JP2023151520A - Adhesive optical film, and laminate sheet - Google Patents

Abstract

To provide an adhesive optical film that has an adhesive layer with a high refractive index and improved flexibility on an optical film and achieves high adhesion reliability to an adherend.SOLUTION: An adhesive optical film contains an optical film and an adhesive layer laminated on the optical film. The adhesive layer contains a high-refractive-index adhesive layer having a refractive index higher than 1.560. The high-refractive-index adhesive layer contains a plasticizer and has a peel strength F1 from a glass sheet of 3 N/25 mm or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive optical film and a laminated sheet.

In general, adhesives (also referred to as pressure-sensitive adhesives, hereinafter the same) exhibit a soft solid state (viscoelastic body) in a temperature range around room temperature, and have the property of easily adhering to an adherend under pressure. Taking advantage of these properties, adhesives are widely used for purposes such as bonding, fixing, and protection in various industrial fields such as home appliances, automobiles, various machines, electrical equipment, and electronic equipment. An example of the use of adhesives is to bond polarizing films, retardation films, cover window members, and various other light-transmissive members with other members in display devices such as liquid crystal displays and organic EL display devices. Examples of uses include: Technical documents regarding adhesives for optical members include Patent Documents 1 and 2. Patent Document 3 is a technical document regarding an adhesive optical film having an adhesive layer.

Japanese Patent Application Publication No. 2014-169382 Japanese Patent Application Publication No. 2017-128732 JP 2022-8014 Publication

Patent Documents 1 and 2 disclose a pressure-sensitive adhesive composition whose main component is a (meth)acrylic acid ester polymer containing a monomer having a plurality of aromatic rings as a monomer unit, and a pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition. discloses the use of a monomer having multiple aromatic rings to increase the refractive index of the adhesive to 1.50 or more, particularly preferably 1.51 or more. Also known is a technique to increase the refractive index by blending particles made of an inorganic material with a high refractive index (for example, inorganic particles such as zirconium oxide particles and titanium oxide particles) into a resin. However, since adhesives containing inorganic particles have a trade-off relationship between refractive index and adhesive properties (for example, peel strength, flexibility, etc.), it is difficult to apply them to the adhesive field. Particularly in adhesives for optical applications, it is necessary to consider the influence on optical properties (for example, total light transmittance, haze, etc.) when blending inorganic particles. Against this background, the present inventors have proposed in Patent Document 3 an adhesive optical film having an adhesive layer that has both a high refractive index and good optical properties.

By the way, as an adhesive, one having good flexibility can be preferably used depending on the application site and usage mode. For example, in recent years, foldable displays and rollable displays have been put into practical use as displays such as organic EL display devices used in electronic devices such as smartphones. It is desirable to have the flexibility to follow the An adhesive having excellent flexibility easily follows and adheres to curved surfaces such as three-dimensional shapes, and is also suitable for use in electronic devices having curved shapes. If the flexibility of an adhesive having a high refractive index can be increased, it is useful because it can be applied to applications that require flexibility.

However, in designing adhesives, there is a trade-off between high refractive index and flexibility, and it is not easy to achieve both. Specifically, high refractive index materials used in adhesives (monomer components of adhesive polymers, adhesive additives, etc.) tend to have aromatic rings and have low flexibility. Adhesives formed using such high refractive index materials tend to have reduced flexibility. Adding a plasticizer can be considered as a method of imparting flexibility to an adhesive, but in general, adding a plasticizer can cause a decrease in the refractive index of the adhesive, so it is necessary to maintain or improve the refractive index of the adhesive. It is necessary to select materials that can be used. Furthermore, adhesives containing plasticizers tend to have lower adhesive strength, and tend to have lower adhesion reliability and anchoring properties to adherends. It is more difficult to realize an adhesive that has both a high refractive index and flexibility, has good optical properties (transparency), and also exhibits practical adhesive performance. If such a pressure-sensitive adhesive is realized, it can be used as a pressure-sensitive adhesive optical film with a wider range of applications and high performance, which is of practical benefit.

The present invention was created in view of the above circumstances, and includes an adhesive layer having a high refractive index and improved flexibility on an optical film, and has a highly reliable adhesive layer to an adherend. The purpose of the present invention is to provide an adhesive optical film. Another object of the present invention is to provide a pressure-sensitive adhesive optical film with a release liner, which includes the pressure-sensitive adhesive optical film described above. Another object of the present invention is to provide a laminated sheet applicable to adhesive optical films.

According to this specification, an adhesive optical film is provided that includes an optical film and an adhesive layer laminated on the optical film. The adhesive layer includes a high refractive index adhesive layer with a refractive index higher than 1.560. Further, the high refractive index adhesive layer contains a plasticizer. Further, the high refractive index adhesive layer has a peel strength F1 of 3 N/25 mm or more with respect to a glass plate. The above-mentioned high refractive index adhesive layer has a high refractive index, contains a plasticizer, and has flexibility, and has an adhesive strength to the glass plate exceeding the above-mentioned predetermined value, so it is reliable for adherends. Achieves good adhesion.

In some embodiments, the adhesive layer further includes a low refractive index adhesive layer having a lower refractive index than the high refractive index adhesive layer. Further, the high refractive index adhesive layer and the low refractive index adhesive layer are laminated in direct contact with each other. The technology disclosed herein can be preferably implemented in an embodiment using an adhesive layer having such a laminated structure. In some preferred embodiments, the adhesive optical film has the optical film, the low refractive index adhesive layer, and the high refractive index adhesive layer laminated in this order.

In some embodiments, the adhesive layer has a peel strength F2 of 5 N/25 mm or more with respect to the optical film. Since the adhesive layer contains a plasticizer and is laminated to the optical film with an adhesive force of 5 N/25 mm or more, it can be used as a highly reliable adhesive optical film with good anchoring properties.

In some embodiments, the difference (F2-F1) between the peel strength F1 [N/25 mm] for the glass plate and the peel strength F2 [N/25 mm] for the optical film is 1.5 or more. By using a pressure-sensitive adhesive layer having such a difference in peel strength, it is possible to have good reworkability (reattachability) when the adhesive layer is attached to an adherend such as glass.

In some embodiments, the adhesive layer has a total light transmittance of 85% or more and a haze value of 3.0% or less. A pressure-sensitive adhesive layer having the optical properties as described above has little influence on the optical properties of an optical film, and is suitable as a pressure-sensitive adhesive for a pressure-sensitive adhesive optical film.

Further, according to this specification, there is provided a pressure-sensitive adhesive optical film with a release liner, which includes any pressure-sensitive adhesive optical film disclosed herein and a release liner disposed on the adhesive surface of the pressure-sensitive adhesive optical film. be done. The adhesive optical film disclosed herein is manufactured, stored, distributed, processed, etc. in the form of an adhesive optical film with a release liner in which a release liner is disposed on the adhesive surface, and is used to attach to an adherend. It can be preferably used in an embodiment in which the release liner is peeled off from the adhesive surface before application.

Further, according to this specification, a laminate sheet including a high refractive index adhesive layer having a refractive index higher than 1.560 and a low refractive index adhesive layer having a lower refractive index than the high refractive index adhesive layer. is provided. The high refractive index adhesive layer contains a plasticizer. Further, the high refractive index adhesive layer has a peel strength F1 of 3 N/25 mm or more with respect to a glass plate. In the laminated sheet, the high refractive index adhesive layer has a high refractive index and also contains a plasticizer, thereby improving flexibility. Furthermore, the high refractive index adhesive layer has adhesive strength to glass of a predetermined value or more even though it contains a plasticizer, and therefore can exhibit practical adhesive performance. The above laminated sheet is suitable as an adhesive constituting an adhesive optical film.

Note that an appropriate combination of each element described in this specification may also be included within the scope of the invention for which protection by patent is sought by the present patent application.

FIG. 1 is a cross-sectional view schematically showing the configuration of an adhesive optical film according to an embodiment. FIG. 1 is a cross-sectional view schematically showing the configuration of an optical laminate including an adhesive optical film according to an embodiment. FIG. 1 is a cross-sectional view schematically showing the configuration of a laminated sheet according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention are based on the teachings for carrying out the invention described in this specification and the common general knowledge at the time of filing. Can be understood by vendors. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the field.
In addition, in the following drawings, the same reference numerals may be attached and explained to members and parts that have the same function, and overlapping explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the products actually provided.

In this specification, a self-luminous element means a light-emitting element whose luminance can be controlled by the value of a flowing current. The self-luminous element may be composed of a single unit or an aggregate. Specific examples of self-luminous elements include, but are not limited to, light emitting diodes (LEDs) and organic EL. When a light emitting device is referred to in this specification, the light emitting device may include such a self-luminous element as a component. Examples of the light emitting device include, but are not limited to, a light source module device used for illumination (for example, a planar light emitting module) and a display device in which pixels are formed.

The technical matters provided by this specification include an adhesive layer having a refractive index of more than 1.560 (high refractive index adhesive layer), an adhesive composition capable of forming the adhesive layer, and the above-mentioned high refractive index adhesive layer. A laminated sheet containing a refractive index adhesive layer and an adhesive optical film containing the above-mentioned adhesive are included. The laminated sheet is, for example, a laminated adhesive layer including the high refractive index adhesive layer and the low refractive index adhesive layer.

<Example of configuration of adhesive optical film>
An example of the structure of the adhesive optical film disclosed in this specification is shown in FIG. This adhesive optical film 1 includes an adhesive layer 10 whose first surface 10A is a surface to be attached to an adherend (adhesive surface), and an optical film laminated on a second surface 10B of the adhesive layer 10. The film 20 is configured as a single-sided adhesive optical film (single-sided adhesive sheet). The second surface 10B of the adhesive layer 10 is bonded to the first surface (non-peelable surface) 20A of the optical film 20. Moreover, the adhesive layer 10 has a laminated structure in which a high refractive index adhesive layer 11 and a low refractive index adhesive layer 12 are laminated in direct contact with each other. In this configuration example, the optical film 20, the low refractive index adhesive layer 12, and the high refractive index adhesive layer 11 are laminated in this order. The high refractive index adhesive layer 11 constitutes the first surface (adhesive surface) 10A of the adhesive layer 10, and the low refractive index adhesive layer 12 constitutes the second surface (adhesive surface) of the adhesive layer 10. ) 10B. The adhesive optical film 1 before use (before being attached to an adherend) is, for example, as shown in FIG. It may be in the form of an adhesive optical film 50 with a release liner protected by a liner 30. Alternatively, the second surface 20B (the surface opposite to the first surface 20A, also referred to as the back surface) of the optical film 20 is a peeling surface, and the adhesive surface 10A is in contact with this second surface 20B. The adhesive surface 10A may be protected by being wound or laminated. The adhesive layer 10 may have a laminated structure in which two or more sub-adhesive layers having different compositions as described above are laminated in direct contact (that is, without being separated by a layer of non-adhesive material), and have a high It may be a single layer structure consisting only of a refractive index adhesive layer.

The adhesive optical film disclosed herein may be a component of an optical laminate in which an optical member is bonded to at least one surface of an adhesive layer. For example, the adhesive optical film 1 shown in FIG. 1 may be a component of an optical laminate 100 in which an optical member 70 is bonded to the first surface 10A of the adhesive layer 10, as shown in FIG. The optical member may be, for example, a glass plate, a resin film, a metal plate, or the like.

In the configuration shown in FIG. 1, the high refractive index adhesive layer 11 and the low refractive index adhesive layer 12 are, for example, as shown in FIG. and a low refractive index adhesive layer 12 (substrate-less double-sided adhesive sheet 2), the surface (first surface) 10A of the laminated sheet 10 on the high refractive index adhesive layer 11 side is The first adhesive surface, the surface (second surface) 10B on the low refractive index adhesive layer 12 side, is the second adhesive surface, and each of these adhesive surfaces is protected by release liners 31 and 32, and is peelable. It may be in the form of a lined laminate sheet.

Further, although not particularly illustrated, the adhesive optical film disclosed herein includes an optical film having a non-peelable first surface and a second surface, and a first adhesive layer is fixedly attached to the first surface. It may be in the form of a double-sided adhesive adhesive optical film in which the optical film is laminated and a second adhesive layer is fixedly laminated on the second surface. As a configuration example of such a double-sided adhesive optical film (hereinafter also referred to as a double-sided adhesive optical film), in the adhesive optical film (single-sided adhesive sheet) 1 shown in FIG. The surface 20B is a non-peelable surface, a second adhesive layer is provided on the second surface 20B, and a second surface of the second adhesive layer is bonded to the second surface 20B of the optical film 20. , a form in which the first surface (the surface opposite to the second surface) of the second adhesive layer is the second adhesive surface of a double-sided adhesive optical film. The composition of the adhesive constituting the second adhesive layer may be the same as or different from the composition of the adhesive constituting the first adhesive layer. Before use, the double-sided adhesive optical film may have a first adhesive surface and a second adhesive surface protected by a release liner.

Note that the adhesive optical film disclosed herein may be in the form of a roll or a sheet. Alternatively, the adhesive optical film may be further processed into various shapes.

<Peel strength characteristics>
(Peel strength F1 against glass plate)
In some embodiments, the peel strength F1 of the adhesive layer (specifically, the high refractive index adhesive layer) to the glass plate is preferably 3 N/25 mm or more, more preferably 4 N/25 mm or more, and even more preferably is 5N/25mm or more, particularly preferably 6N/25mm or more, may be 7N/25mm or more, may be 8N/25mm or more, and may be 10N/25mm or more. An adhesive layer having a peel strength F1 to a glass plate of at least a predetermined value is suitable for joining or fixing, for example, glass members. According to the technology disclosed herein, the high refractive index adhesive layer contains a plasticizer and has flexibility, and has the above-mentioned adhesive strength to the glass plate, so it is reliable to the adherend. It can achieve both good adhesion and flexibility. The upper limit of the peel strength F1 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. Note that the adhesive optical film disclosed herein includes embodiments without the above-mentioned characteristics (the adhesive layer has a peel strength F1 of 3 N/25 mm or more with respect to the glass plate), and includes such embodiments. In this case, the adhesive optical film is not limited to one that satisfies the above characteristics.

Here, the above peel strength F1 is determined by press-bonding to an alkali glass plate as an adherend, leaving it for 30 minutes in an environment of 23°C and 50% RH, and then putting it into a pressurized degassing device (autoclave). After autoclaving for 15 minutes at 50°C and a pressure of 0.5 MPa, and leaving it for 24 hours at 23°C and 50% RH, the peel strength was measured at a peel angle of 180 degrees and a tensile speed of 300 mm/min. It can be understood by measuring. In the measurement, if necessary, the adhesive layer to be measured 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). More specifically, the peel strength can be measured according to the method described in the Examples below.

(Peel strength F2 against optical film)
Further, in the adhesive optical film disclosed herein, it is preferable that the adhesive layer has a peel strength F2 of 5 N/25 mm or more with respect to the optical film. The adhesive layer constituting the adhesive optical film contains a plasticizer to improve flexibility and is laminated to the optical film with an adhesive force of 5N/25mm or more, so it has good anchoring properties and reliability. Excellent in In some embodiments, the peel strength F2 is preferably 7 N/25 mm or more, more preferably 8 N/25 mm or more, even more preferably 9 N/25 mm or more. In some preferred embodiments, the peel strength F2 may be 10 N/25 mm or more, or 11 N/25 mm or more. The upper limit of the peel strength F2 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. Specifically, the peel strength F2 with respect to the optical film is measured by the method described in Examples below.

(Peeling force difference F2-F1)
In some embodiments, the difference (F2-F1) between the peel strength F1 [N/25 mm] for the glass plate and the peel strength F2 [N/25 mm] for the optical film is preferably 1.5 or more. . By using a pressure-sensitive adhesive layer having such a difference in peel strength, it is possible to have good reworkability (reattachability) when the adhesive layer is attached to an adherend such as glass. From the viewpoint of reworkability, the difference (F2-F1) is preferably 2.0 or more, more preferably 2.5 or more, even more preferably 3.0 or more, particularly preferably 3.5 or more, and 4. It may be 0 or more. The upper limit of the above difference (F2-F1) is not particularly limited, and is, for example, 10 or less, and may be 8 or less, from the viewpoint of achieving both adhesive strength to the adherend and anchoring property to the optical film. It may be less than or equal to 5.

<Optical film>
The optical film constituting the adhesive optical film disclosed herein is not particularly limited, and for example, various optical films used in display devices such as liquid crystal display devices and organic EL display devices can be used. Such an optical film may have a single layer structure or a multilayer structure of two or more layers.

In some embodiments, various film base materials can be preferably used as the optical film. The above-mentioned film base material preferably includes a base film that can independently maintain its shape (self-supporting or independent). Here, the term "resin film" refers to a resin film that has a non-porous structure and typically is substantially void-free. Therefore, the resin film is a concept that is distinguished from foam films and nonwoven fabrics. As the resin film, one that can maintain its shape independently (self-supporting or independent) can be preferably used. The resin film may have a single layer structure or a multilayer structure of two or more layers (for example, a three layer structure).

Examples of materials constituting the resin film include polyester resins mainly composed of polyester such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE), and polypropylene (PP). ), polyolefin resins mainly composed of polyolefins such as ethylene-propylene copolymers and ethylene-butene copolymers, cellulose resins such as triacetyl cellulose (TAC), acetate resins, polysulfone resins, and polyethersulfone resins. Resin, polycarbonate resin, nylon 6, nylon 66, polyamide (PA) resin such as partially aromatic polyamide, polyimide (PI) resin, transparent polyimide resin (CPI), polyamideimide (PAI), polyether ether ketone ( PEEK), polyethersulfone (PES), cyclic polyolefin resins such as norbornene resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-acetic acid Vinyl copolymer resin, ethylene-vinyl alcohol copolymer resin, polyarylate resin, polyphenylene sulfide (PPS) resin, polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE) ) and fluororesins such as fluorinated polyimide.

The resin film may be formed using a resin material containing only one type of such resin, or may be formed using a resin material that is a blend of two or more types of resin. Good too. The resin film may be unstretched or may be stretched (for example, uniaxially or biaxially stretched). In some embodiments, for example, PET film, PBT film, PEN film, unoriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) ) film, PP/PE blend film, cycloolefin polymer (COP) film, CPI film, TAC film, etc. can be preferably used. Examples of resin films preferable 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 preferred from the viewpoint of availability, and PET film is particularly preferred.

The resin film may contain known substances 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. Additives may be added as necessary. The blending amount of the additive is not particularly limited, and can be appropriately set depending on the use of the adhesive optical film.

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

The optical film may be substantially composed of such a base film. Alternatively, the optical film may include an auxiliary layer in addition to the base film. Examples of the above-mentioned auxiliary layers include optical property adjustment layers (e.g., colored layers, antireflection layers), printing layers and laminate layers for imparting a desired appearance, antistatic layers, undercoat layers, surface layers such as release layers, etc. A processing layer may be mentioned.

In some embodiments, the total light transmittance of the optical film may be, for example, greater than 50%, and may be greater than or equal to 70%. In some preferred embodiments, the total light transmittance of the optical film 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 in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Research Institute or its equivalent product is used. A preferred example of the above-mentioned optical film is a resin film having light transmittance.

In some embodiments, the optical film is formed using, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, etc., or an alloy containing two or more of these. various resin materials (typical examples include metal materials such as carbon materials such as carbon nanotubes and graphene, liquid crystal polymers, polymer materials represented by PEDOT (poly(3,4-ethylenedioxythiophene)), polyaniline, etc. (plastic materials), metal oxides and mixtures thereof such as alumina, zirconia, titania, SiO ₂ , ITO (indium tin oxide), ATO (antimony doped tin oxide), aluminum nitride, silicon nitride, titanium nitride, gallium nitride, Materials such as nitrides such as indium nitride and composites thereof, inorganic materials such as alkali glass, non-alkali glass, quartz glass, borosilicate glass, and sapphire glass, and mixtures and composites thereof may be used.

In some embodiments, the optical film has optical properties (e.g., polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.) A film having the following characteristics is used. Examples of optical films having the above-mentioned optical properties include polarizing films, wavelength films, retardation films, optical compensation films, brightness enhancement films, light guide films, reflective films, antireflection films, hard coat (HC) films, and impact films. Examples include absorption films, antifouling films, photochromic films, light control films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, and color filters. In addition, the above-mentioned "film" includes shapes such as plate, film, and sheet. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet," and "light guide plate" includes "polarizing plate" and "polarizing sheet." shall include "light guide film", "light guide sheet", etc. Furthermore, the above-mentioned "polarizing plate" includes a circularly polarizing plate.

In some preferred embodiments, an optical film containing at least a polarizing film (also referred to as a polarizing film or a polarizing plate) is used as the optical film. Such an optical film may include, in addition to a polarizing film, a film such as a protective film or a retardation film formed from a transparent resin material. For example, the optical film may include a polarizing film, a protective film made of a transparent resin material disposed on one surface of the polarizing film, and a retardation film disposed on the other surface of the polarizing film. .

The polarizing film (also referred to as a polarizer) included in the above optical film is not particularly limited, and examples include a polyvinyl alcohol (PVA) film, a partially formalized PVA film, and a partially saponified ethylene/vinyl acetate copolymer film. etc. For example, an iodine-oriented polyvinyl alcohol (PVA) resin that has been stretched by a stretching process such as in-air stretching (dry stretching) or a stretching process in boric acid water can be used.

The method for manufacturing the polarizing film included in the optical film disclosed herein includes, for example, a single-layer stretching method as described in JP-A No. 2004-341515, a method described in JP-A-51-069644, and JP-A No. 51-069644. Examples include manufacturing methods such as those described in JP 2000-338329, JP 2001-343521, WO 2010/100917, JP 2012-073563, and JP 2011-2816. Even if the polarizing film manufactured by such a manufacturing method is a thin PVA-based resin layer, it is supported by the stretching resin base material, and problems such as breakage due to stretching are unlikely to occur. An example of the manufacturing method includes the aerial stretching (dry stretching) method described in the above-mentioned JP-A-51-069644, JP-A-2000-338329, and JP-A-2001-343521. In addition, a manufacturing method including a step of stretching in a boric acid aqueous solution, as described in International Publication No. 2010/100917 and JP2012-073563, can be stretched to a high magnification and improve polarization performance. It is preferable. Among these, a manufacturing method (two-stage stretching method) that includes a step of performing auxiliary stretching in air before stretching in a boric acid aqueous solution is particularly preferred, as described in JP-A-2012-073563. In addition, a manufacturing method as described in JP-A No. 2011-2816, in which the PVA resin layer and the resin base material for stretching are stretched in the form of a laminate, the PVA resin layer is excessively dyed, and then the color is decolored. (Overstaining and decolorizing method) may also be preferably employed. In some preferred embodiments, the polarizing film included in the optical film is made of a PVA-based resin oriented with iodine as described above, and is stretched in a two-stage stretching process consisting of auxiliary stretching in the air and stretching in boric acid. It is a polarizing film. The polarizing film is made of a polyvinyl alcohol resin with oriented iodine as described above, and is produced by excessively dyeing a laminate of a stretched PVA resin layer and a stretching resin base material, and then decolorizing it. It can be a polarizing film.

The thickness of the polarizing film is not limited to a particular range, but in some preferred embodiments, it is, for example, 20 μm or less, may be 12 μm or less, or may be 9 μm or less (for example, 1 to 8 μm). , 3 to 6 μm. A thin polarizer is preferable because it hardly inhibits bending of the optical film.

Further, the optical film may include a retardation film. As the retardation film (also referred to as retardation film), one obtained by stretching a polymer film or one obtained by aligning and fixing a liquid crystal material can be used. In this specification, a retardation film has birefringence in the plane and/or in the thickness direction. Examples of the retardation film include a retardation film for antireflection, a retardation film for viewing angle compensation, and an inclined alignment retardation film for viewing angle compensation. The thickness of the retardation film is not limited to a particular range, but in some preferred embodiments, it is 20 μm or less, may be 10 μm or less (for example, 1 to 9 μm), or even 3 to 8 μm. good. A thin retardation film is preferable because it hardly inhibits bending of the optical film.

The optical film may include a protective film made of a transparent resin material. The protective film (also referred to as transparent protective film) may be made of cellulose resin such as TAC, polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin (polyethylene, polypropylene, etc.), (meth ) Acrylic resins, cycloolefin resins (typically norbornene resins), polyarylate resins, polystyrene resins, PVA resins, and mixtures of two or more thereof. The thickness of the protective film is not limited to a particular range, and in some preferred embodiments, it is, for example, 5 to 60 μm, may be 10 to 40 μm, or may be 10 to 30 μm. The protective film may be provided with a surface treatment layer such as an anti-glare layer or an anti-reflection layer, if necessary.

A protective film may be bonded to at least one side of the polarizing film using an adhesive. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, and water-based polyester adhesives. The adhesive is usually used as an adhesive made of an aqueous solution. For example, it may be in the form of an aqueous adhesive solution with a solids content of 0.5 to 60% by weight. Other examples of adhesives include active energy ray curable adhesives such as ultraviolet ray curable adhesives and electron beam curable adhesives. The adhesive may also contain a filler (for example, a metal compound).

The thickness of the optical film is not particularly limited, and can be selected depending on the purpose and manner of use of the adhesive optical film. The thickness of the optical film may be, for example, 500 μm or less, and preferably 300 μm or less from the viewpoint of handleability and processability. In some preferred embodiments, the optical film may be approximately 150 μm or less, approximately 120 μm or less, approximately 100 μm or less, 90 μm or less, or 60 μm or less (eg, 10-50 μm). Thin optical films tend to have excellent flexibility and are preferable for applications such as foldable displays. As the thickness of the optical film decreases, its ability to follow the surface shape of the adherend tends to improve. In addition, from the viewpoint of handleability, processability, etc., the thickness of the optical film may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more. For example, when a protective film is provided, the thickness of the optical film may be about 30 μm or more, or about 50 μm or more from the viewpoint of protective properties.

The surface of the optical film on which the adhesive layer is laminated may be subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of an undercoat (primer) to form an undercoat layer, as necessary. Conventionally known surface treatments such as forming may be applied. Such surface treatment may be a treatment for improving the anchoring ability of the adhesive layer to the optical film. The composition of the primer used to form the undercoat layer is not particularly limited, and can be appropriately selected from known primers. The thickness of the undercoat layer is not particularly limited, but it is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. Other treatments that may be applied to the optical film as needed include antistatic layer formation treatment, colored layer formation treatment, printing treatment, and the like. These treatments can be applied alone or in combination.

<High refractive index adhesive layer>
(Refractive index)
The adhesive optical film disclosed herein has a high refractive index adhesive layer with a refractive index of more than 1.560. Such a high refractive index adhesive layer can be realized by forming at least one surface (adhesive surface) of the adhesive layer with an adhesive having a refractive index of more than 1.560.

Note that in this specification, the refractive index of an 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) at a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO or its equivalent is used. As the 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 Examples below. The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive (for example, the composition of monomer components constituting the base polymer, additives that may be used as necessary, etc.).

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, It may be 1.595 or more, or it may be 1.600 or more. According to an adhesive having such a refractive index, the behavior of light passing through the adhesive can be effectively controlled by utilizing the relative refractive index relationship between the adhesive and the adherend. In addition, in an embodiment in which low refractive index adhesive layers are laminated, which will be described later, the relative refractive index relationship between the high refractive index adhesive layer and the low refractive index adhesive layer directly adjacent thereto is utilized. Therefore, the behavior of light transmitted through the high refractive index adhesive layer can be effectively controlled. The preferable upper limit of the refractive index of the high refractive index pressure-sensitive adhesive layer is not limited to a specific range because it may vary depending on the refractive index of the adjacent layer and the like. In some embodiments, considering 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, It may be 1.650 or less, 1.620 or less, or 1.600 or less.

(Total light transmittance)
In some embodiments, the total light transmittance of the high refractive index adhesive layer is 85.0% or more (e.g., 86.0% or more, 88.0% or more, 90.0% or more, or 90.0%). super) is preferred. An adhesive with a high total light transmittance is suitable as an adhesive for an adhesive optical film. Theoretically, the upper limit of total light transmittance is the value obtained by subtracting light loss (Fresnel loss) due to reflection occurring at the air interface from 100%, and in practice, it may be approximately 98% or less, for example, approximately 96% or less. It may be approximately 95% or less. In some embodiments, the total light transmittance of the high refractive index adhesive layer may be about 94% or less, about 93% or less, or about 92% or less, taking into account the refractive index and adhesive properties.

The total light transmittance of the adhesive layer is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Research Institute or its equivalent product is used. The total light transmittance can be measured according to the method described in Examples below. The total light transmittance of the adhesive layer (eg, high refractive index adhesive layer) can be adjusted by, for example, selecting the composition, thickness, etc. of the adhesive layer. Note that the above-mentioned total light transmittance is sometimes referred to as initial total light transmittance for the purpose of distinguishing it from the total light transmittance after a bending test described later.

In some embodiments, the high refractive index adhesive layer is subjected to a bending test repeated 10 times at 25° C., in which each side of the sheet-like adhesive is bent into a U-shape with a radius of 2 mm. It is preferable that the total light transmittance of the subsequent bent portion (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 properties has little change in optical properties (for example, whitening) even after repeated bending, so it is suitable for optical applications where bending is expected, such as foldable display applications. . The total light transmittance after the bending test is more preferably 90% or more, still more preferably 95% or more, particularly preferably 98% or more (for example, 99% or more) of the total light transmittance before the bending test. The total light transmittance after the above bending test depends on the selection of the composition of the monomer components constituting the base polymer, the setting of the weight average molecular weight (Mw) of the base polymer, the selection of the type and amount of plasticizer used, and whether or not a crosslinking agent is used. It can be adjusted by selecting the type and amount used, whether or not additives are used, and selecting the type and amount 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 rod is fixed horizontally at a height sufficient for measurement, the test piece obtained above is hung on the rod, one side is bent into a U shape with a radius of 2 mm, and held for 1 minute. Specifically, the longitudinal center portion of the test piece is hung on a rod to form an inverted U-shape. Then, both ends located below the test piece are fixed with clips (13 g), and a 60 g weight is suspended and fixed from the clip via a 1 cm long thread to apply a load 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 rod. Next, under the same temperature environment, the other side of the test piece (the opposite side to the above one side) was also heated at a radius of 2 mm on the opposite side of the bent part of the above one side, in the same way as the above one side. Bend it into a U shape and hold for 1 minute. After repeating this bending test 10 times on the above-mentioned folded part of the same test piece, the above-mentioned folded part was measured using the same method as the above-mentioned method for measuring the initial total light transmittance. Measure the total light transmittance [%].

(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, and more preferably 2.0% or less. , more preferably 1.0% or less, 0.9% or less, 0.8% or less, 0.5% or less, or 0.3% or less. Adhesives with such high transparency are advantageous in applications that require high light transmittance (for example, optical applications) and applications that require good visibility of adherends 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, the smaller the haze value is, the more preferable it is. On the other hand, in some embodiments, the haze value of the high refractive index adhesive layer may be, for example, 0.05% or more, or 0.10% or more, taking into account the refractive index and adhesive properties.

Here, the "haze value" refers to the ratio of diffusely transmitted light to the total transmitted light when visible light is irradiated onto the measurement target. Also called cloudiness value. The haze value can be expressed by the following formula.
Th(%)=Td/Tt×100
In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total light transmittance. The haze value can be measured according to the method described in Examples below. The haze value of the adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the adhesive layer.

(Surface smoothness of adhesive surface)
In some embodiments of the adhesive optical film disclosed herein, the adhesive surface of the adhesive optical film (specifically, the 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 have a low arithmetic mean roughness Ra is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic mean roughness Ra, for example, in usage modes where light is extracted through the adhesive surface (eg, modes in which the adhesive layer is disposed closer to the viewpoint than the self-luminous element in a light emitting device), the adhesive layer It is possible to exhibit the effect of suppressing the occurrence of brightness unevenness due to the surface condition of. A low arithmetic mean roughness Ra of the adhesive surface is also advantageous for suppressing optical distortion, and suppressing optical distortion also contributes to improving optical homogeneity.

In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is preferably about 70 nm or less, more preferably about 65 nm or less, still more preferably about 55 nm or less, and may be less than 50 nm, It may be less than 45 nm or 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, about 10 nm or more, about 20 nm or more, or about 30 nm or more (for example, about 40 nm or more).

Further, 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 low maximum height Rz is preferable from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example, in the usage mode where light is extracted through the adhesive surface as described above, it is possible to exhibit the effect of suppressing the occurrence of brightness unevenness due to the surface condition of the adhesive layer. . A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion.

In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600 nm or less, more preferably about 500 nm or less, still more preferably about 450 nm or less, particularly preferably about 400 nm or less, It may be less than 350 nm, may be less than 300 nm, or may be 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. In the form of an adhesive optical film having a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be the same or different. You can leave it there.

In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600 nm or less, more preferably about 500 nm or less, still more preferably about 450 nm or less, particularly preferably about 400 nm or less, It may be less than 350 nm, may be less than 300 nm, or may be 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.

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 type surface roughness measuring device, an optical interference type surface roughness measuring device is used, and for example, a three-dimensional optical profiler (trade name "NewView 7300", manufactured by ZYGO) or its equivalent can be used. can. Specifically, the arithmetic mean roughness Ra and maximum height Rz can be determined by, for example, using the following measurement method, or by setting the measurement operation and measurement conditions so that results equivalent to or corresponding to those obtained by the measurement method are obtained. can be measured.

That is, in an environment of 23° C. and 50% RH, the surface shape of the measurement sample is measured under the following conditions using a three-dimensional optical profiler (trade name “NewView 7300”, manufactured by ZYGO). Arithmetic surface roughness Ra is calculated from the measured data according to JIS B 0601-2001. The maximum height Rz is the height Rp of the highest peak above the average line of the roughness curve and the deepest valley below the average line of the roughness curve for the data obtained by the above measurement (roughness curve). It is calculated as the sum of the depth Rv. Measurements are performed five times (ie N=5) and their average value is used.
The measurement sample can be prepared, for example, by cutting the adhesive layer to be measured or the adhesive sheet containing the adhesive layer into a size of approximately 150 mm in length and 50 mm in width. If the adhesive surface is protected by a release liner, the release liner is gently peeled off (for example, at a pulling speed of 300 mm/min and a peeling angle of 180°) to expose the adhesive surface. It is desirable to carry out the measurement after exposing the adhesive surface and allowing it to stand for about 30 minutes.
[Measurement condition]
Measurement area: 5.62mm x 4.22mm
(Objective lens: 2.5x, internal lens: 0.5x)
Analysis 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, the surface of the release liner that protects the adhesive surface (release surface ) can be adjusted depending on the properties etc.

(Storage modulus G')
Although not particularly limited, the storage modulus G' (0°C) of the high refractive index adhesive layer at 0°C may be less than 1.0x10 ⁸ Pa, for example, 5.0x10 ⁷ It may be less than Pa, it may be less than 1.0×10 ⁷ Pa, it may be less than 5.0×10 ⁶ Pa. The high refractive index adhesive layer having the storage modulus G' (0° C.) has appropriate flexibility in the temperature range from around 0° C. to higher, and can adhere well to an adherend, for example. The lower limit of the storage elastic modulus G' (0° C.) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, and may be 1.0×10 ³ Pa or more. When the storage modulus G' (0° C.) is at least a predetermined value, the high refractive index adhesive layer tends to have appropriate cohesive strength, for example, in a normal temperature range to a high temperature range. In some embodiments, the high refractive index adhesive layer has a storage modulus G' (0° C.) of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. According to the above-mentioned high refractive index adhesive layer, the range of storage elastic modulus G' (0°C) is suppressed to a low range while having a high refractive index, so that it achieves both high refractive index and flexibility. It can be. A high refractive index adhesive layer having a storage modulus G' (0° C.) in the above range can have both a high refractive index and flexibility, and can have flexibility that can withstand repeated bending operations. The storage elastic modulus G' (0° C.) is preferably 5.0×10 ⁵ Pa or less, may be 2.0×10 ⁵ Pa or less, or may be 1.0×10 ⁵ Pa or less, It may be 7.0×10 ⁴ Pa or less, 5.0×10 ⁴ Pa or less, or 3.0×10 ⁴ Pa or less. Further, the storage elastic 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, It may be 1.0×10 ⁵ Pa or more.

The storage modulus G' (-20°C) of the high refractive index adhesive layer disclosed herein is not particularly limited, and may be less than 1.0×10 ¹⁰ Pa, for example. It may be less than 0x10 ⁹ Pa, suitably 5.0x10 ⁸ Pa or less, it may be 1.0x10 ⁸ Pa or less, it may be 5.0x10 ⁷ Pa or less, It may be 1.0×10 ⁷ Pa or less, 5.0×10 ⁶ Pa or less, 1.0×10 ⁶ Pa or less, or 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 may have good flexibility in a lower temperature range, and may have flexibility that can withstand repeated bending operations in a wide temperature range including a low temperature range. The lower limit of the storage elastic 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 3} Pa or more. .0×10 ⁴ Pa or more, more preferably 1.0×10 ⁵ Pa or more, may be 5.0×10 ⁵ Pa or more, or 1.0×10 ⁶ Pa or more. The high refractive index adhesive layer having the above storage modulus G' (-20° C.) can have flexibility and appropriate cohesive strength. Furthermore, the high refractive index adhesive layer having the storage modulus G' (-20° C.) tends to have both high refractive index and flexibility even in a low temperature range.

The storage elastic modulus G' (25°C) of the high refractive index adhesive layer disclosed herein is appropriately set depending on the purpose of use and manner of use, and is not limited to a specific range. From the viewpoint of ease of application to the body, it is appropriate that the pressure is, for example, less than 1.0 x 10 ⁶ Pa, preferably less than 5.0 x 10 ⁵ Pa, more preferably less than 3.0 x 10 ⁵ Pa. The pressure may be less than 1.0×10 ⁵ Pa, and may be less than 5.0×10 ⁴ Pa. The high refractive index adhesive layer whose storage modulus G' (25° C.) is limited as described above has good flexibility at normal usage temperatures such as room temperature environments. The lower limit of the storage 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 in consideration of increasing the refractive index. , 5.0×10 ² Pa or more, preferably 1.0×10 ³ Pa or more, more preferably 3.0×10 3 Pa or more, 5.0× ^{10 3 Pa} or more It may be. A high refractive index pressure-sensitive adhesive layer having the storage modulus G' (25° C.) is preferable because it has a suitable cohesive force even in a high temperature range and tends to have excellent heat resistance.

In some embodiments, the storage modulus G' (25°C) at 25°C of the high refractive index adhesive layer is higher than the storage modulus G' (25°C) at 25°C of the low refractive index adhesive layer described below. Preferably it is low. According to this configuration, adhesion and flexibility are imparted to the laminate of the high refractive index adhesive layer and the low refractive index adhesive layer, thereby improving the ability to follow steps and curved surfaces, etc. A pressure-sensitive adhesive optical film that can be preferably applied to device design applications can be realized.

(Storage modulus ratio)
In some embodiments, the high refractive index adhesive layer has a ratio of storage modulus G'(0°C) at 0°C to storage modulus G'(25°C) at 25°C (G'(0°C)/G (25°C)) is within the range of 1 to 1000. A high refractive index adhesive layer that satisfies the above properties suppresses changes in elastic modulus in a wide temperature range from 0°C to room temperature, so it has stable properties (flexibility, etc.) against temperature changes. Easy to demonstrate. The above 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, or even 10 or less. Often, it may be 5 or less. 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, the high refractive index adhesive layer has a ratio of storage modulus G' (-20°C) to storage modulus G' (25°C) at -20°C (G'(-20°C) )/G'(25°C)) is in the range of 1 to 1000. A high refractive index adhesive layer that satisfies the above properties suppresses changes in elastic modulus in a wide temperature range from lower temperatures to room temperature, so it has stable properties against temperature changes (flexibility, etc.). ) can be demonstrated. The above ratio (G'(-20°C)/G'(25°C)) may be 500 or less, 300 or less, 150 or less, 100 or less, 50 or less, 30 or less. But that's fine. 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 may be set in consideration of flexibility in a low temperature range and cohesive strength (heat resistance, etc.) in a high temperature range. In some embodiments, the Tg of the high refractive index adhesive layer is, for example, 30°C or less, may be 15°C or less, or may be 5°C or less. In some preferred embodiments, the Tg of the high refractive index adhesive layer is 0°C or less from the viewpoint of flexibility, more preferably -5°C or less, still more preferably -10°C or less, and -15°C or less. (for example, −20° C. or lower). The lower the Tg of the high refractive index adhesive layer, the better the adhesive properties such as adhesion to an adherend tend to be. Furthermore, by setting the Tg of the high refractive index adhesive layer low, changes in the 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, suitably -40°C or higher, may be -30°C or higher, or may be -25°C or higher. According to the high refractive index pressure-sensitive adhesive layer having the above-mentioned Tg, an appropriate cohesive force tends to be easily obtained. In addition, there is a tendency to easily form a pressure-sensitive adhesive that has both a high refractive index and flexibility.

The storage modulus G' of the adhesive layer and the glass transition temperature of the adhesive layer at each of the above temperatures can be determined by dynamic viscoelasticity measurement. Dynamic viscoelasticity measurement can be performed by a conventional method using a commercially available dynamic viscoelasticity measuring device. For example, each adhesive layer is laminated to a thickness of about 1.5 mm and then punched out into a disk shape with a diameter of 7.9 mm. This is used as a measurement sample, and the "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific is used Dynamic viscoelasticity measurements are performed using the following conditions. From the measurement results, the storage elastic modulus G' and glass transition temperature at each temperature can be read, and each storage elastic modulus ratio can be calculated.
[Measurement condition]
Deformation mode: Torsion Measurement frequency: 1Hz
Temperature range: -50℃~150℃
Heating rate: 5℃/min Shape: Parallel plate 7.9mmφ

The storage modulus G', storage modulus ratio, and glass transition temperature of the high refractive index adhesive layer can be determined by, for example, selecting the composition of the monomer components constituting the base polymer, setting the Mw of the base polymer, the type of plasticizer, etc. It can be adjusted by selecting the amount to be used, selecting whether or not to use a crosslinking agent, selecting the type and amount to use, selecting whether to use an additive, selecting the type and amount to use, etc.

(Change in elastic modulus after being held at 130°C for 1 hour)
Although not particularly limited, in some embodiments, the storage modulus G'1 at -20°C after holding the adhesive in a 130°C environment for 1 hour, and the storage modulus G'1 after holding the adhesive in a 130°C environment for 1 hour. An adhesive having a ratio (G'1/G'0) of storage elastic modulus G'0 at -20°C before 50 or less (specifically 1 to 50) is used as the high refractive index adhesive layer. It is preferable. A high refractive index adhesive layer that satisfies this property has a change in elastic modulus that is limited within a predetermined range even when exposed to high temperatures, and can exhibit stable properties. The ratio (G'1/G'0) is preferably 30 or less, more preferably 10 or less, still more preferably 3 or less, 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 surface 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 has been silicone-treated, is bonded to the surface of the adhesive layer. One of the release liners is peeled off from the obtained adhesive layer with a release liner (release liner/adhesive layer/release liner), and the mixture is kept in an oven at 130° C. for 1 hour. Use an oven that has sufficient capacity for the sample to be measured and that can be heated while evacuating the sample. For example, an oven manufactured by espec can be used. The adhesive (layers) held at 130° C. for 1 hour are laminated to a thickness of approximately 1.5 mm, and then autoclaved (0.5 MPa, 50° C., 15 minutes) to adhere each layer. The storage modulus G' (G'1 ) Find [Pa]. Then, the ratio (G' 1/G'0).

(Deformation characteristics)
In some embodiments, the high refractive index adhesive layer has a refractive index of more than 1.560 and a deformation amount of 350 in a deformation test conducted at a temperature of -20° C. and a speed of 300 mm/min. % or more. 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 properties desirably has a high refractive index, and can withstand use in applications involving large deformations, such as foldable display applications.

In some embodiments, the high refractive index adhesive layer has a stress of 5.0 N/mm ² or less at a deformation amount of 350% in a deformation test conducted at a temperature of -20°C and a speed of 300 mm/min. It is preferable that 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 predetermined level of flexibility even in a low temperature environment. Therefore, it is suitable for use in applications involving large deformations. In some preferred embodiments, the stress at the deformation amount of 350% is 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. Good, 4.5N/mm ² or less, 4.4N/mm ² or less, 4.3N/mm ² or less, 4.2N/mm 2 or less, 4.1N/mm ^{2 or} less, 4.0N/mm ² or less , 3.9 N/mm ² or less, 3.8 N/mm ² or less, 3.7 N/mm ² or less, 3.6 N/mm ² or less, 3.5 N/mm ² or less, 3.4 N/mm ² 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, 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 stress at the above deformation amount 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. .3N/ ^mm2 or more, 0.4N/ ^mm2 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/mm ² or more, 1.6N/mm ² or more, 1.7N/mm ² or more, 1.8N/mm ² or more, 1.9N/mm ² or more, 2.0N/mm ² or more, 2.1N/mm ² or more Or it may be 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. ^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 3.4 N/mm ² or more, 3.5 N/mm ² or more, 3.6 N/mm ² or more, 3.7 N/mm ² or more, 3.8 N/mm ² or more, 3.9 N/mm ² or more, 4.0 N/mm ² or more, 4.1 N/mm ² or more, 4.2 N/mm ² or more, 4.3 N/mm ² or more, 4.4 N/mm ² or more, 4.5 N/mm ² or more, or 4. It may be 6N/mm ² or more. The high refractive index pressure-sensitive adhesive layer having stress at the deformation amount of 350% can have flexibility and appropriate cohesive force.

In some embodiments, the high refractive index adhesive layer has a stress S (-20°C) at a deformation amount of 350% in a deformation test conducted at a temperature of -20°C and a speed of 300 mm/min, and a temperature of 25°C. , the ratio (S(-20°C)/S(25°C)) of stress at 350% deformation in a deformation test conducted at a speed of 300 mm/min (S(-20°C)/S(25°C)) is 50 or less. preferable. A high refractive index adhesive layer that satisfies the above characteristics can exhibit stable performance in a wide temperature range including low temperature ranges. 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 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 Below, 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, 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 22 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.

Specifically, the deformation test conducted at the temperature of -20° C. or 25° C. and the speed of 300 mm/min is performed in the following manner.
[Deformation test]
The adhesive layer is cut into a width having a length of 300 mm and a cross-sectional area of 1 mm ² , and the adhesive layer is rolled 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 Corporation, device name: "Precision Universal Testing Machine Autograph AG-X plus 5kN"), the above test piece was deformed under the conditions of -20°C, chuck distance 100mm, and tensile speed 300mm/min. A test (tensile test) is performed to determine the SS curve, and it is evaluated whether the test piece deforms (elongates) by 350% or more. If the test piece is deformed by 350% or more, the stress [N/mm ² ] at the time of 350% deformation is measured. In the above deformation test, an adhesive that can deform by 350% or more at -20°C is determined to be an adhesive that can withstand large deformations.
Further, a deformation test was conducted in the same manner as above except that the temperature of the deformation test was changed to 25° C., and the stress [N/mm ² ] at 350% deformation was measured. From the obtained results, the stress S (-20°C) at a deformation amount of 350% in the deformation test conducted at a temperature of -20°C and a speed of 300 mm/min, and the stress S (at -20°C) at a temperature of 25°C and a speed of 300 mm/min. The ratio (S(-20°C)/S(25°C)) to the stress S(25°C) at a deformation amount of 350% in the deformation test to be performed is determined.
In addition, when the thickness of the adhesive layer is relatively small, for the purpose of improving operability, etc., the above deformation test is conducted using a test piece prepared so that the thickness is 5 μm or more (for example, about 5 μm to 200 μm). It's okay. The thickness of the test piece can be adjusted, for example, by appropriately overlapping adhesive layers. In addition, using the same adhesive composition as that used to form the adhesive layer to be measured, a test piece with a thickness that facilitates the deformation test was prepared, and the above deformation test was performed on the test piece. Good too. The above deformation test can be carried out using, for example, a test piece with a thickness of about 10 μm to 50 μm. Further, during the test, it is preferable to apply powder to the adhesive surface of the area to be chucked to remove the influence of stickiness of the adhesive.

The temperature of the adhesive is -20°C, the deformability is 350% at a speed of 300 mm/min, the stress at 350% deformation, and the ratio (S(-20°C)/S(25°C)) of the base polymer. selection of the composition of monomer components to be used, setting of the weight average molecular weight (Mw) of the base polymer, selection of the type and amount of plasticizer used, selection of whether to use a crosslinking agent, selection of the type and amount of use, selection of the use or non-use of additives, type and amount. It can be adjusted by selecting the amount used, etc.

(base polymer)
In the technology disclosed herein, the type of adhesive constituting the high refractive index adhesive layer is not particularly limited. The above adhesive includes acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, which can be used in the adhesive field. It may contain one or more types of various rubbery polymers such as polyamide-based polymers and fluorine-based polymers as an adhesive polymer (hereinafter also referred to as "base polymer" in the sense of a structural polymer that forms an adhesive). . From the viewpoint of adhesive performance, cost, etc., a pressure-sensitive adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably employed. Among these, adhesives having an acrylic polymer as a base polymer (acrylic adhesives) are preferred. The technique disclosed herein is preferably implemented in an embodiment using an acrylic pressure-sensitive adhesive.

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

In addition, in this specification, the "base polymer" of an adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not to be interpreted in any limited manner other than this. The above-mentioned rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. Furthermore, in this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight, unless otherwise specified.
Furthermore, in this specification, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule, as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer." Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. Typical examples of acrylic polymers include polymers in which the proportion of acrylic monomers out of all the 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). It will be done.
Furthermore, in this specification, "(meth)acryloyl" refers comprehensively to acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to acrylic and methacrylic. Therefore, the concept of acrylic monomer here may include both monomers having an acryloyl group (acrylic monomer) and monomers 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 serving as the base polymer of the acrylic pressure-sensitive adhesive is preferably one containing an aromatic ring-containing monomer (A1) as a monomer component constituting the acrylic polymer. That is, an acrylic polymer containing the aromatic ring-containing monomer (A1) as a monomer unit is preferable. Here, in this specification, the term "monomer component constituting the acrylic polymer" refers to a monomer component that is contained in the adhesive composition in the form of a pre-formed polymer (which may be an oligomer) or is a monomer component that is unpolymerized. It means a monomer that constitutes a repeating unit of an acrylic polymer in a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition, regardless of whether it is contained in the pressure-sensitive adhesive composition in any form. That is, the monomer component constituting the acrylic polymer may be contained in the pressure-sensitive adhesive composition in any form of a polymerized product, an unpolymerized product, or a partially polymerized product. From the viewpoint of ease of preparation of the adhesive composition, in some embodiments, an adhesive composition containing 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. Preferably.

(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 kind of such compounds can be used alone or two or more kinds can be used in combination.

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

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 and transparency of the adhesive, the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, and 6 or less. More preferably, the number is 5 or less, 4 or less, 3 or less, or 2 or less.

The aromatic ring possessed by the compound used as the monomer (A1) is a benzene ring (it can be a benzene ring that constitutes a part of a biphenyl structure or a fluorene structure); a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, a phenanthrene ring. It may be a carbocyclic ring such as a condensed ring; , a thiophene ring; and the like may be used. The heteroatoms included as ring constituent atoms in the above-mentioned heterocycle may be, for example, one or more heteroatoms selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatoms making up the heterocycle can be one or both of nitrogen and sulfur. The monomer (A1) may have a structure in which one or more carbon rings and one or more heterocycles are condensed, such as a dinaphthothiophene structure.

The aromatic ring (preferably a carbocyclic ring) may have one or more substituents on the ring-constituting atoms, or may have no substituents. When having a substituent, the substituent includes an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group. Examples include, but are not limited to. In a substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In some embodiments, the aromatic ring has no substituent on the ring constituent atoms, or one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (e.g., a bromine atom). It can be an aromatic ring having Note that the aromatic ring of the monomer (A1) having a substituent on its ring-constituting 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 bonded directly or may be bonded via a linking group. The above-mentioned linking group is, for example, an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, or a structure in which one or more hydrogen atoms in these groups are substituted with a hydroxyl group. (for example, a hydroxyalkylene group), an oxy group (-O- group), a thiooxy group (-S- group), and the like. In some embodiments, the aromatic ring and the ethylenically unsaturated group are bonded directly or through a linking group selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. An aromatic ring-containing monomer having the following structure 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 1 or 2, for example. The repeating number of oxyalkylene units 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 the aromatic ring-containing vinyl compound can each be used singly or in combination of two or more. One or more aromatic ring-containing (meth)acrylates and one or more aromatic ring-containing vinyl compounds may be used in combination.

In some preferred embodiments, a monomer having two or more aromatic rings (preferably carbon 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 via a linking group, and two or more non-fused aromatic rings. Monomers with a structure in which rings are chemically bonded directly (i.e., without intervening other atoms), monomers with a fused aromatic ring structure, monomers with a fluorene structure, monomers with a dinaphthothiophene structure, monomers with a dibenzothiophene structure , etc. Among these, monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group (for example, phenoxybenzyl (meth)acrylate described below) are preferably used. The monomer containing multiple aromatic rings can be used alone or in combination of two or more.

The above-mentioned linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (for example, a -O-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1). , thiooxyalkylene groups (e.g. -S-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1), linear alkylene groups (i.e. -(CH ₂ ) _n - group, where n is 1 to 6, preferably 1 to 3), the alkylene group in the above oxyalkylene group, the above thiooxyalkylene group, and the above linear alkylene group may be partially halogenated or completely halogenated. From the viewpoint of flexibility of the high refractive index pressure-sensitive adhesive layer, preferred examples of the linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a linear alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate (for example, m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl (meth) Examples include acrylate, benzylbenzyl (meth)acrylate, and the like.

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, and the like. Specific examples include o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, and the like.

Examples of the monomer having the fused aromatic ring structure include naphthalene ring-containing (meth)acrylate, anthracene ring-containing (meth)acrylate, vinyl group-containing naphthalene, vinyl group-containing anthracene, and the like. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, -(4-methoxy-1-naphthoxy)ethyl (meth)acrylate and the like.

Specific examples of the monomer having the above fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene (meth)acrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (meth)acrylate etc. In addition, since the monomer having a fluorene structure includes a structural part 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 the monomer having the dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, (meth)allyl group-containing dinaphthothiophene, and the like. As a specific example, (meth)acryloyloxymethyl dinaphthothiophene (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. , R ¹ is a hydrogen atom or a methyl group), (meth)acryloyloxyethyldinaphthothiophene (for example, CH ₂ CH(R ¹ )C(O) at the 5th or 6th position of the dinaphthothiophene ring) A compound with a structure in which OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - is bonded. Here, R ¹ is a hydrogen atom or a methyl group), vinyldinaphthothiophene (For example, a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of a naphthothiophene ring), (meth)allyloxydinaphthothiophene, and the like. In addition, monomers having a dinaphthothiophene structure are included in the above concept of monomers having a fused aromatic ring structure because they include a naphthalene structure or because they have a structure in which a thiophene ring and two naphthalene structures are condensed. Ru.

Examples of the monomer having the dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene, vinyl group-containing dibenzothiophene, and the like. A monomer having a dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings are condensed, and therefore is included in the concept of a monomer having a condensed aromatic ring structure.
Note that 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 carbon ring) in one molecule is used as the monomer (A1). A monomer having one aromatic ring in one molecule (a monomer containing a single aromatic ring) can be useful, for example, in improving the flexibility of the high refractive index adhesive layer, adjusting the adhesive properties, and improving the transparency. The monomer containing a single aromatic ring can be used alone or in combination of two or more. In some embodiments, a monomer having one aromatic ring in one 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 in one molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, and phenoxypropyl (meth)acrylate. , phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, chlorobenzyl (meth)acrylate, and other carbon aromatic ring-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, 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecyl Bromine-substituted aromatic ring-containing (meth)acrylates such as phenyl acrylate; carbon aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, tert-butylstyrene; N-vinylpyridine, N-vinylpyrimidine, N-vinylpyridine, N-vinylpyrimidine, - Compounds having a vinyl substituent on a heteroaromatic ring, such as vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; and the like.

As the monomer (A1), monomers having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in various aromatic ring-containing monomers as described above may be used. A monomer in which an oxyethylene chain is interposed between an ethylenically unsaturated group and an aromatic ring in this way can be understood as an ethoxylated product of the original monomer. The number of repeating oxyethylene units (-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 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol. Examples include di(meth)acrylate.

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, or 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. , 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, only one or more aromatic ring-containing monomers may be used as the monomer (A1). In some other embodiments, the content of the monomer containing multiple aromatic rings in the monomer (A1) is less than 100% by weight, for example, considering the balance between high refractive index, flexibility, and adhesive strength. 98% by weight or less, 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 It may be less than 10% by weight. The technology disclosed herein can also be practiced in an embodiment in which the content of the monomer containing multiple aromatic rings in the monomer (A1) is less than 5% by weight. A monomer containing multiple aromatic rings may not be used.

The content of the monomer containing multiple aromatic rings in the monomer component constituting the acrylic polymer is not particularly limited, and should be set so as to realize a high refractive index adhesive layer that has both desired refractive index and flexibility. I can do it. 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, the content of the monomer containing multiple aromatic rings in the monomer component may be, for example, more than 35% by weight, from the viewpoint of facilitating the realization of a high refractive index adhesive layer having a higher refractive index. , advantageously greater than 50% by weight, preferably greater than 70% by weight, may be greater than 75% by weight, may be greater than 85% by weight, may be greater than 90% by weight, greater than 91% by weight, 92% by weight or greater. It may be at least 93% by weight, at least 94% by weight, at least 95% by weight, at least 96% by weight, at least 97% by weight, at least 98% by weight, or at least 99% by weight. The content of the monomer containing multiple aromatic rings in the above monomer component is advantageously approximately 99% by weight or less, and 98% by weight or less, considering the balance between high refractive index, flexibility, and adhesive strength. It may be 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. In some other embodiments, the content of the monomer containing multiple aromatic rings in the monomer component may be 70% by weight or less, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (for example, transparency). , 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, or 5% by weight or less. The technology disclosed herein can also be practiced 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. , 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, only one or more monomers containing a single aromatic ring may be used as the monomer (A1). Further, in some embodiments, for example, in consideration of the balance between high refractive index and flexibility, the content of the monomer containing a single aromatic ring in the monomer (A1) may be less than 100% by weight, and may be less than 98% by weight. % or less, 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, 10% by weight The following may be used. The technology disclosed herein can also be practiced 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. A monomer containing a single aromatic ring may not be used.

The content of the monomer containing a single aromatic ring in the monomer components constituting the acrylic polymer is not particularly limited, and should be set so as to realize a high refractive index adhesive layer that has both desired refractive index and flexibility. Can be done. The content of the monomer containing a single aromatic ring 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 facilitating the realization of a high refractive index adhesive layer having a higher refractive index, the content of the monomer containing a single aromatic ring in the monomer component may be, for example, more than 35% by weight, Advantageously more than 50% by weight, preferably more than 60% by weight, more preferably more than 70% by weight, even more than 75% by weight, even more than 85% by weight, even more than 90% by weight, It may be 95% by weight or more, or 98% by weight or more. The content of the monomer containing a single aromatic ring in the above monomer component may be about 99% by weight or less, and should be 98% by weight or less, considering the balance between high refractive index, flexibility, and adhesive strength. The content is preferably 96% by weight or less, more preferably 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments, the content of the monomer containing a single aromatic ring in the monomer component may be 70% by weight or less, from the viewpoint of easily realizing higher adhesive properties and/or optical properties (for example, transparency), and 60% by weight or less. It may be less than 50% by weight, less than 40% by weight, less than 25% by weight, less than 15% by weight, and less than 5% by weight. The technology disclosed herein can also be practiced 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 a portion of the monomer (A1). Here, the term "high refractive index monomer" refers to a monomer whose refractive index is, for example, about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more. 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 the acrylic polymer and compatibility with flexibility suitable as an adhesive, it is, for example, 3.000 or less, and 2. It may be 500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less. The high refractive index monomers can be used alone or in combination of two or more.
The refractive index of the monomer is measured using an Abbe refractometer at a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, model "DR-M4" manufactured by ATAGO or its equivalent can be used. If a manufacturer or the like provides a nominal value of the refractive index at 25° C., that nominal value can be used.

The above-mentioned high refractive index monomer is one having a corresponding refractive index 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). may be adopted as appropriate. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, homopolymer Tg: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, homopolymer Tg: 31°C), Ethoxylated o-phenylphenol acrylate (number of repeating oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, homopolymer Tg: 6°C), phenoxyethyl acrylate (Refractive index (nD20): 1.517, homopolymer Tg: 2°C), phenoxydiethylene glycol acrylate (refractive index: 1.510, homopolymer Tg: -35°C), 6-acryloyloxymethyldinaphthothiophene ( 6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6 -Acryloyloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1) .793), but is not limited to these.

The content of the high refractive index monomer (that is, the aromatic ring-containing monomer having a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in the monomer (A1) is particularly The content is not limited, and may be, for example, 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of easily obtaining 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 preferably 70% by weight or more. , 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of monomer (A1) may be a high refractive index monomer. In some embodiments, the content of the high refractive index monomer in the monomer (A1) is less than 100% by weight, for example, from the viewpoint of achieving a good balance between high refractive index, flexibility, and adhesive strength. It may be 98% by weight or less, 90% by weight or less, 80% by weight or less, or 65% by weight or less. In some other embodiments, in consideration of adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer (A1) may be 50% by weight or less, 25% by weight or less, 15% by weight or less. % or less, or 10% by weight or less. The technology disclosed herein can also be practiced in an embodiment in which the content of the high refractive index monomer in the monomer (A1) is less than 5% by weight. High refractive index monomers may not be used.

The content of the high refractive index monomer in the monomer components constituting the acrylic polymer is not particularly limited, and can be set so as to realize a high refractive index adhesive layer that has both desired refractive index and flexibility. can. In addition, if necessary, it may be set in consideration of compatibility with adhesive properties (for example, adhesive strength, etc.) and/or optical properties (for example, 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 components 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 more than 50% by weight. Advantageously, it is preferably greater than 70% by weight, may be greater than 75%, may be greater than 85%, may be greater than 90%, may be greater than 95% by weight. The content of the high refractive index monomer in the above monomer component is preferably 99% by weight or less, and 98% by weight or less from the viewpoint of achieving a good balance between high refractive index, flexibility, and adhesive strength. The content is preferably 96% by weight or less, more preferably 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. . In some other embodiments, in consideration of adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer component may be 70% by weight or less, 50% by weight or less, or 25% by weight. It may be less than 15% by weight, or less than 5% by weight. The technology disclosed herein can also be practiced in an embodiment in which the content of the high refractive index monomer in the monomer components is less than 3% by weight.

In some preferred embodiments, an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") whose homopolymer Tg is 10° C. or less is employed as at least a part of the monomer (A1). The content of the aromatic ring-containing monomer (A1) in the monomer component (in particular, the aromatic ring-containing monomer (A1) that corresponds to at least one of the above-mentioned monomer containing a plurality of aromatic rings, monomer containing a single aromatic ring, and high refractive index monomer) If the amount is increased, the flexibility of the adhesive generally tends to decrease, but by employing monomer L as part or all of the monomer (A1), the decrease in flexibility can be suppressed. Thereby, the refractive index can be improved while maintaining flexibility better. The Tg of the monomer L may be, for example, 5°C or less, 0°C or less, -10°C or less, -20°C or less, or -25°C or less. The lower limit of Tg of the monomer L is not particularly limited. Considering the balance with the refractive index improvement effect, in some embodiments, the Tg of the monomer L may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. In some other embodiments, the Tg of the 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 alone or in combination of two or more.

As the monomer L, one having a corresponding Tg is 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). be able to. 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), phenoxyethyl acrylate (homopolymer Tg: 6°C), Tg: 2°C), and phenoxydiethylene glycol acrylate (homopolymer Tg: -35°C).

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

The content of monomer L in the monomer components 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, the content of monomer L in the monomer component is, for example, more than 35% by weight, from the viewpoint of making it easier to obtain a high refractive index adhesive layer that achieves both high refractive index and flexibility at a higher level. From the viewpoint of improving the refractive index, it is advantageous to be more than 50% by weight, preferably more than 70% by weight, more than 75% by weight, more than 85% by weight, even more than 90% by weight. It may be 95% by weight or more. The content of monomer L in the above monomer component is advantageously approximately 99% by weight or less, and is preferably 98% by weight or less, from the viewpoint of achieving a good balance between high refractive index, flexibility, and adhesive strength. The content is preferably 96% by weight or less, more preferably 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less.

In some embodiments, the aromatic ring-containing monomer (A1) is a combination of monomer L (i.e., an aromatic ring-containing monomer whose homopolymer Tg is 10°C or less) and monomer H whose Tg is higher than 10°C. May be used. The Tg of the monomer H may be, for example, higher than 10°C, higher than 15°C, or higher than 20°C. By using a combination of monomer L and monomer H, in a high refractive index adhesive layer with a high content of the aromatic ring-containing monomer (A1) in the monomer components, the refractive index of the high refractive index adhesive layer is increased; It is possible to achieve a higher level of flexibility suitable for adhesion to adherends. The usage ratio of monomer L and monomer H can be set so that this effect is suitably expressed, and is not particularly limited.

In some embodiments, the aromatic ring-containing monomer (A1) may 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, the monomer component has 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) An acrylic polymer constituted by is preferred. In this way, limiting the amount of compounds that contain a structure in which two or more non-fused aromatic rings are directly chemically bonded makes it possible to achieve a high refractive index that achieves a better balance between high refractive index, flexibility, and adhesive strength. This can be advantageous from the viewpoint of realizing an adhesive layer.

The content of the monomer (A1) in the monomer components constituting the acrylic polymer is not particularly limited, and the content of the monomer (A1) in the monomer component constituting the acrylic polymer is not particularly limited, and the content of the monomer (A1) is not limited to a desired refractive index and flexibility, as well as adhesive properties (for example, adhesive strength, etc.) and/or optical properties (for example, total light rays). Transmittance, haze value, etc.) can be set so as to realize a high refractive index pressure-sensitive adhesive layer. In some embodiments, the content of the monomer (A1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, and 70% by weight. It may be % or more. In some preferred embodiments, the content of the monomer (A1) in the monomer components constituting the acrylic polymer may be, for example, more than 70% by weight, suitably 75% by weight or more, and has a higher refractive index. From the viewpoint of making it easier to obtain the ratio, it is preferably 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, 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 monomer (A1) in the above monomer component is typically less than 100% by weight, and from the viewpoint of achieving both high refractive index and flexibility in a well-balanced manner, it is advantageously approximately 99% by weight or less. It may be 98% by weight or less, 96% by weight or less, 93% by weight or less, or 90% by weight or less. In some embodiments, the content of the monomer (A1) in the monomer component may be less than 90% by weight, and may be less than 85% by weight, from the viewpoint of facilitating the realization of higher adhesive properties and/or optical properties (for example, transparency). % or 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 above monomer (A1). The monomer (A2) is a monomer that corresponds to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxy 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 above-mentioned 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 useful for introducing crosslinking points into the acrylic polymer and imparting appropriate cohesiveness to the high refractive index adhesive layer. Monomers (A2) can be used alone or in combination of two or more. 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. Note that the monomer (A2) is defined as a monomer different from the above-mentioned monomer (A1), and for example, the above-mentioned monomer (A1) can be defined as a monomer having no hydroxyl group or carboxyl group.

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

In some embodiments, a monomer in which the distance between an ethylenically unsaturated group (for example, a (meth)acryloyl group) and a hydroxyl group and/or a carboxy group is relatively long can be used as the monomer (A2). Thereby, in embodiments in which the hydroxyl group and/or carboxy group are used in the crosslinking reaction, a crosslinked structure with high flexibility can be easily obtained. For example, the number of atoms (typically carbon atoms or oxygen atoms) constituting the chain (linking 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). 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). It can be used as A2). The upper limit of the number of atoms constituting the connecting chain is, for example, 45 or less, 20 or less (for example, 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, 10 or less, 9 or less or 8 or less). In addition, the number of atoms forming a linking chain connecting the ethylenically unsaturated group and the hydroxyl group and/or carboxy group refers to the minimum number of atoms required to reach the hydroxyl group or carboxy group from the ethylenically unsaturated group. . For example, when the above-mentioned connecting chain is composed of a linear alkylene group (ie, -(CH ₂ ) _n - group), the number of n is the number of atoms constituting the above-mentioned connecting chain. For example, when the connecting chain is an oxyethylene group (that is, a -(C ₂ H ₄ O) _n - group), 3 and n, which is the sum of 2 carbon atoms and 1 oxygen atom, constituting the oxyethylene group. The product (3n) is the number of atoms constituting the connected chain. Although not particularly limited, such monomers (A2) include, for example, alkylene represented by -(CH ₂ ) _n - between the ethylenically unsaturated group and the hydroxyl group and/or carboxyl group. units, oxyalkylene units represented by -(C _m H _2m O)- (for example, oxyethylene units in which m is 2 in the above formula, oxypropylene units in which m in the above formula is 3, A compound having at least one oxybutylene unit in which m is 4) can be used. The number of alkylene units and 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). Further, n in the formula representing the above alkylene unit is, for example, an integer from 1 to 10, and may be 2 or more, 3 or more, 4 or more, or 6 or less, or 5 or less. good. In the formula representing the above oxyalkylene unit, m is an integer of 2 or more, for example, an integer of 2 to 4. In addition to the above-mentioned ethylenically unsaturated group, hydroxyl group and/or carboxy group, alkylene unit and/or oxyalkylene unit, the monomer (A2) also contains an ester bond, an ether bond, a thioether bond, an aromatic ring, an aliphatic ring, and a heterocyclic ring. (For example, a ring containing a nitrogen atom (N), an oxygen atom (O), or a sulfur atom (S)). Moreover, the above alkylene unit and oxyalkylene unit may have a substituent.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and ) Hydroxy (meth)acrylates such as 8-hydroxyoctyl acrylate, 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, polybutylene glycol mono(meth)acrylate; and the like, 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, which has a lower Tg, is more preferred. In addition, in an embodiment in which hydroxyalkyl (meth)acrylate is used as the hydroxyl group-containing monomer and the hydroxyl group is utilized in the crosslinking reaction, from the viewpoint of obtaining a highly flexible crosslinked structure, the hydroxyalkyl (meth)acrylate is Monomers with a large number of carbon atoms in the hydroxyalkyl group, such as hydroxyalkyl (meth)acrylates (for example, 4-hydroxy acrylate) in which the hydroxyalkyl group has 3 or more carbon atoms (for example, 3 to 12, preferably 4 to 10). butyl) is preferred. In some preferred embodiments, 50% or more (eg, greater than 50%, greater than 70%, or greater than 85%) by weight of monomer (A2) can be 4-hydroxybutyl acrylate. The hydroxyl group-containing monomers can be used alone or in combination of two or more.

In some embodiments in which a hydroxyl group-containing monomer is used as the monomer (A2), the hydroxyl group-containing monomer may be one or more selected from compounds that do not have a methacryloyl group. Preferred examples of the hydroxyl group-containing monomer that does not have a methacryloyl group include the above-mentioned various hydroxyalkyl acrylates. For example, it is preferable that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (A2) is hydroxyalkyl acrylate. The use of hydroxyalkyl acrylates allows the introduction of hydroxy groups into acrylic polymers that help provide cross-linking points and impart appropriate cohesive properties, and allows for the introduction of hydroxyl groups into acrylic polymers that help provide crosslinking points and provide adequate cohesiveness, and is more stable at room temperature than when the corresponding hydroxyalkyl methacrylates are used alone. It is easy to obtain an adhesive with good flexibility and adhesiveness in this area.

Examples of carboxy group-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, Examples include, but are not limited to, isocrotonic acid and the like. Examples of carboxy group-containing monomers that can be preferably used include acrylic acid and methacrylic acid. Further, 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 above 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 as each other. May be different. 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 above can be alkylene having 2 to 5 carbon atoms. Specific examples of the carboxy group-containing monomer represented by the above formula (1) include 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl-phthalic acid, 2-( meth)acryloyloxyethyl-2-hydroxyethyl-phthalic acid, 2-(meth)acryloyloxyethyl-succinic acid, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropylhydrogen phthalate, 2-(meth)acryloyloxypropyltetrahydrohydrogen phthalate, and the like. Carboxy group-containing monomers can be used singly or in combination of two or more. A hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used in combination.

The content of the monomer (A2) in the monomer components 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, suitably 0.1% by weight or more, preferably 0.5% by weight or more. 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 from the viewpoint of obtaining higher usage effects. The upper limit of the content of the monomer (A2) in the monomer component is set so that the total content of the monomer (A2) and the content of the monomer (A1) does not exceed 100% by weight. In some embodiments, it is appropriate for the content of the monomer (A2) to be, for example, 30% by weight or less or 25% by weight or less, and the content of the monomer (A1) is relatively increased to obtain a high refractive index. From the viewpoint of facilitating rate reduction, the content is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, may be less than 10% by weight, and may be less than 7% by weight. . In some preferred embodiments, from the viewpoint of improving the flexibility 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% by weight. It may be less than .5% by weight.

(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. It can also help improve the compatibility of additives within the adhesive and adhesive properties such as adhesive strength. Monomers (A3) can be used alone or in combination of two or more.

As the monomer (A3), an alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms (ie, C _1-20 ) at the ester end can be preferably used. Specific examples of C _1-20 alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and n-(meth)acrylate. Butyl, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, (meth)acrylate, ) heptyl 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, (meth)acrylate ) Heptadecyl acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and the like, but are not limited to these.

In some embodiments, as at least a portion of the monomer (A3), an alkyl (meth)acrylate whose homopolymer has a Tg of -20°C or lower (more preferably -40°C or lower, for example -50°C or lower) is preferably employed. It is possible. Such a low Tg alkyl (meth)acrylate can be useful for improving the flexibility of the high refractive index adhesive layer. It can also help improve adhesive properties such as adhesive strength. 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)acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), heptyl acrylate, octyl acrylate, isononyl acrylate (iNA), and the like. In some other embodiments, an alkyl (meth)acrylate whose homopolymer Tg is higher than -20°C (for example, higher than -10°C) 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. Alkyl (meth)acrylates with Tg in this range can be useful in adjusting the flexibility of the high refractive index adhesive layer. Although not particularly limited, the alkyl (meth)acrylate having the above-mentioned Tg is preferably used in combination with the above-mentioned low-Tg alkyl (meth)acrylate. A specific example of the alkyl (meth)acrylate having the above Tg is lauryl acrylate (LA).

In some embodiments using monomer (A3), it is preferred to use C _4-8 alkyl (meth)acrylate as monomer (A3). Among them, it is more preferable to use C _4-8 alkyl acrylate. The C _4-8 alkyl (meth)acrylates can be used alone or in combination of two or more. By using C _4-8 alkyl (meth)acrylate, it is easy to improve the flexibility of the high refractive index adhesive layer, and there is a tendency that good adhesive properties (adhesion strength, etc.) are easily obtained. In the embodiment in which C _4-8 alkyl (meth)acrylate is used as the monomer (A3), the proportion of C _4-8 alkyl (meth)acrylate among the alkyl (meth)acrylates contained in the monomer component is 30% by weight or more. The content is preferably 50% by weight or more, more preferably 70% by weight or more, still 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 in each temperature range can be adjusted. For example, it is possible to set the storage modulus in the high temperature region relatively high, or to suppress the difference in storage modulus between the low temperature region and the high temperature region from increasing. Furthermore, C _1-6 alkyl (meth)acrylate tends to have excellent copolymerizability with monomer (A1). One type of C _1-6 alkyl (meth)acrylate can be used alone or two or more types can be used in combination. The C _1-6 alkyl (meth)acrylate is preferably C _1-6 alkyl acrylate, more preferably C _2-6 alkyl acrylate, and even more preferably C _4-6 alkyl acrylate. In some other embodiments, the C _1-6 alkyl (meth)acrylate is preferably a C _1-4 alkyl (meth)acrylate, more preferably a C _2-4 alkyl (meth)acrylate, even more preferably is C _2-4 alkyl acrylate. A preferred example of C _1-6 alkyl (meth)acrylate is BA.

The content of C _1-6 alkyl (meth)acrylate in the monomer components constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, and 8% by weight. The above is fine. 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, 20% by weight or more, from the viewpoint of improving flexibility, adhesive strength, etc. It may be at least 25% by weight (for example, at least 30% by weight). 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 17% by weight. It is more preferably less than 12% by weight, may be less than 7% by weight, may be less than 3% by weight, and may be less than 1% by weight. The technology disclosed herein can also be practiced in an embodiment in which C _1-6 alkyl (meth)acrylate is not substantially used.

In some other embodiments using monomer (A3), C _7-12 alkyl (meth)acrylate may be preferably used as monomer (A3). By using C _7-12 alkyl (meth)acrylates, the storage modulus can be advantageously reduced. One type of C _7-12 alkyl (meth)acrylate can be used alone or two or more types can be used in combination. As the C _7-12 alkyl (meth)acrylate, C _7-10 alkyl acrylate is preferred, C _7-9 alkyl acrylate is more preferred, and C ₈ alkyl acrylate is even more preferred. Examples of C _7-12 alkyl (meth)acrylates include 2EHA, iNA, and LA, and a preferred example includes 2EHA.

The content of C _7-12 alkyl (meth)acrylate in the monomer components constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, and 8% by weight. The above is fine. 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, 20% by weight or more, from the viewpoint of improving flexibility, adhesive strength, etc. It may be at least 25% by weight (for example, at least 30% by weight). 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 17% by weight. It is more preferably less than 12% by weight, may be less than 7% by weight, may be less than 3% by weight, and may be less than 1% by weight. The technology disclosed herein can also be practiced in an embodiment that does not substantially use C _7-12 alkyl (meth)acrylate.

In some embodiments using monomer (A3), from the viewpoint of improving flexibility, it is preferable that at least a part of the monomer (A3) is an alkyl acrylate. The use of alkyl acrylates is also advantageous in terms of adhesive properties such as adhesive strength. For example, it is preferable that 50% by weight or more of the monomer (A3) is alkyl acrylate, and the proportion of alkyl acrylate in the monomer (A3) is more preferably 75% by weight or more, still more preferably 90% by weight or more, Substantially 100% by weight of monomer (A3) may be alkyl acrylate. An embodiment may be employed in which only one or more alkyl acrylates are used as the monomer (A3) and no alkyl methacrylate is used.

In the embodiment in which the monomer component contains an alkyl (meth)acrylate, the content of the alkyl (meth)acrylate in the monomer component can be set so that the effect of its use 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 content of monomers (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. In general, the refractive index of alkyl (meth)acrylates is relatively low, so in order to increase the refractive index, the content of monomer (A3) in the monomer component should be limited, and the content of monomer (A1) should be relatively increased. It is advantageous to do so. From this point of view, the content of the monomer (A3) is suitably less than 23% by weight of the monomer components, preferably less than 20% by weight, more preferably less than 17% by weight, and 12% by weight. It may be less than 7% by weight, 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 components constituting the acrylic polymer may contain monomers other than the above monomers (A1), (A2), and (A3) (hereinafter referred to as "other monomers"), if necessary. The above-mentioned other monomers can be used, for example, for purposes such as adjusting the Tg of the acrylic polymer, adjusting the adhesive performance, and improving compatibility within the adhesive layer. The above-mentioned other monomers can be used alone or in combination of two or more.

Examples of the above-mentioned other monomers include monomers having functional groups other than hydroxyl groups and carboxy groups (functional group-containing monomers). For example, other monomers that can improve the cohesive force and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, and the like. In addition, amide group-containing monomers ( For example, (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), and nitrogen atom-containing rings. (for example, N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide group-containing monomers, epoxy group-containing monomers, keto group-containing monomers, isocyanate group-containing monomers, alkoxysilyl group-containing monomers, etc. Can be mentioned. Note that among the monomers having a nitrogen atom-containing ring, some such as N-vinyl-2-pyrrolidone also fall under the category of amide group-containing monomers. The same applies to the relationship between the monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Other monomers that can be used other than the above 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; ethylene, Olefinic monomers such as 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 ethers such as methyl vinyl ether system monomer; etc. A suitable example of other monomers that can be used to improve the flexibility of the adhesive is ethoxyethoxyethyl acrylate (also known as ethyl carbitol acrylate, homopolymer Tg: -67°C).

When using the above-mentioned other monomers, the amount used is not particularly limited, and can be appropriately set within a range where the total amount of the 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 above-mentioned other monomers in the monomer component can be, for example, about 35% by weight or less, and about 25% by weight or less (for example, 0% by weight or less). ~25% by weight), may be approximately 20% by weight or less (for example, 0 to 20% by weight), and advantageously approximately 10% by weight or less (for example, 0 to 10% by weight), Preferably it is about 5% by weight or less, for example about 1% by weight or less. The technique disclosed herein can be preferably carried out in an embodiment in which the monomer component does not substantially contain the other monomers mentioned above.

In some embodiments, the monomer components constituting the acrylic polymer may have a composition in which the amount of the methacryloyl group-containing monomer used is suppressed to a predetermined amount or less. The amount of the methacryloyl group-containing monomer used 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 the methacryloyl group-containing monomer used in this manner can be advantageous from the viewpoint of realizing a pressure-sensitive adhesive that has a good balance of flexibility, adhesiveness, and high refractive index. The monomer component constituting the acrylic polymer may have a composition that does not contain a methacryloyl group-containing monomer (for example, a composition that consists 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 carboxylic acid, from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the high refractive index adhesive layer. The amount of group-containing monomer used is limited. The amount of the carboxy 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, 0. It may be less than .05% by weight. This limitation in the amount of carboxy group-containing monomers means that metal materials that can be placed in contact with or in close proximity to the high refractive index adhesive layer disclosed herein (e.g., metal materials that are present on an adherend) This is also advantageous from the viewpoint of suppressing corrosion of the resulting metal wiring, metal film, etc.). The technique disclosed herein can be practiced in an embodiment in which the monomer component does not contain a carboxy group-containing monomer.
For the same reason, in some embodiments, the monomer components constituting the base polymer of the high refractive index adhesive layer contain acidic functional groups (including carboxy groups, sulfonic acid groups, phosphoric acid groups, etc.). The amount of the monomer used may be limited. As the amount of the acidic functional group-containing monomer used in the monomer component of this embodiment, the above-mentioned preferred amount of the carboxy 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, 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 about 15° C. or lower. In some embodiments, the Tg is preferably 10°C or lower, more preferably 5°C or lower, even more preferably 1°C or lower, and may be 0°C or lower. In some other embodiments, the Tg may be -10°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, or -35°C or lower. A low Tg can be advantageous from the viewpoint of improving the flexibility of the high refractive index adhesive layer. Further, the above Tg may be, for example, -60°C or higher, and from the viewpoint of easily increasing the refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, and -40°C. It may be super. 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 having both high refractive index and flexibility can be preferably formed by using a base polymer having a composition having Tg in the above range.

Here, the Tg based on the composition of the monomer components constituting the base polymer (for example, acrylic polymer) refers to the glass transition temperature determined by the Fox equation based on the composition of the monomer components, unless otherwise specified. The Fox equation, as shown below, is a relation between Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1/Tg=Σ(Wi/Tgi)
In the above 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 on a weight basis), and Tgi is the homopolymer of monomer i. represents the glass transition temperature (unit: K) of
As the glass transition temperature of the homopolymer used to calculate Tg, the value described in publicly known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) is used. For monomers for which multiple values are listed in the Polymer Handbook, the highest value is used. If the Tg of the homopolymer is not described in known materials, the value obtained by the measurement method described in JP-A No. 2007-51271 shall be used.

(Preparation method of base polymer)
In the technology disclosed herein, the method for obtaining the base polymer (for example, acrylic polymer) composed of such monomer components is not particularly limited, and may include solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. , photopolymerization, and other known polymerization methods 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., and is, for example, about 20°C to 170°C (typically 40°C to 140°C). ℃).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetate esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane, etc. halogenated alkanes; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. Any one type of solvent 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 more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds ; etc. Still another example of the polymerization initiator is a redox initiator using a combination of a peroxide and a reducing agent. One type of polymerization initiator can be used alone or two or more types can be used in combination. The amount of the polymerization initiator used may be any normal amount, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer component. ) can be selected from the range.

In the above polymerization, various conventionally known chain transfer agents can be used as necessary. For example, mercaptans such as n-dodecylmercaptan, t-dodecylmercaptan, thioglycolic acid, and α-thioglycerol can be used. Alternatively, a chain transfer agent that does not contain sulfur atoms (non-sulfur chain transfer agent) may be used. Examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylstyrene, α-methylstyrene dimer, etc. styrenes; and the like. One type of chain transfer agent can be used alone or two or more types can be used in combination. When using a chain transfer agent, the amount used can be, for example, approximately 0.01 to 1 part by weight per 100 parts by weight of the monomer component.

The weight average molecular weight (Mw) of the base polymer (for example, acrylic polymer) is not particularly limited, and is, for example, about 30 x 10 ⁴ or more, suitably about 50 x 10 ⁴ or more, and about 70 x 10 The number may be ⁴ or more, and may be approximately 80×10 ⁴ or more. By using a base polymer having Mw of a predetermined value or more, it is easy to obtain an appropriate cohesive force that can exhibit desired adhesive properties. Furthermore, it is possible to contain a larger amount of additives such as plasticizers, which tends to make it easier to achieve desired flexibility. Further, the upper limit of the Mw of the base polymer is, for example, approximately 500×10 ⁴ or less, and from the viewpoint of adhesive performance, approximately 400×10 ⁴ or less (more preferably approximately 150×10 ⁴ or less, for example, approximately 130×10 ⁴ or less). ) is preferably within the range. 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 of the technology disclosed herein can be preferably achieved in an embodiment using an acrylic polymer having Mw within the above range.

Here, the Mw of the polymer can be determined in terms of polystyrene by gel permeation chromatography (GPC). Specifically, it can be determined by measuring under the following conditions using a GPC measurement device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation).
[GPC measurement conditions]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: 1 piece of product name “TSKgel SuperH-RC” (manufactured by Tosoh Corporation)
Detector: Differential refractometer (RI)
Standard sample: polystyrene

(Plasticizer)
In some embodiments, the high refractive index adhesive layer (eg, high refractive index acrylic adhesive layer) described above contains a plasticizer in addition to the base polymer. By using a plasticizer, the flexibility of the high refractive index adhesive layer can be improved. As the plasticizer, it is preferable to select and use one or more plasticizers that can maintain a refractive index of over 1.560 or further improve the refractive index from among the plasticizers described below.

Preferred 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 preferred example is a compound having two or more double bond-containing rings in one molecule. Therefore, 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 increase its large deformability without impairing the refractive index of the high refractive index adhesive layer or while maintaining the refractive index. It can be realized. In addition, by using a plasticizer that has two or more double bond-containing rings (for example, aromatic rings), the interaction and affinity with acrylic polymers that have aromatic rings increases, maintaining and improving adhesive strength, and stabilizing adhesive properties. It can contribute to sexual improvement. From this viewpoint, in some embodiments, the number of double bond-containing rings in the plasticizer is preferably 3 or more, more preferably 4 or more, even more preferably 5 or more, and may be 6 or more. Further, the number of double bond-containing rings in the plasticizer is suitably, for example, 10 or less, and may be 8 or less, from the viewpoint of exhibiting a plasticizing effect. In some other embodiments, the number of double bond-containing rings in the plasticizer is preferably 6 or less, may be 4 or less, or may be 3 or less.

Further, the plasticizer used in the technology disclosed herein is preferably a compound that is liquid at 30°C. Note that in this specification, "liquid" means exhibiting fluidity, and refers to a liquid state as a substance state. Such compounds include those having a melting point of 30°C or less. Since the plasticizer is liquid at 30° C., the plasticizing effect is suitably exhibited, and the flexibility of the high refractive index pressure-sensitive adhesive layer can be improved and, by extension, large deformability can be suitably realized. The plasticizer is preferably a compound that is liquid at 25°C, more preferably a compound that is liquid at 20°C. For example, by using a compound that is liquid at 30°C and has two or more double bond-containing rings as a plasticizer, it is possible to preferably form a high refractive index adhesive layer that has both high refractive index and flexibility. .

The molecular weight of the plasticizer is not particularly limited, but one having a molecular weight smaller than that of the base polymer (eg, acrylic polymer) is usually used. The molecular weight of the plasticizer is suitably 30,000 or less, advantageously 25,000 or less, and may be less than 10,000 (for example, less than 5,000), from the viewpoint of facilitating the expression of the plasticizing effect. It may be less than 3000. 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 less than or equal to 250 (for example, less than 220). It may be advantageous that the molecular weight of the plasticizer is not too large from the viewpoint of improving compatibility within the adhesive layer. In addition, the molecular weight of the plasticizer is suitably 100 or more, preferably 130 or more, more preferably 150 or more, and 170 or more, from the viewpoint of facilitating sufficient plasticizing effect. It may be 200 or more, 220 or more, or 250 or more. It is preferable that the molecular weight of the plasticizer is not too low from the viewpoint of the heat resistance performance of the adhesive and the 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. Plasticizers with large molecular weights are difficult to vaporize, so by using plasticizers with large molecular weights in adhesives, it is easy to obtain adhesives that can exhibit stable characteristics. Furthermore, a plasticizer with a large molecular weight is difficult to move within the adhesive. Therefore, events that affect the adhesive properties, such as the movement of the plasticizer to the adhesive surface, are less likely to occur. The molecular weight of the plasticizer is more preferably 400 or more, still more preferably 450 or more, particularly preferably 500 or more, and may be 530 or more.
Note that, 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 used.

Although not particularly limited, in some embodiments, as a plasticizer, the amount transferred to the gas phase at 130°C (130°C vaporized amount) is 10% or less (specifically 0 to 10% by weight) on a weight basis. ) may be used. By using a plasticizer that satisfies this property, the high refractive index pressure-sensitive adhesive layer containing the plasticizer can suppress changes in properties caused by the plasticizer due to changes in temperature and humidity. For example, the adhesive can exhibit stable properties even when used in an environment exposed to high temperatures and high humidity or when used for a long period of time. The amount of plasticizer vaporized at 130°C 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 holding the plasticizer at 130°C for 1 hour. More specifically, it can be measured by the following method.
[Amount of plasticizer transferred to gas phase]
Approximately 1 g of plasticizer (measurement sample) is dropped into an aluminum cup and weighed to the nearest 0.01 mg using 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. Use an oven that has sufficient capacity for the sample to be measured and that can be heated while evacuating the sample. For example, an oven manufactured by espec can be used. After being held at 130° C. for 1 hour, the cup containing the measurement sample was taken out of the oven, returned to room temperature, and then weighed (W1 g). Substituting 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 formula: 1-W1/W0, the measurement sample at 130 ° C. Find the amount [%] transferred to the gas phase. The measurement is performed on three samples (n=3), and the average value is used.

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

The amount of plasticizer in the high refractive index adhesive layer can be determined, 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 surface 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 has been silicone-treated, is bonded to the surface of the pressure-sensitive adhesive layer. One of the release liners is peeled off from the obtained adhesive layer with a release liner (release liner/adhesive layer/release liner), and the mixture is kept in an oven at 130° C. for 1 hour. Use an oven that has sufficient capacity for the sample to be measured and that can be heated while evacuating the sample. For example, an oven manufactured by espec can be used. Liquid chromatography (LC) measurements are performed on the adhesive before and after heating in an oven under the following conditions. From the above LC results, the amount of plasticizer contained in the adhesive before and after heating was determined, and from the weight ratio, the weight loss [%] of the plasticizer in the adhesive after being kept in an environment of 130°C for 1 hour ] Find. The measurement is performed on three samples (n=3), and the average value is used. Note that, prior to the LC measurement of the adhesive, it is desirable to perform LC measurement of the plasticizer alone, create a calibration curve, and quantify the plasticizer in the adhesive based on this calibration curve.
[LC measurement conditions]
Approximately 0.01 g of the adhesive is collected, 2 mL of chloroform is added, and the mixture is shaken overnight. 8 mL of acetonitrile was added to this solution to reprecipitate the polymer component, and the supernatant was filtered with a 0.45 μm membrane filter. The obtained filtrate is diluted appropriately and injected into an analyzer (manufactured by Shimadzu Corporation, HPLC Prominence) for measurement.
Column: GL Sciences, Inertsil ODS-3 (4.6mmφ×250mm, 5μm)
Column temperature: 40℃
Column flow rate: 1.0mL/min
Eluent: Ultrapure water/acetonitrile gradient conditions Injection volume: 1 μL
Detector: DAD (190nm to 400nm, 272nm extraction)

In an embodiment in which a plasticizer having a double bond-containing ring is used, the double bond-containing ring of the plasticizer may be a conjugated double bond-containing ring (typically an aromatic ring), or a non-conjugated double bond-containing ring. It may be any ring containing a heavy bond. The plasticizer may have at least one type of ring selected from an aromatic ring and a heterocycle (heterocycle) as the double bond-containing ring. Note that the above-mentioned heterocycle may have a structure included in an aromatic ring, or may have a double bond-containing heterocyclic structure different from an 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 that forms part of a biphenyl structure or a fluorene structure); a naphthalene ring, and an indene ring. , an azulene ring, an anthracene ring, a fused ring of a phenanthrene ring; etc.; a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring; It may be a heterocyclic ring such as an oxazole ring, an isoxazole ring, a thiazole ring, or a thiophene ring. The heteroatoms included as ring constituent atoms in the above-mentioned heterocycle may be, for example, one or more heteroatoms selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatoms making up the heterocycle can be one or both of nitrogen and sulfur. The plasticizer may have a structure in which one or more carbon rings and one 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 more substituents on the ring-constituting atoms, or may have no substituents. good. When having a substituent, the substituent includes an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group. Examples include, but are not limited to. In a substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In some embodiments, the double bond-containing ring has no substituents on the ring atoms, or has an alkyl group, an alkoxy group, an ethylenically unsaturated group (e.g. (meth)acryloxy group), a hydroxy group, and a hydroxy group. It may be an aromatic ring having one or more substituents selected from the group consisting of alkyl groups. As the substituent, an alkyl group, an alkoxy group, and a hydroxyalkyl group are preferably used.

In some embodiments, a compound having no ethylenically unsaturated group may be preferably employed as the plasticizer. Thereby, deterioration of the adhesive composition due to heat or light (decrease in leveling properties due to progress of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adopting a plasticizer that does not have ethylenically unsaturated groups means that changes in elastic modulus, dimensional changes, and deformations (warping, waving, etc.) due to reactions of ethylenically unsaturated groups may occur in the adhesive layer containing the plasticizer. ) is preferable also from the viewpoint of suppressing the occurrence of optical distortion.

As the plasticizer, a high refractive index plasticizer having a refractive index of about 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 flexibility. The refractive index of the plasticizer is preferably about 1.51 or more, more preferably about 1.53 or more, and even more preferably about 1.53 or more, from the viewpoint of maintaining and improving the refractive index of the high refractive index adhesive layer while obtaining flexibility. It may be approximately 1.55 or more, it may be approximately 1.56 or more, it may be approximately 1.58 or more, it may be approximately 1.60 or more, and it may be approximately 1.62 or more. In some embodiments, from the viewpoint of ease of preparation of the adhesive composition and compatibility within the adhesive, the refractive index of the plasticizer is suitably 2.50 or less, and 2.00 or less. Advantageously, it may be 1.90 or less, 1.80 or less, or 1.70 or less.
Note that, like the refractive index of the monomer, the refractive index of the plasticizer is measured using an Abbe refractometer at a measurement wavelength of 589 nm and a measurement temperature of 25°C. If a manufacturer or the like provides a nominal value of the refractive index at 25° C., that nominal value can be used.

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 via a linking group, a compound containing two or more non-fused double bonds, Compounds with a structure in which rings (typically aromatic rings) are chemically bonded directly (i.e., without intervening other atoms), compounds with a fused double bond-containing ring structure (typically aromatic rings), fluorene One or more types selected from compounds having a structure, compounds having a dinaphthothiophene structure, compounds having a dibenzothiophene structure, etc. may be used.

In some preferred embodiments, a compound A having a structure in which two or more non-fused double bond-containing rings are bonded via a linking group is used as the plasticizer. The above-mentioned linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (for example, a -O-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1). , thiooxyalkylene groups (e.g. -S-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1), linear alkylene groups (i.e. -(CH ₂ ) _n - group, where n is 1 to 6, preferably 1 to 3), the alkylene group in the above oxyalkylene group, the above thiooxyalkylene group, and the above linear alkylene group may be partially halogenated or completely halogenated. The linking group may have a siloxane bond (-SiOR-) or an ester bond. In the plasticizer, the linking group that connects the first double bond-containing ring (non-fused ring) and the second double bond-containing ring (non-fused ring) may also be selected from the same types as mentioned above. From the viewpoint of flexibility of the high refractive index adhesive layer, preferred examples of the linking group include an oxy group, a thiooxy group, and a linear alkylene group. The number of atoms in the linking group is not particularly limited, and in some embodiments is, for example, 1 to 30, may be 1 to 25, may be 1 to 20, and is suitably 1 to 18. The number is preferably 1 to 12, more preferably 1 to 10, even more preferably 1 to 8, particularly preferably 1 to 5, may be 1 to 3, or may be 1 or 2. Note that the number of atoms in 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 (ie, -(CH ₂ ) _n - group), the number of n is the number of atoms in the linking group. Preferred 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[(methoxy) methyl)benzene]) and the like. Other examples of the above-mentioned compounds include silicone plasticizers (specifically siloxane compounds) described below.

The compound having a structure in which two or more double bond-containing rings (non-fused rings) are directly chemically bonded may be, for example, a biphenyl structure-containing compound, a triphenyl structure-containing compound, or the like. Further, examples of compounds having a ring structure containing a condensed double bond include a naphthalene ring-containing compound, an anthracene ring-containing compound, and the like. Specific examples include 1-acetonaphthone and the like. In addition, since the compound having the above-mentioned fluorene structure includes a structural part in which two benzene rings are directly chemically bonded, the concept of a compound having a structure in which two or more double bond-containing rings (non-fused rings) are directly chemically bonded is different from the above. included in. The above-mentioned compound having a dinaphthothiophene structure is based on the concept of a compound having a fused double bond-containing ring structure because it includes a naphthalene structure and also because it has a structure in which a thiophene ring and two naphthalene structures are condensed. Included. The compound having the above-mentioned dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings are condensed, and therefore is included in the concept of a compound having the above-mentioned fused double bond-containing ring structure.

In some preferred embodiments, a silicone plasticizer is used as the plasticizer. By using a silicone plasticizer, it is easy to obtain a stable plasticizing effect and high adhesive strength, which improves the refractive index, flexibility, and adhesive strength of the high refractive index adhesive layer in a well-balanced manner. be able to. The silicone plasticizer is not particularly limited, and for example, a compound having one or more double bond-containing rings can be used. Further, the silicone plasticizer is preferably a compound that is liquid at 30°C. The silicone plasticizer is specifically a siloxane compound, and the number of Si atoms contained in the compound is 1 or more (typically 2 or more), and the upper limit is not particularly limited, for example, about 10 or less. It can be. In one molecule of silicone plasticizer, the Si atom and the double bond-containing ring may or may not be directly bonded. Preferably, at least one of the Si atoms is directly bonded to at least one double bond-containing ring. The silicone plasticizers can be used alone or in combination of two or more.

In some embodiments, the silicone plasticizer is made of a siloxane compound having 2 or more and 5 or less Si atoms, and at least one of the Si atoms has two or more double bond-containing rings. A combination can be used. A silicone plasticizer made of a siloxane compound having such a structure can exhibit a plasticizing effect based on the flexibility of the siloxane structure, and also has a silicone-based plasticizer containing 2 or more Si atoms and 5 or less Si atoms, and 2 or more double-Si atoms. By having at least one Si atom bonded to the bond-containing ring, it is possible to improve the ease of blending and compatibility with the material to be plasticized, and the stability of the above-mentioned plasticizing effect (for example, the elastic modulus when stored under moist heat). (low rate of increase) can be achieved in a well-balanced manner. From the viewpoint of chemical stability, the siloxane compound preferably does not have a hydrogen atom bonded to a Si atom. That is, siloxane compounds without Si--H bonds are preferred.

When the number of Si atoms in the siloxane compound is 3 or more, the siloxane compound may be chain or cyclic, but is preferably a chain siloxane compound from the viewpoint of suppressing volatilization. The above-mentioned chain siloxane compound having 3 or more Si atoms may be linear or branched, but is preferably linear from the viewpoint of obtaining a higher plasticizing effect. Hereinafter, unless otherwise specified, a siloxane compound having 3 or more Si atoms means a chain (typically linear) siloxane compound having 3 or more Si atoms.

In some embodiments, the double bond-containing ring of the silicone plasticizer may be a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. Good too. The plasticizer may have at least one type of ring selected from an aromatic ring and a heterocycle (heterocycle) as the double bond-containing ring. Note that the above-mentioned heterocycle may have a structure included in an aromatic ring, or may have a double bond-containing heterocyclic structure different from an aromatic ring. The double bond-containing ring (typically an aromatic ring) that the plasticizer may have may be a carbon ring such as a benzene ring or a naphthalene ring, and may include a pyridine ring, an imidazole ring, a triazole ring, an oxazole ring, and a thiazole ring. It may be a ring or a heterocyclic ring such as a thiophene ring. The heteroatoms included as ring constituent atoms in the above-mentioned heterocycle may be, for example, one or more heteroatoms selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatoms making up the heterocycle can be one or both of nitrogen and sulfur.

The double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have one or more substituents on the ring-constituting atoms, or may have no substituents. good. When it has a substituent, examples of the substituent include an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc. However, it is not limited to these. In a substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In some embodiments, each double bond-containing ring possessed by the silicone plasticizer is independently an aromatic ring having no substituent on the ring-constituting atoms, an alkyl group, an alkoxy group, a hydroxy group, and a hydroxyalkyl group. (preferably the group consisting of an alkyl group and an alkoxy group) having one or more substituents selected from the group consisting of an aromatic ring. For example, the double bond-containing ring included in the silicone plasticizer is selected from aromatic rings (preferably carbocycles) having no substituents on ring-constituting atoms. In some preferred embodiments, all double bond-containing rings of the silicone plasticizer are benzene rings.

The number of Si atoms in the above-mentioned siloxane compound is determined from the viewpoint of ease of exerting the plasticizing effect and its stability (for example, suppression of increase in elastic modulus due to volatilization of the plasticizer from the material containing the plasticizer). , preferably 3 or more. Further, the number of Si atoms in the siloxane compound is preferably 4 or less, more preferably 3 or less, from the viewpoint of compatibility within the adhesive. Among these, a silicone plasticizer in which the number of Si atoms in the siloxane compound is 3, that is, a silicone plasticizer made of a trisiloxane compound is preferred.

In some embodiments, the number of double bond-containing rings (e.g., benzene rings with or without substituents) of the siloxane compound is at least 2, and the heat resistance of the plasticizing effect (e.g., under moist heat) is (low rate of increase in elastic modulus with respect to storage) is preferably 3 or more, more preferably 4 or more, and may be 5 or more. Further, the number of double bond-containing rings in the siloxane compound is typically 2n+2 or less, where n is the number of Si atoms in the siloxane compound, and suitably 2n+1 or less from the viewpoint of enhancing the plasticizing effect. and is preferably 2n or less, may be 2n-1 or less, or may be 2n-2 or less. For example, in an embodiment in which the siloxane compound is a trisiloxane compound, the number of double bond-containing rings in the trisiloxane compound is typically 8 or less, for example, it may be 2 or more and 7 or less, and 3 or more. It may be 7 or less, or it may be 4 or more and 7 or less. Among these, trisiloxane compounds in which the number of double bond-containing rings (for example, unsubstituted benzene rings) is 4 or more and 6 or less (for example, 4 or 5) are preferred.

In some embodiments, at least one of the Si atoms (typically, Si atoms constituting a siloxane chain) contained in the siloxane compound is a Si atom to which two or more double bond-containing rings are bonded. It is an atom. From the viewpoint of improving the stability of the plasticizing effect, the number of Si atoms to which two or more double bond-containing rings are bonded in the siloxane compound may be two or more. In a siloxane compound having 3 or more Si atoms, the number of Si atoms to which two or more double bond-containing rings are bonded may be 2 or more, or 3 or more; The number of Si atoms in the compound may be n or less, n-1 or less, or n-2 or less. In some embodiments, from the viewpoint of enhancing the plasticizing effect, at least one of the Si atoms contained in the siloxane compound (preferably a siloxane compound having 3 or more Si atoms) is bonded to the Si atom. The number of double bond-containing rings is 1 or 0. For example, a linear siloxane compound having 3 or more and 5 or less Si atoms, in which the Si atoms at both ends independently have two or three (preferably two) double bond-containing rings; A siloxane compound having a structure in which each Si atom other than the terminal independently has one double bond-containing ring or does not have a double bond-containing ring is preferred.

In some embodiments, the siloxane compound may include a Si atom to which a group other than the double bond-containing ring is bonded. Groups other than the double bond-containing ring mentioned above include alkyl groups, aralkyl groups, alkoxy groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), fluoroalkyl groups, hydroxyl groups, hydroxyalkyl groups, hydroxyalkyloxy groups, Examples include, but are not limited to, epoxy groups, glycidyloxy groups, amino groups, monoalkylamino groups, dialkylamino groups, carboxy groups, carboxyalkyl groups, and mercapto groups. In a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is, for example, 1 to 8, preferably 1 to 4, more preferably 1 to 3, for example 1 or 2. obtain. Groups other than the double bond-containing ring bonded to each Si atom contained in the siloxane compound may be independently selected from the group consisting of the groups exemplified above.

In some embodiments, the siloxane compound preferably does not have an ethylenically unsaturated group (including those in which the double bond in the double bond-containing ring is an ethylenic double bond). A silicone plasticizer made of a siloxane compound that does not have an ethylenically unsaturated group is advantageous from the viewpoint of stability of the plasticizing effect of the plasticizer, and is also advantageous in the high refractive index adhesive layer containing the silicone plasticizer. It is preferable from the viewpoint of the storage stability of the pressure-sensitive adhesive sheet having the above properties, and from the viewpoint of suppressing changes in elastic modulus, dimensional changes and deformations (warping, waving, etc.), optical distortion, etc. caused by reactions of ethylenically unsaturated groups. .

In some embodiments of the silicone plasticizer disclosed herein, at least one of the Si atoms contained in the siloxane compound (at least two in the case of a siloxane compound having 3 or more Si atoms) has a plasticizing effect. From the viewpoint of increasing the resistance, it is preferable to have at least one methyl group on the Si atom. For example, it is preferable that the Si atoms located at both ends of the siloxane chain each independently have one or two (more preferably one) methyl group. In some preferred embodiments, each of the Si atoms contained in the siloxane compound independently has one or two methyl groups. A silicone plasticizer made of a siloxane compound with such a structure has a plasticizing effect due to the flexibility of the siloxane structure and a structure in which two or more double bond-containing rings are bonded to at least one Si atom. The above-mentioned stability of the plasticizing effect can be achieved in a well-balanced manner.

In some embodiments, where the number of Si atoms contained in the siloxane compound is n, the total number of substituents bonded to those Si atoms (hereinafter also referred to as the total number of substituents) is typically is 2n+2, at least two of which are double bond-containing rings. In some embodiments, the ratio SR of the number of double bond-containing rings (preferably aromatic carbocycles, such as benzene rings) to the total number of substituents in the silicone plasticizer is at least 16%, and 20% or more. It may be 25% or more. As the ratio SR increases, the heat resistance of the silicone plasticizer and the stability of the plasticizing effect of the silicone plasticizer generally tend to improve. In some embodiments, the ratio SR is advantageously 33% or more, preferably 40% or more, more preferably 50% or more (for example, 60% or more), and more preferably 65% or more. It may be 75% or more. The above ratio SR may be 100%, but from the viewpoint of ease of blending and compatibility, it is advantageous to be 85% or less, preferably 80% or less, and may be 75% or less, It may be 65% or less, or 60% or less (for example, 50% or less).

In some embodiments, the molecular weight of the silicone plasticizer (specifically, the siloxane compound) is suitably 400 or more, and advantageously 430 or more, from the viewpoint of stability of the plasticizing effect. It is preferably 460 or more, may be 490 or more, or may be 520 or more. Further, the molecular weight of the siloxane compound is suitably 900 or less, advantageously 850 or less, and 700 or less from the viewpoint of plasticizing effect, ease of blending, compatibility, etc. It is preferably 650 or less, more preferably 600 or less, 560 or less, 540 or less, or 500 or less.

As the molecular weight of the siloxane compound, a molecular weight calculated based on the chemical structure or a value measured using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) can be used. If a nominal molecular weight value is provided by a manufacturer, etc., that nominal value can be used.

The refractive index of the silicone plasticizer disclosed herein is not particularly limited, and may be within a range of about 1.30 to 1.80, for example. From the viewpoint of improving flexibility while suppressing a decrease in the refractive index of a high refractive index adhesive layer in which the plasticizer is blended, the silicone plasticizer according to some embodiments has a refractive index of 1.45 or more. It is appropriate that the value is 1.50 or more, more preferably 1.52 or more (for example, 1.53 or more or 1.54 or more), and 1.55 or more (for example, 1.56 or more). or 1.57 or more). Further, the refractive index of the silicone plasticizer may be, for example, 1.70 or less, 1.65 or less, or 1.60 or less, from the viewpoint of ease of blending and compatibility.

In the embodiment in which a silicone plasticizer is used as the plasticizer, the amount of the silicone plasticizer used is not particularly limited, and is set so as to realize the effects of the technology disclosed herein. The amount of silicone plasticizer used per 100 parts by weight of the base polymer (for example, acrylic polymer) may be, for example, 1 part by weight or more, or 10 parts by weight or more. In some preferred embodiments, the amount of silicone plasticizer used per 100 parts by weight of the base polymer is more than 15 parts by weight, more preferably 20 parts by weight or more, even more preferably 25 parts by weight or more, particularly preferably 30 parts by weight. parts or more (for example, more than 30 parts by weight), may be 35 parts by weight or more, or may be 40 parts by weight or more. The amount of the silicone plasticizer used per 100 parts by weight of the base polymer is suitably about 100 parts by weight or less (for example, less than 100 parts by weight), preferably 80 parts by weight or less, and 70 parts by weight. It is more preferably at most 60 parts by weight (for example, less than 60 parts by weight), particularly preferably at most 55 parts by weight, it may be at most 50 parts by weight, it may be at most 45 parts by weight, and it is at most 40 parts by weight. It may be 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less. By using an appropriate amount of silicone plasticizer within the above range, the refractive index, flexibility, and adhesive strength of the high refractive index adhesive layer can be improved in a well-balanced manner.

In addition, in an embodiment in which a silicone plasticizer is used as the plasticizer, the high refractive index adhesive layer may optionally contain one or more plasticizers other than the above silicone plasticizer, or may not contain it. good. Plasticizers other than the silicone plasticizers mentioned above can be used in appropriate amounts as long as they do not impair the effects of the technology disclosed herein. In such an embodiment, the amount of plasticizers other than the silicone plasticizer used is suitably less than 50% by weight, preferably less than 30% by weight of the total plasticizers used in the high refractive index adhesive layer. More preferably it is less than 10% by weight, even 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 does not substantially contain any plasticizer other than the silicone plasticizer described above.

In some embodiments, an ethylene glycol compound having two or more double bond-containing rings in one molecule may be used as a plasticizer; In particular, from the viewpoint of maintaining or improving adhesive strength, the above-mentioned ethylene glycol compound may not be used or the amount thereof may be preferably used in a limited manner. Here, the number of oxyethylene units (that is, -(C ₂ H ₄ O) - units) that the ethylene glycol compound has is, for example, 1 to 10, may be 1 to 6, or may be 2 to 4. good. The above-mentioned ethylene glycol compound has two or more non-fused double bond-containing rings containing oxyethylene units (for example, 1 to 10, preferably 1 to 6, more preferably 2 to 4 oxyethylene units) as a linking group. It may be a compound having a structure bonded via Such compounds may have one or more ester groups. Examples of the ethylene glycol compounds include compounds having a structure in which two or more benzoic acids are linked to ethylene glycol, diethylene glycol, triethylene glycol, or polyethylene glycol through an ester bond.

In some preferred embodiments, the content of the ethylene glycol compound in the plasticizer contained in the high refractive index adhesive layer can be less than 50% by weight. The content ratio of the ethylene glycol compound in the plasticizer may be less than 30% by weight, may be less than 10% by weight, may be less than 3% by weight, may be less than 1% by weight, and the high refractive index adhesive The layer may not substantially contain the above-mentioned ethylene glycol compound as a plasticizer. Similarly, in the high refractive index adhesive layer, the amount of the ethylene glycol compound used per 100 parts by weight of the base polymer (for example, acrylic polymer) can be less than 0.5 parts by weight, and less than 0.1 parts by weight. It may be.

In some other embodiments, liquid rosins such as liquid rosin esters, liquid camphenphenol can be used as plasticizers. The liquid rosin (for example, liquid rosin ester) can correspond to the compound having the fused double bond-containing ring structure.

Furthermore, as a plasticizer, one or more of known plasticizers (for example, phthalate esters, terephthalate esters, adipic esters, adipic acid polyesters, benzoic acid glycol esters, etc.) may be used. Good too.

The amount of plasticizer used is not particularly limited and can be set depending on the purpose. From the viewpoint of improving the flexibility of the high refractive index adhesive layer, the amount of plasticizer used per 100 parts by weight of the base polymer (for example, acrylic polymer) may be, for example, 1 part by weight or more, and may be 10 parts by weight or more. Good too. In some preferred embodiments, the amount of plasticizer used per 100 parts by weight of the base polymer is greater than 15 parts by weight, may be 20 parts by weight or more, and may be 30 parts by weight or more (e.g., more than 30 parts by weight). , more preferably 40 parts by weight or more, further preferably 50 parts by weight or more, particularly preferably 60 parts by weight or more, may be 75 parts by weight or more, and may be 90 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, improving flexibility, and adhesion, the amount of plasticizer used is approximately 200 parts by weight or less per 100 parts by weight of the base polymer. The amount is preferably 150 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, 70 parts by weight or less, 60 parts by weight or less. It may be less than 60 parts by weight (for example less than 60 parts by weight), it may be less than 55 parts by weight, it may be less than 50 parts by weight. In some embodiments where more emphasis is placed on adhesive properties, the amount of plasticizer used per 100 parts by weight of the base polymer may be 45 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less. But that's fine.

(Additive ( _HRO ))
The high refractive index adhesive layer disclosed herein may contain an organic material having a higher refractive index than the base polymer (eg, acrylic polymer) as an optional additive. Hereinafter, such organic materials may be referred to as "additives (H _RO )." Here, the above “H _RO ” represents an organic material with a high refractive index. By using the additive (H _RO ), it is possible to realize a high refractive index adhesive layer that more suitably balances refractive index and adhesive properties (peel strength, flexibility, etc.). The organic material used as the additive (H _RO ) may be polymeric or non-polymeric. Further, it may or may not have a polymerizable functional group. Note that in this specification, the additive (H _RO ) is defined as a compound different from the compound used as the plasticizer described above. For example, the additive (H _RO ) may be non-liquid at 30°C (eg 25°C or 20°C). The additive (H _RO ) can be used singly or in combination of two or more.

The refractive index of the additive (H _RO ) can be set within an appropriate range in relation to the refractive index of the base polymer (eg, acrylic polymer), and is therefore not limited to a specific range. The refractive index of the additive (H _RO ) can be selected, for example, from a range of greater than 1.55, greater than 1.56 or greater than 1.57 and 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 (H _RO ) is advantageously 1.58 or more, and 1.60 or more. It is preferably 1.63 or more, more preferably 1.65 or more, 1.70 or more, or 1.75 or more. With higher refractive index additives (H _RO ), the desired refractive index can also be achieved using smaller amounts of additive (H _RO ). This is preferable from the viewpoint of suppressing deterioration of adhesive properties and optical properties. The upper limit of the refractive index of the additive (H _RO ) is not particularly limited, but from the viewpoint of compatibility within the adhesive and the ease of achieving both a high refractive index and flexibility suitable for the adhesive, for example, 3. 000 or less, may be 2.500 or less, may be 2.000 or less, may be 1.950 or less, may be 1.900 or less, may be 1.850 or less.
Note that, like the refractive index of the monomer, the refractive index of the additive (H _RO ) is measured using an Abbe refractometer at a measurement wavelength of 589 nm and a measurement temperature of 25°C. If a manufacturer or the like provides a nominal value of the refractive index at 25° C., that nominal value can be used.

The molecular weight of the organic material used as the additive (H _RO ) is not particularly limited and can be selected depending on the purpose. In some embodiments, the molecular weight of the additive (H _RO is suitably less than about 10,000, preferably less than 5,000, more preferably less than 3,000 (for example, less than 1,000), may be less than 800, may be less than 600, may be less than 500, It may be less than 400. It may be advantageous that the molecular weight of the additive (H _RO ) is not too large from the viewpoint of improving compatibility within the adhesive. Further, the molecular weight of the additive (H _RO ) may be, for example, 130 or more, or 150 or more. In some embodiments, the molecular weight of the additive (H _RO ) is preferably 170 or more, more preferably 200 or more, and 230 or more, from the viewpoint of increasing the refractive index of the additive (H _RO ). It may be more than 250, it may be more than 270, it may be more than 300, it may be more than 500, it may be more than 1000, it may be more than 2000. In some embodiments, a polymer having a molecular weight of about 1,000 to 10,000 (eg, 1,000 or more and less than 5,000) can be used as the additive (H _RO ).
For the molecular weight of the additive (H _RO ), for non-polymers or polymers with a low degree of polymerization (e.g. dimer to pentamer), the molecular weight calculated based on the chemical structure, or matrix-assisted laser desorption ionization. Measured values using time-of-flight mass spectrometry (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 performed under appropriate conditions can be used. If a nominal molecular weight value is provided by a manufacturer, etc., that nominal value can be used.

Examples of organic materials that can be selected as additives (H _RO ) include organic compounds having an aromatic ring, organic compounds having a heterocycle (either an aromatic ring or a non-aromatic heterocycle), etc. Including, but not limited to:

The aromatic ring possessed by the above-mentioned organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used as the additive (H _RO ) is similar to the aromatic ring possessed by the compound used as the monomer (A1). can be selected from.

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

Examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include: compounds that can be used as monomers (A1); oligomers containing compounds that can be used as monomers (A1) as monomer units; monomers (A1 ), excluding a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring-constituting atom) or a portion of the group constituting an ethylenically unsaturated group, a hydrogen atom or Compounds with a structure in which an ethylenically unsaturated group is replaced with a group that does not have an ethylenically unsaturated group (for example, a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc.); Examples include, but are not limited to, those that do not fall under the plasticizers disclosed herein.

In some embodiments, the additive (H _RO ) is an organic compound having two or more aromatic rings in one molecule (hereinafter referred to as "compound containing multiple aromatic rings") because it is easy to obtain a high refractive index effect. ) can be preferably adopted. The compound containing multiple aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. Further, the compound containing multiple aromatic rings may be a polymer or a non-polymer. Further, the above polymer is an oligomer (preferably an oligomer with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, a low polymer of about 2 to 5 molecules) containing a monomer containing multiple aromatic rings as a monomer unit. obtain. The above oligomers are, for example: homopolymers of monomers containing a plurality of aromatic rings; copolymers of two or more monomers containing a plurality of aromatic rings; copolymers of one or more monomers containing a plurality of aromatic rings with other monomers. It can be a combination; etc. The above-mentioned other monomers may be aromatic ring-containing monomers that do not correspond to monomers containing multiple aromatic rings, may be monomers having no aromatic rings, or may be a combination thereof. In embodiments in which oligomers are used as additives (H _RO ), the oligomers can be obtained by polymerizing the corresponding monomer components by known methods.

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 via a linking group; Examples include a compound having a chemically bonded structure (without intervening), a compound having a fused aromatic ring structure, a compound having a fluorene structure, a compound having a dinaphthothiophene structure, a compound having a dibenzothiophene structure, and the like. The compound containing multiple aromatic rings can be used alone or in combination of two or more.

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

In some embodiments, a compound having no ethylenically unsaturated group can be preferably employed as the additive (H _RO ). Thereby, deterioration of the adhesive composition due to heat or light (decrease in leveling properties due to progress of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adopting an additive (H _RO ) that does not have ethylenically unsaturated groups prevents dimensional changes and deformation (warpage) caused by reactions of ethylenically unsaturated groups in the adhesive layer containing the additive (H _RO ). , waving, etc.) and from the viewpoint of suppressing the occurrence of optical distortion.

The additive (H _RO ) may be used in an appropriate amount as long as the effects of the technology disclosed herein are not significantly impaired. In some embodiments, the amount of the additive (H _RO ) used (if multiple types of compounds are used, the total amount thereof) based on 100 parts by weight of the base polymer (e.g., acrylic polymer) may be greater than 0 parts by weight. It is not particularly limited, and can be set depending on the purpose. In some embodiments, the amount of the additive (H _RO ) to be used with respect to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less. From the viewpoint of achieving well-balanced suppression of deterioration of properties, it is advantageous to set the amount to 60 parts by weight or less, and preferably to set it to 45 parts by weight or less. In some embodiments where more emphasis is placed on adhesive properties and optical properties, the amount of the additive (H _RO ) used relative to 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, 10 parts by weight or less, 3 The amount may be less than 1 part by weight, or less than 1 part by weight. The technology disclosed herein can be preferably implemented in an embodiment 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 the additive (H _RO ) to be used with respect to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, and 3 parts by weight or more. It is advantageous to use 5 parts by weight or more, preferably 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, and 20 parts by weight or more.

(Crosslinking agent)
In the technology disclosed herein, the adhesive composition used to form the high refractive index adhesive layer may contain a crosslinking agent as necessary for the purpose of adjusting the cohesive force of the adhesive. . As the crosslinking agent, use a crosslinking agent known in the adhesive field, such as an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, an oxazoline crosslinking agent, a melamine resin, a metal chelate crosslinking agent, etc. Can be done. Among these, 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, ie, polyfunctional monomers. One type of crosslinking agent can be used alone or two or more types can be used in combination.

As the isocyanate crosslinking agent, a bifunctional or higher-functional isocyanate compound can be used, such as aliphatic polystyrene such as trimethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), dimer acid diisocyanate, etc. Isocyanates; Alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane; 2,4-tolylene diisocyanate, 4,4'- Aromatic isocyanates such as diphenylmethane diisocyanate and xylylene diisocyanate (XDI); the above isocyanate compounds are modified with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds, etc. Examples include modified polyisocyanates (eg, isocyanurate of HDI, allophanate of HDI, etc.). Examples of commercially available products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N, Takenate D178NL (all manufactured by Mitsui Chemicals), Sumidur T80, Sumidur L, Desmodur N3400 (all manufactured by Mitsui Chemicals). (manufactured by Bayer Urethane Co., Ltd.), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX, Coronate 2770 (manufactured by Tosoh Corporation), and Duranate A201H (trade name, manufactured by Asahi Kasei Corporation). The isocyanate compounds can be used alone or in combination of two or more. A bifunctional isocyanate compound and a trifunctional or more functional isocyanate compound may be used together.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, and trimethylol. Propane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. can be mentioned. These can be used alone or in combination of two or more.

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, neopentyl glycol di(meth)acrylate, Pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecane Diol di(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, and the like. One type of polyfunctional monomer can be used alone or two or more types can be used in combination.

In some embodiments, at least a portion of the crosslinker is a bifunctional crosslinker having two crosslinking reactive groups (eg, isocyanate groups) per molecule. By using a bifunctional crosslinking agent, a flexible crosslinked structure can be easily formed. One type of bifunctional crosslinking agent can be used alone or two or more types can be used in combination. Moreover, a bifunctional crosslinking agent may be used in combination with a trifunctional or more functional crosslinking agent.

In some embodiments, as the crosslinking agent, 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. For example, among the above-mentioned isocyanate-based crosslinking agents, it is preferable to use isocyanate-based compounds that do not have a ring structure such as an aromatic ring or an isocyanurate ring. By using an acyclic isocyanate compound as a crosslinking agent, a highly flexible crosslinking agent can be easily formed. Specific examples of the acyclic isocyanates include aliphatic isocyanate compounds (e.g., PDI and HDI) and modified aliphatic isocyanate compounds (e.g., allophanate bonds, biuret bonds, urea bonds, and carbodiimide bonds of PDI and HDI). modified polyisocyanates). One type of acyclic crosslinking agent can be used alone or two or more types can be used in combination. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent.

In some embodiments, a crosslinking agent may be used in which the distance between one crosslinking reactive group (eg, an isocyanate group) and another crosslinking reactive group in one molecule is relatively long. As a result, a flexible crosslinked structure having a length longer than a predetermined length is formed. For example, a compound in which the number of atoms constituting a linking chain connecting one crosslinking reactive group and another crosslinking reactive group in one molecule of the crosslinking agent is 10 or more (for example, 12 or more or 14 or more) is used as a crosslinking agent. It can be used as The upper limit of the number of atoms constituting the connecting chain is not particularly limited as it can be prepared by polymerization etc. 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, It may be 50 or less, 30 or less, or 20 or less. In addition, the number of atoms constituting a linking chain linking the above-mentioned cross-linking-reactive groups refers to the number of atoms constituting a linking chain that connects the above-mentioned cross-linking-reactive groups, from one cross-linking-reactive group to another cross-linking-reactive group (if it has 3 or more cross-linking-reactive groups, the number of The minimum number of atoms required to reach the crosslinking-reactive group (the closest cross-linking-reactive group). The above-mentioned crosslinking agents having a connecting chain can be used alone or in combination of two or more. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent. Examples of commercially available crosslinking agents include Coronate 2770 (manufactured by Tosoh Corporation), Takenate D178NL (manufactured by Mitsui Chemicals), Duranate A201H (manufactured by Asahi Kasei Corporation), and the like.

When using a crosslinking agent, the amount used is not particularly limited, and may range, for example, from about 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 the 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, and more preferably The amount is preferably 2.0 parts by weight or less, may be 1.0 parts by weight or less, and may be 0.5 parts by weight or less. In some preferred embodiments, the amount of crosslinking agent used per 100 parts by weight of the base polymer is less than 0.5 parts by weight, may be less than 0.4 parts by weight, may be less than 0.3 parts by weight, The amount may be 0.2 parts by weight or less. Further, from the viewpoint of appropriately exhibiting the effect of using the crosslinking agent, in some embodiments, the amount of the crosslinking agent used relative to 100 parts by weight of the base polymer may be, for example, 0.005 parts by weight or more, and 0.01 parts by weight. part or more, 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 is greater than 0.1 parts by weight, may be greater than or equal to 0.2 parts by weight, may be greater than or equal to 0.3 parts by weight, and may be greater than or equal to 0.4 parts by weight. It may be more than part by weight. According to the technology disclosed herein, by using an appropriate amount of a crosslinking agent within the above range, a high refractive index adhesive layer that has excellent flexibility and can withstand large deformations can be preferably formed.

A crosslinking catalyst may be used to advance the crosslinking reaction more effectively. Examples of the crosslinking catalyst include metal crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, zirconium tetraacetylacetonate, ferric nathem, butyltin oxide, dioctyltin dilaurate, and the like. Among these, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. The amount of crosslinking catalyst used is not particularly limited. The amount of crosslinking catalyst to be used with respect to 100 parts by weight of the base polymer is, for example, in the range of approximately 0.0001 part by weight or more and 1 part by weight or less, taking into consideration the balance between the speed of the crosslinking reaction and the length of the pot life of the adhesive composition. The content is preferably in the range of 0.001 part by weight or more and 0.5 part by weight or less.

The adhesive composition may contain a compound that causes keto-enol tautomerism as a crosslinking retarder. Thereby, the effect of extending the pot life of the adhesive composition can be realized. For example, in a pressure-sensitive adhesive composition containing an isocyanate-based crosslinking agent, a compound that causes keto-enol tautomerism can be preferably used. Various β-dicarbonyl compounds can be used as the compound that causes keto-enol tautomerism. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetate esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably employed. Compounds that cause keto-enol tautomerism can be used singly or in combination of two or more. The amount of the compound that causes keto-enol tautomerism can be, for example, 0.1 parts by weight or more and 20 parts by weight or less, and 0.5 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the base polymer. Alternatively, the amount may be 1 part by weight or more and 5 parts by weight or less.

(oligomer)
The high refractive index adhesive layer disclosed herein may optionally contain an oligomer. Adhesive strength can be improved by including an oligomer in the high refractive index adhesive layer. The weight average molecular weight (Mw) of the oligomer is about 1,000 or more and less than 50,000 (eg, 8,000 or more and 30,000 or less). Oligomers having the above Mw can be used alone or in combination of two or more. The glass transition temperature (Tg) of the oligomer is suitably approximately 0° C. or higher and 200° C. or lower (for example, 40° C. or higher and 140° C. or lower) in consideration of adhesive strength and the like.

In this specification, the Tg of an oligomer refers to the glass transition temperature (Tg _{, DSC} ) determined by differential scanning calorimetry (DSC measurement). Specifically, a sample (the oligomer to be measured) sealed in an aluminum sample pan and a reference are prepared and heated to a predetermined temperature using a differential scanning calorimeter (for example, the product name "Q2000" manufactured by TA Instruments). A calorimetric curve is created by performing DSC measurement within the range, and the temperature of the inflection point in the obtained calorific curve is determined, and this is defined as the Tg _{and DSC} [° C.] of the oligomer. More specifically, the rate of temperature rise and temperature drop during the above measurement was 10°C/min, and the above temperature range was within ±70°C of the baseline shift derived from Tg _{, DSC} or in a wider temperature range. DSC measurements are performed by repeating at least three cycles of increasing and decreasing the temperature. In the temperature raising process of each cycle, the temperature at the middle point of the inflection point on the low temperature side and the inflection point on the high temperature side of the baseline shift is determined, and Tg _{and DSC} [°C] in that cycle are determined. The average value of Tg _{and DSC} [°C] of the second and third cycles is used as the Tg _{and DSC} [°C] of the oligomer to be measured.

In some preferred embodiments, one or more oligomers selected from (meth)acrylic oligomers and styrene oligomers are used. Here, the (meth)acrylic oligomer refers to an acrylic monomer (including both an acrylic monomer having an acryloyl group and a methacrylic monomer having a methacryloyl group) as a main monomer unit (forming a (meth)acrylic oligomer). It refers to an oligomer contained as a main component (typically a monomer unit contained in an amount exceeding 50% by weight) in a monomer component. The styrenic oligomer refers to an oligomer containing a styrene monomer (a monomer having a styrene skeleton such as styrene or α-methylstyrene) as a monomer unit, and may be, for example, an oligomer containing the above styrene monomer as a main monomer unit. By adding an appropriate amount of (meth)acrylic oligomer or styrene oligomer to the acrylic polymer as the oligomer, it is possible to improve adhesive strength while having a high refractive index and a low elastic modulus.

In some embodiments, suitable examples of (meth)acrylic oligomers include isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), cyclohexyl methacrylate (CHMA), methyl methacrylate (MMA), benzyl methacrylate ( BZMA), copolymers of CHMA and MMA, copolymers of CHMA and ethyl methacrylate (EMA), copolymers of CHMA and isobutyl methacrylate (i-BMA), and copolymers of CHMA and IBXMA. copolymer of CHMA and dicyclopentanyl methacrylate (DCPMA), copolymer of CHMA and dicyclopentenyloxyethyl methacrylate (DCP(EO)MA), CHMA and methacrylic acid (MAA), a copolymer of MMA and MAA, and the like.

Examples of styrene oligomers include styrene-acrylic oligomers and styrene-maleic acid oligomers. These can be copolymers of styrene and other monomers such as (meth)acrylic acid or maleic acid.

Oligomers (eg (meth)acrylic oligomers) can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. Moreover, a commercially available product may be used as the oligomer. Examples of (meth)acrylic oligomers include "ARUFON UC-3000 series" available from Toagosei Co., Ltd., and product names "VS-1028" and "RS-1190" available from Seiko PMC. Can be mentioned. Examples of styrenic oligomers include those manufactured by Seiko PMC under the trade name "X-200" and "US-1071".

The content of oligomer in the high refractive index adhesive layer disclosed herein is not particularly limited. From the viewpoint of obtaining the effect of improving adhesive strength by adding oligomers, the content of oligomers is suitably 1 part by weight or more based on 100 parts by weight of the base polymer, and may be 3 parts by weight or more, and 5 parts by weight. It may be more than one year. In some embodiments, from the viewpoint of refractive index and transparency, the amount of oligomer to be used with respect to 100 parts by weight of the base polymer is suitably 30 parts by weight or less, and may be 10 parts by weight or less, and 5 parts by weight or less. It may be less than parts by weight. The technology disclosed herein can be preferably practiced in an embodiment that does not use oligomers.

(tackifier)
The high refractive index adhesive layer disclosed herein may contain a tackifier. Examples of tackifiers include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomers. Known tackifier resins such as tackifier resins can be used. These can be used alone or in combination of two or more. The amount of the tackifying resin used is not particularly limited, and can be set so that appropriate adhesive performance is exhibited depending on the purpose and 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. , more preferably 5 parts by weight or less. The technology disclosed herein can be preferably practiced without using a tackifier.

(High refractive index particles)
The high refractive index adhesive layer disclosed herein can contain high refractive index particles as an optional component. Here, the term "high refractive index particles" refers to particles that can be incorporated into an adhesive to increase the refractive index of the adhesive. Hereinafter, the high refractive index particles may be referred to as "particles P _HRI ". HRI means high refractive index. The type of particle P _HRI is not particularly limited, and one or more 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 selected and used. As the particles P _HRI , among inorganic oxides (for example, metal oxides), those capable of improving the refractive index of the adhesive can be preferably used. Suitable examples of materials constituting the particles P _HRI include titania (titanium oxide, TiO ₂ ), zirconia (zirconium oxide, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide ( Examples include inorganic oxides (specifically metal oxides) such as Nb ₂ O ₅ etc.). Particles made of these inorganic oxides (for example, metal oxides) can be used singly or in combination of two or more. The average particle size (50% volume average particle size 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 or more and 1000 nm or less, for example.

The content of particle P _HRI in the high refractive index pressure-sensitive adhesive layer can be adjusted to an appropriate amount within a range that does not impair the effects of the technology disclosed herein. Further, the content of the particles P _HRI may vary depending on the desired refractive index. For example, the content of the particles P _HRI can be appropriately set in consideration of required adhesive properties and the like so as to provide a refractive index of a predetermined value or higher. In some embodiments, the content of particle P _HRI in the high refractive index adhesive layer is, for example, less than 10% by weight in the high refractive index adhesive layer, and may be less than 1%, and may be less than 0.1% by weight. It may be less than % by weight. The techniques disclosed herein can be practiced in such a manner that the high refractive index adhesive layer is substantially free of particle P _HRI .

(Leveling agent)
In some embodiments, the adhesive composition used to form the high refractive index adhesive layer includes improvements in the appearance (e.g., improved thickness uniformity) of the high refractive index adhesive layer formed from the composition. If necessary, a leveling agent may be included for the purpose of improving the coating properties of the pressure-sensitive adhesive composition. Non-limiting examples of leveling agents include acrylic leveling agents, fluorine leveling agents, silicone leveling agents, and the like. For example, an appropriate leveling agent can be selected from commercially available leveling agents and used in a conventional manner.

(Other additives)
In the technology disclosed herein, the adhesive composition used to form the high refractive index adhesive layer may contain softeners, colorants (dyes, pigments, etc.), fillers, etc., to the extent that the effects of the present invention are not significantly impaired. If necessary, the adhesive composition may contain known additives that can be used in adhesive compositions, such as antistatic agents, antiaging agents, ultraviolet absorbers, antioxidants, light stabilizers, and preservatives. . Regarding such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed explanations will be omitted.

Although not particularly limited, the effects of the technology disclosed herein are preferably achieved by using a high refractive index adhesive layer containing the above-mentioned base polymer (typically an acrylic polymer) and a plasticizer. obtain. The technique disclosed herein can be preferably implemented in an embodiment using a high refractive index adhesive layer mainly composed of the above base polymer and the above plasticizer. Therefore, in some preferred embodiments, a composition in which the content of components (other components) other than the base polymer and the plasticizer is limited may be employed 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% to 100% by weight or less than 100% by weight) of the high refractive index adhesive layer. 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 achieving a good balance of high refractive index, flexibility, adhesive strength, and optical properties.

<Low refractive index adhesive layer>
The adhesive optical film disclosed herein may include a low refractive index adhesive layer as an adhesive layer in addition to the above-mentioned high refractive index adhesive layer. By arranging the low refractive index adhesive layer, it is possible to adjust the relative relationship between the adhesive forces on each side of the adhesive layer. For example, by arranging a low refractive index adhesive layer on the optical film side, the adhesive force (anchoring ability) to the optical film can be set within a desired range. The refractive index n ₂ of the low refractive index adhesive layer is preferably lower than the refractive index n ₁ of the high refractive index adhesive layer. Thereby, by utilizing the refractive index difference between the high refractive index adhesive layer and the low refractive index adhesive layer, it is possible to control the behavior of light that passes through the laminated sheet containing these layers. The refractive index n ₂ of the low refractive index adhesive layer may be, for example, within a range of about 1.35 to 1.55. In some embodiments, the refractive index _n2 of the low refractive index _adhesive layer is For example, it is preferably 1.49 or less, more preferably 1.47 or less (for example, 1.46 or less, or 1.45 or less), 1.43 or less, 1.41 or less, 1 It may be .40 or less. Further, from the viewpoint of easy availability of materials and compatibility with adhesive properties, in some embodiments, the refractive index _n2 of the low refractive index adhesive layer may be, for example, 1.36 or more, and 1. It may be 38 or more, 1.40 or more, 1.42 or more, or 1.45 or more.

In some embodiments, the ratio (n ₁ /n ₂ ) of the refractive index n ₁ of the high refractive index adhesive layer to the refractive index n ₂ of the low refractive index adhesive layer is, for example, greater than 1.00. Generally, it may be approximately 1.01 or more, suitably approximately 1.02 or more, and approximately 1.03 or more. In some embodiments, the ratio (n ₁ /n ₂ ) is advantageously about 1.05 or greater, preferably about 1.06 or greater, and more preferably about 1.07 or greater. Preferably, it may be approximately 1.08 or more. 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, about 1.20 or less, about 1.18 or less, about 1.16 or less. It may be approximately 1.14 or less, or approximately 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 adhesive layer, that is, the refractive index difference (n ₁ - n ₂ ), is, for example, 0.00. may be larger, may be 0.01 or more, preferably 0.02 or more, may be 0.03 or more, may be 0.05 or more, may be 0.07 or more, and may be 0.09 or more. Generally, it may be 0.10 or more, or 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, or 0.21 or less. It may be 0.18 or less, or 0.16 or less.

In some embodiments, the total light transmittance of the low refractive index adhesive layer is 85.0% or more (e.g., 86.0% or more, 88.0% or more, 90.0% or more, or 90.0%). super) is preferred. An adhesive with a high total light transmittance is suitable as an adhesive for an adhesive optical film. Theoretically, the upper limit of total light transmittance is 100% minus light loss (Fresnel loss) due to reflection that occurs at the air interface, and in practice, it may be approximately 98% or less, for example, approximately 96% or less. It may be approximately 95% or less. In some embodiments, the total light transmittance of the low refractive index adhesive layer may be about 94% or less, about 93% or less, or about 92% or less, taking into account the refractive index and adhesive properties.

In some embodiments, the haze value of the low refractive index adhesive layer may be, for example, 5.0% or less, preferably 3.0% or less, and more preferably 2.0% or less. , more preferably 1.0% or less, 0.9% or less, 0.8% or less, 0.5% or less, 0.3% or less. Adhesives with such high transparency are advantageous in applications that require high light transmittance (for example, optical applications) and applications that require good visibility of adherends through the adhesive. The lower limit of the haze value of the low refractive index adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the more preferable. On the other hand, in some embodiments, the haze value of the low refractive index adhesive layer may be, for example, 0.05% or more, or 0.10% or more, taking into consideration the refractive index and adhesive properties.

The storage modulus G' (25° C.) of the low refractive index adhesive layer is not particularly limited, and may be in the range of 1.0 kPa to 500 kPa, for example. From the viewpoint of enhancing the effect of imparting flexibility and improving followability against deformation by the low refractive index adhesive layer, in some embodiments, the storage modulus G' (25°C) of the low refractive index adhesive layer is 400 kPa or less. Suitably, the pressure is 300 kPa or less, more preferably 200 kPa or less (for example, 180 kPa or less, or 150 kPa), 120 kPa or less, 90 kPa or less, or 70 kPa or less. Further, from the viewpoint of imparting appropriate cohesiveness to the low refractive index adhesive layer, in some embodiments, the storage modulus G' (25°C) of the low refractive index adhesive layer is 5.0 kPa or more. is appropriate, preferably 10 kPa or more, 15 kPa or more, 25 kPa or more, 35 kPa or more, 60 kPa or more, or 80 kPa or more. In some embodiments, the storage modulus G' (25° C.) of the low refractive index adhesive layer may be 95 kPa or more, 110 kPa or more, or 140 kPa, from the viewpoint of easily realizing higher cohesive force and adhesive properties. The above is fine.

In some embodiments, the low refractive index adhesive layer preferably has a deformation amount of 350% or more in a deformation test conducted at 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 adhesive layer also satisfies the above characteristics, so that the laminated adhesive layer (laminated sheet) including the high refractive index adhesive layer and the low refractive index adhesive layer can be used at low temperatures. It can deform sufficiently at high speed even in the environment, and can withstand large deformations. More specifically, the deformation test conducted under the conditions of temperature -20° C. and speed of 300 mm/min is carried out by the method described above.

In some embodiments, the low refractive index adhesive layer has a stress of 5.0 N/mm ² or less at a deformation amount of 350% in a deformation test conducted at a temperature of -20°C and a speed of 300 mm/min. It is preferable that A low 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 predetermined level of flexibility even in a low temperature environment. Therefore, it is suitable for use in applications involving large deformations. In some preferred embodiments, the stress at the deformation amount of 350% may be 4 N/mm ² or less, 3 N/mm ² or less, 2 N/mm ² or less, or 1 N/mm ² or less. , 0.5 N/mm ² or less, or 0.3 N/mm ² or less. The lower limit of the stress at the deformation amount of 350% is theoretically 0.0 N/mm ² or more, and may be 0.1 N/mm ² or more in some preferred embodiments.

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

In some embodiments, the acrylic polymer includes, for example, a monomer raw material that includes an alkyl (meth)acrylate and may further include another monomer (copolymerizable monomer) that is copolymerizable with the alkyl (meth)acrylate. Polymers of 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 monomer components that contain an alkyl (meth)acrylate as a main monomer and may further contain the copolymerizable monomer as a submonomer. 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% 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 materials of the acrylic polymer can be, for example, 70% by weight or more, may be 85% by weight or more, or may be 90% by weight or more. , 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 it is preferably 99.5% by weight or less (for example, 99% by weight or less), or preferably exhibits properties (for example, cohesive force) based on the submonomer. From the viewpoint of achieving this, the content 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 above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as "C _1-20 "). From the viewpoint of the storage modulus of the adhesive, etc., an alkyl (meth)acrylate in which R ² is a C _1-12 (for example, C _2-10 , typically C _4-8 ) chain alkyl group is preferred. The alkyl (meth)acrylates in which R ² is a C _1-20 chain alkyl group can be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include n-butyl acrylate and 2-ethylhexyl acrylate.

The copolymerizable monomer may be useful for introducing crosslinking points into the acrylic polymer or increasing the cohesive strength of the acrylic polymer. Examples of the copolymerizable monomers include carboxy 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 more functional group-containing monomers such as 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, non-aromatic ring-containing (meth)acrylates, alkoxy group-containing monomers, and the like. Specific examples include, but are not limited to, those mentioned above as monomers that can be used in the base polymer of the high refractive index adhesive layer. For example, from the viewpoint of improving cohesive force, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer is preferable as the copolymerizable monomer. Preferred examples of the carboxy group-containing monomer include acrylic acid and methacrylic acid. Suitable examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

In some embodiments, a fluorine-containing monomer can be used as the copolymerizable monomer to lower the refractive index _n2 of the low refractive index adhesive 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 adhesive 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, and 55% by weight or more. It is more preferably at least 60% by weight, at least 75% by weight, at least 85% by weight, at least 90% by weight, and at least 95% by weight. The upper limit of the content of the fluorine-containing monomer in the monomer raw material is not particularly limited, and may be 100% by weight. In some embodiments, from the viewpoint of cohesiveness of the low refractive index adhesive layer, the content of the fluorine-containing monomer is suitably 99.9% by weight or less, and 99.5% or less. is preferable, and may be 99% by weight or less, 97% by weight or less, or 92% by weight or less. The fluorine-containing monomers can be used alone or in combination of two or more.

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 has at least one fluorine atom in its molecule. For example, fluorine-containing (meth)acrylic acid ester can be suitably used. Preferred examples of fluorine-containing (meth)acrylic esters include those having a fluorinated hydrocarbon group at the ester end. 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. Furthermore, in the fluorinated aliphatic hydrocarbon group, the fluorine atom may be bonded to any carbon atom in the aliphatic hydrocarbon group site. The number of fluorine atoms bonded to one carbon atom may be singular or plural. The number of carbon atoms to which fluorine atoms are bonded is not particularly limited.

In the fluorinated aliphatic hydrocarbon group (especially the fluorinated alkyl group), the number of carbon atoms in the hydrocarbon group portion is not particularly limited. In some embodiments, in consideration of compatibility with other copolymerizable monomers, a fluorinated aliphatic hydrocarbon group having, for example, about 1 to 18 (preferably 1 to 12) carbon atoms is preferred. Specific examples of fluorinated aliphatic hydrocarbon groups include fluorinated methyl groups such as trifluoromethyl group, difluoromethyl group, and monofluoromethyl group; pentafluoroethyl group, and 1,1,2,2-tetrafluoroethyl group. , 1,2,2,2-tetrafluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,1 -fluorinated ethyl groups such as -difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1-monofluoroethyl group, and 2-monofluoroethyl group; and the like. As for the fluorinated alkyl group having 3 or more carbon atoms, as with the above-mentioned fluorinated methyl group and fluorinated ethyl group, any one or more of the carbon atoms in the alkyl group may have a single or multiple fluorinated alkyl group. Examples include various fluorinated alkyl groups to which a fluorine atom is bonded.

Examples of the fluorinated alicyclic hydrocarbon group include a fluorinated cycloalkyl group. Similar to the above-mentioned 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 may be bonded to one carbon atom. The number of bonded fluorine atoms may be singular or plural. Furthermore, the number of carbon atoms to which fluorine atoms are bonded is not particularly limited. Examples of the fluorinated alicyclic hydrocarbon group include a cyclohexyl group having one fluorine atom such as a 2-fluorocyclohexyl group, a 3-fluorocyclohexyl group, and a 4-fluorocyclohexyl group; a 2,4-difluorocyclohexyl group, and a 2-fluorocyclohexyl group; , 6-difluorocyclohexyl group and other cyclohexyl groups having two fluorine atoms; 2,4,6-trifluorocyclohexyl group and other cyclohexyl groups having three fluorine atoms.

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

Examples of fluorine atom-containing (meth)acrylic acid ester [fluorinated (meth)acrylate] include fluorine atom-containing (meth)acrylic acid alkyl ester [fluorinated alkyl (meth)acrylate], fluorine atom-containing (meth)acrylic acid These include cycloalkyl esters [fluorinated cycloalkyl (meth)acrylates], fluorine atom-containing (meth)acrylic acid aryl esters [fluorinated aryl (meth)acrylates], and the like.

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

The number of carbon atoms in the fluorinated alkyl group in the fluorinated alkyl (meth)acrylate is advantageously 3 or more, preferably 4 or more, from the viewpoint of low refractive index effect, flexibility, etc. It is more preferably 6 or more, or 7 or more, and particularly preferably 8 or more. The number of carbon atoms in the fluorinated alkyl group is advantageously 18 or less from the viewpoint of adhesive performance, etc., preferably 14 or less, more preferably 12 or less, and may be 10 or less, It may be 9 or less. In some embodiments, the number of carbon atoms in the fluorinated alkyl group may be 7 or less, or 5 or less. 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 1st carbon of the alkyl group, such as 1H, 1H, 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 employed.

In some embodiments, the low refractive index adhesive layer is an acrylic adhesive layer, and the acrylic polymer that is the base polymer of the adhesive is a fluorine-containing acrylic monomer such as those described above (e.g., fluorinated alkyl (fluorinated alkyl)). meth)acrylate) and may further contain another monomer copolymerizable with the fluorine-containing acrylic monomer (copolymerizable 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 adhesive 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. , more preferably 55% by weight or more, 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 cohesiveness of the low refractive index adhesive layer, the content of the fluorine-containing acrylic monomer is suitably 99.9% by weight or less, and 99.5% by weight or less. The content is preferably 99% by weight or less, 97% by weight or less, or 92% by weight or less. The fluorine-containing acrylic monomers can be used alone or in combination of two or more.

The monomer raw material for preparing the base polymer of the low refractive index adhesive layer may have a composition that further contains a copolymerizable monomer in addition to a fluorine-containing acrylic monomer (for example, a fluorinated alkyl (meth)acrylate). Examples of the copolymerizable monomers include carboxy 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 (for example, N-vinyl-2 - N-vinyl cyclic amide such as pyrrolidone), a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and one or more 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, and non-aromatic ring-containing (meth)acrylates such as cycloalkyl (meth)acrylate and isobornyl (meth)acrylate. Acrylates, alkoxy group-containing monomers; and the like. Specific examples include, but are not limited to, those mentioned above as monomers that can be used in the base polymer of the high refractive index adhesive layer. For example, from the viewpoint of improving cohesive force, an acrylic polymer copolymerized with a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer is preferable as the copolymerizable monomer.

In some preferred embodiments, the monomer raw material for preparing the base polymer of the low refractive index adhesive layer may have a composition containing a hydroxyl group-containing monomer. Hydroxyl group-containing monomers can be useful for improving cohesive force, introducing crosslinking points, etc. Preferred examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate may be more preferably used. The content of the hydroxyl group-containing monomer in the monomer raw material is not particularly limited, and may be, for example, 0.01% 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. There may be. 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 3% by weight. %, may be less than 2.5% by weight, and may be less than 1.5% by weight.

In some embodiments, the monomer raw material for preparing the base polymer of the low refractive index adhesive layer is a carboxy group-containing monomer from the viewpoint of suppressing coloring or discoloration (for example, yellowing) of the low refractive index adhesive layer. Preferably, the content is limited. The content of the carboxy 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 0.5% by weight, preferably less than 0.3% by weight. More preferably, it is less than 1% by weight (for example less than 0.05% by weight). The fact that the content of the carboxy group-containing monomer is limited in this way means that metal materials that may be placed in contact with or close to the low refractive index adhesive layer (for example, metal wiring or metal that may be present on the adherend) This is also advantageous from the viewpoint of suppressing corrosion of membranes, etc.). The technology disclosed herein can be preferably implemented in an embodiment in which the monomer raw material does not contain a carboxy group-containing monomer.
For the same reason, in some embodiments, the monomer raw materials for preparing the base polymer of the low refractive index adhesive layer include acidic functional groups (in addition to carboxy groups, sulfonic acid groups, phosphoric acid groups, etc.). ) is preferably limited. As the content of the acidic functional group-containing monomer in the monomer raw material of this embodiment, the above-mentioned preferred content of the carboxy group-containing monomer can be applied. The technique 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, an embodiment in which the base polymer of the low refractive index adhesive layer is acid-free).

The base polymer of the low refractive index adhesive layer can be prepared by suitably employing a known polymerization method, similarly to the base polymer of the high refractive index adhesive layer. The weight average molecular weight (Mw) of the base polymer (for example, acrylic polymer) is not particularly limited, and may be in the range of approximately 10×10 ⁴ to 500×10 ⁴ , for example, approximately 20×10 ⁴ to 300×10 ⁴ It may be within the range of In some embodiments, from the viewpoint of adhesion with the high refractive index adhesive layer, it is appropriate that the Mw of the base polymer of the low refractive index adhesive layer is 250 × 10 ⁴ or less, and 200 × 10 ⁴ or less, 150×10 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, 60× It may be ¹⁰⁴ or less. Further, in some embodiments, from the viewpoint of cohesiveness of the low refractive index adhesive layer, the Mw of the base polymer may be, for example, 30×10 ⁴ or more, 40×10 ⁴ or more, 50×10 It may be ⁴ or more. In some preferred embodiments, the base polymer Mw may be approximately 70×10 ⁴ or more, approximately 100×10 ⁴ or more, 130×10 ⁴ or more, 160×10 ⁴ or more (for example, 180× 10 ⁴ or more). By using a base polymer having Mw of a predetermined value or more, it is easy to obtain an appropriate cohesive force that can exhibit desired adhesive properties. Further, by utilizing the cohesive properties based on the high molecular weight polymer as described above, it is easy to obtain excellent flexibility and, by extension, flexibility that can withstand large deformations. In order to adjust Mw, a conventionally known chain transfer agent can be used as necessary.

Although not particularly limited, from the viewpoint of adhesion, it is advantageous for the base polymer (for example, acrylic polymer) of the low refractive index adhesive layer to have a Tg of about 0°C or less, preferably about -5°C. ℃ or less (for example, approximately -15°C or less, or -25°C or less). In addition, from the viewpoint of the cohesive force of the adhesive layer, the Tg of the base polymer of the low refractive index adhesive layer is approximately -75°C or higher, preferably approximately -70°C or higher (for example, -50°C or higher, and even - 30°C or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and usage ratio of monomers used in the synthesis of the polymer).

A known crosslinking agent may be used in the low refractive index adhesive layer. Further, the low refractive index adhesive layer can contain a tackifier and other additives. The crosslinking agent and tackifier can be appropriately selected from those similar to those that can be used in the high refractive index adhesive layer, and can be used in appropriate amounts.

In an embodiment in which the adhesive composition used to form the low refractive index 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 crosslinking agent used relative to 100 parts by weight of the base polymer of the adhesive composition is, for example, less than 0.5 parts by weight from the viewpoint of adhesion with the high refractive index adhesive layer. The amount may be less than 0.3 parts by weight, less than 0.2 parts by weight, or less than 0.15 parts by weight. Further, from the viewpoint of appropriately exhibiting the effect of using the crosslinking agent, in some embodiments, the amount of the isocyanate crosslinking agent used relative to 100 parts by weight of the base polymer may be, for example, 0.005 parts by weight or more, and 0.005 parts by weight or more. The amount may be 0.01 part by weight or more, 0.05 part by weight or more, or 0.08 part by weight or more.

<Preparation 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 adhesive layer; the same shall apply hereinafter unless otherwise specified) has a pressure-sensitive adhesive composition. It can be formed using objects. The form of the pressure-sensitive adhesive composition to be used is not particularly limited, and examples thereof include a solvent-based pressure-sensitive adhesive composition containing a pressure-sensitive adhesive forming component in an organic solvent, and a pressure-sensitive adhesive composition that is cured by active energy rays such as ultraviolet rays and radiation. An active energy ray-curable adhesive composition prepared to form an active energy ray-curable adhesive composition, a water-dispersed adhesive composition in which an adhesive-forming component is dispersed in water, and a water-dispersed adhesive composition that is applied in a heated molten state and becomes sticky when cooled to around room temperature. It can be in various forms, such as a hot-melt adhesive composition forming an adhesive. The adhesive is an adhesive obtained by curing a solvent-based, active energy ray-curable, water-dispersed, hot-melt, or other adhesive composition by drying, crosslinking, polymerization, cooling, etc., that is, the above-mentioned adhesive. It may be a cured product of the composition. Only one type of curing means (for example, drying, crosslinking, polymerization, cooling, etc.) for the adhesive composition may be applied, or two or more types may be applied simultaneously or in multiple stages. For solvent-based adhesive compositions, the composition can typically be dried (and preferably further crosslinked) to form the adhesive. In active energy ray-curable adhesive compositions, the adhesive is typically formed by irradiating active energy rays to advance a polymerization reaction and/or a crosslinking reaction. When it is necessary to dry the active energy ray-curable pressure-sensitive adhesive composition, it is preferable to irradiate it with active energy rays after drying. Although not particularly limited, the adhesive disclosed herein can be preferably formed using a solvent-based adhesive composition.

The adhesive layer in the technology disclosed herein can be formed by applying (for example, coating) an adhesive composition to a suitable surface and then curing the composition. The adhesive composition can be applied using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, and a spray coater.

The adhesive layer in the technology disclosed herein may be a pressure-sensitive 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 with 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 a base polymer, and an adhesive layer containing an unreacted polyfunctional monomer. In some embodiments, it is preferable that the adhesive layer does not have post-curing properties. An adhesive layer that does not have post-curing properties does not undergo dimensional changes due to post-curing reactions (that is, has good dimensional stability), so it does not cause warping of the adhesive layer or the adherend to which the adhesive layer is attached. easy to suppress. The fact that dimensional changes (for example, curing shrinkage) do not occur due to post-curing can be advantageous from the viewpoint of suppressing optical distortion of the adhesive layer.

The thickness of the adhesive layer in the technique disclosed herein is not particularly limited, and can be, for example, 3 μm or more, and preferably 5 μm or more. A pressure-sensitive adhesive layer having a thickness of 5 μm or more tends to provide good adhesive properties. Further, the adhesive layer having such a thickness absorbs irregularities that may exist on the surface of the adherend and is easily bonded to the adherend with good adhesion. It is preferable that the thickness of the adhesive layer (for example, the thickness of the high refractive index adhesive layer) is 5 μm or more, also from the viewpoint of preventing coloring and color unevenness due to optical 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. Further, 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, even more preferably 70 μm or less, may be 50 μm or less, or may be 30 μm or less. It may be advantageous that the thickness of the adhesive layer is not too large from the viewpoint of making the laminated sheet or adhesive optical film containing the adhesive layer thinner. Moreover, a thin adhesive layer tends to have excellent followability to an adherend. The technology disclosed herein can be preferably carried out, for example, in an embodiment in which the thickness of the adhesive layer is in the range of 3 μm to 200 μm (more preferably 5 μm to 100 μm, still more preferably 5 μm to 75 μm).

In some embodiments, the adhesive layer thicknesses described above may apply at least to the high refractive index adhesive layer thickness T ₁ . The thickness T ₂ of the low refractive index adhesive layer may also be selected from a similar range. The thickness T ₁ of the high refractive index adhesive layer and the thickness T ₂ of the low refractive index adhesive layer may be approximately the same or may be different. The ratio (T ₁ /T ₂ ) between the thickness T ₁ of the high refractive index adhesive layer and the thickness T ₂ of the low refractive index adhesive layer may be, for example, 0.1 or more, or even 0.2 or more. Generally, it may be 0.3 or more, 0.4 or more, 0.5 or more, or 1.0 or more (for example, more than 1.0). Further, 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 some other embodiments, the ratio (T ₁ /T ₂ ) may be 0.8 or less, 0.6 or less, or 0.5 or less.

As a method for obtaining a structure (laminated sheet) in which a high refractive index adhesive layer and a low refractive index adhesive layer are laminated, for example, a high refractive index adhesive layer is placed on a releasable surface (for example, the release surface of a release liner). A method of forming a layer and a low refractive index adhesive layer and bonding them together, or a method of laminating the low refractive index adhesive layer formed as described above to an optical film, and then applying a high refractive index adhesive layer to the low refractive index adhesive layer. A method of laminating refractive index adhesive layers, a method of applying and curing a composition for forming a low refractive index adhesive layer on a high refractive index adhesive layer, and a method of forming a high refractive index adhesive layer on the contrary. A method such as applying a pressure-sensitive adhesive composition on a low refractive index pressure-sensitive adhesive layer and curing it can be adopted, but the method is not limited thereto. When bonding together a high refractive index adhesive layer and a low refractive index adhesive layer that have been formed in advance, a treatment may be performed to promote adhesion between these layers, if necessary. For example, autoclave treatment, roll press treatment, etc. can be performed, but the treatment is not limited thereto.

In some embodiments, total light transmission through the adhesive layer (at least an adhesive layer consisting only of a high refractive index adhesive layer, for example, a laminated adhesive layer of a high refractive index adhesive layer and a low refractive index adhesive layer) The range of the index is preferably the range of the total light transmittance of the above-mentioned high refractive index adhesive layer. Similarly, in some embodiments, an adhesive layer (at least an adhesive layer consisting only of a high refractive index adhesive layer, for example, a laminated adhesive layer of a high refractive index adhesive layer and a low refractive index adhesive layer) The range of the haze value is preferably the range of the haze value of the above-mentioned high refractive index adhesive layer. The range of total light transmittance and haze value of the above adhesive layer (for example, a laminated adhesive layer of a high refractive index adhesive layer and a low refractive index adhesive layer) is It can also be preferably applied to the total light transmittance and haze value of the laminated sheet consisting of the agent layer. The total light transmittance and haze value of the laminated adhesive layer of the high refractive index adhesive layer and the low refractive index adhesive layer are the total light transmittance and haze value measured for the laminated adhesive layer.

<Adhesive optical film>
The thickness of the adhesive optical film disclosed herein may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, 120 μm or less, 75 μm or less, or 50 μm or less. Further, from the viewpoint of handleability, the thickness of the adhesive optical film may be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.
Note that the thickness of the adhesive optical film refers to the thickness of the portion that is attached to the adherend. For example, in the adhesive optical film 1 having the configuration shown in FIG. do not have.

<Adhesive optical film with release liner>
The adhesive optical film disclosed herein can take the form of an adhesive product in which the surface (adhesive surface) of an adhesive layer is brought into contact with the release surface of a release liner. Therefore, according to this specification, a pressure-sensitive adhesive optical film with a release liner ( Adhesive products) are provided.

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

In some embodiments, from the viewpoint of smoothness of the adhesive surface, etc., a release liner (hereinafter referred to as a release liner) having a release treatment layer on a resin film (hereinafter also referred to as a release film base material) as a release liner base material is used. ) can be preferably employed. Various plastic films can be used as the release film base material. In this specification, a plastic film is typically a non-porous sheet, and is a concept that is distinguished from, for example, nonwoven fabric (that is, it does not include nonwoven fabric).

Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer. Polyolefin resins such as ethylene-butene copolymers, cellulose resins such as triacetylcellulose, acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, norbornene resins Cyclic polyolefin resins such as resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymers Examples include coalescent resin, polyarylate resin, polyphenylene sulfide resin, and the like. A release film base material formed from any one type of these resins or a mixture of two or more types can be used. Among them, a preferred release film base material is a polyester resin film (eg, PET film) formed from a 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. Further, the plastic film may have a single layer structure or a multilayer structure including two or more sublayers. The above plastic film contains adhesive sheets such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, and nucleating agents. Known additives that can be used in release film base materials may also be blended. In a multilayer plastic film, each additive may be blended in all sublayers, or may be blended only in some sublayers.

In some preferred embodiments, the release film substrate (typically a plastic film) contains particles such as inorganic particles (for example, pigments, lubricants, fillers, etc.) in the layer on the release side. Those containing limited amounts or substantially free of such particles may preferably be used. Here, "substantially free" 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 including such a release film base material tends to have a low arithmetic mean roughness Ra and 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 side is 1/1/2 of the particle content in layers other than the layer on the release side. It may be 10 or less (for example, 1/50 or less).

In a pressure-sensitive adhesive optical film with a release liner having a release liner on each of the first adhesive surface and the second adhesive surface, a release liner disposed on one adhesive surface (hereinafter also referred to as one release liner); The release liner placed on the other adhesive surface (hereinafter also referred to as the other release liner) may have the same material and configuration, or may have a different material and configuration. Good too.

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 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, 35 μm or more, 40 μm or more, or even 45 μm or more. good. In addition, from the viewpoint of handleability of the release liner (for example, ease of winding), the thickness of the release liner is suitably 300 μm or less, preferably 250 μm or less, and may be 200 μm or less. The thickness may be 150 μm or less, or 130 μm or less. In some preferred embodiments, the thickness of the release liner is about 125 μm or less, may be about 115 μm or less, may be about 105 μm or less, about 90 μm or less, or about 70 μm or less. By keeping the thickness of the release liner below a predetermined value, it is difficult to leave curling marks when rolled, smooth removal from the adhesive layer, and ensure high surface smoothness on the adhesive surface after the release liner is removed. Easy to obtain.

In embodiments that include one release liner and the other release liner, the thickness of the release liners may be the same or different. In some embodiments, from the viewpoint of release workability, 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 different from that of the other release liner. The thickness of the release liner is preferably about 1.1 times or more (for example, about 1.25 times or more; the upper limit is not particularly limited, but for example, 5 times or less).

(Arithmetic mean roughness Ra of adhesive side surface)
In some embodiments, the release liner (preferably the release film) has a high arithmetic mean roughness Ra on the adhesive side surface that is limited to a predetermined value or less (for example, approximately 100 nm or less, further less than 50 nm). This is preferable from the viewpoint of realizing an adhesive surface with surface smoothness. In some embodiments, the arithmetic mean roughness Ra of the adhesive side surface of the release liner is, for example, preferably about 30 nm or less, more preferably about 25 nm or less, may be about 20 nm or less, and may be about 18 nm or less. But that's fine. Further, 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. . In a pressure-sensitive adhesive optical film with a release liner in which a release liner is disposed on each of the first adhesive surface and the second adhesive surface, the surfaces on the adhesive side of both release liners both have one of the above-mentioned arithmetic mean roughness Ra. It is preferable to satisfy the following. The arithmetic mean roughness Ra of the adhesive side surfaces of both release liners may be the same or different.

(Maximum height Rz of adhesive side surface)
In some embodiments, the release liner (preferably the release film) preferably has a maximum height Rz of the adhesive side surface of 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 adhesive side surface of the release liner is preferably about 600 nm or less, may be about 500 nm or less, may be about 400 nm or less, or may be about 300 nm or less. Further, 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, The thickness may be approximately 150 nm or more, or approximately 200 nm or more. In a pressure-sensitive adhesive optical film with a release liner in which a release liner is disposed on the first adhesive surface and the second adhesive surface, the adhesive surface side surfaces of both release liners each have one of the maximum heights Rz mentioned above. It is preferable to meet the requirements. The maximum heights Rz of the adhesive side surfaces of both release liners may be approximately the same or may be different.

(Surface texture of back surface)
The arithmetic mean roughness Ra and maximum height Rz of the back surface (the surface opposite to the adhesive layer side) of the release liner (preferably the release film) are not particularly limited. From the viewpoint of productivity and the like, 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, or even about 50 nm or more). The maximum height Rz of the back surface of the release liner may be, for example, more than 400 nm (for example, approximately 500 nm or more) or more than 800 nm (for example, 1000 nm or more) from the viewpoint of productivity and the like.

The arithmetic mean roughness Ra and maximum height Rz of the release film surface can be adjusted by selecting the film material, molding method, surface treatment such as release treatment, and the like. For example, adjusting the smoothness of the layers that make up the release surface (anti-blocking layer, hard coat layer, oligomer prevention layer, etc.), reducing or not using filler particles in the surface layer or release film base material (particulate-free), etc. ), adjustment of stretching conditions, etc.

The arithmetic mean roughness Ra and maximum height Rz of the release liner (preferably release film) surface are measured using a non-contact surface roughness measuring device. As a non-contact type surface roughness measuring device, an optical interference type surface roughness measuring device is used, and for example, a three-dimensional optical profiler (trade name "NewView 7300", manufactured by ZYGO) or its equivalent can be used. can. For example, a glass plate (soda lime glass plate manufactured by MATSUNAMI, thickness 1.3 mm) is attached and fixed with adhesive to the surface opposite to the measurement surface of the release liner. Under the environment, the surface shape can be measured using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO).

<Application>
The adhesive optical film disclosed herein can be used by being attached to various adherends. The constituent materials of the adherend (adherent material) are not particularly limited, but examples include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, and zinc. or metal materials such as alloys containing two or more of these, such as polyimide resins, acrylic resins, polyether nitrile resins, polyether sulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.) resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, fluorine resins, polycarbonate resins, diacetyl cellulose and triacetyl. Cellulose polymers such as cellulose, vinyl butyral polymers, liquid crystal polymers, various resin materials (typically plastic materials) such as carbon materials such as graphene, metal oxidation such as alumina, zirconia, titania, SiO ₂ , ITO, ATO, etc. nitrides and their mixtures, such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride, and their composites, and inorganic materials such as alkali glass, alkali-free glass, quartz glass, borosilicate glass, and sapphire glass, etc. Can be mentioned. The adhesive optical film disclosed herein can be used by being attached to a member (for example, an optical member) whose at least the surface is made of the above-mentioned material.

The adhesive optical film disclosed herein can be used in an attachment mode that does not require heating to a temperature higher than the room temperature range (for example, 20°C to 35°C) after being attached to an adherend. obtain. In addition, if it is permissible depending on the constituent materials of the adhesive optical film (for example, the material of the optical film) and the type of adherend, it may be necessary to The heat treatment may be performed at least at any one of the previous timings. The heat treatment can be performed for the purpose of improving the adhesiveness of the adhesive to the adherend, promoting adhesion, and the like. The heat treatment temperature is set as appropriate to obtain the desired effect within the allowable range depending on the constituent materials of the adhesive optical film and the type of adherend, taking into account the surface condition of the adherend, etc. For example, the temperature may be about 100°C or lower, 80°C or lower, 60°C or lower, or 50°C or lower.

The member or material to which the adhesive optical film is attached (at least one adherend in a double-sided adhesive optical film) may have light transmittance. In such an adherend, the advantage of increasing the refractive index while suppressing deterioration of optical properties (transparency, etc.) by applying the technology disclosed herein is likely to be obtained. The total light transmittance of the adherend may be, for example, more than 50%, or more than 70%. 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 adhesive optical film disclosed herein can be preferably used in a mode where it is attached to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Research Institute or its equivalent product is used.

The refractive index of the adhesive layer and the refractive index of the adherend may be the same or different. For example, by making the refractive index of the adhesive layer relatively higher than the refractive index of the adherend, light that is incident on the adhesive layer from the adherend side at an angle less than the critical angle is refracted toward the front side. Front brightness can be increased. In this case, the refractive index of the adherend may be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, or less than 1.45; It can be greater than or equal to .10, greater than or equal to 1.20, greater than or equal to 1.30, or greater than or equal to 1.35. Furthermore, when the adherend has a relatively high refractive index with respect to the adhesive layer, light that enters 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 also, for example, 3.00 or less, 2.50 or less, or 2.00 or less. It can be. 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 in the same manner as the refractive index of the adhesive.

In some preferred embodiments, the adherend may have any of the refractive indexes listed above and total light transmittances listed above. The effects of the technique disclosed herein are particularly preferably exhibited in such an embodiment in which the adhesive is attached to an adherend.

An example of a preferred application is an optical application. More specifically, the adhesive sheet disclosed herein is used, for example, as an optical adhesive sheet used for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the above-mentioned optical members. A pressure-sensitive adhesive optical film can be preferably used. The above-mentioned optical member is not particularly limited as long as it has optical properties, but for example, it may be a member constituting a device (optical device) such as a display device (image display device) or an input device, or a member used in these devices. Examples include members. Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a micro LED (μLED), a mini LED (miniLED), a PDP (plasma display panel), and electronic paper. Furthermore, examples of the input device include a touch panel.

The optical member is not particularly limited, but includes, for example, members (for example, sheet-like, film-like, and plate-like members) made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, and the like. Note that the term "optical member" in this specification also includes members (design films, decorative films, surface protection films, etc.) that serve to decorate and protect while maintaining the visibility of display devices and input devices.

The technology disclosed herein uses, for example, an optical film such as a film having one or more functions such as light transmission, reflection, diffusion, waveguide, condensing, and diffraction, or a fluorescent film, etc., with other optical members ( It can be preferably used for bonding to other optical films. For example, by attaching a pressure-sensitive adhesive optical film including the optical film to the other optical member as an adherend, the optical film can be attached to the other optical member through a high refractive index adhesive layer (bonding layer). A structure bonded to the optical member can be formed. In particular, when bonding optical films that have at least one of the functions of light waveguide, condensation, and diffraction, it is desirable that the entire bulk of the bonding layer has a high refractive index, and the technology disclosed herein is preferably applied. Can be targeted.

The technology disclosed herein can be preferably used, for example, for bonding optical films such as light guide films, diffusion films, fluorescent films, toning films, prism sheets, lenticular films, and microlens array films. In these applications, from the viewpoint of the trend toward miniaturization of optical members and higher performance, there is a demand for thinner optical members and improved light extraction efficiency. The technology disclosed herein can be preferably used as an adhesive optical film equipped with an adhesive that can meet such demands. More specifically, for example, when bonding a light guide film or a diffusion film, adjusting the refractive index (for example, increasing the refractive index) of the adhesive layer as a bonding layer can contribute to thinning. In bonding 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. When bonding color toning films, by appropriately adjusting the refractive index of the adhesive so that the difference in refractive index with the color toning pigment is reduced, scattering components can be reduced, contributing to improved light transmittance. When bonding prism sheets, lenticular films, microlens array films, etc., appropriately adjusting the refractive index of the adhesive can control light diffraction and contribute to improving brightness and/or viewing angle.

The adhesive optical film disclosed herein is preferably used in an embodiment in which it is attached to a high refractive index adherend (which may be a high refractive index layer or member, etc.), and the adhesive type optical film disclosed herein is preferably used in an embodiment in which it is attached to a high refractive index adherend (which may be a high refractive index layer or member, etc.), and the interface with the adherend is Reflection can be suppressed. The adhesive optical film used in this embodiment preferably has a small refractive index difference with the adherend and high adhesion at the interface with the adherend, as described above. Further, from the viewpoint of improving the homogeneity of the appearance, it is preferable that the thickness of the adhesive layer is highly uniform, for example, it is preferable that the surface smoothness of the adhesive surface is high. When the thickness of the adherend with a high refractive index is relatively small (for example, 5 μm or less, 4 μm or less, or 2 μm or less), it is necessary to It is particularly useful to suppress reflexes. As an example of such a usage mode, in a polarizing plate with a retardation layer that includes 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 Another example is an embodiment used for bonding the first retardation layer and the second retardation layer.

In addition, the adhesive optical film disclosed herein is suitable for increasing the refractive index of the adhesive layer, so it can be used in light emitting layers such as optical semiconductors (e.g., high refractive light emitting layers mainly composed of inorganic materials). It can be preferably used in the form of being pasted. By reducing the difference in refractive index between the light emitting layer and the adhesive layer, reflection at the interface between them can be suppressed and light extraction efficiency can be improved. The adhesive optical film used in this embodiment preferably includes an adhesive layer with a high refractive index. From the viewpoint of improving brightness, it is preferable that the adhesive optical film has low coloration. This can also be advantageous from the viewpoint of suppressing unintentional coloring caused by the adhesive optical film.

The high refractive index adhesive layer disclosed in this specification is suitable for microlenses and other lens members used as constituent members of cameras, light emitting devices, etc. (for example, microlenses constituting a microlens array film, microlenses for cameras, etc.). (e.g., a lens member such as It can be preferably used as a packed bed, etc. The high refractive index adhesive layer disclosed herein can be applied to 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 is possible to reduce the difference in refractive index between the two. This is advantageous from the standpoint of making the lens and products equipped with the lens thinner, and can also contribute to suppressing aberrations and improving the Abbe number. The adhesive disclosed herein can also be used as a lens resin by itself, for example in the form of being filled in the recesses or voids of a suitable transparent member.

The adhesive optical film disclosed herein can also be understood as an adhesive optical member. Further, when the above-mentioned functional film is used as an optical film in the adhesive optical film disclosed herein, the adhesive optical film disclosed herein has the adhesive film disclosed herein on at least one side of the functional film. It can also be understood as an "adhesive functional film" having an adhesive layer.

As described above, according to the technology disclosed herein, a laminate including the adhesive optical film disclosed herein is provided. The member to which the adhesive optical film is attached may have the refractive index of the adherend material described above. Further, the difference between the refractive index of the adhesive optical film and the refractive index of the member (refractive index difference) may be the refractive index difference between the adherend and the adhesive optical film described above. The members constituting the laminate are the same as those described above as the members, materials, and adherends, so duplicate explanations will not be repeated.

In the adhesive optical film and laminate sheet disclosed herein, the high refractive index adhesive layer has a high refractive index, has improved flexibility, and has good adhesion reliability. Since it has good optical properties (transparency), it can be used for example in liquid crystal display devices, organic EL display devices, touch panels and other input devices in electronic devices such as portable electronic devices. It is suitable as an adhesive optical film or a laminated sheet for equipment (optical equipment) equipped with a light emitting device, particularly for foldable displays and rollable displays. The high refractive index adhesive layer and laminated sheet disclosed herein can have flexibility that can withstand repeated bending operations, so they can be repeatedly bent while attached to a foldable display or rollable display. It can follow adherends (foldable displays, etc.) well. Examples of objects to be pasted in such usage patterns include glass members such as window glasses and cover glasses used in foldable displays and rollable displays. In addition, the high refractive index adhesive layer of the adhesive optical film and laminated sheet disclosed herein can easily follow and adhere to curved surfaces such as three-dimensional shapes of portable electronic devices, so Suitable for use in electronic devices having a shape. In some preferred embodiments, the high refractive index pressure-sensitive adhesive layer and the laminated sheet may not only have flexibility but also have improved stability of properties such as elastic modulus. The above-mentioned portable electronic devices are sometimes used in high-temperature environments, and their internal spaces can become heated due to the heat generated by electronic components, so there is a great advantage of using an adhesive with the above-mentioned characteristics and good stability. .

Examples of portable electronic devices that can include the light emitting device disclosed herein include mobile phones, smartphones, tablet computers, notebook computers, and various wearable devices (for example, wrist-wear devices worn on the wrist such as wristwatches). , modular type that can be attached to a part of the body with a clip or strap, eyewear type that includes glasses type (monocular type and binocular type, including head-mounted type), and accessory type such as shirts, socks, hats, etc. digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), mobile game devices, electronic dictionaries, Includes electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. Note that in this specification, "portable" does not mean that it is simply portable; it also means that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. shall mean.

Hereinafter, some examples related to the present invention will be described, but the present invention is not intended to be limited to what is shown in these specific examples. In the following description, "parts" and "%" expressing usage amounts and contents are based on weight unless otherwise specified.

<Preparation of acrylic adhesive composition C1>
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A", refractive index: 1) was added as a monomer component. .566, hereinafter referred to as "POB-A") 99 parts and 2-acryloyloxyethyl-succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., trade name "HOA-MS (N)", hereinafter referred to as "HOA-MS") ''), 0.2 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator, and ethyl acetate as a polymerization solvent, nitrogen gas was introduced while stirring gently, and the inside of the flask was charged. A polymerization reaction was carried out for 6 hours while maintaining the liquid temperature at around 60° C. to prepare a solution (40%) of acrylic polymer P1. The Mw of the acrylic polymer P1 was 500,000.
The solution of the above acrylic polymer P1 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (non-volatile content: 100 parts) was added with a silicone plasticizer (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "HIVAC F-5"). , trimethylpentaphenyltrisiloxane, molecular weight: 546, refractive index: 1.575, liquid at 20°C) 20 parts, and an epoxy crosslinking agent as a crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C", 1 , 3-bis(N,N-diglycidylaminomethyl)cyclohexane) was added and mixed with stirring to prepare an acrylic adhesive composition C1.

<Preparation of acrylic adhesive composition C2>
Solution of the above acrylic polymer P1 except that the composition of the monomer components was changed to 95 parts of POB-A, 2 parts of lauryl acrylate (LA), 2 parts of 2-ethylhexyl acrylate (2EHA), and 1 part of 4-hydroxybutyl acrylate (4HBA). A solution of acrylic polymer P2 was prepared in the same manner as in the preparation. The Mw of the acrylic polymer P2 was 500,000. The solution of the above acrylic polymer P2 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (100 parts of nonvolatile content) was added with 20 parts of the above silicone plasticizer (HIVAC F-5) and a non-cyclic polymer as a crosslinking agent. 0.3 parts of a bifunctional isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate 2770", hexamethylene diisocyanate (HDI) allophanate), 2 parts of acetylacetone as a crosslinking retarder, and Nasem ferric as a crosslinking catalyst. One part of a 1% ethyl acetate solution (nonvolatile content: 0.01 part) was added and mixed with stirring to prepare acrylic adhesive composition C2.

<Preparation of acrylic adhesive composition C3>
A solution of acrylic polymer P3 was prepared in the same manner as in the preparation of the solution of acrylic polymer P1, except that the composition of the monomer components was changed to 90 parts of POB-A, 9 parts of 2EHA, and 1 part of 4HBA. The Mw of acrylic polymer P3 was 500,000. The solution of the above acrylic polymer P3 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of nonvolatile content), 40 parts of the above silicone plasticizer (HIVAC F-5) and the above isocyanate crosslinking agent were added. (Coronate 2770), 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of Nasem ferric iron (nonvolatile content 0.01 part) as a crosslinking catalyst were added and mixed with stirring, and acrylic adhesive was added. Agent composition C3 was prepared.

<Preparation of acrylic adhesive composition C4>
In preparing the acrylic adhesive composition C1, 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 content) was added with an ethylene glycol plasticizer (Sanyo Chemical Co., Ltd.). Manufactured by Kogyo Co., Ltd., trade name "Sunflex EB-300", polyethylene glycol benzoate ester, molecular weight: 538, refractive index: 1.515, liquid at 20 ° C., hereinafter referred to as "EB-300") 60 parts and 0.5 part of the above epoxy crosslinking agent (Tetrad C) was added and mixed with stirring to prepare acrylic pressure-sensitive adhesive composition C4.

<Preparation of acrylic adhesive composition C5>
A solution of acrylic polymer P4 was prepared in the same manner as in the preparation of the solution of acrylic polymer P1, except that the composition of the monomer components was changed to 98 parts of POB-A, 1 part of 4HBA, and 1 part of HOA-MS. 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 content), 30 parts of the ethylene glycol plasticizer (EB-300) and the isocyanate 0.1 part of a crosslinking agent (Coronate 2770), 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of Naseem ferric as a crosslinking catalyst (0.01 part of non-volatile content) were added and mixed with stirring. A pressure-sensitive adhesive composition C5 was prepared.

<Preparation of acrylic adhesive composition C6>
A solution of acrylic polymer P5 was prepared in the same manner as in the preparation of the solution of acrylic polymer P1, except that the composition of the monomer components was changed to 95 parts of POB-A, 3 parts of 4HBA, and 2 parts of HOA-MS. The Mw of acrylic polymer P5 was 500,000. The solution of the above acrylic polymer P5 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile content), 60 parts of the above ethylene glycol plasticizer (EB-300) and the above isocyanate system were added. 0.3 parts of a crosslinking agent (Coronate 2770), 2 parts of acetylacetone as a crosslinking retarder, and 1 part of a 1% ethyl acetate solution of Naseem ferric as a crosslinking catalyst (0.01 part of non-volatile content) were added and mixed with stirring. A pressure-sensitive adhesive composition C6 was prepared.

<Preparation of acrylic adhesive composition C7>
The acrylic polymer was prepared in the same manner as in the preparation of the solution of acrylic polymer P1, except that the composition of the monomer components was changed to 99 parts of n-butyl acrylate (BA) and 1 part of 4HBA, and the concentration of the monomer components during polymerization was adjusted. A solution of P6 was prepared. The Mw of acrylic polymer P6 was 2 million. The solution of the above acrylic polymer P6 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (100 parts of non-volatile content) was mixed with an isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name: 10 parts (non-volatile content: 0.1 part) of 1% ethyl acetate solution of "Coronate HX" (trifunctional isocyanate compound) was added and mixed with stirring to prepare acrylic pressure-sensitive adhesive composition C7.

<Preparation of polarizing film>
A 100 μm thick amorphous polyethylene terephthalate (PET) film containing 7 mol % of isophthalic acid units was prepared as a base material, and the surface thereof was subjected to corona treatment (58 W/m ² /min). On the other hand, acetoacetyl-modified polyvinyl alcohol (PVA) (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefimer Z200", average degree of polymerization: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) ) to which 1% was added (polymerization degree: 4200, saponification degree: 99.2%) was prepared, and a coating solution of a PVA aqueous solution containing 5.5% of the above PVA was applied so that the film thickness after drying was 12 μm. It was applied to the corona-treated surface of the above PET film. This was dried for 10 minutes by hot air drying in an atmosphere of 60°C to obtain a laminate having a PVA resin layer on a PET film. The free end of this laminate is stretched 1.8 times in air at 130°C (in-air auxiliary stretching) to form a stretched laminate, and then the stretched laminate is insolubilized with boric acid at a liquid temperature of 30°C. The PVA layer in which the PVA molecules contained in the stretched laminate were oriented was insolubilized by immersing it in an aqueous solution for 30 seconds. The boric acid insolubilizing aqueous solution used contained 3 parts of boric acid per 100 parts of water. A colored laminate was obtained by dyeing the stretched laminate. This colored laminate is produced by subjecting the stretched laminate to a dye solution containing iodine and potassium iodide at a liquid temperature of 30°C, so that the single transmittance of the PVA layer constituting the polarizing film finally obtained is 40 to 44%. The PVA layer contained in the above-mentioned stretched laminate was dyed with iodine by dipping it in the following manner. The staining solution used had an iodine concentration in the range of 0.1 to 0.4% and a potassium iodide concentration in the range of 0.7 to 2.8% using water as a solvent. The concentration ratio of iodine and potassium iodide is 1:7. Next, the colored laminate was immersed in a boric acid crosslinking aqueous solution at 30° C. for 60 seconds to crosslink the PVA molecules of the PVA layer on which iodine had been adsorbed. The aqueous boric acid crosslinking solution used contained 3 parts of boric acid per 100 parts of water and 3 parts of potassium iodide per 100 parts of water. Furthermore, the obtained colored laminate was stretched in a boric acid aqueous solution at a stretching temperature of 70°C to 3.05 times in the same direction as the previous stretching in air (boric acid water stretching). An optical film laminate having a stretching ratio of 5.50 times was obtained. This optical film laminate was taken out of the boric acid aqueous solution, and the boric acid adhering to the surface of the PVA layer was washed with an aqueous solution containing 4 parts of potassium iodide per 100 parts of water. The optical film laminate after washing was dried by hot air drying at 60°C. The thickness of the polarizing film included in the obtained optical film laminate was 5 μm.

An acrylic film was used as the protective film. This acrylic film is obtained by extruding methacrylic resin pellets containing glutarimide ring units, forming them into a film shape, and then stretching the film. The thickness of this protective film was 20 μm, and the moisture permeability was 160 g/m ² . The protective film thus obtained was bonded to the polarizing film using an adhesive (active energy ray-curable adhesive) and irradiated with ultraviolet rays to obtain a polarizing film.

<Production of adhesive optical film>
(Example 1)
The acrylic pressure-sensitive adhesive composition C1 prepared above was applied to the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (thickness 50 μm), which was silicone-treated on one side, and heated at 130° C. for 2 minutes. An adhesive layer with a thickness of 20 μm was formed. Next, the silicone-treated side of PET film R2 (thickness: 25 μm), which had been silicone-treated on one side, was bonded to the surface of the pressure-sensitive adhesive layer. In this way, an adhesive layer (high refractive index adhesive layer) having both sides protected by PET films (release liners) R1 and R2 was obtained. Note that the release liner R2 is relatively easy to release than the release liner R1.
In addition, the acrylic adhesive composition C7 prepared above was applied to the silicone-treated surface of PET film R1 (thickness: 50 μm), which was silicone-treated on one side, and heated at 130° C. for 2 minutes to reduce the thickness. A 50 μm adhesive layer was formed. The silicone-treated side of PET film R2 (thickness: 38 μm), which had been silicone-treated on one side, was bonded to the surface of the adhesive layer. In this way, an adhesive layer (low refractive index adhesive layer) having both sides protected by PET films (release liners) R1 and R2 was obtained.
The release liner R2 was peeled off from the low refractive index adhesive layer, and the exposed adhesive surface was bonded to the protective film of the optical film (polarizing film), and a 2 kg roller was moved back and forth once to press it. Next, the release liner R1 is peeled off from the low refractive index adhesive layer attached to the optical film, and the release liner R2 is peeled off from the high refractive index adhesive layer, and the low refractive index adhesive layer and the above The adhesive surfaces of the high refractive index adhesive layers were pasted together and pressed together using a hand roller. After this was left in the same environment for 30 minutes, it was autoclaved for 15 minutes at 50°C and 0.50 MPa, and then aged for 48 hours at 50°C. In this way, an adhesive optical film having a laminated structure of high refractive index adhesive layer/low refractive index adhesive layer/polarizing film was obtained. The surface of the high refractive index adhesive layer of this adhesive optical film is protected by a release liner R1.

(Examples 2 to 6)
High refractive index adhesive layer / low refractive index adhesive layer / polarized light Adhesive optical films each having a laminated film structure were obtained.

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

(Total light transmittance and haze value)
The adhesive layer (high refractive index adhesive layer and laminated adhesive layer of the high refractive index adhesive layer and the low refractive index adhesive layer) according to each example was made of alkali-free glass (with a thickness of 0.8 to 1.5 mm). Using a test piece laminated to 0 mm, total light transmittance 92%, haze 0.4%), a haze meter (manufactured by Murakami Color Research Institute, product name "HAZEMETER HM-150") was used in a measurement environment of 23 ° C. The total light transmittance and haze of the above test piece were measured using the following. The value obtained by subtracting the total light transmittance and haze of the alkali-free glass from the measured value was defined as the total light transmittance and haze value of the adhesive layer. Regarding the total light transmittance and haze value of the laminated adhesive layer of the high refractive index adhesive layer and the low refractive index adhesive layer, release liner R2 is removed from the high refractive index adhesive layer and the low refractive index adhesive layer. Measurements were carried out using a laminated adhesive layer (obtained by peeling off and bonding the adhesive surfaces together). The results are shown in Table 1.

(Peel strength against glass plate F1)
An adhesive layer (high refractive index adhesive layer) with both sides protected by release liners R1 and R2 is prepared, and the release liner is applied from one side of the adhesive layer under a measurement environment of 23°C and 50% RH. The sample was peeled off, lined with a PET film having a thickness of 50 μm, and then cut into a size of 25 mm in width and 100 mm in length to obtain a test piece. The release liner on the other side of the test piece was peeled off, and a 2 kg roller was moved back and forth on the surface of an alkali glass plate (manufactured by Matsunami Glass Industries Co., Ltd., thickness 1.35 mm, blue plate edge polished) as an adherend. I crimped it. This was left in the same environment for 30 minutes, then put into a pressure degassing device (autoclave) and autoclaved for 15 minutes at a temperature of 50°C and a pressure of 0.5 MPa, and then at 23°C and 50% RH. After being left for 24 hours in an atmosphere of [N/25mm] was measured. As a universal tensile compression tester, "Tensile Compression Tester, TG-1kN" manufactured by Minebea was used. The results are shown in Table 1.

(Peel strength against optical film F2)
A test piece was prepared by cutting the adhesive optical film (laminate of high refractive index adhesive layer/low refractive index adhesive layer/polarizing film) according to each example into a size of 25 mm in width and 100 mm in length. Under a measurement environment of 23° C. and 50% RH, the release liner on the high refractive index adhesive layer side of the test piece was peeled off, and an ITO film (125 μm thick) was attached for backing. Further, the back surface of the test piece on the optical film side was bonded to a stainless steel plate (SUS plate) using double-sided adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 500"). The bonding was performed by pressing a 2 kg roller back and forth once. This was left in the same environment for 30 minutes, then put into a pressure degassing device (autoclave) and autoclaved for 15 minutes at a temperature of 50°C and a pressure of 0.5 MPa, and then at 23°C and 50% RH. After leaving it for 30 minutes in an atmosphere of The peel strength F2 [N/25 mm] was measured. As a universal tension and compression tester, "Tensile and Compression Tester, TG-1kN" manufactured by Minebea was used. The results are shown in Table 1.

As shown in Table 1, the adhesive optical films of Examples 1 to 3 have a high refractive index adhesive layer containing a plasticizer, a refractive index higher than 1.560, and a peel strength F1 against a glass plate. It was 3N/25mm or more. On the other hand, in the adhesive optical films of Examples 4 to 6, the high refractive index adhesive layer contained a plasticizer and the refractive index was higher than 1.560, but the adhesive strength to the glass plate was low.
From the above, the high refractive index adhesive layers of Examples 1 to 3 have a high refractive index, improved flexibility, and good adhesion reliability. It can be seen that it can be preferably used in the form of an adhesive optical film laminated on an optical film having at least one function of waveguiding, light condensing, and diffraction.

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

1 Adhesive optical film 2 Substrate-less double-sided adhesive sheet 10 Adhesive layer, 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 20 Optical film 20A First surface 20B Second surface (back)
30, 31, 32 Release liner 50 Adhesive optical film with release liner 70 Optical member (adherent)
100 Optical laminate

Claims (8)

An adhesive optical film comprising an optical film and an adhesive layer laminated on the optical film,
The adhesive layer includes a high refractive index adhesive layer with a refractive index higher than 1.560,
The high refractive index adhesive layer contains a plasticizer,
The high refractive index adhesive layer is an adhesive optical film having a peel strength F1 of 3 N/25 mm or more with respect to a glass plate. The adhesive layer further includes a low refractive index adhesive layer having a lower refractive index than the high refractive index adhesive layer, and the high refractive index adhesive layer and the low refractive index adhesive layer are in direct contact with each other. The pressure-sensitive adhesive optical film according to claim 1, wherein the adhesive optical film is laminated. The adhesive optical film according to claim 2, wherein the optical film, the low refractive index adhesive layer, and the high refractive index adhesive layer are laminated in this order. The adhesive optical film according to any one of claims 1 to 3, wherein the adhesive layer has a peel strength F2 of 5 N/25 mm or more with respect to the optical film. Any one of claims 1 to 4, wherein the difference (F2-F1) between the peel strength F1 [N/25 mm] for the glass plate and the peel strength F2 [N/25 mm] for the optical film is 1.5 or more. The pressure-sensitive adhesive optical film described in 2. The adhesive optical film according to any one of claims 1 to 5, wherein the adhesive layer has a total light transmittance of 85% or more and a haze value of 3.0% or less. The adhesive optical film according to any one of claims 1 to 6,
a release liner disposed on the adhesive surface of the adhesive optical film;
Adhesive optical film with release liner, including: A laminated sheet comprising a high refractive index adhesive layer having a refractive index higher than 1.560 and a low refractive index adhesive layer having a lower refractive index than the high refractive index adhesive layer,
The high refractive index adhesive layer contains a plasticizer,
The high refractive index adhesive layer is a laminated sheet whose peel strength F1 with respect to a glass plate is 3N/25mm or more.

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