituents are not particularly limited and include, for example, hydrocarbon groups such as alkyl groups, alkoxy groups, hydroxy groups, carboxyl groups, amino groups, nitro groups, cyano groups, and halogen atoms. Substituents can be used individually or in combination of two or more types.

Fluorine atom-containing (meth)acrylic acid esters [fluorinated (meth)acrylates] include, for example, fluorine atom-containing (meth)acrylic acid alkyl esters [fluorinated alkyl (meth)acrylates], fluorine atom-containing (meth)acrylic acid cycloalkyl esters. [Fluorinated cycloalkyl (meth)acrylate], fluorine atom-containing (meth)acrylic acid aryl ester [Fluorinated aryl (meth)acrylate], etc.

As the fluorine atom-containing (meth)acrylic acid ester, fluorinated alkyl (meth)acrylate (especially fluorinated alkyl acrylate) is suitable. Examples of the fluorinated alkyl (meth)acrylate include 2,2,2-trifluoroethyl acrylate (trade name "Viscott 3F" manufactured by Osaka Yuki Chemical Co., Ltd., etc.), 2,2,3, 3-Tetrafluoropropyl acrylate (trade name “Viscot 4F”, manufactured by Osaka Yuki Chemical Co., Ltd., etc.), 1H, 1H, 5H-octafluoropentylacrylate (manufactured by Osaka Yuki Chemical Kogyo Co., Ltd.) (trade name "Viscott 8F", etc.), 1H,1H,5H-octafluoropentyl methacrylate (trade name "Viscott 8FM", etc., manufactured by Osaka Yuki Kagaku Kogyo Co., Ltd.), 2-(heptadecafluoro Nonyl) ethyl acrylate (product name "FA-108", manufactured by Kyoesha Chemical Co., Ltd., etc.), 1H, 1H, 2H, 2H-tridecafluorooctyl acrylate (manufactured by Osaka Yuki Chemical Co., Ltd.) (brand name "Viscott 13F", etc.), etc. can be mentioned.

The number of carbon atoms of the fluorinated alkyl group in the fluorinated alkyl (meth)acrylate is advantageously 3 or more, preferably 4 or more, more preferably 5 or more, from the viewpoint of low refractive index effect, flexibility, etc. Or, it is more preferable that it is 7 or more, and it is especially preferable that it is 8 or more. From the viewpoint of adhesion performance, etc., the number of carbon atoms of the fluorinated alkyl group is advantageously 18 or less, preferably 14 or less, more preferably 12 or less, and may be 10 or less, or 9 or less. In some embodiments, the number of carbon atoms of the fluorinated alkyl group may be 7 or less, and may be 5 or less. Furthermore, in some embodiments, the fluorine atom-containing (meth)acrylic acid ester is preferably a fluorinated alkyl (meth)acrylate in which fluorine is not bonded to the carbon at the 1st position of the alkyl group, for example, 1H, 1H, Like 2H,2H-tridecafluorooctyl acrylate, a fluorinated alkyl (meth)acrylate in which fluorine is not bonded to either the carbon at the 1st position or the carbon at the 2nd position of the alkyl group can be preferably used.

In some embodiments, the low refractive index layer is an acrylic adhesive layer, and the acrylic polymer that is the base polymer of the adhesive includes at least a fluorine-containing acrylic monomer (e.g., fluorinated alkyl (meth)acrylate) as described above. , it may be a polymer of monomer raw materials that may further contain another monomer (copolymerizable monomer) having copolymerizability with the fluorine-containing acrylic monomer. This monomer raw material may or may not contain alkyl (meth)acrylate. The content of the fluorine-containing acrylic monomer in the monomer raw material may be, for example, 10% by weight or more, 25% by weight or more, or 35% by weight or more. From the viewpoint of making it easier to realize a low refractive index layer with a lower refractive index, the content of the fluorine-containing acrylic monomer is preferably 40% by weight or more, more preferably 45% by weight or more, and even more preferably 55% by weight or more, It may be 60% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The upper limit of the content of the fluorine-containing acrylic monomer in the monomer raw material is not particularly limited, and may be 100% by weight. In some embodiments, from the viewpoint of cohesion of the low refractive index layer, etc., the content of the fluorine-containing acrylic monomer is suitably 99.9% by weight or less, preferably 99.5% or less, may be 99% by weight or less, and may be 97% by weight. It may be less than or equal to 92% by weight. Fluorine-containing acrylic monomers can be used individually or in combination of two or more types.

The monomer raw material for preparing the base polymer of the low refractive index layer may be a composition containing a copolymerizable monomer in addition to a fluorine-containing acrylic monomer (for example, fluorinated alkyl (meth)acrylate). Examples of the copolymerizable monomer include carboxyl group-containing monomers, hydroxyl group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, and monomers having a nitrogen atom-containing ring (e.g., N-vinyl-2- One or two or more types of functional group-containing monomers such as N-vinyl cyclic amides such as pyrrolidone, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers can be used. Other examples of copolymerizable monomers include vinyl ester monomers such as vinyl acetate, aromatic vinyl compounds such as styrene, and non-aromatic ring-containing (meth)acrylates such as cycloalkyl (meth)acrylate and isobornyl (meth)acrylate. Acrylates, alkoxy group-containing monomers; etc. can be mentioned. Specific examples include those mentioned above as monomers that can be used in the base polymer of the high refractive index adhesive layer, but are not limited to them. For example, from the viewpoint of improving cohesion, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer is preferred as the copolymerizable monomer.

In some preferred embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer may have a composition containing a hydroxyl group-containing monomer. Hydroxyl group-containing monomers can be helpful in improving cohesion or introducing crosslinking points. Suitable examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylate such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutylacrylate can be used more preferably. The content of the hydroxyl group-containing monomer in the monomer raw material is not particularly limited, and may be, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.5% by weight or more). In some embodiments, the content of the hydroxyl group-containing monomer 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% by weight or less or 10% by weight or less. In some embodiments, from the viewpoint of lowering the refractive index, 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, and may be less than 3% by weight. It may be less than 2.5% by weight, or less than 1.5% by weight.

In some embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer has a limited content of carboxyl group-containing monomer from the viewpoint of suppressing coloring or discoloration (for example, yellowing) of the low refractive index layer. desirable. 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 less than 0.1% by weight (for example, 0.05% by weight). It is more preferable that it is less than %). This limited content of carboxyl group-containing monomer suppresses corrosion of metal materials that may be placed in contact with or close to the low refractive index layer (for example, metal wiring or metal films that may be present on the adherend). It is also advantageous from a perspective. The technology disclosed herein can be preferably implemented in an embodiment in which the monomer raw material does not contain a carboxyl group-containing monomer.

For the same reason, in some embodiments, the monomer raw material for preparing the base polymer of the low refractive index layer has a limited content of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxyl groups). It is desirable. As the content of the acidic functional group-containing monomer in the monomer raw material of this embodiment, the preferable content of the carboxyl group-containing monomer described above can be applied. The technology disclosed herein can be preferably implemented in an embodiment in which the monomer raw material does not contain an acidic group-containing monomer (that is, the base polymer of the low refractive index layer is acid-free).

The base polymer of the low refractive index layer, like the base polymer of the high refractive index adhesive layer, can be prepared by appropriately employing a known polymerization method. The weight average molecular weight (Mw) of the base polymer (for example, an acrylic polymer) is not particularly limited, and may be, for example, in the range of approximately 10×10 ⁴ to 500×10 ⁴ or approximately 20×10 ⁴ to 200× It may be in the range of 10 ⁴ . In some embodiments, from the viewpoint of adhesion to the high refractive index adhesive layer, etc., the Mw of the base polymer of the low refractive index adhesive layer is suitably 250×10 ⁴ or less, may be 200×10 ⁴ or less, and may be 150×10 It may be ⁴ or less, 120×10 ⁴ or less (for example, 95×10 ⁴ or less), 75×10 ⁴ or less, 68×10 ⁴ or less, or 60×10 ⁴ or less. In addition, in some embodiments, from the viewpoint of cohesion of the low refractive index adhesive layer, etc., the Mw of the base polymer may be, for example, 30 × 10 ⁴ or more, 40 × 10 ⁴ or more, or 50 × 10 ⁴ or more. You can continue. In some preferred embodiments, the base polymer Mw may be approximately 70×10 ⁴ or greater, approximately 100×10 ⁴ or greater, 130×10 ⁴ or greater, or 160×10 ⁴ or greater (for example, 180×10 4 or greater). 10 ⁴ or more) may be sufficient. By using a base polymer whose Mw is a predetermined value or more, it is easy to obtain an appropriate cohesive force that can exhibit the desired adhesive properties. In addition, by utilizing the cohesiveness based on the above-mentioned high molecular weight polymer, excellent flexibility is achieved and, in addition, flexibility capable of withstanding large deformation is easily obtained. To prepare Mw, a conventionally known chain transfer agent can be used as needed.

Although not particularly limited, from the viewpoint of adhesiveness, it is advantageous for the Tg of the base polymer (e.g., acrylic polymer) of the low refractive index layer to be approximately 0°C or lower, and preferably approximately -5°C or lower (e.g., approximately -5°C or lower). 15℃ or lower, or -25℃ or lower). Additionally, from the viewpoint of the cohesion of the adhesive layer, the Tg of the base polymer of the low refractive index layer is approximately -75°C or higher, preferably approximately -70°C or higher (for example, -50°C or higher, and further -30°C or higher). am. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of monomers used in the synthesis of the polymer).

For the low refractive index layer, a known crosslinking agent can be used. Additionally, the low refractive index layer may contain a tackifier or other additives. The crosslinking agent or tackifier can be appropriately selected from those that can be used in the high refractive index adhesive layer and used in an appropriate amount.

In an embodiment where the pressure-sensitive adhesive composition used to form the low-refractive-index pressure-sensitive adhesive layer contains a crosslinking agent, for example, an isocyanate-based crosslinking agent can be preferably employed as the crosslinking agent. In some embodiments, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer of the adhesive composition may be, for example, less than 0.5 parts by weight, for example, from the viewpoint of adhesion with the high refractive index adhesive layer, and 0.3 parts by weight. It may be less than 0.2 parts by weight, or less than 0.15 parts by weight. In addition, from the viewpoint of appropriately demonstrating the effect of using the cross-linking agent, in some embodiments, the amount of the isocyanate-based cross-linking agent used per 100 parts by weight of the base polymer may be, for example, 0.005 parts by weight or more, and may be 0.01 parts by weight or more. It may be 0.05 parts by weight or more, and may be 0.08 parts by weight or more.

<Production of adhesive layer>

In the technology disclosed herein, the adhesive constituting the adhesive layer (which may be a high refractive index adhesive layer and/or a low refractive index layer; the same applies hereinafter unless otherwise specified) can be formed using an adhesive composition. The form of the adhesive composition used is not particularly limited, and for example, a solvent-based adhesive composition containing an adhesive-forming component in an organic solvent, cured by active energy rays such as ultraviolet rays or radiation to form an adhesive. It can be in various forms, such as an active energy ray-curable adhesive composition, a water-dispersible adhesive composition in which the adhesive-forming ingredients are dispersed in water, and a hot melt-type adhesive composition that is applied in a heated and molten state and forms an adhesive when cooled to around room temperature. there is. The adhesive is an adhesive obtained by curing an adhesive composition in the form of a solvent type, active energy ray curable type, water dispersion type, or hot melt type by drying, crosslinking, polymerization, cooling, etc., that is, it may be a cured product of the adhesive composition. Only one type of means for curing the adhesive composition (for example, drying, crosslinking, polymerization, cooling, etc.) may be applied, or two or more types may be applied simultaneously or in multiple steps. In solvent-based adhesive compositions, the adhesive can typically be formed by drying (preferably, also crosslinking) the composition. In an active energy ray-curable adhesive composition, the adhesive is typically formed by irradiating an active energy ray to advance a polymerization reaction and/or a crosslinking reaction. If it is necessary to dry the active energy ray-curable adhesive composition, the active energy ray may be irradiated after drying. Although not particularly limited, the adhesive disclosed herein can be preferably formed using a solvent-based adhesive composition.

The pressure-sensitive adhesive layer in the technology disclosed herein can be formed by applying (for example, applying) a pressure-sensitive adhesive composition to an appropriate surface and then curing the composition. Application of the adhesive composition can be performed using a common coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater.

The adhesive layer in the technology disclosed here may be an adhesive layer that has post-curing properties, or may be an adhesive layer that does not have post-curing properties. Here, the adhesive layer having post-curing properties refers to an adhesive layer that can be further cured by irradiation of heat or active energy rays (for example, ultraviolet rays). Examples of the adhesive layer having post-curing properties include an adhesive layer having an unreacted ethylenically unsaturated group in the side chain of the base polymer or an adhesive layer containing an unreacted polyfunctional monomer. In some embodiments, it is preferred that the pressure-sensitive adhesive layer does not have post-cure properties. Since the adhesive layer without post-curing property does not cause dimensional change accompanying the post-curing reaction (i.e., has good dimensional stability), it is easy to suppress warping of the adhesive layer or the adherend to which the adhesive layer is attached. The fact that dimensional changes (for example, curing shrinkage) due to post-curing do not occur can be advantageous also from the viewpoint of suppressing optical distortion of the adhesive layer.

The thickness of the adhesive layer in the technology disclosed here is not particularly limited, and can be, for example, 3 μm or more, and is preferably 5 μm or more. With an adhesive layer having a thickness of 5 μm or more, good adhesive properties are easily obtained. In addition, an adhesive layer of this thickness absorbs irregularities that may exist on the surface of the adherend and is easy to bond to the adherend with good adhesion. It is also preferable that the thickness of the adhesive layer (for example, the thickness of the high refractive index adhesive layer) is 5 μm or more from the viewpoint of preventing coloring and color unevenness due to light interference. In some embodiments, the thickness of the adhesive layer may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 85 μm or more. In addition, in some embodiments, the thickness of the adhesive layer may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. In some preferred embodiments, the thickness of the adhesive layer is 100 μm or less, more preferably 75 μm or less, further preferably 70 μm or less, and may be 50 μm or less, or 30 μm or less. The fact that the thickness of the adhesive layer is not too large can be advantageous from the viewpoint of reducing the thickness of the laminated sheet or light-emitting device containing the adhesive layer. Additionally, a thin adhesive layer tends to have excellent followability to the adherend. The technology disclosed herein is preferably carried out in such a way that the thickness of the adhesive layer ranges from 3 ㎛ to 200 ㎛ (more preferably 5 ㎛ to 100 ㎛, more preferably 5 ㎛ to 75 ㎛). It can be.

In some embodiments, the thickness of the adhesive layer described above can be applied to at least the thickness T ₁ of the high refractive index adhesive layer. The thickness T ₂ of the low refractive index adhesive layer can also be selected from the same range. The thickness of the adhesive layer described above can also be applied to the thickness T ₂ of the low refractive index layer, regardless of whether it is an adhesive layer or not. The thickness T ₁ of the high refractive index adhesive layer and the thickness T ₂ of the low refractive index layer may be about the same or different. The ratio (T ₁ /T ₂ ) of the thickness T ₁ of the high refractive index adhesive layer and the thickness T ₂ of the low refractive index layer may be, for example, 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more; It may be 0.5 or more, and may be 1.0 or more (for example, more than 1.0). In addition, the ratio (T ₁ /T ₂ ) may be, for example, 20 or less, 10 or less, 5 or less, or 3 or less. In some embodiments, the ratio (T ₁ /T ₂ ) may be less than 2, less than 1.5, or less than 1. In several other embodiments, the ratio (T ₁ /T ₂ ) may be 0.8 or less, 0.6 or less, or 0.5 or less.

A method of obtaining a structure (laminated sheet) in which a high refractive index adhesive layer and a low refractive index layer (typically a low refractive index adhesive layer) are laminated, for example, on a release surface (e.g., release surface of a release liner). A method of forming a high refractive index adhesive layer and a low refractive index layer and bonding them, a method of applying a composition for forming a low refractive index layer on the high refractive index adhesive layer and curing it, or conversely forming a high refractive index adhesive layer. A method of applying the adhesive composition to the low refractive index layer and curing it may be employed, but is not limited to these. When bonding a previously formed high refractive index adhesive layer and a low refractive index layer, treatment to promote adhesion of the layers may be performed, if necessary. For example, autoclave treatment, roll press treatment, etc. can be performed, but are not limited to these.

(Peel Strength)

The peeling strength of the adhesive layer disclosed herein from the glass plate is not particularly limited. In some embodiments, the adhesive layer has a peeling strength from the glass plate of, for example, 0.1 N/25 mm or more, and may be 0.5 N/25 mm or more. In some preferred embodiments, the peeling strength for the glass plate is 1.0 N/25 mm or more, more preferably 1.5 N/25 mm or more, further preferably 2.0 N/25 mm or more, and 3.0 N/25 mm or more. It may be 25 mm or more, 5.0 N/25 mm or more, or 10 N/25 mm or more. In this way, the adhesive layer having a peeling strength from a glass plate of a predetermined value or more is suitable for bonding or fixing glass members, etc., for example. The upper limit of the peel strength is not particularly limited, and may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less.

Here, the peeling strength is determined by pressing an alkali glass plate as an adherend and leaving it in an environment of 23°C and 50%RH for 30 minutes, then placing it in a pressurized degassing device (autoclave) at a temperature of 50°C and a pressure of 0.5 MPa. After performing autoclave treatment for 30 minutes and leaving it for 24 hours in an atmosphere of 23°C and 50%RH, the peeling strength is measured under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm/min. In the measurement, if necessary, the adhesive layer of the measurement object can be reinforced by attaching an appropriate backing material (for example, a polyethylene terephthalate (PET) film with a thickness of about 25 μm to about 50 μm). Peel strength can be measured more specifically by the following method.

[Peel strength against glass plate]

Under a measurement environment of 23°C and 50%RH, the release liner was peeled from one side of the adhesive layer, a PET film with a thickness of 50 μm was bonded and backed, and the test piece was cut into pieces of 25 mm in width and 100 mm in length. Do it as The peeling liner on the other side is peeled from the test piece, and is pressed to the surface of an alkali glass plate (manufactured by Matsunami Glass Industries, Inc., thickness 1.35 mm, polished plate) as an adherend by making one reciprocation of a 2 kg roller. After leaving it in the same environment for 30 minutes, it was then put into a pressure degassing device (autoclave) and autoclaved for 30 minutes under conditions of a temperature of 50°C and a pressure of 0.5 MPa, and further under an atmosphere of 23°C and 50%RH. After leaving for 24 hours, the peel strength (adhesive force) [N/25 mm] is measured under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees, according to JIS Z 0237:2000, using a universal tensile compression tester. . As a universal tensile and compression tester, for example, "Tensile and Compression Tester, TG-1kN" manufactured by Minebea Co., Ltd. can be used.

When the high refractive index adhesive layer disclosed herein is laminated with a low refractive index adhesive layer to form a laminated sheet in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, in some embodiments, The above-mentioned peel strength is preferably applied to at least the first adhesive surface (an adhesive surface comprised of a high refractive index adhesive layer), and more preferably applied to both the first adhesive surface and the second adhesive surface. The peeling strength of the first adhesive surface to the glass plate and the peeling strength of the second adhesive surface to the glass may be the same or different.

<Supporting description>

The high refractive index adhesive layer and the low refractive index layer may be laminated on one side of the support base material in this order or in the reverse order. In this way, a configuration in which a high-refractive-index adhesive layer and a low-refractive-index layer are laminated on a support substrate can also be understood as an adhesive sheet including a substrate. Therefore, according to this specification, an adhesive sheet (adhesive product) is provided with a base material including a laminated sheet made of a high refractive index adhesive layer and a low refractive index layer (preferably a low refractive index adhesive layer), and a support base material for supporting the laminated sheet. ) is provided.

The material of the support base material is not particularly limited and can be appropriately selected depending on the purpose of use, usage mode, etc. Non-limiting examples of substrates that can be used include polyolefin films mainly containing polyolefins such as polypropylene (PP) and ethylene-propylene copolymer, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene film. Plastic films such as polyester films containing polyester such as phthalate (PEN) as a main ingredient, and polyvinyl chloride films containing polyvinyl chloride as a main ingredient; Foam sheets made of foam such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; Woven fabrics and non-woven fabrics made by spinning alone or in a blend of various fibrous materials (which may be natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate); Paper such as Japanese paper, fine paper, kraft paper, and crepe paper; Metal foil such as aluminum foil and copper foil; etc. can be mentioned. It may be a base material composed of a combination of these. Examples of such composite substrates include, for example, a substrate having a structure in which metal foil and the above plastic film are laminated, a plastic substrate reinforced with inorganic fibers such as glass cloth, etc.

In some embodiments, various film substrates can be preferably used. The film substrate may be a porous substrate such as a foam film or a non-woven fabric sheet, may be a non-porous substrate, or may be a substrate having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, the film substrate may preferably include a resin film capable of independently maintaining its shape (self-supporting or non-dependent) as a base film. Here, “resin film” means a resin film that has a non-porous structure and typically contains substantially no air bubbles (voidless). Therefore, the resin film is a concept that is distinct from foam films or nonwoven fabrics. As the resin film, one that can independently maintain its shape (self-supporting or non-dependent) can be preferably used. The resin film may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

Materials constituting the resin film include, for example, polyester-based resins containing polyester as a main component such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), and polyethylene (PE). , polyolefin-based resins mainly containing polyolefins such as polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer, cellulose resins such as triacetylcellulose, acetate-based resins, polysulfone-based resins, and polyethersulfone-based resins. Resin, polycarbonate-based resin, nylon 6, nylon 66, polyamide (PA)-based resin such as partially aromatic polyamide, polyimide (PI)-based resin, transparent polyimide resin, polyamideimide (PAI), poly Etheretherketone (PEEK), polyethersulfone (PES), cyclic polyolefin resin such as norbornene resin, (meth)acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol -based resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl alcohol copolymer resin, polyarylate-based resin, polyphenylene sulfide (PPS)-based resin, polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), Examples include fluorine-based resins such as polytetrafluoroethylene (PTFE) and fluorinated polyimide.

The resin film may be formed using a resin material that contains one type of such resin alone, or may be formed using a resin material that is a blend of two or more types. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, non-oriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, PP/ PE blend film, etc. may be preferably used. Examples of preferable resin films from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film, and PEEK film. PET film and PPS film are particularly preferable from the viewpoint of ease of availability, etc., and among them, PET film is preferable.

The resin film needs to contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, anti-blocking agents, etc., to the extent that the effects of the present invention are not significantly impaired. It can be mixed accordingly. The amount of additives is not particularly limited and can be set appropriately depending on the purpose of the adhesive sheet.

The manufacturing method of the resin film is not particularly limited. For example, conventionally known general resin film molding methods such as extrusion molding, inflation molding, T die cast molding, and calendar roll molding can be appropriately employed.

The substrate may be substantially composed of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an optical property adjustment layer (e.g., a colored layer, an anti-reflection layer), a surface treatment layer such as a printing layer, a laminate layer, an antistatic layer, an undercoating layer, and a peeling layer for giving the substrate a desired appearance. I can hear it.

In some embodiments, a substrate having light transparency (hereinafter also referred to as a light transparency substrate) can be preferably used as the support substrate. This makes it possible to construct an adhesive sheet provided with a light-transmitting substrate. The total light transmittance of the light-transmitting substrate may be, for example, more 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 (for example, 95 to 100%). The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used. A suitable example of the light-transmitting substrate includes a resin film having light transparency. The light-transmitting substrate may be an optical film.

The thickness of the base material is not particularly limited and can be selected depending on the purpose of use, usage mode, etc. The thickness of the substrate may be, for example, 500 μm or less, preferably 300 μm or less from the viewpoint of handling and processability, 150 μm or less, 100 μm or less, 50 μm or less, and 25 μm or less. It may be 10㎛ or less. As the thickness of the substrate decreases, followability to the surface shape of the adherend tends to improve. Additionally, from the viewpoint of handling, processability, etc., the thickness of the substrate may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

The surface of the substrate on which the adhesive layer is laminated is subjected to conventional treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of an undercoat layer by applying an undercoat (primer), as needed. Known surface treatment may be performed. Such surface treatment may be a treatment to improve the anchoring properties of the adhesive layer to the substrate. The composition of the primer used to form the undercoat layer is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoating layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and is preferably about 0.1 μm to 1 μm. Other treatments that can be performed on the substrate as needed include antistatic layer formation treatment, colored layer formation treatment, and printing treatment. These treatments can be applied individually or in combination.

In the technology disclosed herein, when the high refractive index adhesive layer and the low refractive index layer constitute an adhesive sheet including a base material, the thickness of the adhesive sheet may be, for example, 1000 μm or less, or 350 μm or less. , may be 200 μm or less, may be 120 μm or less, may be 75 μm or less, and may be 50 μm or less. In addition, the thickness of the adhesive sheet may be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more from the viewpoint of handleability and the like.

In addition, the thickness of the adhesive sheet refers to the thickness of the portion attached to the adherend. For example, in the inorganic double-sided adhesive sheet 2 of the configuration shown in FIG. 2, the area from the first surface (first adhesive surface) 10A of the adhesive layer to the second surface (second adhesive surface) 10B It refers to the thickness and does not include the thickness of the release liners 31 and 32.

<Laminated sheets>

The laminated sheet (adhesive sheet) including the high refractive index adhesive layer and the low refractive index layer disclosed herein may be a laminated sheet composed of the high refractive index adhesive layer and the low refractive index layer (preferably the low refractive index adhesive layer) as described above. , the laminated sheet may be provided with a base material that further includes a support base material for supporting the laminated sheet.

In some embodiments, the haze value of the laminated sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, and even 0.9% or less. , may be 0.8% or less, may be 0.5% or less, and may be 0.3% or less. Such a highly transparent laminated sheet is advantageous in applications requiring high light transparency. The lower limit of the haze value of the laminated sheet is not particularly limited, and from the viewpoint of improving transparency, a smaller haze value is more preferable. On the other hand, in some embodiments, taking the refractive index and adhesive properties into consideration, the haze value may be, for example, 0.05% or more, or 0.10% or more. The haze value of the laminated sheet can be measured by a method similar to the measurement of the haze value of the adhesive layer. Specifically, it can be measured by the method described in the test example described later. The above-mentioned haze value of the laminated sheet can be obtained by the composition of the adhesive layer described above, etc., or, in the case of a structure having a base material, by selecting the base material type or base material thickness.

In some embodiments, the total light transmittance of the laminated sheet is preferably 85.0% or more (for example, 88.0% or more, 90.0% or more, or more than 90.0%). Such a highly transparent laminated sheet is advantageous in applications requiring high light transparency. For practical purposes, the upper limit of the total light transmittance may be approximately 98% or less, approximately 96% or less, or approximately 95% or less. In some embodiments, taking into account the refractive index and adhesive properties, the total light transmittance of the laminated sheet may be approximately 94% or less, approximately 93% or less, or approximately 92% or less. The total light transmittance of the laminated sheet can be measured by the same method as the measurement of the total light transmittance of the adhesive layer. Specifically, it can be measured by the method described in the test example described later. The total light transmittance of the laminated sheet can be obtained by the composition of the adhesive layer described above, etc., or, in the case of a structure having a substrate, by selecting the substrate species or substrate thickness.

The thickness of the laminated sheet disclosed herein (a laminated sheet without a base material or a laminated sheet with a base material) may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, or 120 μm or less. It may be 75㎛ or less, and may be 50㎛ or less. In addition, from the viewpoint of handling, etc., the thickness of the adhesive sheet may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 25 μm or more, 80 μm or more, or 130 μm. It can be more than that.

In addition, the thickness of the adhesive sheet refers to the thickness of the portion attached to the adherend. For example, in the inorganic double-sided adhesive sheet 2 of the configuration shown in FIG. 2, the area from the first surface (first adhesive surface) 10A of the adhesive layer to the second surface (second adhesive surface) 10B It refers to the thickness and does not include the thickness of the release liners 31 and 32.

<Laminated sheet with release liner>

The high refractive index adhesive layer and the low refractive index layer disclosed herein are, before being incorporated into a light emitting device, a form of adhesive in which the adhesive surface of the laminated sheet including the high refractive index adhesive layer and the low refractive index layer is brought into contact with the peeling surface of the release liner. It may take the form of a product (laminated sheet with release liner). Accordingly, this specification provides a laminated sheet (adhesive product) comprising a laminated sheet of a high refractive index adhesive layer and a low refractive index layer, and a release liner including a release liner having a release surface that contacts the adhesive surface of the laminated sheet. do.

The release liner is not particularly limited and includes, for example, a release liner having a release treatment layer on a release liner base material such as a resin film or paper (can be paper laminated with a resin such as polyethylene), or a fluorine-based polymer ( A release liner made of a resin film formed of a low-adhesion material such as polytetrafluoroethylene or polyolefin resin (polyethylene, polypropylene, etc.) can be used. The release treatment layer may be formed by surface treating a release liner base material with a release treatment agent. The peeling treatment agent may be a known peeling treatment agent such as a silicone-based peeling treatment agent, a long-chain alkyl-based peeling treatment agent, a fluorine-based peeling treatment agent, or molybdenum (IV) sulfide. In some embodiments, a release liner having a release treatment layer using a silicone-based release treatment agent can be preferably employed. The thickness or formation method of the release treatment layer is not particularly limited, and can be set so that appropriate release properties are exhibited on the surface on the adhesive side of the release liner.

In some embodiments, from the viewpoint of smoothness of the adhesive surface, etc., a release liner (hereinafter also referred to as release film) is configured to have a release treatment layer on a resin film (hereinafter also referred to as release film substrate) as the release liner base material. can be preferably employed. As a release film base material, various plastic films can be used. In this specification, a plastic film is typically a non-porous sheet, and is a concept that is distinct from, for example, non-woven fabric (i.e., does not include non-woven fabric).

Materials for the plastic film include, for example, polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), Polyolefin-based resins such as ethylene-propylene copolymers and ethylene-butene copolymers, cellulose resins such as triacetylcellulose, acetate-based resins, polysulfone-based resins, polyethersulfone-based resins, polycarbonate-based resins, and polyamide-based resins Resins, polyimide-based resins, cyclic polyolefin resins such as norbornene-based resins, (meth)acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and ethylene-vinyl acetate. Examples include copolymer resin, ethylene-vinyl alcohol copolymer resin, polyarylate-based resin, and polyphenylene sulfide-based resin. A release film substrate formed from any one of these resins or a mixture of two or more types can be used. Among these, a preferred release film base material includes a polyester resin film (for example, PET film) formed of polyester resin.

The plastic film used as the above-mentioned release film base material may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Additionally, the plastic film may have a single-layer structure or a multi-layer structure including two or more sub-layers. The plastic film includes known antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, nucleating agents, etc. that can be used in the release film base of the adhesive sheet. Additives may be mixed. In a plastic film with a multilayer structure, each additive may be blended in all sub-layers or only in some of the sub-layers.

In some preferred embodiments, the release film substrate (typically a plastic film) has a limited content of particles such as inorganic particles (which may be pigments, lubricants, fillers, etc.) in the layer on the release surface side. Those that are or do not substantially contain such particles can be preferably used. Here, substantially not included means that the amount of particles (for example, inorganic particles) in the layer is less than 1% by weight, preferably less than 0.1% by weight (for example, 0 to 0.01% by weight). . A release film provided with such a release film base material tends to have a low arithmetic mean roughness Ra or maximum height Rz of the release surface. When the release film base material (typically a plastic film) has a multilayer structure, the particle content in the layer on the release surface side is 1/10 or less (for example, 1/10) of the particle content in layers other than the release surface side layer. /50 or less).

A laminated sheet comprising a release liner of a type having a release liner on each of the first adhesive surface and the second adhesive surface, comprising: a release liner (hereinafter also referred to as one release liner) disposed on one of the adhesive surfaces; The release liner (hereinafter also referred to as the other release liner) disposed on the other adhesive surface may have the same material and structure, or may have different materials and structure.

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

In a laminated sheet with a release liner in an aspect including a release liner on one side and a release liner on the other side, the thickness of the release liners may be the same or different. In some embodiments, from the viewpoint of peelability, etc., it is preferable that one release liner and the other release liner have different thicknesses, for example, the thickness of the thicker release liner is greater than that of the thinner release liner. It is preferably approximately 1.1 times or more (for example, approximately 1.25 times or more. The upper limit is not particularly limited, but, for example, 5 times or less) of the thickness of the release liner.

(Arithmetic average roughness Ra of the surface on the adhesive side)

In some embodiments, the release liner (preferably the release film) has an arithmetic mean roughness Ra of the adhesive side surface limited to a predetermined value or less (e.g., approximately 100 nm or less, further less than 50 nm). This is desirable from the viewpoint of realizing an adhesive surface with high surface smoothness. In some embodiments, the arithmetic mean roughness Ra of the surface on the adhesive side of the release liner is preferably, for example, approximately 30 nm or less, more preferably approximately 25 nm or less, may be approximately 20 nm or less, and may be approximately 18 nm or less. It's okay. In addition, from the viewpoint of ease of manufacturing and handling of the release liner, in some embodiments, the arithmetic mean roughness Ra may be, for example, approximately 5 nm or more, approximately 10 nm or more, or approximately 15 nm or more. You can continue. In a laminated sheet having a release liner in a form in which a release liner is disposed on the first adhesive surface and the second adhesive surface, it is preferable that the adhesive surface side surfaces of both release liners satisfy any of the above-mentioned arithmetic mean roughness Ra. do. The arithmetic mean roughness Ra of the surfaces on the adhesive side of both release liners may be the same or different.

(Maximum height Rz of the surface on the adhesive side)

In some embodiments, it is preferable that the maximum height Rz of the surface on the adhesive surface side of the release liner (preferably the release film) is 700 nm or less from the viewpoint of realizing an adhesive surface with high surface smoothness. In some embodiments, the maximum height Rz of the surface on the adhesive side of the release liner is preferably approximately 600 nm or less, may be approximately 500 nm or less, may be approximately 400 nm or less, or may be approximately 300 nm or less. In addition, from the viewpoint of ease of manufacturing and handling of the release liner, in some embodiments, the maximum height Rz may be, for example, approximately 50 nm or more, approximately 80 nm or more, or approximately 100 nm or more. It may be approximately 200 nm or more, and may be approximately 300 nm or more. In a laminated sheet having a release liner in a form in which a release liner is disposed on the first adhesive surface and the second adhesive surface, it is preferable that the adhesive surface side surfaces of both release liners satisfy the maximum height Rz of any of the above. . The maximum height Rz of the surfaces on the adhesive side of both release liners may be about the same or different.

(Surface properties of the back)

The arithmetic mean roughness Ra and maximum height Rz of the back surface (opposite the adhesive layer side) of the release liner (preferably the release film) are not particularly limited. The arithmetic mean roughness Ra of the back surface of the release liner may be, for example, more than 30 nm (for example, more than 35 nm, and further approximately 50 nm or more) from the viewpoint of productivity and the like. The maximum height Rz of the back surface of the release liner may be, for example, greater than 400 nm (e.g., approximately 500 nm or more) or greater than 800 nm (e.g., approximately 1,000 nm or more) from the viewpoint of productivity or the like.

The arithmetic mean roughness Ra and maximum height Rz of the surface of the peeling film can be adjusted by selection of the film material, molding method, surface treatment such as peeling treatment, etc. For example, adjustment of the smoothness of the layers constituting the peelable surface (anti-blocking layer, hard coat layer, anti-oligomer layer, etc.), reduction or non-use (reduction of particles) of filler particles in the surface layer or release film base material, etc. Additionally, adjustment of stretching conditions, etc. may be mentioned.

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

<Use>

In the technology disclosed herein, the high refractive index adhesive layer can be used by bonding to various adherends constituting a light emitting device. The constituent material (material of the adherend) of the adherend is not particularly limited, but includes, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, etc., or these. Metal materials such as alloys containing two or more types, for example, polyimide-based resin, acrylic resin, polyethernitrile-based resin, polyethersulfone-based resin, polyester-based resin (PET-based resin, polyethylene naphthalate-based resin) etc.), polyvinyl chloride-based resin, polyphenylene sulfide-based resin, polyether ether ketone-based resin, polyamide-based resin (so-called aramid resin, etc.), polyarylate-based resin, fluorine-based resin, polycarbonate-based resin, di Cellulose-based polymers such as acetylcellulose and triacetylcellulose, vinyl butyral polymers, liquid crystal polymers, various resin materials such as carbon materials such as graphene (typically plastic materials), alumina, zirconia, titania, SiO ₂ , ITO ( Metal oxides such as indium tin oxide (indium tin oxide) and ATO (antimony doped tin oxide) and mixtures thereof, nitrides such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride and their complexes, alkaline glass, alkali-free glass, quartz glass, Inorganic materials such as borosilicate glass, sapphire glass, and carbon can be mentioned. The high refractive index adhesive layer disclosed herein can be used by attaching it to a member (for example, an optical member) whose surface is made of at least the above material. Additionally, the low refractive index layer (preferably a low refractive index adhesive layer) in the technology disclosed herein can be used by laminating (for example, bonding) to the various adherends described above.

The high refractive index adhesive layer disclosed herein can be used in a sticking form that does not require heating treatment to a temperature higher than the room temperature temperature range (for example, 20°C to 35°C) after bonding to the adherend. . Additionally, if permitted depending on the type of the adherend, etc., heat treatment may be performed at least at any of the following timings: after bonding to the adherend, at the time of bonding, or before bonding. Heat treatment can be performed for purposes such as improving the adhesion of the adhesive to the adherend or promoting adhesion. The heat treatment temperature can be set appropriately to obtain the desired effect within an allowable range depending on the constituent materials of the adhesive sheet or the type of the adherend, taking into consideration the surface condition of the adherend, etc., for example, around 100°C or less. It may be below, 80°C or below, 60°C or below, or 50°C or below.

The member or material to which the adhesive layer is attached may have light transparency. In such an adherend, the advantage that the high refractive index adhesive layer disclosed herein is highly transparent is easily obtained. The total light transmittance of the adherend may be, for example, more than 50% or 70% or more. In some preferred embodiments, the total light transmittance of the adherend is 80% or more, more preferably 90% or more, and still more preferably 95% or more (for example, 95 to 100%). The high refractive index adhesive layer disclosed herein can be preferably used in the form of sticking it to an adherend (for example, an optical member) whose total light transmittance is a predetermined value or more. The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used.

The refractive index of the adherend and the refractive index of the adhesive layer (high refractive index adhesive layer or low refractive index layer) disposed in contact with the adherend may be the same or different. For example, by making the refractive index of the adhesive layer relatively high with respect to the refractive index of the adherend, light incident on the adhesive layer from the adherend side at an angle less than the critical angle is refracted toward the front side, thereby increasing the front brightness. 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, and may be, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. Additionally, with an adherend having a relatively high refractive index with respect to the adhesive layer, light incident on the adherend from the adhesive layer side can be refracted toward the front side, thereby increasing front brightness. In this case, the refractive index of the adherend may be, for example, 1.60 or more, 1.65 or more, or 1.70 or more, and may be, for example, 3.00 or less, 2.50 or less, or 2.00 or less. On the other hand, by reducing the difference in refractive index between the adhesive layer and the adherend, light reflection at the interface can be suppressed. In this case, the refractive index of the adherend may be about 1.55 to 1.80, 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 adhesive.

In some preferred embodiments, the adherend may have a refractive index of any of the above and a total light transmittance of any of the above. In a light emitting device in which a high refractive index adhesive layer and/or a low refractive index layer are attached or laminated to such an adherend, the effect of the technology disclosed herein is particularly preferably exhibited.

The high refractive index adhesive layer and the low refractive index layer disclosed herein can be used by attaching them to various adherends as described above in the form of a laminated sheet containing them. An example of a preferable use is optical use. More specifically, the laminated sheet disclosed herein is an optical adhesive sheet used, for example, for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical members. can be preferably used. The laminated sheet used in this aspect can also be understood as an interlayer sheet disposed between layers of an optical laminated body.

The optical member refers to a member having optical properties (e.g., polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, light rotation, visibility, etc.). The optical member is not particularly limited as long as it has optical properties, but examples include members constituting devices (optical devices) such as display devices (image display devices) and input devices, or members used in these devices. For example, polarizer, wave plate, retardation plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, anti-reflection film, hard coat (HC) film, shock absorption film, antifouling film, photochromic film, Illuminated films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and even members in which they are laminated (sometimes these are collectively referred to as “functional films”) ), etc. In addition, the above-mentioned “plate” and “film” include forms such as plate, film, and sheet, respectively. For example, “polarizing film” includes “polarizing plate” and “polarizing sheet”, etc. , “Light guide plate” shall include “light guide film”, “light guide sheet”, etc. In addition, the above-mentioned “polarizing plate” shall include a circularly polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, micro LED (μLED), mini LED (miniLED), PDP (plasma display panel), electronic paper, etc. Additionally, examples of the input device include a touch panel and the like.

The optical member is not particularly limited, but includes, for example, members made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, etc. (e.g., sheet-shaped, film-shaped, plate-shaped members), etc. I can hear it. In addition, “optical members” in this specification shall also include members (such as decoration films, decorative films, and surface protection films) that play a role in decoration or protection while maintaining the visibility of the display device or input device.

The high refractive index adhesive layer disclosed herein (which may be in the form of a laminated sheet with a low refractive index layer) is, for example, a film having one or two or more functions such as light transmission, reflection, diffusion, wave guidance, light collection, and diffraction. It can be used in the form of being disposed between an optical film such as a fluorescent film and another optical member (which may be another optical film), and preferably can be used to bond the optical film and the other optical member. Among them, in the case of bonding optical films that have at least one of the functions of light guiding, condensing, and diffraction, it is preferable that the entire bulk of the bonding layer has a high refractive index, and the technology disclosed herein can be preferably applied.

The high refractive index adhesive layer disclosed herein can be preferably used for bonding optical films such as light guide films, diffusion films, fluorescent films, tinting films, prism sheets, lenticular films, and microlens array films. In these applications, from the viewpoint of the trend towards miniaturization and improved performance of optical members, reduction in thickness and improvement in light extraction efficiency are required. As an adhesive layer that can meet these requests, the high refractive index adhesive layer disclosed herein can be preferably used. More specifically, for example, in bonding a light guide film or a diffusion film, adjusting the refractive index of the adhesive layer as a bonding layer (for example, increasing the refractive index) can contribute to thinning. In the bonding of fluorescent films, light extraction efficiency (which can also be understood as luminous efficiency) can be improved by appropriately adjusting the refractive index difference between the fluorescent emitter and the adhesive. In bonding of a coloring film, the scattering component can be reduced by appropriately adjusting the refractive index of the adhesive so that the difference in refractive index with the coloring pigment is small, thereby contributing to the improvement of light transmittance. In bonding prism sheets, lenticular films, microlens array films, etc., diffraction of light can be controlled by appropriately adjusting the refractive index of the adhesive, contributing to improvement of brightness and/or viewing angle.

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

In addition, the high refractive index adhesive layer disclosed herein can be preferably used in the form of being affixed to a light emitting layer of an optical semiconductor or the like (for example, a high refractive index light emitting layer mainly composed of an inorganic material). By reducing the difference in refractive index between the light emitting layer and the high refractive index adhesive layer, reflection at their interface can be suppressed and light extraction efficiency can be improved. From the viewpoint of improving brightness, it is preferable that the high refractive index adhesive layer is low-colored. This can also be advantageous from the viewpoint of suppressing unintentional coloring due to the high refractive index adhesive layer.

The high refractive index adhesive layer disclosed herein is a microlens or other lens member used as a structural member of a camera or light emitting device (for example, a microlens constituting a microlens array film or a lens such as a microlens for a camera) member), a coating layer covering the lens surface, a bonding layer with a member opposing the lens surface (for example, a member having a surface shape corresponding to the lens surface), and a filling layer filled between the lens surface and the member. It can be preferably used as such. The high refractive index adhesive layer disclosed herein maintains a refractive index difference with the lens even when placed in contact with a high refractive index lens (for example, a lens made of a high refractive index resin or a lens having a surface layer made of a high refractive index resin). It can be reduced. This is advantageous from the viewpoint of reducing the thickness of the lens and products equipped with the lens, and can also contribute to suppressing aberrations and improving the Abbe number. In the technology disclosed herein, the adhesive (viscoelastic material) constituting the high refractive index adhesive layer can also be used as a lens resin itself, for example, in the form of filling the recesses or voids of a suitable transparent member.

The mode of bonding optical members using the adhesive layer disclosed herein (a high refractive index adhesive layer and/or a low refractive index adhesive layer, preferably a high refractive index adhesive layer that may be laminated on a low refractive index layer) is not particularly limited. However, for example, (1) optical members are bonded to each other through the adhesive layer disclosed herein, or (2) optical members are bonded to members other than the optical member through the adhesive layer disclosed herein. and (3) the adhesive layer disclosed herein may be in the form of an adhesive sheet including an optical member, and the adhesive sheet may be bonded to an optical member or a member other than the optical member. Additionally, in the aspect (3) above, the pressure-sensitive adhesive sheet including an optical member may be, for example, a pressure-sensitive adhesive sheet whose support is an optical member (eg, an optical film). In this way, a pressure-sensitive adhesive sheet including an optical member as a support can also be considered as a pressure-sensitive adhesive optical member (for example, a pressure-sensitive adhesive optical film). In addition, when the pressure-sensitive adhesive layer disclosed herein constitutes a pressure-sensitive adhesive sheet having a support, and the functional film is used as the support, the pressure-sensitive adhesive sheet has the pressure-sensitive adhesive layer disclosed herein on at least one side of the functional film. It can also be understood as an “adhesive functional film” having .

From the above, according to the technology disclosed herein, an optical laminate is provided including the adhesive layer disclosed herein and a member (for example, a resin film such as an optical film) on which the adhesive layer is laminated by sticking or the like. The member on which the adhesive layer is laminated by sticking or the like may have the refractive index of the adherend material described above. Additionally, the difference between the refractive index of the adhesive layer and the refractive index of the member (refractive index difference) may be the difference in refractive index between the above-mentioned adherend and the adhesive layer. The members constituting the laminate are as described above as members, materials, and adherends, so overlapping explanations will not be repeated.

Since the high refractive index adhesive layer and laminated sheet disclosed herein are capable of withstanding large deformations, their characteristics can be utilized to be used in electronic devices such as portable electronic devices such as liquid crystal displays, organic EL displays, and touch panels. It is suitable for devices (optical devices) equipped with a light-emitting device such as an input device. In particular, it is suitable as a light-emitting device in a foldable display or rollable display. The high refractive index adhesive layer and laminated sheet disclosed herein can have flexibility to withstand repeated bending operations, so that when attached to a foldable display or rollable display, the adherend is repeatedly bent (foldable display etc.) can be followed well. Examples of objects to be attached in this form of use include glass members such as window glass and cover glass used in foldable displays and rollable displays. In addition, the high refractive index adhesive layer and laminated sheet disclosed herein are easy to follow and adhere to curved surfaces, such as the three-dimensional shape of portable electronic devices, for example, and thus can be used in electronic devices having such a curved shape. It is also suitable as a light emitting device. Additionally, in some preferred embodiments, the high refractive index adhesive layer and the laminated sheet may have improved stability of properties such as elastic modulus in addition to having flexibility. Since the above-described portable electronic devices are sometimes used in high-temperature environments, and their internal spaces may become heated due to heat generation from electronic components, there is a great advantage in using an adhesive with good stability as described above.

Examples of portable electronic devices that can be equipped with the light-emitting device disclosed herein include, for example, mobile phones, smartphones, tablet-type personal computers, notebook-type personal computers, and various wearable devices (e.g., devices mounted on the wrist such as a wrist watch). wrist wear type, modular type that is attached to a part of the body with a clip or strap, etc., eyewear type including glasses (monocular or binocular type, including head mounted type), accessories such as shirts, socks, hats, etc. (clothing type attached in the form of, earwear type worn on the ear such as earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (electronic calculators, etc.), portable game devices, These include electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In addition, in this specification, “carrying” is not sufficient simply to be able to carry, but means having a level of portability that allows an individual (a standard adult) to carry around with relative ease.

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

[1] A self-luminous element,

a low refractive index layer disposed on a viewing side of the self-luminous element;

A high refractive index adhesive layer laminated in direct contact with the low refractive index layer.

Including,

A light emitting device in which the high refractive index adhesive layer has a refractive index of more than 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20° C. and a speed of 300 mm/min.

[2] A self-luminous element,

a low refractive index layer disposed on a viewing side of the self-luminous element;

A high refractive index adhesive layer laminated in direct contact with the low refractive index layer.

Including,

A light emitting device wherein the high refractive index adhesive layer has a refractive index of more than 1.560 and further contains a plasticizer.

[3] The high refractive index adhesive layer has a stress of 5.0 N/mm 2 or less at a deformation of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. [1] or [2] The light-emitting device described in ].

[4] The light emitting device according to any one of [1] to [3] above, wherein the ratio (n ₁ /n ₂ ) of the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer is 1.05 or more.

[5] A laminated sheet including a low refractive index layer and a high refractive index adhesive layer laminated on the low refractive index layer,

A laminated sheet in which the high refractive index adhesive layer has a refractive index of more than 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min.

[6] A laminated sheet including a low refractive index layer and a high refractive index adhesive layer laminated on the low refractive index layer,

A laminated sheet in which the high refractive index adhesive layer has a refractive index of more than 1.560 and further contains a plasticizer.

[7] The high refractive index adhesive layer has a stress of 5.0 N/mm 2 or less at a deformation of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min, [5] or [6]. The laminated sheet described in ].

[8] The laminated sheet according to any one of [5] to [7] above, wherein the ratio (n ₁ /n ₂ ) of the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer is 1.05 or more.

[9] A laminated sheet including the laminated sheet according to any one of [5] to [8] above, and a release liner that protects the surface of the high refractive index adhesive layer.

Hereinafter, several test examples related to the present invention will be described, but it is not intended to limit the present invention to those shown in these specific examples. In addition, in the following description, “part” and “%” indicating the usage amount or content are based on weight unless otherwise specified.

<Preparation of acrylic adhesive composition C1>

In a four-neck flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser, m-phenoxybenzyl acrylate (manufactured by Kyoesha Chemical Co., Ltd., brand name “Light Acrylate POB-A”) as a monomer component, refractive index: 1.566. , hereinafter referred to as “POB-A”) 95 parts, 4-hydroxybutylacrylate (4HBA) 3 parts and 2-acryloyloxyethyl-succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., brand name “HOA-MS”) (N)”, hereinafter referred to as “HOA-MS”) 2 parts, 0.2 part of 2,2'-azobisisobutyronitrile as a polymerization initiator, and ethyl acetate as a polymerization solvent were added while gently stirring. Nitrogen gas was introduced, the liquid temperature in the flask was maintained at around 60°C, and a polymerization reaction was performed for 6 hours to prepare a solution (40%) of acrylic polymer P1. The Mw of acrylic polymer P1 was 500,000.

The solution of the acrylic polymer P1 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (100 parts of non-volatile matter) was added with polyethylene glycol benzoic acid ester (Sanyo Kasei Co., Ltd., brand name “Sanflex EB-300”) as plasticizer A1. ", molecular weight: 538, refractive index: 1.515, liquid at 20°C, hereinafter referred to as "EB-300"), 60 parts, acyclic bifunctional isocyanate-based crosslinking agent as a crosslinking agent (manufactured by Tosoh Corporation, brand name "Coronate 2770", Add 0.3 parts of hexamethylene diisocyanate (HDI) allophanate), 2 parts of acetylacetone as a crosslinking retardant, and 1 part of 1% ethyl acetate solution of ferric ferric acid (0.01 part of non-volatile matter) as a crosslinking catalyst, stir and mix. Thus, acrylic adhesive composition C1 was prepared.

<Preparation of acrylic adhesive composition C2>

A solution of acrylic polymer P2 was prepared in the same manner as the preparation of the acrylic polymer P1 solution except that the composition of the monomer component was changed to 99 parts of POB-A and 1 part of HOA-MS. The Mw of acrylic polymer P2 was 500,000. The solution of the acrylic polymer P2 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 60 parts of the plasticizer A1 (EB-300) and an epoxy-based crosslinking agent (Mitsubishi Gas Chemical) were added as a crosslinking agent. 0.5 part of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane), brand name "Tetrad C", manufactured by KUSA, was added and mixed with stirring to prepare acrylic adhesive composition C2.

<Preparation of acrylic adhesive composition C3>

The preparation of the acrylic polymer P1 solution was similar to that of the acrylic polymer P1 except that the composition of the monomer components was changed to 95 parts POB-A, 2 parts lauryl acrylate (LA), 2 parts 2-ethylhexyl acrylate (2EHA), and 1 part 4HBA. , a solution of acrylic polymer P3 was prepared. The Mw of acrylic polymer P3 was 500,000. The solution of the acrylic polymer P3 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 3-phenoxybenzyl alcohol (manufactured by Tokyo Kasei Kogyo Co., Ltd., refractive index: 1.591, 20) was added as a plasticizer A2. 60 parts (liquid at ℃, hereinafter referred to as “POB-AL”), 0.3 parts of the above isocyanate-based crosslinking agent (Coronate 2770), 2 parts of acetylacetone as a crosslinking retardant, and 1% acetic acid of ferric nasem as a crosslinking catalyst. 1 part of ethyl solution (0.01 part of non-volatile matter) was added and mixed with stirring to prepare acrylic adhesive composition C3.

<Preparation of acrylic adhesive composition C4>

A solution of acrylic polymer P4 was prepared in the same manner as the preparation of the acrylic polymer P1 solution except that the composition of the monomer component was changed to 90 parts of POB-A, 9 parts of 2EHA, and 1 part of 4HBA. The Mw of acrylic polymer P4 was 500,000. The solution of the acrylic polymer P4 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 60 parts of the plasticizer A2 (POB-AL) and the isocyanate-based crosslinking agent (Coronate 2770) were added. Acrylic adhesive composition C4 was prepared by adding 0.5 parts of acetylacetone as a crosslinking retardant, 2 parts of acetylacetone as a crosslinking catalyst, and 1 part of a 1% ethyl acetate solution of ferric ferric acid (0.01 part of non-volatile matter) as a crosslinking catalyst and mixing with stirring.

<Preparation of acrylic adhesive composition C5>

A solution of acrylic polymer P5 was prepared in the same manner as the preparation of the acrylic polymer P1 solution except that the composition of the monomer component was changed to 98 parts of POB-A, 1 part of 4HBA, and 1 part of HOA-MS. The Mw of acrylic polymer P5 was 500,000. The solution of the acrylic polymer P5 was diluted with ethyl acetate to a polymer concentration of 30%, and 20 parts of the plasticizer A1 (EB-300) and the isocyanate-based crosslinking agent (Coronate 2770) were added to 334 parts of the solution (100 parts of non-volatile matter). ) 0.1 part, 2 parts of acetylacetone as a crosslinking retardant, and 1 part of 1% ethyl acetate solution of ferric ferric acid (0.01 part of non-volatile matter) as a crosslinking catalyst were added and mixed with stirring to prepare acrylic adhesive composition C5.

<Preparation of acrylic adhesive composition C6>

A solution of acrylic polymer P6 was prepared in the same manner as the preparation of the acrylic polymer P1 solution except that the composition of the monomer component was changed to 99 parts of n-butylacrylate (BA) and 1 part of 4HBA and the concentration of the monomer component during polymerization was adjusted. was prepared. The Mw of acrylic polymer P6 was 2 million. The solution of the acrylic polymer P6 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts (100 parts of non-volatile matter) of this solution were mixed with an isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, brand name “Koro”) as a crosslinking agent. 10 parts (0.1 part non-volatile matter) of a 1% ethyl acetate solution of "Nate HX", trifunctional isocyanate compound) was added and mixed with stirring to prepare acrylic adhesive composition C6.

<Production of adhesive sheet>

(Example 1)

The acrylic adhesive composition C1 prepared above was applied to the silicone-treated side of a polyethylene terephthalate (PET) film R1 (50㎛ thick), one side of which was silicone-treated, and heated at 130°C for 2 minutes to form an adhesive with a thickness of 20㎛. A layer was formed. Next, the silicone-treated side of PET film R2 (thickness 25 μm), on which one side was silicone-treated, was bonded to the surface of the adhesive layer. In this way, an adhesive layer (high refractive index adhesive layer) with both sides protected by PET films (release liners) R1 and R2 was obtained. Additionally, the release liner R2 peels relatively lightly compared to the release liner R1.

Additionally, the acrylic adhesive composition C6 prepared above was applied to the silicone-treated side of PET film R1 (50㎛ thick), one side of which was silicone-treated, and heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 50㎛. did. The silicone-treated side of PET film R2 (thickness 38 μm), on which one side had been silicone-treated, was bonded to the surface of the adhesive layer. In this way, a pressure-sensitive adhesive layer (low-refractive-index pressure-sensitive adhesive layer) with both sides protected by PET films (release liners) R1 and R2 was obtained.

The release liner R2 was peeled from the high refractive index adhesive layer and the low refractive index adhesive layer, and the adhesive surfaces were bonded to each other and pressed together with a hand roller. This laminate was autoclaved for 30 minutes at 50°C and 0.60 MPa, and then aged for 48 hours in a 50°C environment. In this way, a laminated sheet (baseless double-sided adhesive sheet) having a two-layer structure of a high refractive index adhesive layer/low refractive index adhesive layer was obtained. The surface of this adhesive sheet is protected by two sheets of release liner R1.

(Examples 2 to 5)

Except that the type of adhesive composition used to form each adhesive layer was changed as shown in Table 1, in the same manner as Example 1, a laminated sheet consisting of a two-layer structure of a high refractive index adhesive layer/low refractive index adhesive layer (baseless double-sided adhesive sheet) were obtained, respectively.

<Measurement and evaluation>

(refractive index)

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

(Storage modulus G')

Each adhesive layer was laminated to a thickness of about 1.5 mm, which was punched into a disk shape with a diameter of 7.9 mm, and this was used as a sample for measurement. Dynamic viscoelasticity measurements were performed using the “Advanced Rheometric Expansion System (ARES)” manufactured by Rheometric Scientific under the following conditions. From the measurement results, the storage modulus G' at 25°C was read. The results are shown in Table 1.

[Measuring conditions]

Deformation Mode: Torsion

Measurement frequency: 1Hz

Temperature range: -50℃ to 150℃

Temperature increase rate: 5℃/min

Shape: Parallel plate 7.9mmϕ

(Total light transmittance and haze value)

A test piece was used in which the adhesive sheet for each example was bonded to alkali-free glass (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.4%), and a haze meter (Murakami Shikisai Kijutsu Kenkyu) was used in a measurement environment of 23°C. The total light transmittance and haze of the test piece were measured using a preparation (trade name: "HAZEMETER HM-150"). The values obtained by subtracting the total light transmittance and haze of the alkali-free glass from the measured values were used as the total light transmittance and haze values of the adhesive sheet. The results are shown in Table 1.

(Deformation test)

Each adhesive layer was cut to a width of 300 mm in length and 1 mm2 in cross-sectional area, and the adhesive layer was rounded into a cylindrical shape in an environment of 23°C and 50%RH to obtain a test piece. Using a tensile tester (manufactured by Shimadzu Seisakusho, device name “Precision Universal Tester Autograph AG-X plus 5kN”), a deformation test ( A tensile test) was performed to obtain an S-S curve to evaluate whether the test piece was deformed (elongated) by more than 350%. When the test piece was deformed by more than 350%, the stress [N/mm2] at the time of 350% deformation was measured. The results are shown in Table 1. In the above deformation test, an adhesive that can be deformed by more than 350% at -20°C is judged to be an adhesive that can withstand large deformation.

In addition, when the thickness of the adhesive layer is relatively small, the above deformation test may be performed using a test piece prepared to have a thickness of 5 μm or more (for example, about 5 μm to 200 μm) for purposes such as improving operability. The thickness of the test piece can be adjusted, for example, by appropriately overlapping the adhesive layer. Additionally, the same adhesive composition as that used to form the adhesive layer to be measured may be used to produce a test piece with a thickness that is easy to perform the deformation test, and the deformation test may be performed on the test piece. The deformation test can be performed, for example, using a test piece with a thickness of about 10 μm to 50 μm. Additionally, during the test, it is desirable to apply powder to the adhesive surface at the chucked location to eliminate the influence of the stickiness of the adhesive.

As shown in Table 1, the adhesive sheets of Examples 1 to 4 have a refractive index exceeding 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. It included a high refractive index adhesive layer and a low refractive index layer. In addition, the high refractive index adhesive layer according to these examples had a stress of 5.0 N/mm2 or less at a deformation amount of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. Additionally, the ratio (n ₁ /n ₂ ) between the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer was 1.05 or more. This pressure-sensitive adhesive sheet is recognized as having a head-on brightness improvement effect evaluated by the method described in the examples of Japanese Patent Application Laid-Open No. 2022-8015. It can be seen that by using the adhesive sheet, it is possible to construct a light-emitting device in which an adhesive layer that has a high refractive index and can withstand large deformation is disposed on the viewing side of the self-luminous element. On the other hand, the adhesive sheet according to Example 5 had a refractive index of the high refractive index adhesive layer exceeding 1.560, but in a deformation test at a temperature of -20°C and a speed of 300 mm/min, it fractured at an early stage of deformation and could not withstand large deformation. I couldn't.

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

2: Inorganic double-sided adhesive sheet
10: Laminated sheet (adhesive sheet)
10A: first surface (first adhesive surface)
10B: second surface (second adhesive surface)
11: High refractive index adhesive layer
12: Low refractive index adhesive layer (low refractive index layer)
70: Self-luminous element
80: Absence of cover window
100: light emitting device

Claims (3)

A self-luminous element,
a low refractive index layer disposed on a viewing side of the self-luminous element;
A high refractive index adhesive layer laminated in direct contact with the low refractive index layer.
Including,
A light emitting device in which the high refractive index adhesive layer has a refractive index of more than 1.560 and a deformation amount of 350% or more in a deformation test conducted under the conditions of a temperature of -20° C. and a speed of 300 mm/min. According to paragraph 1,
A light emitting device in which the high refractive index adhesive layer has a stress of 5.0 N/mm2 or less at a deformation amount of 350% in a deformation test conducted under the conditions of a temperature of -20°C and a speed of 300 mm/min. According to claim 1 or 2,
A light emitting device wherein the ratio (n ₁ /n ₂ ) of the refractive index n ₁ of the high refractive index adhesive layer and the refractive index n ₂ of the low refractive index layer is 1.05 or more.