JP7650716B2 - Pressure-sensitive adhesive composition, photocurable pressure-sensitive adhesive layer, and photocurable pressure-sensitive adhesive sheet - Google Patents

Description

The present invention relates to an adhesive composition, a photocurable adhesive layer, and a photocurable adhesive sheet. More specifically, the present invention relates to an adhesive composition, a photocurable adhesive layer, and a photocurable adhesive sheet that are suitable for sealing light-emitting elements of self-luminous display devices such as mini/micro LEDs.

In recent years, self-emitting display devices, such as mini/micro LED display devices (mini/micro light emitting diode displays), have been devised as next-generation display devices. In the basic configuration of a mini/micro LED display device, a substrate on which numerous tiny LED light emitting elements (LED chips) are densely arranged is used as the display panel, the LED chips are sealed with a sealant, and a cover member such as a resin film or glass plate is laminated on the outermost layer.

There are several types of self-luminous display devices such as mini/micro LED display devices, including a white backlight type, a white light-emitting color filter type, and an RGB type. In the white light-emitting color filter type and the RGB type, a black-colored adhesive may be used as a sealant (see, for example, Patent Documents 1 to 3).
The black adhesive contributes to preventing color mixing and improving contrast by filling in the spaces between the RGB LED chips arranged on the display panel substrate, and also prevents reflections from metal wiring and metal oxides such as ITO arranged on the display panel substrate.

In mini/micro LED display devices, LED chips are densely packed on a substrate, and there are many fine steps between the LED chips. The encapsulant used in mini/micro LED display devices is required to have the ability to fill these steps, i.e., excellent step absorption (also called "step conformability"). Therefore, the black adhesive needs to be designed to have high fluidity in order to improve step absorption.

On the other hand, adhesives that exhibit high fluidity have excellent step absorption properties, but have the problem of reduced processability, such as shape stability and handleability. For example, laminates with adhesive layers that exhibit high fluidity are prone to glue chipping during cutting and the adhesive layer protruding or sagging from the edges during storage, and foreign matter may adhere to the protruding adhesive layer, causing problems such as process contamination.

A photocurable adhesive (hybrid adhesive) is known as an adhesive that combines the above-mentioned step absorption and processability (see, for example, Patent Document 4). A hybrid adhesive has the advantage that it can be made to first be semi-cured, which has high fluidity and excellent step absorption properties, so that it can adequately conform to steps, and then irradiated with light to complete the curing, improving processability.

JP 2019-204905 A JP 2017-203810 A Special table 2018-523854 publication International Publication No. WO2016/170875

However, for example, if carbon black or the like is added to the hybrid adhesive to color it black, light cannot penetrate the adhesive, inhibiting curing and making it difficult to improve processability.

The present invention was conceived under the circumstances described above, and the object of the present invention is to provide an adhesive composition, an adhesive layer, and an adhesive sheet that are suitable for manufacturing light-emitting display devices such as mini/micro LED display devices that have anti-reflection functions such as metal wiring and improved contrast, and that also have excellent step absorption properties and processability.

As a result of intensive research to achieve the above object, the present inventors have found that, by coloring an adhesive composition, a photocurable adhesive layer, and a photocurable adhesive sheet so that they are absorbent in the visible light range but highly transparent in the ultraviolet range, they can be cured by ultraviolet irradiation while exhibiting high light blocking properties against visible light. In addition, by using an adhesive composition containing a polymer having a benzophenone structure in the side chain, a mixture of monomer components constituting the polymer, or a partial polymer of a mixture of monomer components constituting the polymer as the adhesive composition, it is possible to provide a photocurable adhesive layer and a photocurable adhesive sheet that can achieve both excellent step absorption before photocuring and excellent processability after photocuring, and that the anti-reflection function and contrast of metal wiring and the like in a self-luminous display device can be improved, while also achieving both excellent step absorption and processability. The present invention has been completed based on these findings.

A first aspect of the present invention provides a pressure-sensitive adhesive composition comprising a colorant and a polymer (A) having a benzophenone structure in a side chain, the pressure-sensitive adhesive composition having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than a maximum transmittance in the wavelength region of 400 to 700 nm.
A second aspect of the present invention provides a pressure-sensitive adhesive composition comprising a colorant and a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain or a partial polymer of the mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain, and having a maximum transmittance at a wavelength of 200 to 400 nm greater than a maximum transmittance at a wavelength of 400 to 700 nm. The pressure-sensitive adhesive compositions of the first and second aspects of the present invention may further comprise an ethylenically unsaturated compound (B).

In this specification, the pressure-sensitive adhesive compositions according to the first and second aspects of the present invention may be collectively referred to as "pressure-sensitive adhesive composition (A)".
In addition, in this specification, unless otherwise specified, the term "polymer (A) having a benzophenone structure in its side chain" or "BP polymer (A)" includes "polymer (A) having a benzophenone structure in its side chain" and "a mixture of monomer components constituting polymer (A) having a benzophenone structure in its side chain or a partial polymer of a mixture of monomer components constituting polymer (A) having a benzophenone structure in its side chain."

A third aspect of the present invention provides a photocurable adhesive layer formed of a cured product of the adhesive composition (A), the cured product being a cured product that allows the benzophenone structure to remain. A fourth aspect of the present invention provides a photocurable adhesive sheet having the photocurable adhesive layer of the third aspect of the present invention.
In this specification, the photocurable pressure-sensitive adhesive layer according to the third aspect of the present invention may be referred to as a "photocurable pressure-sensitive adhesive layer (A)". Also, the photocurable pressure-sensitive adhesive sheet according to the fourth aspect of the present invention may be referred to as a "photocurable pressure-sensitive adhesive sheet (A)".

The photocurable adhesive layer (A) is a cured product of the adhesive composition (A) and is formed by a cured product in which the benzophenone structure of the BP polymer (A) remains. This benzophenone structure can be cured by forming a crosslinked structure by ultraviolet irradiation. The photocurable adhesive layer (A) before curing is in a semi-cured state with high fluidity and exhibits excellent step absorption. Therefore, when the photocurable adhesive layer (A) before curing is bonded to a display panel in which light-emitting elements (LED chips) are densely arranged, it sufficiently follows the fine steps between the light-emitting elements (LED chips) and adheres without gaps without leaving any air bubbles. On the other hand, the photocurable adhesive layer (A) after curing exhibits excellent processability. Therefore, the occurrence of glue chipping during cutting processing of a laminate including the photocurable adhesive layer (A) after curing and the protrusion or sagging of the adhesive layer from the edge during storage is suppressed. In this way, the photocurable adhesive layer (A) composed of the above-mentioned cured product of the adhesive composition (A) can be suitably combined with excellent step absorption and processability.

The adhesive composition (A) has a maximum transmittance of 200 to 400 nm wavelengths greater than the maximum transmittance of 400 to 700 nm wavelengths. In addition, the photocurable adhesive layer (A) preferably has a maximum transmittance of 200 to 400 nm wavelengths greater than the maximum transmittance of 400 to 700 nm wavelengths. That is, the adhesive composition (A) and the photocurable adhesive layer (A) have high absorption for visible light (wavelength 400 to 700 nm) and excellent light-shielding properties. The configuration in which the adhesive composition (A) and the photocurable adhesive layer (A) have excellent light-shielding properties for visible light is preferable in that the photocurable adhesive layer (A) filled without gaps in the fine steps between the LED chips prevents reflections due to metal wiring on the display panel, prevents color mixing between the arranged light-emitting elements (LED chips), and improves contrast. On the other hand, the adhesive composition (A) and the photocurable adhesive layer (A) have high transmittance to ultraviolet light (wavelength 200 to 400 nm). The adhesive composition (A) and the photocurable adhesive layer (A) have excellent transmittance to ultraviolet light, which is preferable in that the curing reaction proceeds by irradiating the photocurable adhesive layer (A) with ultraviolet light, and the processability of the photocurable adhesive layer (A) is improved. In other words, the adhesive composition (A) and the photocurable adhesive layer (A) have a maximum transmittance at wavelengths of 200 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm, which is preferable in that excellent light blocking properties for visible light and a curing reaction due to ultraviolet light irradiation can be achieved at the same time.

The colorant is preferably a colorant having a higher maximum transmittance at wavelengths of 200 to 400 nm than at wavelengths of 400 to 700 nm. This configuration is preferable in order to realize that the pressure-sensitive adhesive composition (A) and the photocurable pressure-sensitive adhesive layer (A) have a higher maximum transmittance at wavelengths of 200 to 400 nm than at wavelengths of 400 to 700 nm.
In this specification, a "colorant having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than the maximum transmittance in the wavelength region of 400 to 700 nm" may be referred to as a "colorant (A)".

The adhesive composition (A) preferably further contains a photopolymerization initiator (C) that absorbs ultraviolet light with a wavelength of 300 nm to 500 nm to generate radicals. This configuration is preferable for obtaining a photocurable adhesive layer (A) by curing the adhesive composition (A) into a cured product that retains the benzophenone structure of the BP polymer (A).

The storage modulus (G'b85) of the photocurable adhesive layer (A) at 85°C before curing is preferably less than 65 kPa. This configuration is preferable for the photocurable adhesive layer (A) before curing to exhibit excellent step absorption properties.

It is preferable that the storage modulus (G'a10) at 10°C of the cured photocurable pressure-sensitive adhesive layer (A) and the storage modulus (G'b85) at 85°C of the photocurable pressure-sensitive adhesive layer (A) before curing satisfy the following relational expression (1).
2.8<G'a10/G'b85 (1)
This configuration is preferable since the photocurable pressure-sensitive adhesive layer (A) before curing exhibits excellent step absorbency, and the photocurable pressure-sensitive adhesive layer (A) after curing exhibits excellent processability.

It is preferable that the storage modulus (G'a10) of the photocurable adhesive layer (A) at 10°C after curing is 90 kPa or more. This configuration is preferable in that the photocurable adhesive layer (A) after curing exhibits excellent processability.

The curing is preferably performed by irradiation with ultraviolet light having a wavelength of less than 300 nm and an integrated light quantity of 3000 mJ/cm ^2. This configuration is preferable in that the photocurable pressure-sensitive adhesive layer (A) is cured by the ultraviolet light irradiation, with the benzophenone structure forming a crosslinked structure, and thus exhibits excellent processability.

The fifth aspect of the present invention provides a self-luminous display device including a display panel having a plurality of light-emitting elements arranged on one side of a substrate and the photocurable adhesive sheet (A), in which the light-emitting elements of the display panel are sealed with the photocurable adhesive layer (A) of the photocurable adhesive sheet (A), and the photocurable adhesive layer (A) is cured. In the self-luminous display device of the fifth aspect of the present invention, the display panel may be an LED panel having a plurality of LED chips arranged on one side of the substrate. This configuration is preferable in that the photocurable adhesive layer (A) that fills the minute steps between the light-emitting elements (LED chips) without gaps in the self-luminous display device of the fifth aspect of the present invention can prevent reflection of metal wiring on the substrate, prevent RGB color mixing, and improve contrast.

The self-luminous display device according to the fifth aspect of the present invention can be manufactured by a method including the following steps.
A step of laminating a photocurable adhesive layer (A) of a photocurable adhesive sheet (A) on a display panel having a plurality of light-emitting elements arranged on one side of a substrate, and sealing the light-emitting elements with the photocurable adhesive layer (A); and a step of curing the photocurable adhesive layer (A) by irradiating it with ultraviolet light.
The photocurable adhesive layer (A) before curing has excellent step absorption properties, so that it can sufficiently conform to the minute steps between the light-emitting elements and adhere closely without leaving any air bubbles or gaps. The photocurable adhesive layer (A) is cured by irradiating it with ultraviolet light, and has excellent processability.

In the method for producing a self-luminous display device according to the fifth aspect of the present invention, the ultraviolet light is preferably ultraviolet light having a wavelength of less than 300 nm. This configuration is preferable in that the photocurable adhesive layer (A) is cured by irradiating the photocurable adhesive layer with ultraviolet light, and the benzophenone structure forms a crosslinked structure, thereby exhibiting excellent processability.

The adhesive composition, photocurable adhesive layer, and photocurable adhesive sheet of the present invention have high light blocking properties against visible light and excellent step absorption properties, so when used to manufacture a self-luminous display device, the steps between multiple light-emitting elements are filled without gaps, preventing reflection from metal wiring and suppressing color mixing between multiple light-emitting elements, thereby improving contrast. In addition, they are cured by irradiation with ultraviolet light, improving processability, and suppressing the occurrence of glue chipping during cutting processing and the adhesive layer protruding or sagging from the edges during storage. Therefore, by using the adhesive composition, photocurable adhesive layer, and photocurable adhesive sheet of the present invention to manufacture a self-luminous display device, a self-luminous display device with improved anti-reflection function for metal wiring and improved contrast can be efficiently manufactured.

FIG. 1 is a schematic diagram (cross-sectional view) illustrating one embodiment of the photocurable pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram (cross-sectional view) illustrating one embodiment of the photocurable pressure-sensitive adhesive sheet of the present invention. FIG. 3 is a schematic diagram (cross-sectional view) illustrating one embodiment of the photocurable pressure-sensitive adhesive sheet of the present invention. FIG. 4 is a schematic diagram (cross-sectional view) showing one embodiment of a self-luminous display device (mini/micro LED display device) of the present invention. FIG. 5 is a schematic diagram (cross-sectional view) showing steps for carrying out one embodiment of a method for manufacturing a self-luminous display device (mini/micro LED display device) of the present invention.

Embodiments of the present invention will be described with reference to the drawings as necessary, but the present invention is not limited thereto and is merely illustrative.

In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of an acrylic monomer. The above-mentioned acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group in one molecule. In addition, in this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

In this specification, "ethylenically unsaturated compound" refers to a compound having at least one ethylenically unsaturated group in the molecule. Examples of ethylenically unsaturated groups include (meth)acryloyl groups, vinyl groups, and allyl groups. Hereinafter, a compound having one ethylenically unsaturated group may be referred to as a "monofunctional monomer," and a compound having two or more ethylenically unsaturated groups may be referred to as a "polyfunctional monomer." Furthermore, among polyfunctional monomers, a compound having X ethylenically unsaturated groups may be referred to as an "X-functional monomer."

In this specification, unless otherwise specified, the PSA composition containing an ethylenically unsaturated compound means that the PSA composition contains the ethylenically unsaturated compound in the form of a partial polymer. Such a partial polymer is usually a mixture containing the ethylenically unsaturated compound in which the ethylenically unsaturated group is unreacted (unreacted monomer) and the ethylenically unsaturated compound in which the ethylenically unsaturated group has been polymerized.

In this specification, the total amount of monomer components constituting the adhesive composition refers to the total amount of monomer components constituting the polymer contained in the adhesive composition and monomer components contained in the adhesive composition in the form of unreacted monomers. The composition of the monomer components constituting the adhesive composition is usually roughly the same as the composition of the monomer components of the adhesive layer formed from the adhesive composition and the composition of the monomer components constituting the photocured product thereof.

In this specification, the term "active energy rays" refers to light such as ultraviolet rays, visible light, and infrared rays, as well as radiation such as alpha rays, beta rays, gamma rays, electron beams, neutron beams, and X-rays.

[Adhesive composition (A)]
The pressure-sensitive adhesive composition according to the first aspect of the present invention contains a colorant and a polymer (A) having a benzophenone structure in a side chain, and has a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than the maximum transmittance in the wavelength region of 400 to 700 nm.
The pressure-sensitive adhesive composition according to the second aspect of the present invention contains a colorant and a mixture of monomer components constituting polymer (A) having a benzophenone structure in a side chain, or a partial polymer of the mixture of monomer components constituting polymer (A) having a benzophenone structure in a side chain, and has a maximum transmittance at wavelengths of 200 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm.
The pressure-sensitive adhesive compositions (pressure-sensitive adhesive composition (A)) according to the first and second aspects of the present invention may further contain an ethylenically unsaturated compound (B).
The pressure-sensitive adhesive composition (A) may contain, in addition to the above, a photopolymerization initiator (C) that absorbs ultraviolet light having a wavelength of 300 nm to 500 nm to generate radicals, which will be described later, and other additives.
In this specification, the above-mentioned "mixture of monomer components" includes a case where the mixture is composed of a single monomer component and a case where the mixture is composed of two or more monomer components. Also, the above-mentioned "partially polymerized product of the mixture of monomer components" means a composition in which one or more of the constituent monomer components of the above-mentioned "mixture of monomer components" are partially polymerized.

The adhesive composition (A) may have any form, for example, a solvent type, an emulsion type, a heat-melting type (hot melt type), a solventless type (active energy ray curing type, for example, a monomer mixture, or a monomer mixture and a partial polymer thereof, etc.). The adhesive composition (A) of the present invention is preferably an active energy ray curing type from the viewpoint of obtaining an adhesive layer with excellent appearance. In this specification, the adhesive composition means a composition used to form an adhesive layer, and includes the meaning of a composition used to form an adhesive.

The adhesive composition (A) is not particularly limited, but examples thereof include a composition having BP polymer (A) as an essential component; a composition having a mixture of monomer components constituting BP polymer (A) or a partial polymer thereof as an essential component, and the like. Although not particularly limited, examples of the former include so-called solvent-based adhesive compositions and water-dispersed adhesive compositions (emulsion-type adhesive compositions), and examples of the latter include so-called active energy ray-curable adhesive compositions, and the like.

The pressure-sensitive adhesive composition (A) may be a solvent-based composition, as described above. The solvent is not particularly limited as long as it is an organic compound that can be used as a solvent, and examples of the solvent include hydrocarbon solvents such as cyclohexane, hexane, and heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, butanol, and isopropyl alcohol. The solvent may be a mixed solvent containing two or more types of solvents.

The pressure-sensitive adhesive composition (A) may be an acrylic pressure-sensitive adhesive composition in which more than 50% by weight (preferably more than 70% by weight, e.g., more than 90% by weight) of the total monomer components constituting the pressure-sensitive adhesive composition is an acrylic monomer.

The pressure-sensitive adhesive composition (A) has a maximum transmittance at wavelengths of 200 to 400 nm (preferably 330 to 400 nm) that is greater than the maximum transmittance at wavelengths of 400 to 700 nm.

The adhesive composition (A) has low transparency to visible light (wavelength 400 to 700 nm), i.e., high light-shielding properties. The photocurable adhesive layer (A) formed from the cured product of the adhesive composition (A), which has excellent light-shielding properties against visible light, seals the minute steps between the metal wiring layer and the light-emitting element (LED chip) of a self-luminous display device (mini/micro LED display device) without any gaps, thereby preventing reflections from the metal wiring, preventing color mixing of the light-emitting element (LED chip), and improving the contrast of the image.

On the other hand, the adhesive composition (A) has a higher transmittance in the ultraviolet region (wavelength 200 to 400 nm, preferably wavelength 330 to 400 nm) than in visible light. Therefore, the photocurable adhesive layer (A) formed from the cured product of the adhesive composition (A) can be cured by irradiating it with ultraviolet light, with the benzophenone structure forming a crosslinked structure. The photocurable adhesive layer (A) cured by ultraviolet light irradiation has improved processability, and is less susceptible to glue chipping during cutting and to protrusion or sagging of the adhesive layer from the edges during storage.

In this specification, "maximum transmittance at wavelengths of 200 to 400 nm" means the highest transmittance within the range of wavelengths of 200 to 400 nm. For example, if there is one maximum transmittance in the range of wavelengths of 200 to 400 nm, that maximum value will be the maximum transmittance. Also, if there is no maximum transmittance in the range of wavelengths of 200 to 400 nm, the higher of the transmittances at wavelengths of 200 nm and 400 nm will be the maximum transmittance. The same applies to "maximum transmittance at wavelengths of 330 to 400 nm" and "maximum transmittance at wavelengths of 400 to 700 nm."

The maximum transmittance of the adhesive composition (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

In a preferred embodiment of the present invention, the adhesive composition (A) has an average transmittance at wavelengths of 200 to 400 nm (preferably 330 to 400 nm) that is greater than the average transmittance at wavelengths of 400 to 700 nm. The average transmittance of the adhesive composition (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[Coloring agent]
The pressure-sensitive adhesive composition (A) contains a colorant. The colorant is not particularly limited, but is preferably a colorant (colorant (A)) whose maximum transmittance at a wavelength of 200 to 400 nm (preferably a wavelength of 330 to 400 nm) is greater than the maximum transmittance at a wavelength of 400 to 700 nm.

The pressure sensitive adhesive composition (A) having a maximum transmittance at wavelengths of 200 to 400 nm (preferably 330 to 400 nm) greater than the maximum transmittance at wavelengths of 400 to 700 nm is not particularly limited, but can be achieved by including a colorant (A) in the pressure sensitive adhesive composition (A).

When the adhesive composition (A) contains a colorant (A), the transmittance to visible light (wavelength 400 to 700 nm) decreases, i.e., the light blocking properties improve, while the transmittance to the ultraviolet region (wavelength 200 to 400 nm, preferably wavelength 330 to 400 nm) becomes higher than that to visible light.

The maximum transmittance of the colorant (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

In a preferred embodiment of the present invention, the colorant (A) has an average transmittance at wavelengths of 200 to 400 nm (preferably 330 to 400 nm) that is greater than the average transmittance at wavelengths of 400 to 700 nm. The average transmittance of the colorant (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

The transmittance of the colorant can be measured using a solution or dispersion diluted with an appropriate solvent or dispersion medium (an organic solvent with low absorption in the wavelength range of 200 to 700 nm) such as tetrahydrofuran (THF) so that the transmittance at a wavelength of 400 nm is approximately 50 to 60%.

The colorant may be either a dye or a pigment, so long as it is soluble or dispersible in the adhesive composition (A). Dyes are preferred because even a small amount of dye can achieve low haze, and they are not prone to settling like pigments and can be distributed uniformly. Pigments are also preferred because they have high color expression even when added in small amounts. When using a pigment as the colorant, it is preferable for it to have low or no electrical conductivity. When using a dye, it is preferable to use it in combination with an antioxidant, etc.

Examples of UV-transmitting black pigments include "9050BLACK", "9256BLACK", "9170BLACK", and "UVBK-0001" manufactured by Tokushiki, and "UB-1" manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd. Examples of UV-transmitting black dyes include "SOC-L-0123" manufactured by Orient Chemical Industries Co., Ltd.

The content of the colorant in the adhesive composition (A) is, for example, about 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight, per 100 parts by weight of the adhesive composition (A), and may be set appropriately depending on the type of colorant, the color tone and light transmittance of the photocurable adhesive layer (A), etc. The colorant may be added as a solution or dispersion in which it is dissolved or dispersed in an appropriate solvent.

[Polymer (A) having a benzophenone structure in the side chain]
The base polymer constituting the pressure-sensitive adhesive composition (A) of the present invention contains a polymer (A) having a benzophenone structure in a side chain (BP polymer (A)). That is, the pressure-sensitive adhesive composition (A) of the present invention is a pressure-sensitive adhesive composition containing the BP polymer (A) as a base polymer. The BP polymer (A) may be used alone or in combination of two or more kinds.

Monomer components that can form the BP polymer (A) include compounds having an ethylenically unsaturated group and a benzophenone structure in the molecule (hereinafter sometimes referred to as "ethylenically unsaturated BPs"), and can also include ethylenically unsaturated compounds that do not fall under the category of ethylenically unsaturated BPs (hereinafter sometimes referred to as "other ethylenically unsaturated compounds").

A suitable example of the BP polymer (A) is an acrylic polymer having a benzophenone structure in the side chain. The BP polymer (A) is preferably a polymer that does not substantially contain ethylenically unsaturated groups.

In this specification, the term "benzophenone structure" refers to a diaryl ketone structure represented by the general formula: Ar ¹ -(C═O)-Ar ² -; or -Ar ³ -(C═O)-Ar ² -;. Here, Ar ¹ in the above general formula is selected from phenyl groups which may have a substituent. In the above general formula, Ar ² and Ar ³ are each independently selected from phenylene groups which may have a substituent. Ar ² and Ar ³ may be the same or different. The benzophenone structure can be excited by irradiation with ultraviolet light, and in the excited state, it can abstract hydrogen radicals from other molecules or other parts of the molecule.

The photocurable adhesive layer (A) formed from the cured product of the adhesive composition (A) containing the BP polymer (A) may contain a benzophenone structure. The benzophenone structure is excited by ultraviolet irradiation to form a crosslinked structure using an abstraction reaction of hydrogen radicals, thereby curing the photocurable adhesive layer (A).

The BP polymer (A) is preferably a polymer having a benzophenone structure in the side chain, in which Ar ¹ in the general formula Ar ¹ -(C═O)-Ar ² - is a phenyl group which may have a substituent and Ar ² is a phenylene group which may have a substituent. When at least one of Ar ¹ and Ar ² has one or more substituents, the substituents may each independently be selected from the group consisting of an alkoxy group (e.g., an alkoxy group having 1 to 3 carbon atoms, preferably a methoxy group), a halogen atom (e.g., F, Cl, Br, etc., preferably Cl or Br), a hydroxyl group, an amino group, and a carboxyl group.

The BP polymer (A) may have a side chain in which the benzophenone structure as described above is directly bonded to the main chain, or may have a side chain bonded to the main chain via one or more of an ester bond, an oxyalkylene structure, etc. A suitable example of the BP polymer (A) is a polymer containing a repeating unit derived from an ethylenically unsaturated BP. The repeating unit may be a polymerized residue obtained by reacting an ethylenically unsaturated group of the corresponding ethylenically unsaturated BP.

Examples of the ethylenically unsaturated BP include acryloyloxybenzophenones which may have a substituent, such as 4-acryloyloxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, and 2-hydroxy-4-acryloyloxybenzophenone; acryloyloxyalkoxybenzophenones which may have a substituent, such as 4-[(2-acryloyloxy)ethoxy]benzophenone and 4-[(2-acryloyloxy)ethoxy]-4'-bromobenzophenone; 4-methacryloyloxybenzophenone and 4-methacryloyloxy-4'-methoxybenzophenone; Examples of methacryloyloxybenzophenones which may have a substituent, such as 4-[(2-methacryloyloxy)ethoxy]benzophenone and 4-[(2-methacryloyloxy)ethoxy]-4'-methoxybenzophenone, and vinyl benzophenones which may have a substituent, such as 4-vinylbenzophenone, 4'-bromo-3-vinylbenzophenone and 2-hydroxy-4-methoxy-4'-vinylbenzophenone, but are not limited thereto. The ethylenically unsaturated BP may be used alone or in combination of two or more kinds in the preparation of the BP polymer (A). The ethylenically unsaturated BP may be commercially available, or may be synthesized by a known method. From the viewpoint of reactivity, etc., it is preferable to use an ethylenically unsaturated BP having a (meth)acryloyl group, i.e., an ethylenically unsaturated BP that is an acrylic monomer.

The BP polymer (A) may be a copolymer having a repeating unit derived from an ethylenically unsaturated BP and a repeating unit derived from an ethylenically unsaturated compound (another ethylenically unsaturated compound) that does not fall under the category of ethylenically unsaturated BP. Such a BP polymer (A) may be a copolymer of monomer components containing the above-mentioned ethylenically unsaturated BP and the above-mentioned other ethylenically unsaturated compound. The BP polymer may also be a copolymer in which a partial polymer (prepolymer) of a monomer mixture consisting only of the above-mentioned other ethylenically unsaturated compound is copolymerized with the above-mentioned ethylenically unsaturated BP. One or more acrylic monomers may be preferably used as the above-mentioned other ethylenically unsaturated compound. A suitable example of the BP polymer (A) is an acrylic BP polymer in which more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of the monomer components constituting the BP polymer (A) are acrylic monomers.

The monomer component constituting the BP polymer (A) may contain, as the other ethylenically unsaturated compound, one or more selected from (meth)acrylic acid alkyl esters having an alkyl group at the ester end. Hereinafter, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group with a carbon number of X to Y at the ester end may be referred to as "(meth)acrylic acid C _XY alkyl ester". The monomer component constituting the BP polymer (A) preferably contains at least a (meth)acrylic acid C _1-20 alkyl ester as the other monomer, more preferably a (meth)acrylic acid C _4-20 alkyl ester, and even more preferably a (meth)acrylic acid C _4-18 alkyl ester (e.g., an acrylic acid C _4-9 alkyl ester).

Non-limiting specific examples of the (meth)acrylic acid C _1-20 alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and (meth)acrylic acid. Examples of the alkyl esters of (meth)acrylic acid include isooctyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. Particularly preferred examples of the alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate, etc. Other specific examples of (meth)acrylic acid alkyl esters that can be preferably used include n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), etc. The (meth)acrylic acid alkyl esters can be used alone or in combination of two or more. The monomer component constituting the BP polymer (A) may contain, as the other ethylenically unsaturated compound, one or more selected from the copolymerizable monomers described below.

The pressure-sensitive adhesive composition (A) may be a photocurable acrylic pressure-sensitive adhesive composition in which more than 50% by weight (preferably more than 70% by weight, e.g., more than 90% by weight) of the total monomer components constituting the composition is an acrylic monomer. The photocurable acrylic pressure-sensitive adhesive composition forms an acrylic photocured product by photocuring.

The weight average molecular weight (Mw) of the BP polymer (A) is not particularly limited, and may be, for example, about 0.5×10 ⁴ to 500×10 ^4. From the viewpoint of the cohesiveness of the photocurable pressure-sensitive adhesive layer (A) and the handleability of the photocurable pressure-sensitive adhesive sheet (A), the Mw of the BP polymer (A) is usually appropriate to be 1×10 ⁴ or more, preferably 5×10 ⁴ or more, may be 10×10 ⁴ or more, may be 15×10 ⁴ or more, or may be 20×10 ⁴ or more. In addition, from the viewpoint of the step absorbency of the photocurable pressure-sensitive adhesive layer (A), the Mw of the BP polymer (A) is usually appropriate to be 200×10 ⁴ or less, preferably 150×10 ⁴ or less, may be 100×10 ⁴ or less, may be 70×10 ⁴ or less, or may be 50×10 ⁴ or less.
The weight average molecular weight (Mw) of the polymer refers to a value calculated based on standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC device, for example, a model named "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

The glass transition temperature (Tg) of the BP polymer (A) is not particularly limited. The Tg of the BP polymer (A) may be, for example, -80°C or more and 150°C or less, -80°C or more and 50°C or less, or -80°C or more and 10°C or less. From the viewpoint of the step absorption of the photocurable adhesive layer (A), the Tg of the BP polymer (A) is suitably less than 0°C, preferably -10°C or less, may be -20°C or less, may be -30°C or less, may be -40°C or less, or may be -50°C or less. In addition, from the viewpoint of the cohesiveness of the photocurable adhesive layer (A) and improvement of the processability after photocuring, the Tg of the BP polymer (A) is usually advantageously -75°C or more, and may be -70°C or more. In some embodiments, the Tg of the BP polymer (A) may be -55°C or more, or may be -45°C or more. The Tg of BP polymer (A) can be adjusted by the type and amount of the monomer components that make up the BP polymer.

Here, the glass transition temperature (Tg) of a polymer refers to the glass transition temperature calculated by the Fox formula based on the composition of the monomer components constituting the polymer. The Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature (unit: K) of a homopolymer of monomer i.

The glass transition temperature of the homopolymer used in calculating Tg is a value described in a publicly known document. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
2-Ethylhexyl acrylate: -70°C
n-Butyl acrylate: -55°C
Isostearyl acrylate: -18°C
Methyl methacrylate: 105°C
Methyl acrylate: 8°C
Cyclohexyl acrylate: 15°C
N-vinyl-2-pyrrolidone: 54°C
2-Hydroxyethyl acrylate: -15°C
4-Hydroxybutyl acrylate: -40°C
Isobornyl acrylate: 94°C
Acrylic acid: 106°C
Methacrylic acid: 228°C

For the glass transition temperatures of homopolymers of monomers other than those listed above, the values listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) shall be used. If multiple values are listed in this document, the highest value shall be used. For monomers for which the glass transition temperature of homopolymers is not listed in the Polymer Handbook, the value obtained by the measurement method described in JP 2007-51271 A shall be used. For polymers for which the nominal value of the glass transition temperature is provided by the manufacturer, etc., that nominal value may be used.

BP polymer (A) preferably contains, for example, approximately 0.5 mg or more of benzophenone structures per 1 g of the polymer, calculated as 4-benzoylphenyl acrylate. Hereinafter, the number of benzophenone structures contained in 1 g of BP polymer converted into the amount of 4-benzoylphenyl acrylate may be referred to as the BP equivalent of the BP polymer (unit: mg/g). For example, when 40 μmol of benzophenone structures are contained per 1 g, the BP equivalent of the polymer is calculated to be 10 mg/g.

From the viewpoint of obtaining a higher photocuring effect (for example, the effect of increasing processability by photocuring), in some embodiments, the BP equivalent of the BP polymer (A) is usually appropriate to be 0.1 mg/g or more, and may be 0.5 mg/g or more, 1 mg/g or more, 5 mg/g or more, 8 mg/g or more, 10 mg/g or more, 15 mg/g or more, or 20 mg/g or more. In some embodiments, from the viewpoint of increasing the impact resistance and peel strength of the joint formed by the photocured product, the BP equivalent of the BP polymer (A) is usually appropriate to be 100 mg/g or less, and may be 80 mg/g or less, 60 mg/g or less, 40 mg/g or less, 25 mg/g or less, or 15 mg/g or less. The BP equivalent of the BP polymer (A) can be adjusted by the composition of the monomer components constituting the BP polymer (A).

In addition, from the viewpoint of reducing the peel strength by photocuring and enabling rework or repair, the BP equivalent is preferably 50 mg/g or more, and may be 100 mg/g or more.

The weight ratio of the BP polymer (A) in the entire pressure-sensitive adhesive composition (A), that is, the weight fraction of the BP polymer in the pressure-sensitive adhesive composition (A), is not particularly limited, and can be set so as to favorably balance the step absorption of the photocurable pressure-sensitive adhesive layer (A) and the processability of the photocured product. In some embodiments, the weight fraction of the BP polymer (A) may be, for example, 1 wt% or more, and is usually suitably 5 wt% or more, and may be 10 wt% or more, 15 wt% or more, 25 wt% or more, 35 wt% or more, 45 wt% or more, or 55 wt% or more. When the weight fraction of the BP polymer (A) increases, the G'a10/G'b85 described below tends to increase.
The pressure-sensitive adhesive composition (A) may have a weight fraction of the BP polymer (A) of substantially 100% by weight (e.g., 99.5% by weight or more). From the viewpoint of ease of adhesive performance, in some embodiments, the weight fraction of the BP polymer (A) in the pressure-sensitive adhesive composition (A) may be, for example, less than 99% by weight, less than 95% by weight, less than 85% by weight, less than 70% by weight, less than 50% by weight, or less than 40% by weight.

It is preferable that the adhesive composition (A) contains, for example, about 0.1 mg or more of the benzophenone structure in terms of 4-benzoylphenyl acrylate per 1 g of the adhesive composition (A). Hereinafter, the weight of the benzophenone structure contained per 1 g of the adhesive composition (A) in terms of 4-benzoylphenyl acrylate may be referred to as the BP equivalent (unit: mg/g) of the adhesive composition. From the viewpoint of obtaining a higher photocuring effect (for example, the effect of improving processability by photocuring), in some embodiments, the BP equivalent of the adhesive composition is usually appropriate to be 0.3 mg/g or more, and may be 0.5 mg/g or more, 1 mg/g or more, 5 mg/g or more, 10 mg/g or more, or 20 mg/g or more. In some embodiments, from the viewpoint of the impact resistance of the joint formed by the photocured product and the suppression of distortion within the photocured product, the BP equivalent of the pressure-sensitive adhesive composition is usually appropriate to be 100 mg/g or less, and may be 80 mg/g or less, 60 mg/g or less, 40 mg/g or less, 25 mg/g or less, or 15 mg/g or less.

[Ethylenically unsaturated compound (B)]
The adhesive composition (A) may further contain an ethylenically unsaturated compound (B) in addition to the BP polymer (A). When the adhesive composition (A) is a solventless type (active energy ray curable type) adhesive composition, the adhesive composition (A) preferably contains an ethylenically unsaturated compound (B). On the other hand, when the adhesive composition (A) is a solvent type or emulsion type adhesive composition, it does not need to contain an ethylenically unsaturated compound (B).

In addition, when the adhesive composition (A) contains a mixture of monomer components constituting the BP polymer (A) or a partial polymer of the mixture of monomer components constituting the BP polymer (A), the monomer components may contain the other ethylenically unsaturated compounds described above, and therefore the adhesive composition (A) does not necessarily need to contain the ethylenically unsaturated compound (B). When the adhesive composition (A) containing the mixture of monomer components or a partial polymer thereof contains an ethylenically unsaturated compound (B), the ethylenically unsaturated compound (B) may be the same as or different from the other ethylenically unsaturated compound described above.

Examples of compounds that can be used as the ethylenically unsaturated compound (B) include the above-mentioned (meth)acrylic acid alkyl esters and the above-mentioned ethylenically unsaturated BPs. Of these, it is preferable to use at least a (meth)acrylic acid alkyl ester (for example, a (meth)acrylic acid C _1-20 alkyl ester, more preferably a (meth)acrylic acid C _4-18 alkyl ester, and even more preferably an acrylic acid C _4-9 alkyl ester). Particularly preferable (meth)acrylic acid alkyl esters include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). Other specific examples of (meth)acrylic acid alkyl esters that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), and the like. The (meth)acrylic acid alkyl esters can be used alone or in combination of two or more. In some embodiments, the ethylenically unsaturated compound (B) preferably includes one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), and more preferably includes at least BA.

The ethylenically unsaturated compound (B) may contain 40% by weight or more of _C4-9 alkyl acrylate. The ratio of the _C4-9 alkyl acrylate in the monomer component may be, for example, 50% by weight or more, 60% by weight or more, or 65% by weight or more. In addition, from the viewpoint of increasing the cohesiveness of the photocurable pressure-sensitive adhesive layer (A), the ratio of the _C4-9 alkyl acrylate in the ethylenically unsaturated compound (B) is usually appropriate to be 99.5% by weight or less, and may be 95% by weight or less, 85% by weight or less, 70% by weight or less, or 60% by weight or less.

Other examples of compounds that can be used as the ethylenically unsaturated compound (B) include ethylenically unsaturated compounds (copolymerizable monomers) that are copolymerizable with (meth)acrylic acid alkyl esters. As the copolymerizable monomer, a monomer having a polar group (e.g., a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) can be suitably used. The monomer having a polar group can be useful, for example, for introducing a crosslinking point into a polymer containing a repeating unit derived from the monomer, or for increasing the cohesive strength of the photocurable adhesive layer (A). The copolymerizable monomers can be used alone or in combination of two or more.

Non-limiting examples of copolymerizable monomers include the following:
Carboxy group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.
Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride.
Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.
Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloylphosphate, and the like.
Epoxy group-containing monomers: for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl ether (meth)acrylate, allyl glycidyl ether, and glycidyl ether (meth)acrylate.
Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile, etc.
Isocyanate group-containing monomers: for example, 2-(meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, and the like.
Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)(meth)acrylamide; N-hydroxyalkyl (meth)acrylamides such as N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, and N-(4-hydroxybutyl) (meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl (meth)acrylamide such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; and others, N,N-dimethylaminopropyl (meth)acrylamide, N-(meth)acryloylmorpholine, and the like.
Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, etc. (for example, lactams such as N-vinyl-2-caprolactam).
Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, and the like.
Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, and the like.
Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and the like.
Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate.
Alkoxy group-containing monomers: for example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; alkoxyalkylene (meth)acrylates (for example, alkoxypolyalkylene glycol (meth)acrylates) such as methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.
Alkoxysilyl group-containing monomers: for example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane.
Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.
Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene, etc.
(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, (meth)acrylates containing an alicyclic hydrocarbon group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.
(Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, (meth)acrylates containing an aromatic hydrocarbon group such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate.
Other examples include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from alcohols derived from terpene compounds.

When such a copolymerizable monomer is used, the amount used is not particularly limited, but is usually appropriate to be 0.01% by weight or more of the total monomer components constituting the adhesive composition (A). From the viewpoint of better exerting the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used (i.e., the weight fraction of the copolymerizable monomer in the total monomer components) may be 0.1% by weight or more of the total monomer components, or may be 0.5% by weight or more. Also, from the viewpoint of easily balancing the adhesive properties, the amount of the copolymerizable monomer used is usually appropriate to be 50% by weight or less of the total monomer components, and preferably 40% by weight or less.

で表わされるＮ－ビニル環状アミドを用いることができる。ここで、一般式（１）中、Ｒ¹は２価の有機基であり、具体的には－（ＣＨ₂）_n－である。ｎは２～７（好ましくは２，３または４）の整数である。なかでも、Ｎ－ビニル－２－ピロリドンを好ましく採用し得る。窒素原子を有するモノマーの他の好適例としては、（メタ）アクリルアミドが挙げられる。 The copolymerizable monomer may include a monomer having a nitrogen atom. The use of a monomer having a nitrogen atom can increase the cohesive force of the photocurable pressure-sensitive adhesive layer (A) and favorably improve the peel strength after photocuring. A suitable example of a monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring. The monomer having a nitrogen atom-containing ring can be one of those exemplified above, and for example, a monomer represented by the general formula (1):

In the general formula (1), R ¹ is a divalent organic group, specifically, -(CH ₂ ) _n -. n is an integer of 2 to 7 (preferably 2, 3, or 4). Of these, N-vinyl-2-pyrrolidone is preferably used. Another suitable example of a monomer having a nitrogen atom is (meth)acrylamide.

When a monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring such as an N-vinyl cyclic amide) is used, the amount used is not particularly limited, and may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, or even 5% by weight or more or 7% by weight or more of the total monomer components. In one embodiment, the amount of the nitrogen atom-containing monomer used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer components. In addition, the amount of the nitrogen atom-containing monomer used is suitably, for example, 40% by weight or less of the total monomer components, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. In another embodiment, the amount of the nitrogen atom-containing monomer used may be, for example, 20% by weight or less, or 15% by weight or less of the total monomer components. Alternatively, the nitrogen atom-containing monomer may not be used as the copolymerizable monomer.

The copolymerizable monomer may include a hydroxyl group-containing monomer. By using the hydroxyl group-containing monomer, the cohesive strength of the photocurable adhesive layer (A) and the degree of crosslinking (for example, crosslinking by an isocyanate crosslinking agent) can be suitably adjusted. When using the hydroxyl group-containing monomer, the amount used is not particularly limited, and may be, for example, 0.01% by weight or more of the total monomer components, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 5% by weight or more, or 10% by weight or more. In addition, from the viewpoint of suppressing the water absorption of the photocurable adhesive layer (A) or its photocured product, in some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer components, and may be 30% by weight or less, 25% by weight or less, or 20% by weight or less. In another embodiment, the amount of the hydroxyl group-containing monomer used may be, for example, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer components. Alternatively, it is not necessary to use a hydroxyl group-containing monomer as the copolymerizable monomer.

The proportion of the carboxyl group-containing monomer in the total monomer components may be, for example, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less (for example, less than 0.1% by weight). The adhesive composition (A) may not substantially contain a carboxyl group-containing monomer as a constituent monomer component. Here, "substantially not containing a carboxyl group-containing monomer" means that a carboxyl group-containing monomer is not used at least intentionally. This can be advantageous from the viewpoint of the metal corrosion prevention properties of the photocurable adhesive layer (A) formed from the adhesive composition (A) and the photocured product thereof.

The copolymerizable monomer may contain an alicyclic hydrocarbon group-containing (meth)acrylate. This can increase the cohesive force of the photocurable adhesive layer (A) and improve the peel strength after photocuring. As the alicyclic hydrocarbon group-containing (meth)acrylate, the above-mentioned examples can be used, and for example, cyclohexyl acrylate and isobornyl acrylate can be preferably used. When using an alicyclic hydrocarbon group-containing (meth)acrylate, the amount used is not particularly limited, and can be, for example, 1% by weight or more, 3% by weight or more, or 5% by weight or more of the total monomer components. In one embodiment, the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used may be 10% by weight or more, or 15% by weight or more of the total monomer components. The upper limit of the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is suitably about 40% by weight or less, and may be, for example, 30% by weight or less, or 25% by weight or less (for example, 15% by weight or less, or even 10% by weight or less). Alternatively, it is not necessary to use an alicyclic hydrocarbon group-containing (meth)acrylate as the copolymerizable monomer.

The copolymerizable monomer may include an alkoxysilyl group-containing monomer. The alkoxysilyl group-containing monomer is typically an ethylenically unsaturated compound having at least one (preferably two or more, e.g., two or three) alkoxysilyl group in one molecule, and specific examples thereof are as described above. The alkoxysilyl group-containing monomer may be used alone or in combination of two or more. By using the alkoxysilyl group-containing monomer, a crosslinked structure can be introduced into the photocurable adhesive layer (A) by a condensation reaction of silanol groups (silanol condensation).

When an alkoxysilyl group-containing monomer is used, the amount of the alkoxysilyl group-containing monomer used is not particularly limited. In some embodiments, the amount of the alkoxysilyl group-containing monomer used can be, for example, 0.005% by weight or more of the total monomer components constituting the adhesive composition (A), and is usually appropriately set to 0.01% by weight or more, and may be 0.03% by weight or more, or may be 0.05% by weight or more. In addition, from the viewpoint of the step absorbency of the adhesive composition (A), the amount of the alkoxysilyl group-containing monomer used is usually appropriately set to 1.0% by weight or less of the total monomer components, and may be 0.5% by weight or less, or may be 0.1% by weight or less.

Further examples of compounds that can be used as the ethylenically unsaturated compound (B) include polyfunctional monomers. When a pressure-sensitive adhesive composition (A) containing a polyfunctional monomer is cured to produce a photocurable pressure-sensitive adhesive layer (A), the photocurable pressure-sensitive adhesive layer (A) crosslinked by the polyfunctional monomer can be obtained by reacting the polyfunctional monomer. Examples of the polyfunctional monomer include bifunctional monomers such as 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 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, allyl (meth)acrylate, vinyl (meth)acrylate, and divinylbenzene; trifunctional or higher polyfunctional monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; and others such as epoxy acrylate, polyester acrylate, and urethane acrylate. Among these, preferred examples include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The polyfunctional monomers can be used alone or in combination of two or more.

When a polyfunctional monomer is used, the amount of the polyfunctional monomer used is not particularly limited and can be less than 5.0% by weight of the total monomer components constituting the adhesive composition (A). This can avoid the formation of an excessive crosslinking structure during the formation of the photocurable adhesive layer (A) (i.e., at the stage before photocuring), and can improve the step absorption of the photocurable adhesive layer (A). The amount of the polyfunctional monomer used may be, for example, 4.0% by weight or less of the total monomer components, 3.0% by weight or less, 2.0% by weight or less, 1.0% by weight or less, 0.5% by weight or less, or 0.3% by weight or less. The polyfunctional monomer may not be used. In some embodiments, from the viewpoint of imparting appropriate cohesiveness to the photocurable adhesive layer (A), the amount of the polyfunctional monomer used relative to the total monomer components may be, for example, 0.001% by weight or more, 0.005% by weight or more, 0.01% by weight or more, or 0.03% by weight or more.

The weight ratio of the BP polymer (A) to the total amount of the BP polymer (A) and the ethylenically unsaturated compound (B) contained in the adhesive composition (A) is not particularly limited, and can be set so as to provide a good balance between the step absorption of the photocurable adhesive layer (A) formed from the adhesive composition (A) and the processability of the photocured product. In some embodiments, the weight fraction of the BP polymer (A) may be, for example, 0.5% by weight or more, and is usually 1% by weight or more, preferably 1.5% by weight or more, and more preferably 5% by weight or more. From the viewpoint of enhancing the effect of photocuring, it may be 10% by weight or more, 15% by weight or more, 25% by weight or more, 35% by weight or more, 45% by weight or more, or 55% by weight or more. In addition, from the viewpoint of ease of preparation and coatability of the pressure-sensitive adhesive composition (A), in some embodiments, the weight ratio of the BP polymer (A) to the total amount may be, for example, less than 99% by weight, less than 95% by weight, less than 85% by weight, less than 70% by weight, less than 50% by weight, or less than 40% by weight.

The weight ratio of the organic solvent to the total weight of the pressure-sensitive adhesive composition (A) may be, for example, 30% by weight or less, advantageously 20% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. In some embodiments, the weight ratio of the organic solvent may be 3% by weight or less, 1% by weight or less, 0.5% by weight or less, 0.1% by weight or less, 0.05% by weight or less, or may be substantially free of organic solvent.

From the viewpoint of coatability in the above-mentioned normal temperature range, the viscosity of the adhesive composition (A) is suitably 1000 Pa·s or less, preferably 100 Pa·s or less, and more preferably 50 Pa·s or less (measured with a BH type viscometer, No. 5 rotor, 10 rpm, and measuring temperature 30°C; the same applies below). The viscosity of the adhesive composition (A) may be, for example, 30 Pa·s or less, 20 Pa·s or less, 10 Pa·s or less, or 5 Pa·s or less. The lower limit of the viscosity of the adhesive composition (A) is not particularly limited, but from the viewpoint of suppressing repelling of the adhesive composition within the coating range and overflow of the adhesive composition at the outer edge of the coating range, it is usually suitable to be 0.1 Pa·s or more, and may be 0.5 Pa·s or more, or may be 1 Pa·s or more.

The pressure-sensitive adhesive composition (A) contains at least a compound having one ethylenically unsaturated group (i.e., a monofunctional monomer) (B1) as the ethylenically unsaturated compound (B). The monofunctional monomer (B1) can be selected from the examples of the ethylenically unsaturated compound (B) described above. The monofunctional monomer can be used alone or in combination of two or more kinds.

The weight ratio of the monofunctional monomer (B1) in the total amount of the BP polymer (A) and the ethylenically unsaturated compound (B) may be, for example, 1% by weight or more, 5% by weight or more, or 15% by weight or more. In some embodiments, from the viewpoint of the ease of preparation and coatability of the pressure-sensitive adhesive composition (A), the weight ratio of the monofunctional monomer (B1) may be 25% by weight or more, 35% by weight or more, or 45% by weight or more. In addition, the weight ratio of the monofunctional monomer (B1) in the total amount may be, for example, 99% by weight or less, and is usually suitably 95% by weight or less, and may be 85% by weight or less, 75% by weight or less, 65% by weight or less, 55% by weight or less, or 45% by weight or less.

In an embodiment in which the adhesive composition (A) contains a monofunctional monomer (B1), the glass transition temperature (Tg) calculated by the Fox formula based on the composition of the monofunctional monomer (B1) is not particularly limited and may be, for example, -80°C or more and 250°C or less. From the viewpoint of compatibility between the polymer derived from the monofunctional monomer (B1) and other components, the Tg based on the composition of the monofunctional monomer (B1) is usually preferably 150°C or less, may be 100°C or less, may be 70°C or less, may be 50°C or less, or may be 30°C or less. In some embodiments, from the viewpoint of step absorption of the photocurable adhesive layer (A), the Tg based on the composition of the monofunctional monomer (B1) is preferably less than 0°C, more preferably -10°C or less, may be -20°C or less, may be -30°C or less, or may be -40°C or less. In addition, from the viewpoint of the cohesiveness of the photocurable adhesive layer (A) and the processability after photocuring, the Tg based on the composition of the monofunctional monomer (B1) is usually advantageously -60°C or higher, and may be -54°C or higher, -50°C or higher, -45°C or higher, -35°C or higher, or -25°C or higher. The above Tg can be adjusted by the compounds used as the monofunctional monomers and the ratio of their amounts used.

In the pressure-sensitive adhesive composition (A) containing the BP polymer (A) and the monofunctional monomer (B1), the photocurable pressure-sensitive adhesive layer (A) formed from the pressure-sensitive adhesive composition, and the photocured product thereof, the Tg of the BP polymer (A) (hereinafter referred to as "Tg _A ") and the Tg based on the monomer composition of the monofunctional monomer (B1) (hereinafter also referred to as "Tg _B1 ") can be set so that the Tg difference [°C] (hereinafter also referred to as ΔTg) calculated by Tg _B1 [°C] - Tg _A [°C] is, for example, in the range of -50°C or more and 70°C or less. It can be advantageous from the viewpoint of compatibility in the photocurable pressure-sensitive adhesive layer (A) and the photocured product thereof if the absolute value of the Tg difference is not too large. In some embodiments, ΔTg may be, for example, -10°C or more, preferably 0°C or more, 7°C or more, 10°C or more, 20°C or more, or 30°C or more.

The pressure-sensitive adhesive composition (A) may contain at least a compound having two or more ethylenically unsaturated groups (i.e., a polyfunctional monomer) (B2) as the ethylenically unsaturated compound (B). The polyfunctional monomer (B2) may be one type alone or two or more types in combination from the examples of polyfunctional monomers listed above. The amount of polyfunctional monomer (B2) used may be set to the same ratio as the proportion of the polyfunctional monomer in the total monomer components constituting the pressure-sensitive adhesive composition (A).

In an embodiment in which a monofunctional monomer (B1) and a polyfunctional monomer (B2) are used in combination as the ethylenically unsaturated compound (B), the weight ratio of the monofunctional monomer (B1) in the ethylenically unsaturated compound (B) may be, for example, 1% by weight or more, and is usually 25% by weight or more, and may be 50% by weight or more, 75% by weight or more, 95% by weight or more, or 99% by weight or more. In addition, the weight ratio of the monofunctional monomer (B1) in the ethylenically unsaturated compound (B) may be, for example, 99.9% by weight or less, or 99.8% by weight or less.

In the pressure-sensitive adhesive composition (A), the ethylenically unsaturated compound (B) may be contained in the form of a partial polymer, or the entire amount may be contained in the form of an unreacted monomer. The pressure-sensitive adhesive composition (A) according to a preferred embodiment contains the ethylenically unsaturated compound (B) in the form of a partial polymer. The polymerization method for partially polymerizing the ethylenically unsaturated compound (B) is not particularly limited, and various conventionally known polymerization methods such as photopolymerization performed by irradiating with light such as ultraviolet rays; radiation polymerization performed by irradiating with radiation such as β rays and γ rays; and thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization can be appropriately selected and used. From the viewpoints of efficiency and simplicity, the photopolymerization method can be preferably adopted. According to photopolymerization, the polymerization conversion rate (monomer conversion) can be easily controlled by polymerization conditions such as the amount of light irradiation (light amount).

The polymerization conversion rate of the ethylenically unsaturated compound (B) in the partial polymer is not particularly limited. From the viewpoint of ease of preparation and coatability of the pressure-sensitive adhesive composition (A), the polymerization conversion rate is usually about 50% by weight or less, and preferably about 40% by weight or less (e.g., about 35% by weight or less). There is no particular lower limit to the polymerization conversion rate, but it is typically about 1% by weight or more, and usually about 5% by weight or more.

The adhesive composition (A) containing the partial polymer of the ethylenically unsaturated compound (B) can be obtained, for example, by partially polymerizing a monomer mixture containing the entire amount of the ethylenically unsaturated compound (B) used in the preparation of the adhesive composition by an appropriate polymerization method (for example, photopolymerization method). The adhesive composition (A) containing the partial polymer of the ethylenically unsaturated compound (B) may also be a mixture of a partial polymer of a monomer mixture containing a part of the ethylenically unsaturated compound (B) used in the preparation of the adhesive composition and the remaining ethylenically unsaturated compound (B) or a partial polymer thereof. In this specification, the term "completely polymerized product" refers to a polymerization conversion rate of more than 95% by weight.

The partial polymer can be prepared, for example, by irradiating the ethylenically unsaturated compound (B) with ultraviolet light. When the partial polymer is prepared in the presence of the BP polymer (A), the ethylenically unsaturated groups are reacted and the ultraviolet light irradiation conditions are set so that the benzophenone structure is not photoexcited, thereby obtaining a pressure-sensitive adhesive composition (A) containing a partial polymer of the ethylenically unsaturated compound (B) and the BP polymer (A). As the light source, a light source capable of irradiating ultraviolet light that does not contain components with wavelengths of less than 300 nm or that contains only a small amount of such components, such as the above-mentioned black light and UV-LED lamp, can be preferably used.

Alternatively, a partial polymer of the ethylenically unsaturated compound (B) may be prepared in advance, and then the partial polymer may be mixed with the BP polymer (A) to prepare the pressure-sensitive adhesive composition (A). When the partial polymer is prepared by irradiating the ethylenically unsaturated compound (B) with ultraviolet light in the absence of a benzophenone structure-containing component, the ultraviolet light source may be either a light source that does not excite the benzophenone structure or a light source that does excite the benzophenone structure.

In preparing the partial polymer of the ethylenically unsaturated compound (B), a photopolymerization initiator can be used to promote the reaction of the ethylenically unsaturated group. As the photopolymerization initiator, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, an alkylphenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, or the like can be used. A photopolymerization initiator that absorbs light with a wavelength of 300 nm or more (for example, light with a wavelength of 300 nm or more and 500 nm or less) to generate radicals can be preferably used. The photopolymerization initiator can be used alone or in appropriate combination of two or more types.

[Photopolymerization initiator]
The adhesive composition (A) may contain a photopolymerization initiator as necessary for the purpose of improving or imparting photocurability. When the adhesive composition (A) is a solventless (active energy ray curable) adhesive composition, the adhesive composition (A) preferably contains a photopolymerization initiator. On the other hand, when the adhesive composition (A) is a solvent-type or emulsion-type adhesive composition, the adhesive composition (A) may not contain a photopolymerization initiator.

As the photopolymerization initiator, ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, alkylphenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, etc. can be used. The photopolymerization initiators can be used alone or in appropriate combination of two or more.

Specific examples of ketal-based photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one and the like.
Specific examples of acetophenone-based photopolymerization initiators include 1-hydroxycyclohexyl-phenyl-ketone, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, and the like.
Specific examples of the benzoin ether-based photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acylphosphine oxide photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like.
Specific examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like.
Specific examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride.
Specific examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime.
Specific examples of benzoin-based photopolymerization initiators include benzoin.
Specific examples of benzyl photoinitiators include benzyl and the like.
Specific examples of the benzophenone-based photopolymerization initiator include benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like.
Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

As the photopolymerization initiator contained in the adhesive composition (A), a photopolymerization initiator (sometimes referred to as "photopolymerization initiator (C)") that absorbs light with a wavelength of 300 nm or more (for example, light with a wavelength of 300 nm or more and 500 nm or less) and generates radicals can be preferably used. When the adhesive composition (A) contains the photopolymerization initiator (C), it is preferable to cure the adhesive composition (A) into a cured product that retains the benzophenone structure of the BP polymer (A).

The photopolymerization initiator may be used alone or in appropriate combination of two or more. In some embodiments, a photopolymerization initiator that does not contain a phosphorus element in the molecule may be preferably used. The pressure-sensitive adhesive composition (A) may be substantially free of a photopolymerization initiator that contains a phosphorus element in the molecule.

The content of the photopolymerization initiator in the adhesive composition (A) is not particularly limited and can be set so that the desired effect is appropriately exhibited. In some embodiments, the content of the photopolymerization initiator can be, for example, approximately 0.005 parts by weight or more relative to 100 parts by weight of the monomer components constituting the adhesive composition (A), and is usually appropriate to be 0.01 parts by weight or more, preferably 0.05 parts by weight or more, may be 0.10 parts by weight or more, may be 0.15 parts by weight or more, or may be 0.20 parts by weight or more. By increasing the content of the photopolymerization initiator, the photocurability of the adhesive composition (A) is improved. In addition, the content of the photopolymerization initiator relative to 100 parts by weight of the monomer components constituting the adhesive composition (A) is usually appropriate to be 5 parts by weight or less, preferably 2 parts by weight or less, may be 1 part by weight or less, may be 0.7 parts by weight or less, or may be 0.5 parts by weight or less. It may be advantageous from the viewpoint of suppressing gelation of the adhesive composition (A) when the content of the photopolymerization initiator is not too high.

[Crosslinking agent]
The adhesive composition (A) may contain a known crosslinking agent, such as an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, a melamine crosslinking agent, a urea crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, a hydrazine crosslinking agent, or an amine crosslinking agent, if necessary. Peroxide may be used as the crosslinking agent. When the adhesive composition (A) is a solvent-based or emulsion-based adhesive composition, it is preferable to contain a crosslinking agent.

The above crosslinking agents can be used alone or in combination of two or more. The photocurable adhesive layer (A) formed from the adhesive composition (A) containing the crosslinking agent preferably contains the crosslinking agent mainly in the form after the crosslinking reaction. By using the crosslinking agent, the cohesive strength, etc. of the photocurable adhesive layer (A) can be appropriately adjusted.

When a crosslinking agent is used, the amount used (the total amount when two or more crosslinking agents are used) is not particularly limited. From the viewpoint of realizing an adhesive that exhibits adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, the amount of the crosslinking agent used is usually about 5 parts by weight or less relative to 100 parts by weight of the monomer components constituting the adhesive composition (A), and may be 3 parts by weight or less, 1 part by weight or less, 0.50 parts by weight or less, 0.30 parts by weight or less, or 0.20 parts by weight or less. The lower limit of the amount of the crosslinking agent used is not particularly limited, and may be more than 0 parts by weight relative to 100 parts by weight of the monomer components constituting the adhesive composition (A). In some embodiments, the amount of the crosslinking agent used may be, for example, 0.001 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.10 parts by weight or more relative to 100 parts by weight of the monomer components constituting the adhesive composition (A).

[Chain transfer agent]
The pressure-sensitive adhesive composition (A) may contain various conventionally known chain transfer agents. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol may be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. Specific 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; styrenes such as α-methylstyrene and α-methylstyrene dimer; compounds having a benzylidene group such as dibenzylideneacetone, cinnamyl alcohol, and cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; olefins such as 2,3-dimethyl-2-butene and 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene; and the like. The chain transfer agent can be used alone or in combination of two or more. When a chain transfer agent is used, the amount of the agent used can be, for example, about 0.01 to 1 part by weight based on 100 parts by weight of the monomer component. An embodiment in which no chain transfer agent is used can also be preferably carried out.

Other components that may be included in the adhesive composition (A) include a silane coupling agent. Use of a silane coupling agent can improve the peel strength from an adherend (e.g., a glass plate). In addition, the photocurable adhesive layer (A) may contain a silane coupling agent. The photocurable adhesive layer (A) containing a silane coupling agent can be suitably formed using the adhesive composition (A) containing a silane coupling agent. The silane coupling agents may be used alone or in combination of two or more.

The adhesive composition (A) may contain, as necessary, various additives commonly used in the field of adhesives, such as tackifier resins (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based, etc. tackifier resins), viscosity modifiers (e.g., thickeners), leveling agents, antioxidants, plasticizers, fillers, stabilizers, preservatives, and antiaging agents, as other optional components. As for such various additives, those conventionally known can be used in the usual manner, and detailed explanations are omitted since they do not particularly characterize the present invention.

The adhesive composition (A) can exhibit good adhesive strength without using the above-mentioned tackifier resin. Therefore, in some embodiments, the content of the tackifier resin in the photocurable adhesive layer (A) or the adhesive composition (A) can be, for example, less than 10 parts by weight, or even less than 5 parts by weight, relative to 100 parts by weight of the monomer component. The content of the tackifier resin may be less than 1 part by weight (for example, less than 0.5 parts by weight), or may be less than 0.1 parts by weight (0 parts by weight or more and less than 0.1 parts by weight). The photocurable adhesive layer (A) or the adhesive composition (A) may not contain a tackifier resin.

[Photocurable adhesive layer (A)]
The photocurable adhesive layer (A) is a cured product of the adhesive composition (A) and is formed by a cured product with a benzophenone structure remaining. This benzophenone structure can form a crosslinked structure by ultraviolet irradiation to cure the photocurable adhesive layer (A). The photocurable adhesive layer (A) before curing is in a semi-cured state with high fluidity and exhibits excellent step absorption. Therefore, when the photocurable adhesive layer (A) of the photocurable adhesive sheet (A) is bonded to a display panel in which light-emitting elements (LED chips) are densely arranged, it sufficiently follows the fine steps between the light-emitting elements (LED chips) and adheres without gaps without leaving any air bubbles. On the other hand, the photocurable adhesive layer (A) after curing exhibits excellent processability. Therefore, the occurrence of glue chipping during cutting processing of a laminate including the photocurable adhesive layer (A) after curing and the occurrence of protrusion or sagging of the adhesive layer from the edge during storage are suppressed. In this way, the photocurable pressure-sensitive adhesive layer (A) constituted by the cured product of the pressure-sensitive adhesive composition (A) can suitably achieve both excellent level difference absorbency and processability.

The method for producing the photocurable adhesive layer (A) is not particularly limited, but it can be produced, for example, by irradiating the adhesive composition (A) with active energy rays, drying by heating, etc. Specifically, the adhesive composition (A) is applied (coated) onto a substrate or a release liner, and, if necessary, dried, cured, or dried and cured.

A known coating method may be used to apply (coat) the adhesive composition (A). For example, a coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, or direct coater may be used.

When the pressure-sensitive adhesive composition (A) is cured by irradiation with active energy rays, it is preferable to carry out the curing so as to react the ethylenically unsaturated groups contained in the pressure-sensitive adhesive composition (A) and to leave the benzophenone structure contained in the photocurable pressure-sensitive adhesive layer (A). As the active energy rays for forming the photocurable pressure-sensitive adhesive layer (A), ultraviolet rays are preferable, and ultraviolet rays that do not contain components with wavelengths of less than 300 nm or that contain only a small amount of such components are more preferable.

When the adhesive composition (A) contains a BP polymer (A) and an ethylenically unsaturated compound (B), the photocurable adhesive layer (A) may contain a BP polymer (A) and a polymer (E) derived from the ethylenically unsaturated compound (B). In this embodiment, the adhesive composition (A) may have a composition in which the ethylenically unsaturated compound (B) does not contain an ethylenically unsaturated BP. According to the adhesive composition (A) of such a composition, a photocurable adhesive layer (A) can be produced that contains a BP polymer (A) and a polymer (E) derived from the ethylenically unsaturated compound (B), and the polymer (E) is a polymer that does not have a benzophenone structure (sometimes referred to as a "non-BP polymer").

On the other hand, when the pressure-sensitive adhesive composition (A) contains a mixture of monomer components constituting the BP polymer (A) or a partial polymer of the mixture of monomer components, the photocurable pressure-sensitive adhesive layer (A) may be a photocurable pressure-sensitive adhesive layer containing two or more polymers having different monomer compositions, at least one of which has a benzophenone structure in its side chain (sometimes referred to as "BP polymer (A')"). The photocurable pressure-sensitive adhesive layer may contain only two or more BP polymers (A') as the two or more polymers, or may contain a combination of a non-BP polymer and a BP polymer (A'). The non-BP polymer may be formed by using a pressure-sensitive adhesive composition containing an ethylenically unsaturated compound that does not have a benzophenone structure and polymerizing the ethylenically unsaturated compound. The BP polymer (A') may be, for example, the BP polymer (A) contained in the above-mentioned pressure-sensitive adhesive composition (A), or may be a modified product thereof, or may be formed by copolymerizing the ethylenically unsaturated BP contained in the above-mentioned pressure-sensitive adhesive composition (A) with another ethylenically unsaturated compound.
The two or more polymers may be chemically bonded or not. The photocurable pressure-sensitive adhesive layer (A) according to some embodiments may contain at least one BP polymer in a form that is not chemically bonded to any polymer other than the BP polymer.

The irradiation of active energy rays for curing the adhesive composition (A) is preferably carried out so as to react the ethylenically unsaturated groups and leave the benzophenone structure. As the adhesive composition (A), an adhesive composition containing a BP polymer (A) and an ethylenically unsaturated compound (B) can be preferably used. As a light source for curing the adhesive composition (A) to form a photocrosslinkable adhesive, a light source capable of irradiating ultraviolet light that does not contain components with wavelengths of less than 300 nm or has a small amount of such components, such as the above-mentioned black light and UV-LED lamp, can be preferably used.

In a preferred embodiment of the present invention, the photocurable adhesive layer (A) has a maximum transmittance of 200 to 400 nm (preferably 330 to 400 nm) greater than the maximum transmittance of 400 to 700 nm. The photocurable adhesive layer (A), which has excellent light-shielding properties against visible light, seals the minute steps between the metal wiring layer and the light-emitting element (LED chip) of the self-luminous display device (mini/micro LED display device) without any gaps, thereby preventing reflection due to metal wiring, preventing color mixing of the light-emitting element (LED chip), and improving the contrast of the image. On the other hand, the photocurable adhesive layer (A), which has a high transmittance in the ultraviolet region (200 to 400 nm, preferably 330 to 400 nm), improves processability by curing the benzophenone structure by forming a crosslinked structure when irradiated with ultraviolet light, thereby suppressing glue chipping during cutting processing and protrusion or sagging of the adhesive layer from the edge during storage.

In a preferred embodiment of the present invention, the maximum transmittance of the photocurable adhesive layer (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

In a preferred embodiment of the present invention, the photocurable adhesive layer (A) has an average transmittance at wavelengths of 200 to 400 nm (preferably 330 to 400 nm) that is greater than the average transmittance at wavelengths of 400 to 700 nm. The average transmittance of the photocurable adhesive layer (A) at wavelengths of 400 to 700 nm (visible light region) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

The photocurable adhesive layer (A) preferably contains, for example, about 0.1 mg or more of a benzophenone structure in terms of 4-benzoylphenyl acrylate per 1 g of the adhesive layer. Hereinafter, the weight of the benzophenone structure contained in 1 g of the photocurable adhesive layer (A) in terms of 4-benzoylphenyl acrylate may be referred to as the BP equivalent (unit: mg/g) of the adhesive layer. From the viewpoint of obtaining a higher photocuring effect (for example, the effect of improving processability by photocuring), the BP equivalent of the adhesive layer is usually appropriate to be 0.3 mg/g or more, and may be 0.5 mg/g or more, 1 mg/g or more, 5 mg/g or more, 10 mg/g or more, or 20 mg/g or more. In addition, from the viewpoint of the impact resistance of the joint formed by the photocured product and suppression of distortion within the photocured product, the BP equivalent of the adhesive layer is usually appropriate to be 100 mg/g or less, and may be 80 mg/g or less, 60 mg/g or less, 40 mg/g or less, 25 mg/g or less, or 15 mg/g or less.

(Storage Modulus)
The storage modulus (G'b85) at 85 ° C. of the photocurable pressure-sensitive adhesive layer (A) before curing is not particularly limited, but may be, for example, less than 65 kPa, more preferably 60 kPa or less, even more preferably 55 kPa or less, particularly preferably 50 kPa or less, and even more preferably 45 kPa or less. Such a configuration is preferable in terms of achieving excellent step absorption of the photocurable pressure-sensitive adhesive layer (A) before curing. In addition, G'b85 is not particularly limited, but from the viewpoint of handleability and workability, it is, for example, preferably 5 kPa or more, more preferably 10 kPa or more, and even more preferably 15 kPa or more. The storage modulus (G'b85) at 85°C of the photocurable pressure-sensitive adhesive layer (A) before curing can be adjusted by the composition of the pressure-sensitive adhesive composition (A) (e.g., Mw and Tg of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional groups; type and amount of crosslinking agent), etc.

The storage modulus (G'a10) at 10 ° C. of the cured photocurable adhesive layer (A) is not particularly limited, but may be, for example, preferably 90 kPa or more, more preferably 100 kPa or more, more preferably 110 kPa or more, more preferably 120 kPa or more, more preferably 130 kPa or more, more preferably greater than 146 kPa, more preferably 180 kPa or more, even more preferably 200 kPa or more, particularly preferably 250 kPa or more, even more preferably 300 kPa or more, or even 350 kPa or more. Such a configuration is preferable in terms of achieving excellent processability of the cured photocurable adhesive layer (A). In addition, G'a10 is not particularly limited, but from the viewpoint of adhesion reliability, it is, for example, 5000 kPa or less, preferably 2500 kPa or less, more preferably 1000 kPa or less. The storage modulus (G'a10) at 10°C of the cured photocurable adhesive layer (A) can be adjusted by the composition of the adhesive composition (A) (e.g., Mw, Tg, and BP equivalent of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional groups; type and amount of crosslinking agent), etc.

The ratio (G'a10/G'b85) of the storage modulus (G'a10) of the photocurable adhesive layer (A) at 10°C after curing to the storage modulus (G'b85) of the photocurable adhesive layer (A) at 85°C before curing is not particularly limited, but may be, for example, preferably greater than 2.8, more preferably greater than 2.9, even more preferably greater than 3, particularly preferably greater than 3.1, even greater than 3.2, greater than 3.3, greater than 3.4, greater than 3.5, greater than 3.6, greater than 3.7, greater than 3.8, greater than 3.9, greater than 4, greater than 5, greater than 6, greater than 7, greater than 8, greater than 9, greater than 10, greater than 11, or greater than 11. Such a configuration is preferable in that it can achieve both excellent step absorption of the photocurable adhesive layer (A) before curing and excellent processability of the photocurable adhesive layer (A) after curing. In addition, G'a10/G'b85 is not particularly limited, but is preferably 100 or less, more preferably 50 or less, and even more preferably 30 or less, from the viewpoint of handling, workability, and adhesion reliability. The ratio (G'a10/G'b85) of the storage modulus (G'a10) of the photocurable adhesive layer (A) at 10 ° C. after curing to the storage modulus (G'b85) of the photocurable adhesive layer (A) at 85 ° C. before curing can be adjusted by the composition of the adhesive composition (A) (for example, Tg, Mw, BP equivalent of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional group; type and amount of crosslinking agent), etc.

The storage modulus (G'b10) of the photocurable adhesive layer (A) at 10°C before curing is not particularly limited, but from the viewpoint of handling and workability, it is preferably 10 kPa or more, more preferably 50 kPa or more, and even more preferably 70 kPa or more, or 90 kPa or more, or 100 kPa or more. In addition, G'b10 is not particularly limited, but from the viewpoint of adhesion reliability, it is, for example, 5000 kPa or less, preferably 2500 kPa or less, and more preferably 1000 kPa or less. The storage modulus (G'b10) of the photocurable adhesive layer (A) at 10°C before curing can be adjusted by the composition of the adhesive composition (A) (for example, Mw and Tg of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional group; type and amount of crosslinking agent), etc.

The storage modulus (G'a85) of the cured photocurable adhesive layer (A) at 85°C is not particularly limited, but is preferably 10 kPa or more, preferably 20 kPa or more, and more preferably 30 kPa or more, from the viewpoint of handling and workability. G'a85 is not particularly limited, but is, for example, 1000 kPa or less, preferably 500 kPa or less, and more preferably 200 kPa or less, from the viewpoint of adhesion reliability. The storage modulus (G'a85) of the cured photocurable adhesive layer (A) at 85°C can be adjusted by the composition of the adhesive composition (A) (e.g., Mw, Tg, and BP equivalent of the BP polymer (A); the weight fraction of the BP polymer (A); the composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), the type and amount of the functional group; the type and amount of the crosslinking agent), etc.

The storage modulus (G'a25) of the cured photocurable adhesive layer (A) at 25°C is not particularly limited, but is, for example, preferably 70 kPa or more, more preferably greater than 100 kPa, more preferably 150 kPa or more, and even more preferably 170 kPa or more. Such a configuration is preferable in terms of achieving excellent processability of the cured photocurable adhesive layer (A). In addition, G'a25 is not particularly limited, but is, for example, 5000 kPa or less, preferably 2500 kPa or less, more preferably 1000 kPa or less, from the viewpoint of adhesion reliability. The storage modulus (G'a25) at 25°C of the cured photocurable adhesive layer (A) can be adjusted by the composition of the adhesive composition (A) (e.g., Mw, Tg, and BP equivalent of the BP polymer (A); the weight fraction of the BP polymer (A); the composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), the type and amount of functional groups; the type and amount of the crosslinking agent), etc.

The storage modulus (G'b25) of the photocurable adhesive layer (A) at 25°C before curing is not particularly limited, but is, for example, 300 kPa or less, preferably 250 kPa or less, and more preferably 200 kPa or less. Such a configuration is preferable in terms of achieving excellent step absorption of the photocurable adhesive layer (A) before curing. In addition, G'b25 is not particularly limited, but is, for example, preferably 10 kPa or more, more preferably 30 kPa or more, and even more preferably 50 kPa or more, from the viewpoint of adhesion reliability. The storage modulus (G'b25) of the photocurable adhesive layer (A) at 25°C before curing can be adjusted by the composition of the adhesive composition (A) (for example, Mw and Tg of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional group; type and amount of crosslinking agent), etc.

The ratio (G'a25/G'b85) of the storage modulus (G'a25) of the cured adhesive layer A at 25°C to the storage modulus (G'b85) of the photocurable adhesive layer (A) at 85°C before curing is not particularly limited, but is preferably 0.3 or more, more preferably 0.5 or more, more preferably 1 or more, more preferably greater than 3, preferably 3.5 or more, more preferably 4 or more. Such a configuration is preferable in that it can achieve both excellent step absorption properties of the adhesive layer A before curing and excellent processability of the adhesive layer A after curing. In addition, G'a25/G'b85 is not particularly limited, but is, for example, 100 or less, preferably 50 or less, more preferably 30 or less, from the viewpoint of handleability, workability, and adhesion reliability. The ratio (G'a25/G'b85) of the storage modulus (G'a25) of the cured adhesive layer A at 25°C to the storage modulus (G'b85) of the photocurable adhesive layer (A) at 85°C before curing can be adjusted by the composition of the adhesive composition (A) (e.g., Mw, Tg, BP equivalent of the BP polymer (A); weight fraction of the BP polymer (A); composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), type and amount of functional groups; type and amount of crosslinking agent), etc.

The curing conditions in the above-mentioned "cured photocurable adhesive layer (A)" are not particularly limited, but ultraviolet light through which the adhesive layer (A) exhibits transparency is preferred. More preferably, ultraviolet light with a wavelength of 200 to 400 nm is used, and even more preferably, ultraviolet light with a wavelength of less than 300 nm is used. As a light source for irradiating ultraviolet light, for example, a high pressure mercury lamp, a low pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light, or an LED can be used. In addition, the irradiation energy, irradiation time, and irradiation method of the radiation for curing can be appropriately set as long as the photocurable adhesive layer (A) can be cured and the adherend is not unduly affected. For example, when ultraviolet light is used as the radiation for curing, the irradiation amount (accumulated light amount) is preferably 1000 mJ/cm ² to 10000 mJ/cm ² , more preferably 2000 mJ/cm ² to 4000 mJ/cm ² , and even more preferably 3000 mJ/cm ² .
The storage modulus is measured by dynamic viscoelasticity measurement.

[VOC emission amount]
The amount of VOC (volatile organic compounds) emitted from the photocurable pressure-sensitive adhesive layer (A) is not particularly limited. The amount of VOC emitted may be, for example, 5000 μg/g or less, 3000 μg/g or less, or 1000 μg/g or less. In some embodiments, the amount of VOC emitted from the photocurable pressure-sensitive adhesive layer (A) is preferably 500 μg/g or less, more preferably 300 μg/g or less, and even more preferably 100 μg/g or less. A photocurable pressure-sensitive adhesive layer (A) having a low amount of VOC emitted is low odor and is preferable from the viewpoint of environmental hygiene. A low amount of VOC emitted from the photocurable pressure-sensitive adhesive layer (A) is also preferable from the viewpoint of foaming suppression caused by volatile organic compounds (VOCs) in the photocurable pressure-sensitive adhesive layer (A) and low contamination. The VOC emission amount of the photocurable pressure-sensitive adhesive layer (A) is measured by the following method using an appropriate amount (e.g., about 1 mg to 2 mg) of the photocurable pressure-sensitive adhesive layer (A) as a measurement sample. The thickness of the measurement sample is preferably 1 mm or less.

[VOC measurement test]
The measurement sample is placed in a 20 mL vial and sealed. Next, the vial is heated at 80° C. for 30 minutes, and 1.0 mL of the heated gas (sample gas) is injected into a gas chromatograph (GC) measurement device using a headspace autosampler (HSS). Based on the obtained gas chromatogram, the amount of gas generated from the measurement sample is calculated as an n-decane equivalent. From the obtained value, the amount of VOC emitted per 1 g of the measurement sample (μg/g) is calculated. Note that this n-decane equivalent is calculated by considering the detection intensity of the generated gas obtained by GC Mass as the detection intensity of n-decane and applying a calibration curve of n-decane created in advance. The settings of the HSS and GC are as follows.
HSS: Agilent Technologies, model number "7694"
Heating time: 30 min Pressurization time: 0.12 min Loop filling time: 0.12 min Loop equilibration time: 0.05 min Injection time: 3 min Sample loop temperature: 160° C.
Transfer line temperature: 200°C
GC device: Manufactured by Agilent Technologies, model “6890”
Column: GL Sciences J&W Capillary Column, product name "DB-ffAP" (inner diameter 0.533 mm x length 30 m, film thickness 1.0 μm)
Column temperature: 250°C (heat from 40°C to 90°C at 10°C/min, then heat to 250°C at 20°C/min and hold for 5 minutes)
Column pressure: 24.3 kPa (constant flow mode)
Carrier gas: Helium (5.0 mL/min)
Inlet: Split (split ratio 12:1)
Inlet temperature: 250℃
Detector: FID
Detector temperature: 250°C

In general, volatile organic compounds that can be a factor in increasing the VOC emission amount of a pressure-sensitive adhesive include organic solvents (e.g., residues of organic solvents contained in the pressure-sensitive adhesive composition (A)) and unreacted ethylenically unsaturated compounds contained in the pressure-sensitive adhesive composition (e.g., unpolymerized acrylic monomers, hereinafter also referred to as "residual monomers"). The photocurable pressure-sensitive adhesive layer (A) can have such organic solvents and residual monomers contained therein suppressed to a level that satisfies any of the above-mentioned VOC emission amounts. Although the photocurable pressure-sensitive adhesive layer (A) has such a configuration in which the amount of residual monomers is limited, it can form new crosslinks in the system by utilizing the benzophenone structure of the BP polymer (A), thereby forming a photocured product with improved processability.
In principle, the lower the VOC emission amount of the photocurable pressure-sensitive adhesive layer (A) disclosed herein, the more preferable. However, from the practical viewpoint of productivity, cost, etc., in some embodiments, the VOC emission amount may be, for example, 10 μg/g or more, 30 μg/g or more, 80 μg/g or more, 150 μg/g or more, or 200 μg/g or more.
The amount of VOC emission from the photocurable pressure-sensitive adhesive layer (A) can be adjusted by the composition of the pressure-sensitive adhesive composition (A) (e.g., the composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), the amount of the organic solvent), the curing conditions of the pressure-sensitive adhesive composition (A) (heating conditions, ultraviolet irradiation conditions), etc.

(Gel Fraction)
The gel fraction of the photocurable pressure-sensitive adhesive layer (A) is not particularly limited, but from the viewpoint of the cohesiveness of the photocurable pressure-sensitive adhesive layer (A) and the handleability of the pressure-sensitive adhesive sheet having the photocurable pressure-sensitive adhesive layer (A), it is usually appropriate to be 5% or more, preferably 15% or more, and may be 25% or more, or may be 35% or more. In principle, the gel fraction of the photocurable pressure-sensitive adhesive layer (A) is 100% or less. In addition, from the viewpoint of the step absorbency with respect to the surface shape of the adherend, the gel fraction of the photocurable pressure-sensitive adhesive layer (A) is preferably less than 85%, may be less than 70%, may be less than 55%, or may be less than 40%.

The gel fraction is measured by the following method. That is, about 0.5 g of a measurement sample is precisely weighed, and its weight is designated as W1. This measurement sample is wrapped in a porous PTFE (polytetrafluoroethylene) sheet and immersed in ethyl acetate at room temperature for one week, and then dried to measure the weight W2 of the ethyl acetate insoluble matter, and W1 and W2 are calculated using the following formula:
Gel fraction (%) = W2/W1 × 100;
As the porous PTFE sheet, a product named "Nitoflon NTF1122" manufactured by Nitto Denko Corporation or an equivalent product can be used.

In some embodiments of the photocurable pressure-sensitive adhesive layer (A), the photocurable pressure-sensitive adhesive layer (A) is irradiated with ultraviolet light using a high-pressure mercury lamp under conditions of an illuminance of 300 mW/cm ² and an integrated light quantity of 10,000 mJ/cm ² , and the gel fraction of the photocured product obtained may be, for example, 70% or more, preferably 90% or more, may be 95% or more, or may be 98% or more. The gel fraction of the photocured product is, in principle, 100% or less. The gel fraction is measured by the above-mentioned method.
The gel fraction of the photocurable pressure-sensitive adhesive layer (A) can be adjusted by the composition of the pressure-sensitive adhesive composition (A) (e.g., Mw, Tg, and BP equivalent of the BP polymer (A); the weight fraction of the BP polymer (A); the composition of the monomer components constituting the BP polymer (A) and the ethylenically unsaturated compound (B), the type and amount of functional groups; and the type and amount of the crosslinking agent), the pressure-sensitive adhesive composition (A), and the curing conditions of the photocurable pressure-sensitive adhesive layer (A) (heating conditions, UV irradiation conditions), etc.

The glass transition point (Tg) of the photocurable adhesive layer (A) is not particularly limited, but is preferably -60 to 20°C, more preferably -40 to 10°C, and even more preferably -30 to 0°C. If the Tg is higher than 20°C, the adhesive strength cannot be expressed at room temperature.

The above Tg is not particularly limited, but can be measured, for example, by differential scanning calorimetry (DSC) using the pressure-sensitive adhesive layer as a measurement sample in accordance with JIS K 7121. Specifically, for example, the measurement can be performed using a measuring device manufactured by TA Instruments, named "Q-2000," at a heating rate of 10°C/min from -80°C to 80°C.

The thickness of the photocurable adhesive layer (A) is not particularly limited, and may be appropriately set so as to adequately seal the light-emitting elements arranged on the display panel described below. For example, the thickness of the photocurable adhesive layer (A) is adjusted to be 1.0 to 4.0 times, preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and even more preferably 1.3 to 2.0 times, the height of the light-emitting element. By setting the thickness to 1.0 times or more, the photocurable adhesive layer (A) can easily conform to steps, improving step absorption. Furthermore, by setting the thickness to 4.0 or less, the photocurable adhesive layer (A) is less likely to deform, improving processability.

The thickness of the photocurable adhesive layer (A) is, for example, about 10 to 500 μm, and may be 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. The thickness of the photocurable adhesive layer (A) may be 400 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. By making the thickness 10 μm or more, the photocurable adhesive layer (A) can easily conform to the step portion, improving the step absorption. In addition, by making the thickness 500 μm or less, the photocurable adhesive layer (A) is less likely to deform, improving the processability.

Since the photocurable adhesive layer (A) exhibits excellent light shielding properties against visible light, even when a metal adherend is laminated on the photocurable adhesive layer (A), reflection and gloss on the metal surface can be prevented. When a metal adherend is laminated on the photocurable adhesive layer (A), the reflectance in the visible light region of 5° regular reflection is preferably 50% or less, more preferably 30% or less, even more preferably 15% or less, and particularly preferably 10% or less. When a metal adherend is laminated on the photocurable adhesive layer (A), the gloss (based on JIS Z 8741-1997) is preferably 100% or less, more preferably 80% or less, even more preferably 60% or less, and particularly preferably 50% or less.
The metal adherend that can be used is made of copper, aluminum, stainless steel, or the like.

[Formation of photocured product]
The photocurable adhesive layer (A) can be photocrosslinked, for example, by irradiating ultraviolet light containing a wavelength component capable of exciting the benzophenone structure. It is preferable to use a light source capable of irradiating ultraviolet light containing a component having a wavelength of less than 300 nm. Examples of such light sources include, but are not limited to, high pressure mercury lamps, low pressure mercury lamps, metal halide lamps, super UV lamps, etc. The light irradiated by the light source may contain a component having a wavelength of 300 nm or more.

Examples of light sources capable of irradiating ultraviolet light that does not contain or has few wavelength components capable of exciting the benzophenone structure (for example, components with wavelengths of less than 300 nm) include black lights and UV-LED lamps. These light sources can be preferably used as light sources for promoting the reaction (polymerization reaction or curing reaction) of ethylenically unsaturated groups by light irradiation in the presence of a benzophenone structure. In the irradiation of ultraviolet light to react with ethylenically unsaturated groups, the above-mentioned photopolymerization initiator (C) can be used to promote the reaction.

The photocurable adhesive layer (A) may be a composition that is substantially free of a photopolymerization initiator that absorbs light having a wavelength of 300 nm or more to generate radicals, and may be a composition that is substantially free of a photopolymerization initiator that absorbs visible light having a wavelength of 380 nm or more (particularly 400 nm or more) to generate radicals. This may be advantageous in terms of the optical properties of the photocurable adhesive layer (A). In addition, not containing a photopolymerization initiator that absorbs light having a wavelength of 300 nm or more to generate radicals means that the photopolymerization initiator in a form capable of generating the above radicals (a form having a site cleaved by the above light) is not contained, and it is acceptable to contain the cleavage residue of the photopolymerization initiator. The photocurable adhesive layer (A) according to a preferred embodiment does not substantially contain a photopolymerization initiator containing a phosphorus element in the molecule. The photocurable adhesive layer (A) disclosed herein may be a layer that is substantially free of both a photopolymerization initiator containing a phosphorus element in the molecule and a cleavage residue of the photopolymerization initiator.

[Photocurable adhesive sheet (A)]
The photocurable pressure-sensitive adhesive sheet (A) has a photocurable pressure-sensitive adhesive layer (A).
The form of the photocurable adhesive sheet (A) is not particularly limited as long as it has an adhesive surface formed by the surface of the photocurable adhesive layer (A). The photocurable adhesive sheet (A) may be a single-sided adhesive sheet having only one adhesive surface, or a double-sided adhesive sheet having adhesive surfaces on both sides. When the photocurable adhesive sheet (A) is a double-sided adhesive sheet, the photocurable adhesive sheet (A) may have a form in which both adhesive surfaces are provided by the photocurable adhesive layer (A), or one adhesive surface is provided by the photocurable adhesive layer (A) and the other adhesive surface is provided by an adhesive layer (other adhesive layer) other than the photocurable adhesive layer (A). From the viewpoint of bonding the adherends together, a double-sided adhesive sheet is preferred, and more preferably, the sheet is a double-sided adhesive sheet in which both surfaces of the sheet are the surfaces of the photocurable adhesive layer (A).

The photocurable adhesive sheet (A) may be an adhesive sheet without a substrate (substrate layer), i.e., a so-called "substrate-less type" adhesive sheet (sometimes referred to as a "substrate-less adhesive sheet"), or an adhesive sheet with a substrate (sometimes referred to as a "substrate-attached adhesive sheet"). Examples of substrate-less adhesive sheets in the present invention include double-sided adhesive sheets consisting of only the photocurable adhesive layer (A), and double-sided adhesive sheets consisting of the photocurable adhesive layer (A) and other adhesive layers (adhesive layers other than the photocurable adhesive layer (A)). Examples of substrate-attached adhesive sheets in the present invention include single-sided adhesive sheets having a photocurable adhesive layer (A) on one side of the substrate, double-sided adhesive sheets having a photocurable adhesive layer (A) on both sides of the substrate, and double-sided adhesive sheets having a photocurable adhesive layer (A) on one side of the substrate and other adhesive layers on the other side.

Among the above, from the viewpoint of improving optical properties such as transparency, a substrateless pressure-sensitive adhesive sheet is preferred, and more preferably, a double-sided pressure-sensitive adhesive sheet (substrateless double-sided pressure-sensitive adhesive sheet) without a substrate, which is composed only of the photocurable pressure-sensitive adhesive layer (A). In addition, when the photocurable pressure-sensitive adhesive sheet (A) is a pressure-sensitive adhesive sheet with a substrate, although there is no particular limitation, from the viewpoint of processability, a double-sided pressure-sensitive adhesive sheet (substrate-attached double-sided pressure-sensitive adhesive sheet) having the photocurable pressure-sensitive adhesive layer (A) on both sides of the substrate is preferred.
The above-mentioned "substrate (substrate layer)" refers to a portion that is attached to an adherend together with the adhesive layer when the photocurable adhesive layer (A) is used (applied) to an adherend (such as an optical member), and does not include a release film (separator) that is peeled off when the adhesive sheet is used (applied).

As described above, the photocurable adhesive sheet A may be an adhesive sheet with a substrate. Examples of such substrates include various optical films such as plastic films, anti-reflection (AR) films, polarizing plates, and retardation plates. Examples of materials for the plastic films include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, and cyclic olefin polymers such as "Arton" (cyclic olefin polymer, manufactured by JSR Corporation) and "ZEONOR" (cyclic olefin polymer, manufactured by Zeon Corporation). These plastic materials may be used alone or in combination of two or more.

The substrate is preferably transparent. The total light transmittance (according to JIS K7361-1) of the substrate in the visible light wavelength region is not particularly limited, but is preferably 85% or more, more preferably 88% or more. The haze (according to JIS K7136) of the substrate is not particularly limited, but is preferably 1.5% or less, more preferably 1.0% or less. Examples of such transparent substrates include PET films and non-oriented films such as those sold under the product names "Arton" and "Zeonor".

The thickness of the substrate is not particularly limited, but is preferably 12 to 75 μm. The substrate may have either a single layer or multiple layers. The surface of the substrate may be appropriately subjected to a known and commonly used surface treatment, such as anti-reflection treatment (AR treatment), anti-glare treatment, or other anti-reflection treatment, physical treatment such as corona discharge treatment or plasma treatment, or chemical treatment such as undercoat treatment.

As described above, the photocurable adhesive sheet (A) may have another adhesive layer (an adhesive layer other than the adhesive layer A). The other adhesive layer is not particularly limited, but examples thereof include adhesive layers formed from known or conventional adhesives such as urethane-based adhesives, acrylic-based adhesives, rubber-based adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, and fluorine-based adhesives. The above adhesives may be used alone or in combination of two or more.

In addition, the photocurable adhesive sheet (A) may have other layers (e.g., an intermediate layer, an undercoat layer, etc.) in addition to the photocurable adhesive layer (A), the substrate, and other adhesive layers, as long as the effects of the present invention are not impaired.

The photocurable adhesive sheet (A) may have a release film (separator) on the adhesive surface until it is used. The manner in which the adhesive surface of the photocurable adhesive sheet (A) is protected by a release film is not particularly limited, but may be a form in which each adhesive surface is protected by two release films, or a form in which each adhesive surface is protected by a single release film with release surfaces on both sides by rolling up into a roll. The release film is used as a protective material for the adhesive layer, and is peeled off when the sheet is attached to the adherend. In the photocurable adhesive sheet (A), the release film also plays a role as a support for the adhesive layer. The release film does not necessarily have to be provided.

The thickness (total thickness) of the photocurable adhesive sheet (A) is not particularly limited, but is preferably 10 μm to 1 mm, more preferably 100 to 500 μm, and even more preferably 150 to 350 μm. By making the thickness 10 μm or more, the photocurable adhesive layer (A) can easily conform to the stepped portion, thereby improving the step absorption. Note that the thickness of the photocurable adhesive sheet (A) does not include the thickness of the release film.

The photocurable adhesive sheet (A) contains the photocurable adhesive layer (A) and therefore has optical absorption properties for visible light. The total light transmittance of the photocurable adhesive sheet (A) is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

Because the photocurable adhesive sheet (A) has a photocurable adhesive layer (A), it has excellent step absorption properties before curing. For example, in addition to steps of 5 to 10 μm, it has excellent step absorption properties even for steps that are higher than 40 μm. Furthermore, it has step absorption properties even for steps that are higher than 80 μm.

In addition, since the photocurable adhesive sheet (A) has a photocurable adhesive layer (A), it has excellent processability after curing, and glue chipping during cutting processing and protrusion or drooping of the adhesive layer from the edges during storage are suppressed.
Furthermore, the photocurable pressure-sensitive adhesive sheet (A) has excellent adhesive reliability since it has the photocurable pressure-sensitive adhesive layer (A).

1 to 3 are diagrams (cross-sectional views) that diagrammatically show one embodiment of the photocurable pressure-sensitive adhesive sheet (A) of the present invention.
One embodiment of the photocurable adhesive sheet (A) is shown in FIG. 1. This photocurable adhesive sheet 1A is configured as a one-sided adhesive photocurable adhesive sheet including a photocurable adhesive layer 10, one surface 10A of which is an attachment surface (adhesive surface) to an adherend, and a substrate S1 laminated on the other surface 10B of the photocurable adhesive layer 10. The photocurable adhesive layer 10 is bonded to one surface S1A of the substrate S1. As the substrate S1, for example, a plastic film such as a polyester film can be used. The substrate S1 may be, for example, an optical film such as a polarizing plate or a cover member. In the embodiment shown in FIG. 1, the photocurable adhesive layer 10 has a single layer structure. The adhesive sheet 1A before use (before being attached to an adherend) may be in the form of an adhesive sheet 50 with a release film, in which the adhesive surface 10A is protected by a release film S2, at least the adhesive layer side of which is a release surface (release surface), as shown in FIG. 1, for example. Alternatively, the second surface S1B of the substrate S1 (the surface opposite to the first surface S1A, also called the back surface) may be the release surface, and the adhesive surface 10A may be protected by being wound or laminated so that the adhesive surface 10A abuts against the second surface S1B of the substrate S1.

The release film is not particularly limited, and examples of the release film include a release film in which the surface of a film substrate such as a resin film or paper has been treated for release, and a release film made of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.). For the release treatment, for example, a silicone-based or long-chain alkyl-based release treatment agent can be used. In some embodiments, a resin film that has been subjected to a release treatment can be preferably used as the release film.

The photocurable adhesive sheet (A) may be in the form of a substrateless double-sided adhesive sheet consisting of a photocurable adhesive layer (A). As shown in FIG. 2, the substrateless double-sided adhesive sheet 1B may be in a form in which, before use, each surface 10A, 10B of the adhesive layer 10 is protected by release films S3, S4 in which at least the adhesive layer side is a release surface (release surface). Alternatively, the back surface (surface opposite to the adhesive side) of the release film S4 is the release surface, and the adhesive surface 10B may be wound or laminated so that it abuts against the back surface of the release film S4, thereby protecting the adhesive surfaces 10A, 10B. Such a substrateless double-sided adhesive sheet may be used, for example, by bonding a substrate to one surface of the adhesive layer.

The photocurable adhesive sheet (A) may be a component of an optical member with an adhesive sheet in which an optical member is bonded to one surface of the adhesive layer. For example, the photocurable adhesive sheet 1A shown in FIG. 1 may be a component of an optical member with an adhesive sheet 100 in which an optical member S5 is bonded to one surface 10A of the adhesive layer 10 as shown in FIG. 3. The optical member may be, for example, a glass plate, a resin film, a metal plate, an LED panel as described below, or the like.

The photocurable adhesive layer (A) constituting the photocurable adhesive sheet (A) may be a cured layer of the corresponding adhesive composition (A). For example, the photocurable adhesive layer (A) may be obtained by applying (e.g., coating) the adhesive composition (A) to a suitable surface and then curing the adhesive composition (A). The adhesive composition (A) may be cured preferably by irradiation with active energy rays. As the active energy ray for forming the photocurable adhesive layer (A), ultraviolet rays are preferred, and ultraviolet rays that do not contain components with wavelengths of 300 nm or less or that contain only a small amount of such components are more preferred.

The adhesive composition (A) can be applied using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater. In the case of a photocurable adhesive sheet (A) having a substrate, a direct method of forming a photocurable adhesive layer (A) by directly applying the adhesive composition (A) to the substrate may be used as a method of providing the photocurable adhesive layer (A) on the substrate, or a transfer method of transferring the photocurable adhesive layer (A) formed on the release surface to the substrate may be used.

<Self-luminous display device>
The self-luminous display device according to the fifth aspect of the present invention is a display device in which a large number of minute light-emitting elements are arranged on a wiring board, and each light-emitting element is selectively caused to emit light by a light-emitting control means connected thereto, thereby directly displaying visual information such as characters, images, and videos on a display screen by blinking each light-emitting element. Examples of the self-luminous display device include a mini/micro LED display device and an organic EL (electroluminescence) display device. The photocurable adhesive sheet A according to the first aspect of the present invention is particularly suitable for use in the manufacture of a mini/micro LED display device.

FIG. 4 is a schematic diagram (cross-sectional view) showing one embodiment of a self-luminous display device (mini/micro LED display device) according to the fifth aspect of the present invention.
4, the mini/micro LED display device 200A is composed of a display panel having a plurality of LED chips 23 arranged on one side of a substrate 21 via a metal wiring layer 22, an adhesive layer 20 laminated on the display panel and sealing the metal wiring layer 22 and the plurality of LED chips 23, and a cover member 24 laminated on the upper part (image display side) of the adhesive layer 20. The cover member 24 is not particularly limited, but can be composed of the same material as the above-mentioned "base material".

In the mini/micro LED display device 2A of this embodiment, a metal wiring layer 22 for sending light emission control signals to each LED chip 23 is laminated on the substrate 21 of the display panel. Each LED chip 23 emitting light of each color of red (R), green (G), and blue (B) is arranged alternately on the substrate 21 of the display panel via the metal wiring layer 22. The metal wiring layer 22 is formed of a metal such as copper, and reflects the light emitted by each LED chip 23, reducing the visibility of the image. In addition, the light emitted by each LED chip 23 of each color of RGB is mixed, reducing the contrast.

In the mini/micro LED display device 200A of this embodiment, each LED chip 23 arranged on the display panel is sealed with an adhesive layer 20. The adhesive layer 20 is composed of a cured product of the photocurable adhesive layer (A) of the present invention. The adhesive layer 20 sufficiently conforms to the minute steps between the multiple LED chips 23, sealing them without any gaps.

The adhesive layer 20 has sufficient light-shielding properties in the visible light range. The highly light-shielding adhesive layer 20 seals the minute steps between the LED chips 23 without any gaps, preventing reflections from the metal wiring layer 22, preventing color mixing between the LED chips 23, and improving contrast.

In addition, since the adhesive layer 20 is a cured product of the photocurable adhesive layer (A), it has excellent processability. Therefore, the mini/micro LED display device 200A of this embodiment is prevented from having glue chipping during cutting processing, and the adhesive layer 20 is prevented from protruding or sagging from the edges during storage.

The self-luminous display device (mini/micro LED display device) of this embodiment may include optical members other than the display panel, adhesive layer, and cover member. Examples of the optical members include, but are not limited to, a polarizing plate, a retardation plate, an anti-reflection film, a viewing angle adjustment film, and an optical compensation film. The optical members also include members (design films, decorative films, surface protection plates, etc.) that play a role in decoration and protection while maintaining the visibility of the display device and input device.

The self-luminous display device (mini/micro LED display device) of this embodiment is not particularly limited, but can be preferably manufactured by a method including the following steps.
(1) A step of laminating a photocurable adhesive layer (A) of a photocurable adhesive sheet (A) on a display panel having a plurality of light-emitting elements arranged on one side of a substrate, and sealing the light-emitting elements with the photocurable adhesive layer (A).
(2) A step of curing the photocurable pressure-sensitive adhesive layer (A) by irradiating it with ultraviolet light.

Figure 5 is a diagram that shows a schematic diagram of steps for carrying out one embodiment of a manufacturing method for a self-luminous display device (mini/micro LED display device) according to the fifth aspect of the present invention. In this embodiment, as shown in Figure 5 (a), a photocurable adhesive sheet 1C according to the fourth aspect of the present invention and a display panel in which a plurality of light-emitting elements (LED chips) 23 are arranged on one side of a substrate 21 via a metal wiring layer 22 are used.

In this embodiment, the photocurable adhesive sheet 1C is composed of a photocurable adhesive layer 10 and a support S6. In this embodiment, the photocurable adhesive sheet 1C has a cover member 24, but the cover member 24 may be omitted. The cover member 24 is not particularly limited, but may be composed of the same material as the "substrate" described above, and may be a release film (separator).

Next, as shown in FIG. 5(b), the main surface 10A of the photocurable adhesive layer 10 of the photocurable adhesive sheet 1C, on which the cover member 24 is not laminated, is laminated on the surface of the display panel on which the multiple LEDs are arranged, and the LED chips 23 and the metal wiring layer 22 are sealed with the photocurable adhesive layer 10. The lamination can be performed by a known method, for example, under heat and pressure conditions using an autoclave. The photocurable adhesive layer 10 of the photocurable adhesive sheet 1C has high fluidity and exhibits excellent step absorption properties. Therefore, the photocurable adhesive layer 10 is sealed so as to fill the steps between the metal wiring layer 22 and the multiple LED chips 23 without any gaps.

Next, as shown in FIG. 5(c), the photocurable adhesive layer 10 is irradiated with ultraviolet light to cure it. The benzophenone structure contained in the photocurable adhesive layer 10 is excited by the irradiation of ultraviolet light, and a crosslinking structure is formed by utilizing a hydrogen radical abstraction reaction, and a curing reaction is initiated. The ultraviolet light is not particularly limited as long as it excites the benzophenone structure to cure the photocurable adhesive layer 10, but ultraviolet light that exhibits transparency to the photocurable adhesive layer 10 is preferred. That is, the photocurable adhesive layer 10 has high light blocking properties against visible light while having high transparency against ultraviolet light, so that the photocurable adhesive layer 10 can be cured by ultraviolet light. FIG. 5(c) shows an embodiment in which the photocurable adhesive layer 10 is irradiated with ultraviolet light U to cure it.

The ultraviolet light preferably has a wavelength of 200 to 400 nm, and more preferably has a wavelength of less than 300 nm.

As the light source for ultraviolet irradiation, for example, a high pressure mercury lamp, a low pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light, or an LED can be used. The irradiation time and irradiation method of ultraviolet rays can be appropriately set as long as the photocurable adhesive layer 10 can be cured, the display panel is not unduly affected, and the photocurable adhesive layer 10 is cured and exhibits sufficient processability. For example, the irradiation amount (accumulated light amount) of ultraviolet rays is preferably 1000 mJ/cm ² to 10000 mJ/cm ² , more preferably 2000 mJ/cm ² to 4000 mJ/cm ² , and even more preferably 3000 mJ/cm ² .

By curing the photocurable adhesive layer 10, a self-luminous display device (mini/micro LED display device) 200B is obtained as shown in FIG. 5(d). In FIG. 5(d), the adhesive layer 20 is an adhesive layer formed by curing the photocurable adhesive layer 10. The self-luminous display device (mini/micro LED display device) 200B is an embodiment showing an example of a self-luminous display device (mini/micro LED display device) according to the fifth aspect of the present invention.

The adhesive layer 20 has improved processability, and prevents glue chipping during cutting and the adhesive layer from spilling out or sagging from the edges during storage. The adhesive layer 20 also suppresses the generation of gases such as carbon dioxide caused by heating the display panel, preventing the generation of air bubbles and improving adhesion reliability.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
(Preparation of Pressure-Sensitive Adhesive Composition)
A separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube was charged with 50 parts by weight of an acrylic copolymer having a benzophenone structure in a side chain (manufactured by BASF, product name "acResin A260UV", Tg: -39°C, Mw: 19 x 10 ⁴ , BP equivalent: 2 mg/g), 26 parts by weight of butyl acrylate (BA), 8 parts by weight of N-vinyl-2-pyrrolidone (NVP), 16 parts by weight of isobornyl acrylate (IBXA), and 0.2 parts by weight of a photopolymerization initiator having an absorption peak in the wavelength range of 300 nm to 500 nm (manufactured by IGM Regins, product name "Omnirad 184"), and mixed to prepare a pressure-sensitive adhesive composition A.

(Preparation of black adhesive composition)
A black adhesive composition B1 was prepared by adding 0.5 parts by weight of a 20% dispersion of a black pigment ("9256BLACK" manufactured by Tokushiki) to 100 parts by weight of the above adhesive composition A.

(Preparation of photocurable adhesive sheet)
The black adhesive composition B1 prepared above was applied to the release surface of a 38 μm thick release film R1 (manufactured by Mitsubishi Plastics, MRF#38) with one side of a polyester film being the release surface, and a release film R2 (manufactured by Mitsubishi Plastics, MRE#38) with one side of a polyester film being the release surface was placed over it to block air. One side of this laminate was irradiated with ultraviolet light using a black light (manufactured by Toshiba, product name FL15BL) at an illuminance of 5 mW/cm ² and an accumulated light quantity of 1300 mJ/cm ^2. As a result, a photocurable adhesive sheet D1 in which a photocurable adhesive layer C1 with a thickness of about 100 μm, which is a cured product of the black adhesive composition B1, was sandwiched between the release films R1 and R2 was obtained in the form of a substrateless double-sided adhesive sheet.
The illuminance value of the black light is a value measured using an industrial UV checker (manufactured by Topcon Corporation, product name: UVR-T1, light receiving unit type UD-T36) with a peak sensitivity wavelength of about 350 nm.

[Example 2]
A photocurable adhesive sheet D2 in the form of a substrate-less double-sided adhesive sheet was obtained in the same manner as in Example 1, except that black adhesive composition B2 was prepared by adding 1 part by weight of a 20% dispersion of black pigment ("9256BLACK" manufactured by TOKUSHIKI) to 100 parts by weight of adhesive composition A. The photocurable adhesive sheet D2 in the form of a substrate-less double-sided adhesive sheet was obtained in which a photocurable adhesive layer C2 with a thickness of approximately 100 μm, which was a cured product of the black adhesive composition B2, was sandwiched between the release films R1 and R2.

[Example 3]
A photocurable adhesive sheet D3 in the form of a substrate-less double-sided adhesive sheet was obtained in the same manner as in Example 1, except that a black adhesive composition B3 was prepared by adding 2 parts by weight of a 20% dispersion of a black pigment ("9256BLACK" manufactured by TOKUSHIKI) to 100 parts by weight of adhesive composition A. The photocurable adhesive sheet D3 in the form of a substrate-less double-sided adhesive sheet was obtained in which a photocurable adhesive layer C3 with a thickness of approximately 100 μm, which was a cured product of the black adhesive composition B3, was sandwiched between the release films R1 and R2.

[Example 4]
A photocurable adhesive sheet D4 in the form of a substrate-less double-sided adhesive sheet was obtained in the same manner as in Example 1, except that black adhesive composition B4 was prepared by adding 4 parts by weight of a 20% dispersion of black pigment ("9256BLACK" manufactured by TOKUSHIKI) to 100 parts by weight of adhesive composition A. The photocurable adhesive sheet D4 in the form of a substrate-less double-sided adhesive sheet was obtained in which a photocurable adhesive layer C4 with a thickness of approximately 100 μm, which was a cured product of the black adhesive composition B4, was sandwiched between the release films R1 and R2.

[Comparative Example 1]
A photocurable adhesive sheet D5 in the form of a substrate-less double-sided adhesive sheet was obtained in the same manner as in Example 1, except that no black pigment was added to 100 parts by weight of adhesive composition A, in which a photocurable adhesive layer C5 with a thickness of approximately 100 μm, which was a cured product of the adhesive composition A, was sandwiched between the release films R1 and R2.

[Comparative Example 2]
(Preparation of Prepolymer)
In a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube, 67 parts by weight of butyl acrylate (BA), 14 parts by weight of cyclohexyl acrylate (CHA), 19 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.09 parts by weight of a photopolymerization initiator (manufactured by BASF, product name "Irgacure 184"), and 0.09 parts by weight of a photopolymerization initiator (manufactured by BASF, product name "Irgacure 651") were charged as monomer components, and then nitrogen gas was introduced and nitrogen substitution was performed for about 1 hour while stirring. Thereafter, polymerization was performed by irradiating UVA at 5 mW/cm ² , and the reaction rate was adjusted to 5 to 15%, to obtain an acrylic prepolymer solution.

(Preparation of Pressure-Sensitive Adhesive Composition)
To the acrylic prepolymer solution obtained above (total amount of prepolymer is 100 parts by weight), 9 parts by weight of 2-hydroxyethyl acrylate (HEA), 8 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.02 parts by weight of dipentaerythritol hexaacrylate (manufactured by Shin-Nakamura Industrial Chemical Industry, trade name "KAYARAD DPHA") as a polyfunctional monomer, 0.35 parts by weight of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent, and 0.45 parts by weight of a polymerization initiator (manufactured by BASF "Irgacure 651") were added to obtain a pressure-sensitive adhesive composition.

(Preparation of black adhesive composition)
To 100 parts by weight of the above adhesive composition, 5.8 parts by weight of a 20% dispersion of black pigment ("9256BLACK" manufactured by TOKUSHIKI) and 0.2 parts by weight of an additional photopolymerization initiator ("Irgacure 651" manufactured by BASF) were added to obtain a black adhesive composition.

(Preparation of adhesive sheet)
The black adhesive composition prepared above was applied to the release surface of a 38 μm thick release film R1 (Mitsubishi Plastics, MRF#38) with one side of a polyester film being the release surface, and a release film R2 (Mitsubishi Plastics, MRE#38) with one side of a polyester film being the release surface was placed over it to block air. One side of this laminate was irradiated with ultraviolet light using a black light (Toshiba, product name FL15BL) at an illuminance of 5 mW/cm ² and an accumulated light amount of 1300 mJ/cm ^2. As a result, an adhesive sheet in which an adhesive layer with a thickness of about 50 μm, which is a cured product of the black adhesive composition, was sandwiched between the release films R1 and R2 was obtained in the form of a substrateless double-sided adhesive sheet.

[Example 5]
(Preparation of black adhesive composition)
To 100 parts by weight of the adhesive composition prepared in Comparative Example 2, 4 parts by weight of a 20% dispersion of black pigment ("9256BLACK" manufactured by TOKUSHIKI), 0.2 parts by weight of an additional photopolymerization initiator ("Irgacure 651" manufactured by BASF), and 1 part by weight of 4-acryloyloxybenzophenone manufactured by Ark Pharm were added to obtain a black adhesive composition.

(Preparation of photocurable adhesive sheet)
The black adhesive composition prepared above was applied to the release surface of a 38 μm thick release film R1 (Mitsubishi Plastics, MRF#38) with one side of a polyester film being the release surface, and a release film R2 (Mitsubishi Plastics, MRE#38) with one side of a polyester film being the release surface was placed over it to block air. One side of this laminate was irradiated with ultraviolet light using a black light (Toshiba, product name FL15BL) at an illuminance of 5 mW/cm ² and an accumulated light amount of 1300 mJ/cm ^2. As a result, an adhesive sheet in which an adhesive layer with a thickness of about 100 μm, which is a cured product of the black adhesive composition, was sandwiched between the release films R1 and R2 was obtained in the form of a substrateless double-sided adhesive sheet.
The illuminance value of the black light is a value measured using an industrial UV checker (manufactured by Topcon Corporation, product name: UVR-T1, light receiving unit type UD-T36) with a peak sensitivity wavelength of about 350 nm.

[Example 6]
A photocurable adhesive sheet was prepared in the same manner as in Example 5, except that 2 parts of 4-acryloyloxybenzophenone was used.

(evaluation)
The following evaluations were carried out using the pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples. The evaluation methods are shown below. The results are shown in Table 1.

[Evaluation of Transmittance]
The release film on one side was peeled off from the pressure-sensitive adhesive sheet, and non-alkali glass was attached to the exposed surface. Thereafter, the release film on the other side was peeled off from the pressure-sensitive adhesive sheet to obtain a sample in which the pressure-sensitive adhesive sheet was attached to the non-alkali glass plate.
The total light transmittance was measured by the method defined in JIS K7361 using a haze meter (manufactured by Murakami Color Science Laboratory, product name "HN-150").

[Evaluation of storage modulus]
The evaluation was carried out using ARES GII manufactured by TA Instruments.
An adhesive sheet laminated to a thickness of approximately 1 mm was sandwiched between 8 mm parallel plates, and measurement was performed from -50°C to 100°C with an initial strain of 1%, a frequency of 1 Hz, and a heating rate of 5°C/min. The storage modulus G' at 10°C, 25°C, and 85°C was read and used as the storage modulus G' before curing (G'b10, G'b25, G'b85).
The storage modulus G' after curing was measured by irradiating the pressure-sensitive adhesive sheet sandwiched between release films with a high-pressure mercury lamp at an integrated light intensity of 3000 mJ/ ^cm2 , laminating the sheet to a thickness of approximately 1 mm, and evaluating the storage modulus G' after curing in the same manner as above (G'a10, G'a25, G'a85).
This integrated light amount is a value measured by an industrial UV checker (manufactured by Topcon Corporation, product name: UVR-T1, light receiving unit type UD-T36) with a peak sensitivity wavelength of about 350 nm.
Since the pressure-sensitive adhesive sheet of Comparative Example 2 does not exhibit photocurability, the storage modulus G' after curing was not evaluated.

[Evaluation of step-following ability]
(Preparation of uneven adherend)
A laminate of TAC film (thickness 60 μm) and adhesive (thickness 20 μm) was bonded to a 45 mm × 50 mm glass plate, and then a _CO2 laser (wavelength 10.6 μm, laser diameter 0 μm) was used to perform linear etching within a central 10 mm × 10 mm area at a vertical pitch of 150 μm and a horizontal pitch of 225 μm to obtain adherend A in which the TAC film and adhesive layer were processed into a lattice-like uneven shape.
This adherend A imitates an LED panel in which a plurality of LED films are arranged on a substrate.
(Preparation of adhesive sheet)
The adhesive sheets produced in Examples 1 to 4 and Comparative Example 1 were stacked in two sheets to a thickness of approximately 200 μm, and the adhesive sheet produced in Comparative Example 2 was stacked in five sheets to a thickness of approximately 250 μm. The release film on one side of these laminated adhesive sheets was peeled off, and a PET film with a thickness of 75 μm was attached to the exposed surface.
(Vacuum bonding)
The adhesive surface exposed by peeling off the other release film of the laminated adhesive sheet obtained above was bonded to the processed surface of adherend A using a vacuum bonding device (SE340aaH, manufactured by CRIMB Products) with a precision such that the adhesive sheet could completely cover the processed area of adherend A, thereby obtaining evaluation samples each consisting of PET film/laminated adhesive sheet/adherend A. The samples were then autoclaved (50° C., 0.5 MPa, 60 minutes) to allow for adhesion.
(Evaluation of step-following ability)
In the above evaluation sample, when the adhesive sheet is able to follow the uneven pattern portion, the processed portion of the adherend A appears transparent, and the portion that is unable to follow appears white. Taking advantage of this property, the area of the white portion was calculated by photographing with a fixed camera to evaluate the step-following ability.

Level difference conformability (%)=100−{[area of white portion at time of evaluation]/[area of white portion before lamination=1 cm ² ]×100}

[Evaluation of processability]
(Preparation of laminates for processability evaluation)
The release film of the laminated adhesive sheet prepared in the evaluation of step conformability was peeled off and the laminate was attached to a Misumi fr-4 substrate (thickness 1.2 mm). After autoclaving (15 minutes under conditions of 50°C and 0.5 MPa), UV rays were irradiated for Examples 1 to 4 and Comparative Example 1, which show photocuring properties. The UV irradiation conditions were a high-pressure mercury lamp with an accumulated light quantity of 3000 mJ/ ^cm2 . The accumulated light quantity was measured using an industrial UV checker (manufactured by Topcon Corporation, product name: UVR-T1, light receiving unit type UD-T36) with a peak sensitivity wavelength of approximately 350 nm.
(processing)
The laminate for evaluating processability obtained above was cut using a DTF6450 manufactured by Disco Corp. The cutting conditions were as follows: blade type P1A861 (abrasive grain #400), spindle 30 krpm, speed 30 mm/s, and cooling water 1 L/min.
(Evaluation of processability)
The cut end was observed from the laminated adhesive sheet side with a stereomicroscope, and the processability was evaluated based on the amount of glue protruding from the cut end. The evaluation criteria were as follows:
○: 0 to 150 μm
△: 150-200μm
×: 200 μm or more

[Evaluation of reflectance]
A plate was prepared by laminating aluminum foil on a black acrylic plate. The release film on one side of the adhesive sheet prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was peeled off, and a PET film with a thickness of 75 μm was attached to the exposed surface. The other release film was peeled off to expose the adhesive surface, which was laminated on the aluminum foil side of the plate to prepare a sample. The obtained sample was placed in a spectrophotometer U4100 (manufactured by Hitachi High-Technologies Corporation) with the PET film facing the light source, and the reflectance (%) of the visible light region at 5° regular reflection was measured.

Examples 1 to 6, which are photocurable adhesive sheets, exhibit excellent step conformability (step absorption) and processability, and also have suppressed transmittance and reflectance. When used as an encapsulant for LED panels, excellent anti-reflection effects and improved contrast can be expected. On the other hand, Comparative Example 1, which is a photocurable adhesive sheet but does not contain a colorant, exhibits excellent step conformability (step absorption) and processability, but has high transmittance and reflectance, and when used as an encapsulant for ED panels, anti-reflection effects and improved contrast cannot be expected. Comparative Example 2, which is an adhesive sheet that contains a colorant but does not exhibit photocurability, exhibits excellent step conformability (step absorption) but is poor in processability.

Variations of the present invention are listed below.
[Appendix 1] A colorant and a polymer (A) having a benzophenone structure in a side chain,
A pressure-sensitive adhesive composition having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than a maximum transmittance in the wavelength region of 400 to 700 nm.
[Appendix 2] A colorant and a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain or a partial polymer of a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain,
A pressure-sensitive adhesive composition having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than a maximum transmittance in the wavelength region of 400 to 700 nm.
[Appendix 3] The pressure-sensitive adhesive composition according to appendix 1 or 2, wherein the colorant has a maximum transmittance at wavelengths of 200 to 400 nm that is greater than a maximum transmittance at wavelengths of 400 to 700 nm.
[Appendix 4] The pressure-sensitive adhesive composition according to any one of Appendices 1 to 3, further comprising an ethylenically unsaturated compound (B).
[Appendix 5] The pressure-sensitive adhesive composition according to any one of Appendices 1 to 4, further comprising a photopolymerization initiator (C) that absorbs ultraviolet light having a wavelength of 300 nm to 500 nm and generates radicals.
[Appendix 6] A pressure-sensitive adhesive layer formed from a cured product of the pressure-sensitive adhesive composition according to any one of appendices 1 to 5,
The photocurable pressure-sensitive adhesive layer, wherein the cured product is a cured product in which the benzophenone structure of the polymer (A) having a benzophenone structure in a side chain remains.
[Appendix 7] The photocurable pressure-sensitive adhesive layer according to appendix 6, wherein the maximum transmittance at wavelengths of 200 to 400 nm is greater than the maximum transmittance at wavelengths of 400 to 700 nm.
[Appendix 8] The photocurable pressure-sensitive adhesive layer according to appendix 6 or 7, wherein the storage modulus (G'b85) of the photocurable pressure-sensitive adhesive layer at 85°C before curing is less than 65 kPa.
[Appendix 9] The photocurable pressure-sensitive adhesive layer according to any one of Appendices 6 to 8, wherein the storage modulus (G'a10) at 10°C of the photocurable pressure-sensitive adhesive layer after curing and the storage modulus (G'b85) at 85°C of the photocurable pressure-sensitive adhesive layer before curing satisfy the following relational expression (1):
2.8<G'a10/G'b85 (1)
[Appendix 10] The photocurable pressure-sensitive adhesive layer according to any one of Appendices 6 to 9, wherein the storage modulus (G'a10) of the photocurable pressure-sensitive adhesive layer at 10°C after curing is 90 kPa or more.
[Appendix 11] The photocurable pressure-sensitive adhesive layer according to any one of Appendices 6 to 10, wherein the curing is performed by irradiation with ultraviolet light having a wavelength of less than 300 nm and an accumulated light quantity of 3000 mJ/ ^cm2 .
[Appendix 12] A photocurable adhesive sheet having the photocurable adhesive layer according to any one of appendices 6 to 11.
[Appendix 13] A display panel having a plurality of light-emitting elements arranged on one surface of a substrate;
A self-luminous display device comprising the photocurable adhesive sheet according to claim 12,
a light-emitting element of the display panel is sealed with a photocurable adhesive layer of the photocurable adhesive sheet,
The self-luminous display device, wherein the photocurable adhesive layer is cured.
[Appendix 14] The self-luminous display device according to appendix 13, wherein the display panel is an LED panel having a plurality of LED chips arranged on one surface of a substrate.
[Appendix 15] A method for manufacturing a self-luminous display device according to appendix 13 or 14, comprising the steps of: laminating a photocurable adhesive layer of the photocurable adhesive sheet according to appendix 9 on a display panel having a plurality of light-emitting elements arranged on one side of a substrate, and sealing the light-emitting elements with the photocurable adhesive layer; and irradiating the photocurable adhesive layer with ultraviolet light to cure it.
[Appendix 16] The manufacturing method described in Appendix 15, wherein the ultraviolet light has a wavelength of less than 300 nm.

1A to 1C Photocurable adhesive sheet 10 Photocurable adhesive layer 10A One surface (adhesive surface)
10B: other surface S1: substrate S1A: first surface S1B: second surface (rear surface)
S2 to S4 Release film S5 Optical member 50 Release film-attached adhesive sheet 100 Adhesive sheet-attached member 200A, 200B Self-luminous display device (mini/micro LED display device)
20 Adhesive layer (after curing)
21: Substrate 22: Metal wiring layer 23: Light emitting element (LED chip)
24 Cover member

Claims (16)

The ink contains a colorant, a polymer (A) having a benzophenone structure in a side chain , and an ethylenically unsaturated compound (B) ,
A pressure-sensitive adhesive composition having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than a maximum transmittance in the wavelength region of 400 to 700 nm. The composition contains a colorant, a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain or a partial polymer of a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain , and an ethylenically unsaturated compound (B) ,
A pressure-sensitive adhesive composition having a maximum transmittance in the wavelength region of 200 to 400 nm that is greater than a maximum transmittance in the wavelength region of 400 to 700 nm. The adhesive composition according to claim 1 or 2, wherein the colorant has a maximum transmittance at wavelengths of 200 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm. The pressure-sensitive adhesive composition according to any one of claims 1 to 3 , further comprising a photopolymerization initiator (C) that absorbs ultraviolet light having a wavelength of 300 nm to 500 nm to generate radicals. A pressure-sensitive adhesive layer formed of a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 4 ,
The photocurable pressure-sensitive adhesive layer, wherein the cured product is a cured product in which the benzophenone structure of the polymer (A) having a benzophenone structure in a side chain remains. The photocurable pressure-sensitive adhesive layer according to claim 5 , wherein the maximum transmittance at wavelengths of 200 to 400 nm is greater than the maximum transmittance at wavelengths of 400 to 700 nm. The photocurable pressure-sensitive adhesive layer according to claim 5 or 6 , wherein the photocurable pressure-sensitive adhesive layer before curing has a storage modulus (G'b85) at 85°C of less than 65 kPa. The photocurable pressure-sensitive adhesive layer according to any one of claims 5 to 7, wherein a storage modulus (G'a10) at 10°C of the photocurable pressure-sensitive adhesive layer after curing and a storage modulus (G'b85) at 85 ° C of the photocurable pressure-sensitive adhesive layer before curing satisfy the following relational expression (1):
2.8<G'a10/G'b85 (1) The photocurable pressure-sensitive adhesive layer according to any one of claims 5 to 8 , wherein the photocurable pressure-sensitive adhesive layer after curing has a storage modulus at 10°C (G'a10) of 90 kPa or more. The photocurable pressure-sensitive adhesive layer according to any one of claims 5 to 9 , wherein the curing is performed by irradiation with ultraviolet light having a wavelength of less than 300 nm and an integrated light quantity of 3000 mJ/ ^cm2 . A photocurable pressure-sensitive adhesive sheet having the photocurable pressure-sensitive adhesive layer according to any one of claims 5 to 10 . A display panel having a plurality of light-emitting elements arranged on one surface of a substrate;
A self-luminous display device comprising: a photocurable adhesive sheet having a photocurable adhesive layer ,
the photocurable pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from a cured product of a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition contains a colorant and a polymer (A) having a benzophenone structure in a side chain, and has a maximum transmittance at a wavelength of 200 to 400 nm that is greater than a maximum transmittance at a wavelength of 400 to 700 nm;
the cured product is a cured product in which the benzophenone structure of the polymer (A) having a benzophenone structure in a side chain remains,
a light-emitting element of the display panel is sealed with a photocurable adhesive layer of the photocurable adhesive sheet,
The self-luminous display device, wherein the photocurable adhesive layer is cured. A display panel having a plurality of light-emitting elements arranged on one surface of a substrate;
A self-luminous display device comprising: a photocurable adhesive sheet having a photocurable adhesive layer,
The photocurable pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from a cured product of a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition contains a colorant and a mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain or a partial polymer of the mixture of monomer components constituting a polymer (A) having a benzophenone structure in a side chain, and has a maximum transmittance at a wavelength of 200 to 400 nm that is greater than a maximum transmittance at a wavelength of 400 to 700 nm;
the cured product is a cured product in which a benzophenone structure remains in a mixture of monomer components constituting the polymer (A) having a benzophenone structure in a side chain or a partial polymer of a mixture of monomer components constituting the polymer (A) having a benzophenone structure in a side chain,
a light-emitting element of the display panel is sealed with a photocurable adhesive layer of the photocurable adhesive sheet,
The self-luminous display device, wherein the photocurable adhesive layer is cured. 14. The self-luminous display device according to claim 12 , wherein the display panel is an LED panel having a plurality of LED chips arranged on one surface of a substrate. A method for manufacturing the self-luminous display device according to any one of claims 12 to 14, comprising the steps of: laminating a photocurable adhesive layer of the photocurable adhesive sheet according to claim 9 on a display panel having a plurality of light-emitting elements arranged on one side of a substrate, and sealing the light-emitting elements with the photocurable adhesive layer; and irradiating the photocurable adhesive layer with ultraviolet light to cure it. The method according to claim 15, wherein the ultraviolet light has a wavelength of less than 300 nm.

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