Photocurable adhesive sheet

Abstract

To provide a photocurable adhesive sheet suitably usable as a sealant for a self-luminous type display device such as mini / micro LED display devices, etc., excellent in reworkability, and difficult to cause a removal of the sealant in a use environment of the self-luminous type display device.SOLUTION: A photocurable adhesive sheet 10 is provided. The photocurable adhesive sheet 10 includes an adhesive layer 1 curable by a radiation exposure. The adhesive layer 1 has a 180° peel force of 11 N / 20 mm or less after exposure to a high-pressure mercury lamp.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photocurable adhesive sheet, and more particularly to a photocurable adhesive sheet suitable for sealing optical semiconductor elements of self-luminous display devices such as mini / micro LEDs. [Background technology]

[0002] In recent years, self-luminous display devices, such as mini / micro LED display devices (Mini / Micro Light Emitting Diode Displays), have been devised as next-generation display devices. Mini / micro LED display devices are basically configured such that a substrate on which a large number of minute optical semiconductor elements (LED chips) are densely arranged is used as a display panel, the optical semiconductor elements on the display panel are sealed with a sealing material, and a cover member such as a resin film or a glass plate is laminated on the outermost layer (see, for example, Patent Document 1).

[0003] In the case of self-luminous display devices such as mini / micro LED display devices, there are several methods such as a white backlight method, a white light-emitting color filter method, and an RGB method. In all cases, thousands to hundreds of thousands of optical semiconductor elements are arranged on a mounting board, and there is a problem that mounting defects cause the optical semiconductor elements to not light up, have different colors, be missing, or be misaligned, resulting in a decrease in yield. In addition, when sealing the display panel, mistakes such as wrinkles, contamination with foreign matter, and air bubbles may occur. When such a decrease in yield or sealing mistake occurs, the display panel is expensive, so rather than discarding it, the sealing material is peeled off and removed from the display panel, and the defective parts are repaired as necessary and reused, which is called rework. In addition, even in the case of self-luminous display devices manufactured as approved products, if a failure such as the optical semiconductor elements not lighting up occurs, it is desirable to peel off and remove the sealing material to repair it.

[0004] In the above-mentioned rework, the encapsulant must be easily peelable from the display panel so that the optoelectronic device is not damaged during peeling. Further, it is required to have the property that no encapsulant remains on the display panel after peeling (hereinafter referred to as "reworkability"). As a peeling method with excellent reworkability, a method is known in which a photocurable adhesive sheet is used and irradiated with light such as ultraviolet light to cause the adhesive sheet to cure and shrink, thereby reducing the anchor effect with the adherend and improving the reworkability (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The photocurable adhesive sheet of Patent Document 2 contains an acrylic resin, a crosslinking agent, a photopolymerization initiator, etc. When the photopolymerization initiator is cleaved by the action of light to generate radicals and the curing proceeds, a crosslinked structure is formed and the curing shrinkage proceeds. However, when a photocurable adhesive sheet such as that of Patent Document 2 is used as an encapsulant for a self-luminous display device, there is a problem that peeling of the encapsulant occurs in the use environment even in a self-luminous display device that is manufactured as a qualified product and does not require rework. This is because a part of the photopolymerization initiator is cleaved by ultraviolet rays contained in external light or light emitted from a blue optoelectronic device to generate radicals, and the curing shrinkage of the adhesive sheet proceeds.

[0007] The present invention has been conceived under the above circumstances, and an object of the present invention is to provide a photocurable adhesive sheet that can be suitably used as a sealing material for self-emitting display devices such as mini / micro LED display devices, has excellent reworkability, and is less likely to have the sealing material peeled off in the usage environment of the self-emitting display device. Another object of the present invention is to provide an optoelectronic device, a self-emitting display device, and an image display device that include the above photocurable adhesive sheet, are less likely to have the sealing material peeled off in the usage environment, and can peel off the sealing material for repair with good reworkability when a failure occurs.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the inventors of the present invention have found that by using a photocurable adhesive sheet whose curing reaction proceeds by a light source including a wavelength not included in external light or light emitted from a blue optoelectronic device as a sealing material for a self-emitting display device, it has excellent reworkability and is less likely to have the sealing material peeled off in the usage environment of the self-emitting display device. The present invention has been completed based on these findings.

[0009] A first aspect of the present invention provides a photocurable adhesive sheet. The photocurable adhesive sheet according to the first aspect of the present invention can be suitably used as a sealing material for self-emitting display devices such as mini / micro LEDs. In self-emitting display devices, there are problems such as non-lighting, color difference, missing, and misalignment of optoelectronic elements, which result in a decrease in yield. In addition, when sealing the display panel, mistakes such as wrinkles, foreign matter contamination, and air bubbles remaining may occur. When such a decrease in yield and sealing mistakes occur, so-called rework is performed, in which the sealing material is peeled off and removed from the display panel and reused.

[0010] The photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention has a pressure-sensitive adhesive layer that cures upon irradiation with radiation, and the pressure-sensitive adhesive layer has a 180° peel strength of 11 N / 20 mm or less after irradiation with a high-pressure mercury lamp. This configuration is such that when the photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention is used as a sealing material for a self-luminous display device, if there is a reduction in yield or a sealing error, the pressure-sensitive adhesive layer (sealing material) after irradiation with a high-pressure mercury lamp cures and shrinks, resulting in a reduction in the anchor effect with the substrate of the display panel or the optical semiconductor element, and thus it can be easily peeled off, and it is less likely for the sealing material to remain on the display panel after peeling. That is, it is suitable in that the sealing material can be peeled off with excellent reworkability. Further, when a failure such as non-lighting of the optical semiconductor element occurs in the self-luminous display device, the pressure-sensitive adhesive layer can be peeled off and removed with good reworkability by irradiating the pressure-sensitive adhesive layer with a high-pressure mercury lamp, which is also preferable.

[0011] In the photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention, it is preferable that the change rate of the 180° peel strength of the pressure-sensitive adhesive layer before and after UV-LED irradiation is within 10%. This configuration is suitable in that in a self-luminous display device using the photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention as a sealing material, the pressure-sensitive adhesive layer can be prevented from curing and shrinking due to ultraviolet rays contained in external light in the use environment or light emitted from a blue optical semiconductor element, and thus the pressure-sensitive adhesive layer (sealing material) can be prevented from peeling off from the display panel.

[0012] In the photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention, it is preferable that the tensile storage modulus (E’a25) of the pressure-sensitive adhesive layer at 25°C after irradiation with a high-pressure mercury lamp is 400 kPa or more. This configuration is suitable in that when the photocurable pressure-sensitive adhesive sheet according to the first aspect of the present invention is used as a sealing material for an optical semiconductor element of a self-luminous display device, if there is a reduction in yield or a sealing error, the reworkability of the pressure-sensitive adhesive layer (sealing material) after irradiation with a high-pressure mercury lamp is improved.

[0013] In the photocurable adhesive sheet according to the first aspect of the present invention, it is preferable that the maximum value of the transmittance of the adhesive layer at a wavelength of 200 to 400 nm is 5% or more. This configuration is preferable in that the adhesive layer can be cured and shrunk by irradiation with the high-pressure mercury lamp, thereby improving the reworkability.

[0014] In the photocurable adhesive sheet according to the first aspect of the present invention, it is preferable that the ratio (kPa / μm) of the tensile storage modulus (E’a25: kPa) at 25°C after irradiation with the high-pressure mercury lamp to the thickness (μm) of the adhesive layer is 1 to 50. This configuration is preferable in that the above-mentioned reworkability can be adjusted according to the thickness of the adhesive layer.

[0015] In the photocurable adhesive sheet according to the first aspect of the present invention, the light irradiated by the high-pressure mercury lamp preferably includes radiation having a wavelength of 200 to 280 nm. Further, in the photocurable adhesive sheet according to the first aspect of the present invention, the light irradiated by the UV-LED is preferably radiation having a wavelength of 350 nm or more. These configurations are such that the adhesive layer is cured and shrunk by a high-pressure mercury lamp, which is a light source including radiation having a wavelength of 200 to 280 nm and not included in the light emitted from external light or a blue light semiconductor element, thereby improving the reworkability. On the other hand, the curing shrinkage does not proceed due to radiation having a wavelength of 350 nm or more included in the light emitted from external light or a blue light semiconductor element. Therefore, in the usage environment of the self-luminous display device, it is preferable in that peeling of the adhesive layer (sealing material) can be prevented.

[0016] The second aspect of the present invention provides a semiconductor device including a substrate, one or more semiconductor elements disposed on the substrate, and the photocurable adhesive sheet according to the first aspect of the present invention, wherein the photocurable adhesive sheet seals the semiconductor element. The semiconductor device according to the second aspect of the present invention is preferably a self-luminous display device. Further, the third aspect of the present invention provides an image display device including the self-luminous display device.

[0017] The optical semiconductor device according to the second aspect of the present invention (preferably a self-luminous display device), and the image display device according to the third aspect of the present invention are manufactured using the photocurable adhesive sheet according to the first aspect of the present invention. Therefore, it is preferable in that the curing shrinkage of the adhesive layer hardly proceeds due to ultraviolet rays contained in external light or light emitted from a blue optical semiconductor element in the use environment, and peeling of the adhesive layer (sealing material) can be prevented. Further, when a failure such as non-lighting of the optical semiconductor element occurs, by irradiating the adhesive layer with a high-pressure mercury lamp, the adhesive layer (sealing material) can be peeled off with good reworkability and repaired, which is preferable.

Advantages of the Invention

[0018] When the photocurable adhesive sheet of the present invention is used as a sealing material for a self-luminous display device, when a yield reduction or a sealing error occurs, the adhesive layer after irradiation with a high-pressure mercury lamp cures and shrinks, and can be peeled off with excellent reworkability, which is preferable in that the display panel can be reused.

[0019] Further, in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, the adhesive layer cures and shrinks due to ultraviolet rays contained in external light or light emitted from a blue optical semiconductor element in the use environment, which is preferable in that peeling of the adhesive layer (sealing material) from the display panel can be prevented.

[0020] Furthermore, when a failure such as non-lighting of the optical semiconductor element occurs in the self-luminous display device, by irradiating the adhesive layer with a high-pressure mercury lamp, the adhesive layer can be peeled off and removed with good reworkability for repair, which is also preferable.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0022] The first aspect of the present invention provides a photocurable adhesive sheet having an adhesive layer that cures by radiation irradiation. The adhesive layer has a 180° peel strength of 11 N / 20 mm or less after irradiation with a high-pressure mercury lamp. The photocurable adhesive sheet of the first aspect of the present invention may be referred to as "the photocurable adhesive sheet of the present invention", and the "adhesive layer that cures by radiation irradiation" may be referred to as "the adhesive layer of the present invention".

[0023] Further, the second aspect of the present invention provides a semiconductor optical device including a substrate, one or more semiconductor optical elements disposed on the substrate, and the photocurable adhesive sheet of the first aspect of the present invention, wherein the photocurable adhesive sheet seals the semiconductor optical elements. The semiconductor optical device of the second aspect of the present invention is preferably a self-emitting display device. Further, the third aspect of the present invention provides an image display device including the self-emitting display device. The semiconductor optical device and the self-emitting display device of the second aspect of the present invention may be referred to as "the semiconductor optical device of the present invention" and "the self-emitting display device of the present invention", respectively. Also, the image display device of the third aspect of the present invention may be referred to as "the image display device of the present invention".

[0024] Hereinafter, embodiments of the present invention will be described in relation to the drawings, but the present invention is not limited thereto and is merely illustrative. FIGS. 1 and 2 are cross-sectional views showing an embodiment of the photocurable adhesive sheet of the present invention.

[0025] The photocurable adhesive sheet 10 according to an embodiment of the present invention in FIG. 1 is composed of an adhesive layer 1, a release film S1 laminated on one main surface of the adhesive layer 1, and a release film S2 laminated on the other main surface of the adhesive layer 1.

[0026] The photocurable adhesive sheet 11 according to an embodiment of the present invention in FIG. 2 is composed of an adhesive layer 1, a base material S3 laminated on one main surface of the adhesive layer 1, and a release film S4 laminated on the other main surface of the adhesive layer 1.

[0027] In FIGS. 1 and 2, the adhesive layer 1 has two opposing main surfaces and may be a single layer or a laminated structure of two or more layers.

[0028] FIG. 3 is a schematic diagram (cross-sectional view) showing an embodiment of the self-luminous display device (mini / micro LED display device) of the present invention.

[0029] The self-luminous display device (mini / micro LED display device) 20 according to an embodiment of the present invention in FIG. 3 includes a display panel in which a plurality of optical semiconductor elements (LED chips) 4 are arranged on one side of a substrate 2, and the photocurable adhesive sheet 11 of the present invention. The optical semiconductor elements 4 on the substrate 2 are sealed by the adhesive layer 1 of the photocurable adhesive sheet 11. Hereinafter, each component will be described in detail.

[0030] <Photocurable Adhesive Sheet, Adhesive Layer> The photocurable adhesive sheet of the present invention is preferably used in a form for sealing optical semiconductor elements of a self-luminous display device such as a mini / micro LED display device in which a plurality of optical semiconductor elements are arranged on a substrate. The optical semiconductor element is not particularly limited as long as it is a semiconductor element having a light-emitting function, and includes a light-emitting diode (LED), a semiconductor laser, and the like.

[0031] The form of the photocurable pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as the pressure-sensitive adhesive surface is the pressure-sensitive adhesive surface (the surface of the pressure-sensitive adhesive layer) formed by the pressure-sensitive adhesive layer of the present invention. For example, it may be a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive surface on only one side, or a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive surfaces on both sides. Further, when the photocurable pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, the photocurable pressure-sensitive adhesive sheet of the present invention may have a form in which both pressure-sensitive adhesive surfaces are provided by the pressure-sensitive adhesive layer of the present invention, or may have a form in which one pressure-sensitive adhesive surface is provided by the pressure-sensitive adhesive layer of the present invention and the other pressure-sensitive adhesive surface is provided by a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer of the present invention (other pressure-sensitive adhesive layer). From the viewpoint of encapsulating the optical semiconductor element of the self-luminous display device, a single-sided pressure-sensitive adhesive sheet is preferred.

[0032] The photocurable pressure-sensitive adhesive sheet of the present invention may be a so-called "substrate-less type" pressure-sensitive adhesive sheet having no substrate (substrate layer), or may be a type of pressure-sensitive adhesive sheet having a substrate. In this specification, the "substrate-less type" pressure-sensitive adhesive sheet may be referred to as a "substrate-less pressure-sensitive adhesive sheet", and the type of pressure-sensitive adhesive sheet having a substrate may be referred to as a "pressure-sensitive adhesive sheet with substrate". Examples of the substrate-less pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet composed only of the pressure-sensitive adhesive layer of the present invention, and a double-sided pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer of the present invention and other pressure-sensitive adhesive layers (pressure-sensitive adhesive layers other than the pressure-sensitive adhesive layer of the present invention). Examples of the pressure-sensitive adhesive sheet with substrate include a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on one side of the substrate, a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on both sides of the substrate, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on one side of the substrate and other pressure-sensitive adhesive layers on the other side.

[0033] Among the above, from the viewpoint of improving optical physical properties such as transparency, a substrate-less pressure-sensitive adhesive sheet is preferred, and more preferably, a double-sided pressure-sensitive adhesive sheet having no substrate (substrate-less double-sided pressure-sensitive adhesive sheet) composed only of the pressure-sensitive adhesive layer of the present invention. Further, when the photocurable pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet having a substrate, although not particularly limited, from the viewpoint of processability, it is preferably a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on both sides of the substrate (double-sided pressure-sensitive adhesive sheet with substrate). Note that the above-mentioned "base material (base material layer)" is the part that is pasted onto the adherend (such as an optical member) together with the pressure-sensitive adhesive layer when the pressure-sensitive adhesive layer of the present invention is used (pasted) on the adherend, and does not include the release film (separator) that is peeled off when the adhesive sheet is used (pasted).

[0034] In a self-luminous display device, there is a problem that the yield decreases due to non-lighting, color difference, missing, misalignment, etc. of the optical semiconductor element. In addition, when sealing the display panel, there may be mistakes such as wrinkles, foreign matter mixing, and air bubbles remaining. When such a decrease in yield and sealing mistakes occur, so-called rework is performed, in which the sealing material is peeled off and removed from the display panel and reused.

[0035] The pressure-sensitive adhesive layer of the present invention has a 180° peel strength of 11 N / 20 mm or less after irradiation with a high-pressure mercury lamp. This configuration is such that when the photocurable pressure-sensitive adhesive sheet of the present invention is used as a sealing material for a self-luminous display device, if a decrease in yield or a sealing mistake occurs, the pressure-sensitive adhesive layer (sealing material) shrinks due to curing after irradiation with a high-pressure mercury lamp, resulting in a reduced anchor effect with the substrate or optical semiconductor element of the display panel. As a result, it can be easily peeled off, and it is difficult for the sealing material to remain on the display panel after peeling. That is, it is suitable in terms of being able to peel off the sealing material with excellent reworkability. In addition, when a failure such as non-lighting of the optical semiconductor element occurs in the self-luminous display device of the present invention, it is also preferable in that the pressure-sensitive adhesive layer can be peeled off and removed for repair with good reworkability by irradiating the pressure-sensitive adhesive layer of the present invention with a high-pressure mercury lamp.

[0036] From the viewpoint of further improving the reworkability of the photocurable pressure-sensitive adhesive sheet of the present invention, the 180° peel strength of the pressure-sensitive adhesive layer of the present invention after irradiation with a high-pressure mercury lamp is preferably 10.5 N / 20 mm or less, more preferably 10 N / 20 mm or less, still more preferably 9.8 N / 20 mm or less, and may even be 9.5 N / 20 mm or less. In addition, the lower limit value of the 180° peel strength of the pressure-sensitive adhesive layer of the present invention after irradiation with a high-pressure mercury lamp is not particularly limited, and the lower it is, the more preferable it is. That is, 0 N / 20 mm is preferable, but it may also be 0.1 N / 20 mm or more.

[0037] The 180° peel strength of the pressure-sensitive adhesive layer of the invention after irradiation with a high-pressure mercury lamp can be measured by the method of the following examples. The composition of the monomers of the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the invention (for example, the Mw, Tg, and BP equivalent of the BP polymer (A) described below; 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 crosslinking agent, etc.) can be adjusted.

[0038] It is preferable that the rate of change of the 180° peel strength of the pressure-sensitive adhesive layer of the invention before and after UV-LED irradiation (the percentage of the change amount when the 180° peel strength before UV-LED irradiation is taken as 100%) is within 10%. This configuration is suitable in that in a self-luminous display device using the photocurable pressure-sensitive adhesive sheet of the invention as a sealing material, the pressure-sensitive adhesive layer is cured and shrunk by ultraviolet rays contained in external light or light emitted from a blue light semiconductor element in the use environment, and the pressure-sensitive adhesive layer (sealing material) can be prevented from peeling from the display panel. From the viewpoint of preventing peeling of the sealing material of the self-luminous display device in the use environment, the rate of change is preferably within 9%, more preferably within 8%, still more preferably within 7%, and may be within 6% or within 5%. The lower limit value of the rate of change of the peel strength is not particularly limited, and the lower it is, the more preferable it is. That is, 0% is preferable, but it may be 0.01% or more.

[0039] The 180° peel strength of the pressure-sensitive adhesive layer of the invention before radiation irradiation is not particularly limited, but from the viewpoint of the adhesion reliability to the display panel, it is preferably more than 11 N / 20 mm, more preferably 11.5 N / 20 mm or more, and may be 12 N / 20 mm or more. Further, the upper limit of the 180° peel strength of the invention before radiation irradiation is not particularly limited, and the higher it is, the more preferable it is. For example, it may be 100 N / 20 mm or less.

[0040] The adhesive layer of the present invention preferably has a 180° peel strength exceeding 11 N / 20 mm after UV-LED irradiation. This configuration is suitable in that, in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, the adhesive layer is cured and shrunk by ultraviolet rays contained in external light in the usage environment or light emitted from a blue light semiconductor element, thereby preventing the adhesive layer (sealing material) from peeling off from the display panel. From the viewpoint of preventing peeling of the sealing material of the self-luminous display device in the usage environment, the 180° peel strength after UV-LED irradiation is more preferably 11.5 N / 20 mm or more, and may be 12 N / 20 mm or more. Further, the upper limit of the 180° peel strength after UV-LED irradiation of the present invention is not particularly limited, and the higher the better, but it may be 100 N / 20 mm or less.

[0041] The 180° peel strength before radiation irradiation or before and after UV-LED irradiation of the adhesive layer of the present invention, and its change rate can be measured by the examples described later, and the composition of the monomers of the adhesive composition constituting the adhesive layer of the present invention (for example, Mw, Tg, BP equivalent of the BP polymer (A) described later; 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.) can be adjusted.

[0042] The adhesive layer of the present invention preferably has a tensile storage modulus (E’a25) at 25°C of 400 kPa or more after high-pressure mercury lamp irradiation. This configuration is suitable in that, when the photocurable adhesive sheet of the present invention is used as a sealing material for a light semiconductor element of a self-luminous display device, if there is a reduction in yield or a sealing error, the reworkability of the adhesive layer (sealing material) after high-pressure mercury lamp irradiation is improved. From the viewpoint of further improving the reworkability of the adhesive layer of the present invention, E’a25 is more preferably 500 kPa or more, and even more preferably 600 kPa or more. Further, the upper limit of E’a25 is not particularly limited, and the higher the better, but it may be 10,000 kPa or less.

[0043] The adhesive layer of the present invention preferably has a tensile storage elastic modulus (E’a85) at 85°C after high-pressure mercury lamp irradiation of 500 kPa or more. This configuration is suitable in that when the photocurable adhesive sheet of the present invention is used as a sealing material for a light semiconductor element of a self-luminous display device, the reworkability of the adhesive layer (sealing material) after high-pressure mercury lamp irradiation is improved in the case of yield reduction or sealing failure. From the viewpoint of further improving the reworkability of the adhesive layer of the present invention, E’a85 is more preferably 520 kPa or more, still more preferably 550 kPa or more, and may be 570 kPa or more. Further, the upper limit of E’a85 is not particularly limited, and the higher the better, but it may be 10,000 kPa or less.

[0044] The adhesive layer of the present invention preferably has a shear storage elastic modulus (G’a25) at 25°C after UV-LED irradiation of 500 kPa or less. This configuration is suitable in that in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, the adhesive layer is cured and shrunk by ultraviolet rays contained in external light or light emitted from a blue light semiconductor element in the use environment, and peeling of the adhesive layer (sealing material) from the display panel can be prevented. From the viewpoint of preventing peeling of the sealing material of the self-luminous display device in the use environment, G’a25 is more preferably 300 kPa or less, still more preferably 200 kPa or less, and may be 180 kPa or less. Further, the lower limit value of G’a25 is not particularly limited, but it may be 10 kPa or more.

[0045] The adhesive layer of the present invention preferably has a shear storage modulus (G’a85) at 85°C after UV-LED irradiation of 95 kPa or less. This configuration is suitable in that in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, the adhesive layer is cured and shrunk by ultraviolet rays contained in external light or light emitted from a blue light semiconductor element in the usage environment, and peeling of the adhesive layer (sealing material) from the display panel can be prevented. From the viewpoint of preventing peeling of the sealing material of the self-luminous display device in the usage environment, G’a85 is more preferably 90 kPa or less, still more preferably 85 kPa or less, and may be 80 kPa or less. Further, G’a85 is not particularly limited, but may be 10 kPa or more.

[0046] The adhesive layer of the present invention preferably has a shear storage modulus (G’b25) at 25°C before radiation irradiation of 500 kPa or less. This configuration is suitable in that in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, it is excellent in step followability to the optical semiconductor element. From the viewpoint of further improving the step followability, G’b25 is more preferably 300 kPa or less, still more preferably 200 kPa or less, and may be 160 kPa or less. Further, G’b25 is not particularly limited, but from the viewpoint of adhesion reliability, 50 kPa or more is preferable, and it may be 100 kPa or more.

[0047] The adhesive layer of the present invention preferably has a shear storage modulus (G’b85) at 85°C before radiation irradiation of 95 kPa or less. This configuration is suitable in that in a self-luminous display device using the photocurable adhesive sheet of the present invention as a sealing material, it is excellent in step followability to the optical semiconductor element. From the viewpoint of further improving the step followability, it is more preferably 90 kPa or less, still more preferably 85 kPa or less, and may be 80 kPa or less. Further, G’b85 is not particularly limited, but may be 50 kPa or more from the viewpoint of adhesion reliability.

[0048] It is preferable that the ratio (kPa / μm) of the tensile storage modulus (E’a25: kPa) at 25°C after high-pressure mercury lamp irradiation to the thickness (μm) of the adhesive layer is 1 or more. This configuration is suitable in that when the photocurable adhesive sheet of the present invention is used as a sealing material for a photodiode element of a self-luminous display device, the reworkability of the adhesive layer (sealing material) after high-pressure mercury lamp irradiation is improved when yield reduction or sealing failure occurs. From the viewpoint of further improving the reworkability of the adhesive layer of the present invention, E’a25 / thickness is preferably 5 or more, and may be 10 or more. Further, E’a25 / thickness is not particularly limited, but may be 50 or less.

[0049] It is preferable that the ratio (kPa / μm) of the tensile storage modulus (E’a85: kPa) at 85°C after high-pressure mercury lamp irradiation to the thickness (μm) of the adhesive layer is 1 or more. This configuration is suitable in that when the photocurable adhesive sheet of the present invention is used as a sealing material for a photodiode element of a self-luminous display device, the reworkability of the adhesive layer (sealing material) after high-pressure mercury lamp irradiation is improved when yield reduction or sealing failure occurs. From the viewpoint of further improving the reworkability of the adhesive layer of the present invention, E’a85 / thickness is preferably 5 or more, and may be 10 or more. Further, E’a85 / thickness is not particularly limited, but may be 50 or less.

[0050] The tensile storage modulus (E’a25; E’a85) at 25°C or 85°C after high-pressure mercury lamp irradiation, the shear storage modulus (G’a25; G’a85) at 25°C or 85°C after UV-LED irradiation, and the storage modulus (G’b25; G’b85) at 25°C or 85°C before radiation irradiation in the adhesive layer of the present invention can be measured by the examples described later, and can be adjusted by the composition of the monomers of the adhesive composition constituting the adhesive layer of the present invention (for example, the Mw, Tg, BP equivalent of the BP polymer (A) described later; 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 crosslinking agent), etc.

[0051] In the photocurable adhesive sheet of the present invention, the light irradiated by the high-pressure mercury lamp preferably includes radiation with a wavelength of 200 to 280 nm, and the light irradiated by the UV-LED is preferably radiation with a wavelength of 350 nm or more. These configurations are such that while the adhesive layer of the present invention is cured and shrunk by a high-pressure mercury lamp, which is a light source containing radiation with a wavelength of 200 to 280 nm not included in the light emitted from external light or a blue light semiconductor element, improving the reworkability, on the other hand, the curing shrinkage does not progress due to radiation with a wavelength of 350 nm or more included in the light emitted from external light or a blue light semiconductor element. Therefore, in the usage environment of the self-luminous display device, it is preferable in that peeling of the adhesive layer (sealing material) can be prevented.

[0052] Preferably, the maximum value of the transmittance of the adhesive layer of the present invention in the wavelength range of 200 to 400 nm is 5% or more. This configuration is preferable in that the adhesive layer can be cured and shrunk by the irradiation of the high-pressure mercury lamp, improving the reworkability. In terms of improving the reworkability, the maximum value of the transmittance of the adhesive layer in the wavelength range of 200 to 400 nm is preferably 10% or more, more preferably 15% or more, and may be 20% or more or 25% or more.

[0053] The "maximum value of the transmittance in the wavelength range of 200 to 400 nm" means the highest transmittance within the range of the wavelength range of 200 to 400 nm. For example, when there is one maximum value of transmittance in the wavelength range of 200 to 400 nm, the maximum value is the maximum value of the transmittance. Also, when there is no maximum value of transmittance in the wavelength range of 200 to 400 nm, the higher transmittance among the transmittances at wavelengths of 200 nm or 400 nm is the maximum value. The same applies to the "maximum value of the transmittance in the wavelength range of 400 to 700 nm".

[0054] The maximum value of the transmittance of the pressure-sensitive adhesive layer of the present invention at a wavelength of 200 to 400 nm can be adjusted by the composition of the monomers of the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the present invention (for example, the Mw, Tg, and BP equivalent of the BP polymer (A) described later; 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), the type and blending amount of the colorant described later, and the like.

[0055] The thickness of the pressure-sensitive adhesive layer of the present invention 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 pressure-sensitive adhesive layer of the present invention may be 400 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. By setting the above thickness to 10 μm or more, the pressure-sensitive adhesive layer easily follows the stepped portion, and the stepped absorption property is improved. Further, by setting the above thickness to 500 μm or less, the reworkability of the pressure-sensitive adhesive layer of the present invention is improved.

[0056] The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer of the present invention is not particularly limited as long as it can achieve the above-described desired characteristics, but preferably has a form containing a polymer (A) having a benzophenone structure in the side chain. Further, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer of the present invention preferably has a form containing a mixture of monomer components constituting the polymer (A) having a benzophenone structure in the side chain or a partial polymer of a mixture of monomer components constituting the polymer (A) having a benzophenone structure in the side chain. Hereinafter, this embodiment will be described, but the present invention is not limited to this embodiment. The pressure-sensitive adhesive layer in this embodiment may be referred to as "pressure-sensitive adhesive layer (A)", the pressure-sensitive adhesive composition may be referred to as "pressure-sensitive adhesive composition (A)", and the polymer (A) having a benzophenone structure in the side chain contained in the pressure-sensitive adhesive composition (A) may be referred to as "BP polymer (A)".

[0057] As used herein, the “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 acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group in one molecule. Also, in this specification, “(meth)acryloyl” means comprehensively referring to acryloyl and methacryloyl. Similarly, “(meth)acrylate” means comprehensively referring to acrylate and methacrylate, and “(meth)acrylic” means comprehensively referring to acrylic and methacrylic, respectively.

[0058] As used herein, the “ethylenically unsaturated compound” refers to a compound having at least one ethylenically unsaturated group in the molecule. Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, an allyl group, etc. 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”. Also, among the polyfunctional monomers, a compound having X ethylenically unsaturated groups may be denoted as an “X-functional monomer”.

[0059] In this specification, when it is said that the pressure-sensitive adhesive composition contains an ethylenically unsaturated compound, unless otherwise specified, it means including containing the above ethylenically unsaturated compound in the form of a partial polymer. Such a partial polymer is usually a mixture containing the above ethylenically unsaturated compound with unreacted ethylenically unsaturated groups (unreacted monomer) and the above ethylenically unsaturated compound with polymerized ethylenically unsaturated groups.

[0060] In this specification, the total monomer components constituting the pressure-sensitive adhesive composition refers to the total amount of the monomer components constituting the polymer contained in the pressure-sensitive adhesive composition and the monomer components contained in the form of unreacted monomers in the pressure-sensitive adhesive composition. The composition of the monomer components constituting the pressure-sensitive adhesive composition generally coincides with the composition of the monomer components of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition and the composition of the monomer components constituting the photocured product thereof.

[0061] In this specification, the "active energy ray" is a concept including light such as ultraviolet rays, visible light, and infrared rays, and radiation such as α-rays, β-rays, γ-rays, electron beams, neutron beams, and X-rays.

[0062] [Adhesive composition (A)] The adhesive composition (A) contains a polymer (A) having a benzophenone structure in the side chain. Further, the adhesive composition (A) may be in a form containing a mixture of monomer components constituting the polymer (A) having a benzophenone structure in the side chain or a partial polymer of a mixture of monomer components constituting the polymer (A) having a benzophenone structure in the side chain. The adhesive composition (A) may further contain an ethylenically unsaturated compound (B). In addition to the above, the adhesive composition (A) may contain a photopolymerization initiator (C) that absorbs ultraviolet rays with a wavelength of 300 nm to 500 nm described later and generates radicals, and other additives. In this specification, the above "mixture of monomer components" includes both the case composed of a single monomer component and the case composed of two or more monomer components. Further, the above "partial polymer of a mixture of monomer components" means a composition in which one or more of the constituent monomer components of the above "mixture of monomer components" are partially polymerized.

[0063] The adhesive composition (A) may have any form, and examples include a solvent type, an emulsion type, a hot melt type (hot melt type), a solvent-free type (active energy ray curable type, for example, a monomer mixture, or a monomer mixture and its partial polymer, etc.). From the viewpoint of obtaining an adhesive layer with excellent appearance properties, the adhesive composition (A) is preferably an active energy ray curable type. 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.

[0064] The pressure-sensitive adhesive composition (A) is not particularly limited. For example, a composition containing a BP polymer (A) as an essential component; a composition containing a mixture of monomer components constituting the BP polymer (A) or a partial polymer thereof as an essential component, etc. may be mentioned. Although not particularly limited, examples of the former include so-called solvent-based pressure-sensitive adhesive compositions, water-dispersed pressure-sensitive adhesive compositions (emulsion-type pressure-sensitive adhesive compositions), etc., and examples of the latter include so-called active energy ray-curable pressure-sensitive adhesive compositions, etc.

[0065] As described above, the pressure-sensitive adhesive composition (A) may be solvent-based. The above solvent is not particularly limited as long as it is an organic compound used as a solvent. For example, 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; alcohol solvents such as methanol, ethanol, butanol, and isopropyl alcohol, etc. may be mentioned. Incidentally, the above solvent may be a mixed solvent containing two or more solvents.

[0066] [Polymer (A) having a benzophenone structure in the side chain] As the base polymer constituting the pressure-sensitive adhesive composition (A) of the present invention, a polymer (A) (BP polymer (A)) having a benzophenone structure in the side chain is included. That is, the pressure-sensitive adhesive composition (A) of the present invention is a pressure-sensitive adhesive composition containing a BP polymer (A) as a base polymer. Incidentally, the BP polymer (A) can be used alone or in combination of two or more.

[0067] The monomer components that can constitute 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 BP"). Further, ethylenically unsaturated compounds that do not correspond to ethylenically unsaturated BP (hereinafter also referred to as "other ethylenically unsaturated compounds") may be included.

[0068] Preferable examples of the BP polymer (A) include acrylic polymers having a benzophenone structure in the side chain. The above BP polymer (A) is preferably a polymer that substantially does not contain ethylenically unsaturated groups.

[0069] In this specification, the "benzophenone structure" refers to the general formula: Ar 1 -(C=O)-Ar 2 -; or, -Ar 3 -(C=O)-Ar 2 -; which represents a diaryl ketone structure. Here, Ar 1 in the above general formula is selected from phenyl groups which may have substituents. In the above general formula, Ar 2 , Ar 3 are each independently selected from phenylene groups which may have substituents. Ar 2 and Ar 3 may be the same or different. The benzophenone structure can be excited by ultraviolet irradiation, and in its excited state, it can extract hydrogen radicals from other molecules or other parts of the molecule.

[0070] The adhesive layer (A) formed from the cured product of the adhesive composition (A) containing the BP polymer (A) may contain a benzophenone structure. By utilizing the hydrogen radical extraction reaction through excitation by ultraviolet irradiation of the benzophenone structure to form a crosslinked structure, the adhesive layer (A) can be cured.

[0071] As the above BP polymer (A), a polymer having a benzophenone structure with Ar 1 -(C=O)-Ar 2 -; in the above general formula, where Ar 1 is a phenyl group which may have substituents and Ar 2 is a phenylene group which may have substituents in the side chain is preferable. The above Ar 1 and Ar 2When at least one of them has one or more substituents, each of the substituents may be independently selected from the group consisting of an alkoxy group (for example, an alkoxy group having 1 to 3 carbon atoms. Preferably a methoxy group), a halogen atom (for example, F, Cl, Br, etc. Preferably Cl or Br), a hydroxyl group, an amino group, and a carboxyl group.

[0072] 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 through one or more of, for example, an ester bond, an oxyalkylene structure, etc. Preferred examples of the BP polymer (A) include polymers containing repeating units derived from ethylenically unsaturated BP. The above repeating unit may be a polymerization residue obtained by reacting the ethylenically unsaturated group of the corresponding ethylenically unsaturated BP.

[0073] Examples of the ethylenically unsaturated BP include, but are not limited to, acryloyloxybenzophenones which may have substituents such as 4-acryloyloxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 2-hydroxy-4-acryloyloxybenzophenone; acryloyloxyalkoxybenzophenones which may have substituents such as 4-[(2-acryloyloxy)ethoxy]benzophenone, 4-[(2-acryloyloxy)ethoxy]-4'-bromobenzophenone; methacryloyloxybenzophenones which may have substituents such as 4-methacryloyloxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, 2-hydroxy-4-methacryloyloxybenzophenone; methacryloyloxyalkoxybenzophenones which may have substituents such as 4-[(2-methacryloyloxy)ethoxy]benzophenone, 4-[(2-methacryloyloxy)ethoxy]-4'-methoxybenzophenone; vinylbenzophenones which may have substituents such as 4-vinylbenzophenone, 4'-bromo-3-vinylbenzophenone, 2-hydroxy 4-methoxy-4'-vinylbenzophenone. The ethylenically unsaturated BP can be used alone or in combination of two or more for the preparation of the BP polymer (A). As the ethylenically unsaturated BP, commercially available products can be used, or it can be synthesized by known methods. From the viewpoint of reactivity and the like, an ethylenically unsaturated BP having a (meth)acryloyl group, that is, an ethylenically unsaturated BP which is an acrylic monomer, can preferably be employed.

[0074] The above BP polymer (A) may be a copolymer having repeating units derived from ethylenically unsaturated BP and repeating units derived from an ethylenically unsaturated compound (other ethylenically unsaturated compound) that does not correspond to ethylenically unsaturated BP. Such a BP polymer (A) can be a copolymer of monomer components including the above ethylenically unsaturated BP and the above other ethylenically unsaturated compound. Further, the BP polymer can also be a copolymer obtained by copolymerizing a prepolymer (a partial polymer of a monomer mixture consisting only of the above other ethylenically unsaturated compound) and the ethylenically unsaturated BP. One or more acrylic monomers can be preferably employed as the above other ethylenically unsaturated compound. As a preferred example of the BP polymer (A), 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 can be mentioned.

[0075] The monomer components constituting the BP polymer (A) can include one or more selected from alkyl (meth)acrylates having an alkyl group at the ester terminal as the above other ethylenically unsaturated compound. Hereinafter, an alkyl (meth)acrylate having a linear or branched alkyl group having X or more and Y or less carbon atoms at the ester terminal may be referred to as "(meth)acrylic acid C X-Y alkyl ester". The monomer components constituting the BP polymer (A) preferably include at least (meth)acrylic acid C 1-20 alkyl ester, more preferably include (meth)acrylic acid C 4-20 alkyl ester, and even more preferably include (meth)acrylic acid C 4-18 alkyl ester (for example, acrylic acid C 4-9 alkyl ester).

[0076] (meth)acrylic acid C 1-20Non-limiting specific examples of the 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, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and the like. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate, and the like. Other specific examples of the alkyl (meth)acrylate that can be preferably used include n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), and the like. The alkyl (meth)acrylate can be used alone or in combination of two or more. The monomer component constituting the BP polymer (A) may contain one or more selected from the copolymerizable monomers as the other ethylenically unsaturated compounds described below.

[0077] The pressure-sensitive adhesive composition (A) can be a photocurable acrylic pressure-sensitive adhesive composition in which more than 50% by weight (preferably more than 70% by weight, for example, more than 90% by weight) of the total monomer components constituting it are acrylic monomers. The photocurable acrylic pressure-sensitive adhesive composition forms an acrylic photocured product by photocuring.

[0078] The weight average molecular weight (Mw) of the BP polymer (A) is not particularly limited and can be, for example, 0.5×10 4 ~500×10 4 or so. From the viewpoints of the cohesiveness of the pressure-sensitive adhesive layer (A) and the handleability of the photocurable pressure-sensitive adhesive sheet of the present invention, etc., the Mw of the above BP polymer (A) is usually suitably 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, may be 20×10 4 or more. Further, from the viewpoint of the reworkability of the pressure-sensitive adhesive layer (A), the Mw of the BP polymer (A) is usually suitably 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, may be 50×10 4 or less. Note that the weight average molecular weight (Mw) of the polymer refers to the value in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used.

[0079] 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 higher and 150°C or lower, may be -80°C or higher and 50°C or lower, or may be -80°C or higher and 10°C or lower. From the viewpoint of the step absorptivity of the pressure-sensitive adhesive layer (A), the Tg of the BP polymer (A) is preferably less than 0°C, more preferably -10°C or lower, and may be -20°C or lower, -30°C or lower, -40°C or lower, or -50°C or lower. Also, from the viewpoints of the cohesiveness of the pressure-sensitive adhesive layer (A) and the improvement of the reworkability after photocuring, the Tg of the BP polymer (A) is usually advantageously -75°C or higher, and may be -70°C or higher. In some embodiments, the Tg of the BP polymer (A) may be -55°C or higher, or may be -45°C or higher. The Tg of the BP polymer (A) can be adjusted by the types and amounts of the monomer components constituting the BP polymer.

[0080] Here, the glass transition temperature (Tg) of a polymer refers to the glass transition temperature determined by Fox's equation based on the composition of the monomer components constituting the polymer. As shown below, Fox's equation is a relational equation between the Tg of a copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing each of the monomers constituting the copolymer. 1 / Tg = Σ(Wi / Tgi) In the above Fox's equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0081] As the glass transition temperatures of the homopolymers used for calculating Tg, the values described in known materials shall be used. 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

[0082] Regarding the glass transition temperatures of homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this literature, the highest value shall be adopted. For monomers for which the glass transition temperatures of homopolymers are not described in the above Polymer Handbook, the values obtained by the measurement method described in JP-A-2007-51271 shall be used. In addition, for polymers for which the nominal values of the glass transition temperatures are provided by manufacturers or the like, the nominal values may be adopted.

[0083] BP polymer (A) preferably contains a benzophenone structure of, for example, about 0.5 mg or more per 1 g of the polymer, in terms of 4-benzoylphenyl acrylate. Hereinafter, the value obtained by converting the number of benzophenone structures contained per 1 g of the BP polymer into the amount in terms of 4-benzoylphenyl acrylate may be referred to as the BP equivalent (unit: mg / g) of the BP polymer. For example, when 1 g contains 40 μmol of benzophenone structures, the BP equivalent of the polymer is calculated to be 10 mg / g.

[0084] From the viewpoint of obtaining a higher photocuring effect (for example, the effect of enhancing processability by photocuring), in some embodiments, the BP equivalent of the BP polymer (A) is usually suitably 0.1 mg / g or more, may be 0.5 mg / g or more, may be 1 mg / g or more, may be 5 mg / g or more, may be 8 mg / g or more, may be 10 mg / g or more, may be 15 mg / g or more, or may be 20 mg / g or more. Also, in some embodiments, from the viewpoint of enhancing the impact resistance and peel strength of the joint by the photocured product, the BP equivalent of the BP polymer (A) is usually suitably 100 mg / g or less, may be 80 mg / g or less, may be 60 mg / g or less, may be 40 mg / g or less, may be 25 mg / g or less, or may be 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).

[0085] In addition, from the viewpoint of reducing the peel force by photocuring and implementing reworkability and repair, the BP equivalent is preferably 50 mg / g or more, and may be 100 mg / g or more.

[0086] 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 that the step absorption property of the pressure-sensitive adhesive layer (A) and the reworkability of its photocured product are preferably balanced. In some embodiments, the weight fraction of the above BP polymer (A) may be, for example, 2% by weight or more, and is usually suitably 4% by weight or more, may be 10% by weight or more, may be 15% by weight or more, may be 25% by weight or more, may be 35% by weight or more, may be 45% by weight or more, or may be 55% by weight or more. When the weight fraction of the BP polymer (A) increases, the reworkability tends to improve. Aspects in which the weight fraction of the BP polymer (A) in the pressure-sensitive adhesive composition (A) is substantially 100% by weight (for example, 99.5% by weight or more) can also be implemented. Further, from the viewpoint of ease of pressure-sensitive adhesive performance, in some aspects, the weight fraction of the BP polymer (A) in the pressure-sensitive adhesive composition (A) may be, for example, less than 99% by weight, may be less than 95% by weight, may be less than 85% by weight, may be less than 70% by weight, may be less than 50% by weight, or may be less than 40% by weight.

[0087] Preferably, per 1 g of the pressure-sensitive adhesive composition (A), the benzophenone structure is contained in an amount of, for example, at least about 0.1 mg in terms of 4-benzoylphenyl acrylate. Hereinafter, the weight of the benzophenone structure in terms of 4-benzoylphenyl acrylate contained per 1 g of the pressure-sensitive adhesive composition (A) may be referred to as the BP equivalent (unit: mg / g) of the pressure-sensitive adhesive composition. From the viewpoint of obtaining a higher photocuring effect (for example, the effect of enhancing the reworkability by photocuring), in some aspects, the BP equivalent of the pressure-sensitive adhesive composition is usually suitably 0.3 mg / g or more, may be 0.5 mg / g or more, may be 1 mg / g or more, may be 5 mg / g or more, may be 10 mg / g or more, or may be 20 mg / g or more. Also, in some aspects, from the viewpoints of the impact resistance of the joint by the photocured product and the suppression of strain in the photocured product, the BP equivalent of the pressure-sensitive adhesive composition is usually suitably 100 mg / g or less, may be 80 mg / g or less, may be 60 mg / g or less, may be 40 mg / g or less, may be 25 mg / g or less, or may be 15 mg / g or less.

[0088] [Ethylenically unsaturated compound (B)] In addition to the BP polymer (A), the pressure-sensitive adhesive composition (A) may further contain an ethylenically unsaturated compound (B). When the pressure-sensitive adhesive composition (A) is a solventless (active energy ray curable) pressure-sensitive adhesive composition, it is preferable that the pressure-sensitive adhesive composition (A) contains the ethylenically unsaturated compound (B). On the other hand, when the pressure-sensitive adhesive composition (A) is a solvent-based or emulsion-based pressure-sensitive adhesive composition, it may not contain the ethylenically unsaturated compound (B).

[0089] In addition, 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 constituting the BP polymer (A), since the other ethylenically unsaturated compounds described above may be included as the monomer components, it is not necessarily required to contain the ethylenically unsaturated compound (B). When the pressure-sensitive adhesive composition (A) containing the mixture of monomer components or a partial polymer thereof contains the ethylenically unsaturated compound (B), the ethylenically unsaturated compound (B) may be the same as or different from the other ethylenically unsaturated compounds described above.

[0090] Examples of compounds that can be used as the ethylenically unsaturated compound (B) include the above-described alkyl (meth)acrylates and the above-described ethylenically unsaturated BP. Among these, it is preferable to use at least an alkyl (meth)acrylate (for example, C 1-20 alkyl acrylate, more preferably C 4-18 alkyl acrylate, still more preferably C 4-9 alkyl acrylate). Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). Other specific examples of alkyl (meth)acrylates that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), and the like. The alkyl (meth)acrylate can be used alone or in combination of two or more. In some embodiments, the ethylenically unsaturated compound (B) preferably contains either or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), and more preferably contains at least BA.

[0091] The ethylenically unsaturated compound (B) may contain an acrylic acid C 4-9 alkyl ester in a proportion of 40% by weight or more. The acrylic acid C 4-9The proportion of the alkyl ester may be, for example, 50% by weight or more, may be 60% by weight or more, and may be 65% by weight or more. Further, from the viewpoint of enhancing the cohesiveness of the pressure-sensitive adhesive layer (A), acrylic acid C in the ethylenically unsaturated compound (B). 4-9 The proportion of the alkyl ester is usually suitably 99.5% by weight or less, may be 95% by weight or less, may be 85% by weight or less, may be 70% by weight or less, and may be 60% by weight or less.

[0092] Other examples of the compound that can be used as the ethylenically unsaturated compound (B) include ethylenically unsaturated compounds (copolymerizable monomers) copolymerizable with (meth)acrylic acid alkyl esters. As the copolymerizable monomer, a monomer having a polar group (for example, a carboxy group, a hydroxy group, a nitrogen atom-containing ring, etc.) can be preferably 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 enhancing the cohesive force of the pressure-sensitive adhesive layer (A). The copolymerizable monomer can be used alone or in combination of two or more kinds.

[0093] Non-limiting specific examples of the copolymerizable monomer 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, etc. Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride. Hydroxy group-containing monomers: for example, 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, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, etc., such as hydroxyalkyl (meth)acrylates. Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropane sulfonic acid, (meth)acrylamide propane sulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxy naphthalene sulfonic acid, 2-hydroxyethyl acryloyl phosphate, etc. 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, glycidyl ether (meth)acrylate, etc. 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, etc. 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, 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, N-n-butyl(meth)acrylamide; N-vinyl carboxamides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-hydroxyalkyl(meth)acrylamides such as N-(2-hydroxyethyl)(meth)acrylamide, 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, N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide; and others, N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acryloylmorpholine, etc. Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Monomers having an epoxy group: 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-vinyl oxazole, 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, etc. Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc. Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc. Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Alkoxy group-containing monomers: For example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylate) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxypropyl (meth)acrylate, etc.; alkoxyalkylene glycol (meth)acrylates (such as alkoxypolyalkylene glycol (meth)acrylate) such as methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, etc. Alkoxysilyl group-containing monomers: For example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, etc., and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, etc. 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. Aliphatic cyclic hydrocarbon group-containing (meth)acrylate esters: For example, aliphatic cyclic hydrocarbon group-containing (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, etc. Aromatic hydrocarbon group-containing (meth)acrylate esters: For example, aromatic hydrocarbon group-containing (meth)acrylates such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. In addition, heterocyclic ring-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylate, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols, etc.

[0094] When using such copolymerizable monomers, their usage amounts are not particularly limited, but usually, it is appropriate to set them at 0.01% by weight or more of the total monomer components constituting the pressure-sensitive adhesive composition (A). From the viewpoint of more effectively exerting the effects of the copolymerizable monomer, the usage amount of the copolymerizable monomer (that is, 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, and may also be 0.5% by weight or more. Further, from the viewpoint of facilitating the balance of the adhesive properties, the usage amount of the copolymerizable monomer is usually appropriately set at 50% by weight or less of the total monomer components, and preferably 40% by weight or less.

[0095] The above copolymerizable monomer may include a monomer having a nitrogen atom. By using a monomer having a nitrogen atom, the cohesive force of the pressure-sensitive adhesive layer (A) can be increased, and the peel strength after photocuring can be preferably improved. As a preferred example of the monomer having a nitrogen atom, a monomer having a nitrogen atom-containing ring can be mentioned. As the monomer having a nitrogen atom-containing ring, those exemplified above can be used, for example, the general formula (1):

Chemical formula

[0096] When using a monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring such as N-vinyl cyclic amide), the amount used is not particularly limited. For example, it may be 1% by weight or more of the total monomer component, 2% by weight or more, 3% by weight or more, and may further be 5% by weight or more or 7% by weight or more. In one aspect, 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 component. Also, it is appropriate that the amount of the nitrogen atom-containing monomer used is, for example, 40% by weight or less of the total monomer component, 35% by weight or less, 30% by weight or less, or 25% by weight or less. In another aspect, the amount of the nitrogen atom-containing monomer used may be, for example, 20% by weight or less, 15% by weight or less of the total monomer component. Alternatively, it is not necessary to use a nitrogen atom-containing monomer as the copolymerizable monomer.

[0097] The copolymerizable monomer may include a hydroxyl group-containing monomer. By using a hydroxyl group-containing monomer, the cohesive force and the degree of crosslinking (for example, crosslinking with an isocyanate crosslinking agent) of the pressure-sensitive adhesive layer (A) can be suitably adjusted. The amount used when using a hydroxyl group-containing monomer is not particularly limited. For example, it may be 0.01% by weight or more of the total monomer component, 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. Also, from the viewpoint of suppressing water absorption of the pressure-sensitive adhesive layer (A) or its photocured product, in some aspects, it is appropriate that the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer component, 30% by weight or less, 25% by weight or less, or 20% by weight or less. In another aspect, 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 component. Alternatively, it is not necessary to use a hydroxyl group-containing monomer as the copolymerizable monomer.

[0098] The proportion of the carboxyl group-containing monomer in the total monomer components may be, for example, 2% by weight or less, may be 1% by weight or less, and may be 0.5% by weight or less (for example, less than 0.1% by weight). The pressure-sensitive adhesive composition (A) may not substantially contain a carboxyl group-containing monomer as its constituent monomer components. Here, not substantially containing a carboxyl group-containing monomer means that, at least intentionally, a carboxyl group-containing monomer is not used. This can be advantageous from the viewpoint of preventing metal corrosion of the pressure-sensitive adhesive layer (A) formed from the pressure-sensitive adhesive composition (A) and its photocured product.

[0099] The above copolymerizable monomer may include an alicyclic hydrocarbon group-containing (meth)acrylate. Thereby, the cohesive force of the pressure-sensitive adhesive layer (A) can be increased, and the peel strength after photocuring can be improved. As the alicyclic hydrocarbon group-containing (meth)acrylate, those exemplified above can be used, and for example, cyclohexyl acrylate or isobornyl acrylate can be preferably employed. The amount used when using an alicyclic hydrocarbon group-containing (meth)acrylate 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 aspect, the amount used of the alicyclic hydrocarbon group-containing (meth)acrylate may be 10% by weight or more, or 15% by weight or more of the total monomer components. The upper limit of the amount used of the alicyclic hydrocarbon group-containing (meth)acrylate 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, and further 10% by weight or less). Alternatively, the above copolymerizable monomer may not use an alicyclic hydrocarbon group-containing (meth)acrylate.

[0100] The above 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, for example, two or three) alkoxysilyl groups in one molecule, and specific examples thereof are as described above. The above alkoxysilyl group-containing monomer can 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 pressure-sensitive adhesive layer (A) by a condensation reaction of silanol groups (silanol condensation).

[0101] The amount used in the case of using the alkoxysilyl group-containing monomer is not particularly limited. In some embodiments, the amount used of the alkoxysilyl group-containing monomer can be, for example, 0.005% by weight or more of the total monomer components constituting the pressure-sensitive adhesive composition (A), and usually it is appropriate to be 0.01% by weight or more, it may be 0.03% by weight or more, and it may be 0.05% by weight or more. Further, from the viewpoint of the step absorbency of the pressure-sensitive adhesive composition (A), the amount used of the alkoxysilyl group-containing monomer is usually appropriately 1.0% by weight or less of the total monomer components, it may be 0.5% by weight or less, and it may be 0.1% by weight or less.

[0102] As still other examples of the compounds that can be used as the ethylenically unsaturated compound (B), polyfunctional monomers can be mentioned. According to the pressure-sensitive adhesive composition (A) containing a polyfunctional monomer, when the composition is cured to produce the pressure-sensitive adhesive layer (A), by reacting the above polyfunctional monomer, a pressure-sensitive adhesive layer (A) crosslinked by the polyfunctional monomer can be obtained. 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, divinylbenzene, etc.; polyfunctional monomers having three or more functional groups such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc.; and others such as epoxy acrylate, polyester acrylate, urethane acrylate, etc. Among them, preferred examples include 1,6 - hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The polyfunctional monomer can be used alone or in combination of two or more kinds.

[0103] When using a polyfunctional monomer, the amount used is not particularly limited and can be less than 5.0% by weight of the total monomer components constituting the pressure-sensitive adhesive composition (A). This can avoid the formation of an excessive crosslinked structure during the formation of the pressure-sensitive adhesive layer (A) (i.e., at the stage before photocuring), and can enhance the step absorption property of the pressure-sensitive adhesive layer (A). The amount of the above 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. It is not necessary to use a polyfunctional monomer. Further, in some embodiments, from the viewpoint of imparting appropriate cohesiveness to the pressure-sensitive 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.

[0104] The weight ratio of the BP polymer (A) contained in the pressure-sensitive adhesive composition (A) to the total amount of the ethylenically unsaturated compound (B) is not particularly limited and can be set so that the step absorption property of the pressure-sensitive adhesive layer (A) formed from the pressure-sensitive adhesive composition (A) and the processability of its photocured product are suitably balanced. In some embodiments, the weight fraction of the above BP polymer (A) may be, for example, 0.5% by weight or more, usually 1% by weight or more, preferably 1.5% by weight or more, more preferably 5% by weight or more, and 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 from the viewpoint of enhancing the effect of photocuring. Further, from the viewpoints of ease of preparation and coatability of the pressure-sensitive adhesive composition (A), in some embodiments, the weight ratio of the BP polymer (A) in the above 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.

[0105] The proportion of the weight of the organic solvent in the total weight of the above 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, and may not substantially contain an organic solvent.

[0106] From the viewpoint of coating properties in the above room temperature range and the like, the pressure-sensitive adhesive composition (A) preferably has a viscosity (measured under the conditions of a BH viscometer, No. 5 rotor, 10 rpm, and a measurement temperature of 30 °C. The same applies hereinafter.) of 1000 Pa·s or less, preferably 100 Pa·s or less, and more preferably 50 Pa·s or less. The viscosity of the pressure-sensitive 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 pressure-sensitive adhesive composition (A) is not particularly limited, but from the viewpoint of suppressing the repellency of the pressure-sensitive adhesive composition within the coating range and the overhang of the pressure-sensitive adhesive composition at the outer edge of the coating range, it is usually appropriately 0.1 Pa·s or more, and may be 0.5 Pa·s or more or 1 Pa·s or more.

[0107] The pressure-sensitive adhesive composition (A) may contain at least a compound having one ethylenically unsaturated group (i.e., a monofunctional monomer) (B1) as the above ethylenically unsaturated compound (B). The monofunctional monomer (B1) can be selected from the exemplified compounds of the above ethylenically unsaturated compound (B). The monofunctional monomer can be used alone or in combination of two or more.

[0108] Among the total amount of the BP polymer (A) and the ethylenically unsaturated compound (B), the weight ratio of the monofunctional monomer (B1) 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 viewpoints of 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. Also, the weight ratio of the monofunctional monomer (B1) among the total amount may be, for example, 99% by weight or less, and it is usually appropriate that it is 95% by weight or less, and it 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.

[0109] In an embodiment where the pressure-sensitive adhesive composition (A) contains the monofunctional monomer (B1), the glass transition temperature (Tg) determined by Fox's equation based on the composition of the monofunctional monomer (B1) is not particularly limited and can be, for example, -80°C or higher and 250°C or lower. The Tg based on the composition of the monofunctional monomer (B1) is usually preferably 150°C or lower, may be 100°C or lower, may be 70°C or lower, may be 50°C or lower, or may be 30°C or lower from the viewpoints of compatibility between the polymer derived from the monofunctional monomer (B1) and other components. In some embodiments, from the viewpoints of step absorption of the pressure-sensitive adhesive layer (A), etc., the Tg based on the composition of the monofunctional monomer (B1) is preferably less than 0°C, more preferably -10°C or lower, and may be -20°C or lower, -30°C or lower, or -40°C or lower. Also, from the viewpoints of cohesiveness of the pressure-sensitive adhesive layer (A) and 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 monomer and their usage ratios.

[0110] In the pressure-sensitive adhesive composition (A) containing a BP polymer (A) and a monofunctional monomer (B1), the 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 ") are such that the Tg difference [°C] (hereinafter also referred to as ΔTg) calculated by Tg B1 [°C] - Tg A [°C] can be set to be in the range of, for example, -50°C or higher and 70°C or lower. The fact that the absolute value of the above Tg difference is not too large can be advantageous from the viewpoint of compatibility in the pressure-sensitive adhesive layer (A) and the photocured product thereof. In some embodiments, ΔTg may be, for example, -10°C or higher, preferably 0°C or higher, may be 7°C or higher, may be 10°C or higher, may be 20°C or higher, or may be 30°C or higher.

[0111] 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 above ethylenically unsaturated compound (B). The polyfunctional monomer (B2) can be used singly or in combination of two or more from the examples of the above polyfunctional monomers. The amount of the polyfunctional monomer (B2) used can be set in the same manner as the ratio of the polyfunctional monomer in the total monomer components constituting the pressure-sensitive adhesive composition (A).

[0112] In the embodiment where the monofunctional monomer (B1) and the 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, usually appropriately 25% by weight or more, may be 50% by weight or more, may be 75% by weight or more, may be 95% by weight or more, or may be 99% by weight or more. Also, 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 may be 99.8% by weight or less.

[0113] 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 thereof 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. For example, photopolymerization carried out by irradiating light such as ultraviolet light; radiation polymerization carried out by irradiating radiation such as beta rays and gamma rays; thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization; etc. Various conventionally known polymerization methods can be appropriately selected and used. From the viewpoints of efficiency and simplicity, the photopolymerization method can preferably be employed. According to photopolymerization, the polymerization conversion rate (monomer conversion) can be easily controlled by polymerization conditions such as the irradiation amount (light amount) of light.

[0114] The polymerization conversion rate of the ethylenically unsaturated compound (B) in the above partial polymer is not particularly limited. From the viewpoints of ease of preparation and coatability of the pressure-sensitive adhesive composition (A), etc., the polymerization conversion rate is usually suitably about 50% by weight or less, and preferably about 40% by weight or less (for example, about 35% by weight or less). The lower limit of the polymerization conversion rate is not particularly limited, but typically is about 1% by weight or more, and usually is suitably about 5% by weight or more.

[0115] The pressure-sensitive adhesive composition (A) containing a 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 pressure-sensitive adhesive composition by an appropriate polymerization method (for example, the photopolymerization method). Further, the pressure-sensitive adhesive composition (A) containing a partial polymer of the ethylenically unsaturated compound (B) may 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 pressure-sensitive adhesive composition and the remaining ethylenically unsaturated compound (B) or its partial polymer. In this specification, "complete polymer" means that the polymerization conversion rate is more than 95% by weight.

[0116] The above partial polymer can be prepared, for example, by irradiating an ethylenically unsaturated compound (B) with ultraviolet light. When the preparation of the above partial polymer is carried out in the presence of a BP polymer (A), by setting the ultraviolet irradiation conditions so that the ethylenically unsaturated groups react and the benzophenone structure is not photoexcited, an adhesive composition (A) containing a partial polymer of the ethylenically unsaturated compound (B) and the BP polymer (A) can be obtained. As the light source, a light source capable of irradiating ultraviolet light containing no component with a wavelength less than 300 nm or having a small amount of such a wavelength component, such as the above-mentioned black light or UV-LED lamp, can preferably be employed.

[0117] Alternatively, after previously preparing a partial polymer of the ethylenically unsaturated compound (B), the partial polymer and the BP polymer (A) may be mixed to prepare the adhesive composition (A). When preparing the partial polymer of the ethylenically unsaturated compound (B) by irradiating it with ultraviolet light in the absence of a benzophenone structure-containing component, as the ultraviolet light source, either a light source that does not excite the benzophenone structure or a light source that excites it can be used.

[0118] In the preparation of the partial polymer of the ethylenically unsaturated compound (B), the reaction of the ethylenically unsaturated groups can be promoted by using a photopolymerization initiator. 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, etc. 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) and generates radicals can preferably be employed. The photopolymerization initiator can be used alone or in an appropriate combination of two or more.

[0119] [Photopolymerization initiator] In the pressure-sensitive adhesive composition (A), a photoinitiator can be contained as needed for the purpose of improving or imparting photocurability, etc. When the pressure-sensitive adhesive composition (A) is a solventless (active energy ray-curable) pressure-sensitive adhesive composition, it is preferable that the pressure-sensitive adhesive composition (A) contains a photoinitiator. On the other hand, when the pressure-sensitive adhesive composition (A) is a solvent-based or emulsion-based pressure-sensitive adhesive composition, it may not contain a photoinitiator.

[0120] As the photoinitiator, a ketal-based photoinitiator, an acetophenone-based photoinitiator, a benzoin ether-based photoinitiator, an acylphosphine oxide-based photoinitiator, an α-ketol-based photoinitiator, an aromatic sulfonyl chloride-based photoinitiator, a photoactive oxime-based photoinitiator, a benzoin-based photoinitiator, a benzyl-based photoinitiator, a benzophenone-based photoinitiator, an alkylphenone-based photoinitiator, a thioxanthone-based photoinitiator, etc. can be used. The photoinitiator can be used alone or in an appropriate combination of two or more.

[0121] Specific examples of the ketal-based photoinitiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, etc. Specific examples of the acetophenone-based photoinitiator 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, etc. Specific examples of the benzoin ether-based photoinitiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether. Specific examples of acylphosphine oxide-based photoinitiators 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 α-ketol-based photoinitiators include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. Specific examples of aromatic sulfonyl chloride-based photoinitiators include 2-naphthalenesulfonyl chloride and the like. Specific examples of photoactive oxime-based photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime and the like. Specific examples of benzoin-based photoinitiators include benzoin and the like. Specific examples of benzyl-based photoinitiators include benzyl and the like. Specific examples of benzophenone-based photoinitiators include benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Specific examples of thioxanthone-based photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

[0122] As the photoinitiator to be incorporated into the pressure-sensitive adhesive composition (A), a photoinitiator 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 (which may be referred to as "photoinitiator (C)") can preferably be employed. When the pressure-sensitive adhesive composition (A) contains the photoinitiator (C), it is preferable for curing the pressure-sensitive adhesive composition (A) into a cured product in which the benzophenone structure of the BP polymer (A) remains.

[0123] The photoinitiator can be used alone or in an appropriate combination of two or more. In some embodiments, a photoinitiator that does not contain a phosphorus element in its molecule can preferably be employed. The pressure-sensitive adhesive composition (A) can be substantially free of a photoinitiator that contains a phosphorus element in its molecule.

[0124] The content of the photoinitiator in the pressure-sensitive 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 photoinitiator can be, for example, approximately 0.005 parts by weight or more, usually suitably 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, and may be 0.20 parts by weight or more, based on 100 parts by weight of the monomer component constituting the pressure-sensitive adhesive composition (A). With an increase in the content of the photoinitiator, the photocurability of the pressure-sensitive adhesive composition (A) is improved. Also, the content of the photoinitiator based on 100 parts by weight of the monomer component constituting the pressure-sensitive adhesive composition (A) is usually suitably 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, and may be 0.5 parts by weight or less. The content of the photoinitiator not being too much can be advantageous from the viewpoint of suppressing gelation of the pressure-sensitive adhesive composition (A).

[0125] [Crosslinking agent] In the pressure-sensitive adhesive composition (A), if necessary, known crosslinking agents such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, etc. can be blended. A peroxide may be used as the crosslinking agent. When the pressure-sensitive adhesive composition (A) is a solvent-type or emulsion-type pressure-sensitive adhesive composition, it is preferable to contain a crosslinking agent.

[0126] The above crosslinking agents can be used singly or in combination of two or more. The pressure-sensitive adhesive layer (A) formed from the pressure-sensitive adhesive composition (A) containing a crosslinking agent preferably contains the crosslinking agent mainly in the form after the crosslinking reaction. By using the crosslinking agent, the cohesive force etc. of the pressure-sensitive adhesive layer (A) can be appropriately adjusted.

[0127] The amount of use (the total amount in the case of using two or more crosslinking agents) when using a crosslinking agent is not particularly limited. From the viewpoint of realizing a pressure-sensitive adhesive that exhibits well-balanced adhesive properties such as adhesive strength and cohesive force, the amount of use of the crosslinking agent is usually preferably about 5 parts by weight or less, may be 3 parts by weight or less, may be 1 part by weight or less, may be 0.50 part by weight or less, may be 0.30 part by weight or less, may be 0.20 part by weight or less, with respect to 100 parts by weight of the monomer components constituting the pressure-sensitive adhesive composition (A). The lower limit of the amount of use of the crosslinking agent is not particularly limited, and it may be an amount more than 0 part by weight with respect to 100 parts by weight of the monomer components constituting the pressure-sensitive adhesive composition (A). In some embodiments, the amount of use of the crosslinking agent may be, for example, 0.001 part by weight or more, may be 0.01 part by weight or more, may be 0.05 part by weight or more, may be 0.10 part by weight or more, with respect to 100 parts by weight of the monomer components constituting the pressure-sensitive adhesive composition (A).

[0128] [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 can be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur-based chain transfer agent) may be used. Specific examples of the non-sulfur-based chain transfer agent 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 cinnamaldehyde; 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; etc. The chain transfer agent can be used alone or in combination of two or more. When using a chain transfer agent, the amount 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 without using a chain transfer agent can also be preferably implemented.

[0129] As other components that can be included in the pressure-sensitive adhesive composition (A), a silane coupling agent can be mentioned. By using a silane coupling agent, the peel strength against an adherend (for example, a glass plate) can be improved. Further, the pressure-sensitive adhesive layer (A) can contain a silane coupling agent. The pressure-sensitive adhesive layer (A) containing a silane coupling agent can be preferably formed using the pressure-sensitive adhesive composition (A) containing a silane coupling agent. The silane coupling agent can be used alone or in combination of two or more.

[0130] The pressure-sensitive adhesive composition (A) may contain a colorant. The colorant is not particularly limited, but it is preferably a colorant (which may be referred to as "colorant (A)") having a maximum transmittance at a wavelength of 200 to 400 nm (preferably 330 to 400 nm) that is greater than the maximum transmittance at a wavelength of 400 to 700 nm.

[0131] When the pressure-sensitive adhesive composition (A) contains the colorant (A), the transmittance to visible light (wavelength 400 to 700 nm) decreases, that is, the light-shielding property improves. On the other hand, the transmittance in the ultraviolet region (wavelength 200 to 400 nm, preferably 330 to 400 nm) is higher than that of visible light.

[0132] When the pressure-sensitive adhesive composition (A) contains the colorant (A), the transmittance to visible light (wavelength 400 to 700 nm) is low, that is, the light-shielding property is high. By sealing the fine step between the metal wiring layer and the light-emitting element (LED chip) of the self-luminous display device (mini / micro LED display device) without a gap with the cured product of the pressure-sensitive adhesive composition (A) having a high light-shielding property to visible light, reflection by the metal wiring or the like is prevented, color mixing of the light-emitting element (LED chip) is prevented, and the contrast of the image is improved.

[0133] On the other hand, when the pressure-sensitive adhesive composition (A) contains the colorant (A), the transmittance in the ultraviolet region (wavelength 200 to 400 nm, preferably 330 to 400 nm) is higher than that of visible light. Therefore, the pressure-sensitive adhesive layer (A) formed from the pressure-sensitive adhesive composition (A) can be cured by forming a crosslinked structure of the benzophenone structure by irradiating with a high-pressure mercury lamp. The pressure-sensitive adhesive layer (A) cured by irradiation with a high-pressure mercury lamp has improved reworkability, can be easily peeled from the display panel, and is less likely to remain on the display panel.

[0134] The maximum transmittance of the colorant (A) at a wavelength 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.

[0135] Further, 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.

[0136] 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 about 50 to 60%.

[0137] The colorant may be a dye or a pigment as long as it can be dissolved or dispersed in the pressure-sensitive adhesive composition (A). Dyes are preferred because low haze can be achieved even with a small amount of addition, and they are easily and uniformly distributed without sedimentation like pigments. Also, pigments are preferred because high color expressibility can be achieved even with a small amount of addition. When using a pigment as the colorant, it is preferably one with low conductivity or no conductivity. When using a dye, it is preferably used in combination with an antioxidant or the like.

[0138] Examples of the ultraviolet-transmitting black pigment include "9050BLACK", "9256BLACK", "9170BLACK", "UVBK-0001" manufactured by Toxiki, and "UB-1" manufactured by Mitsubishi Materials Electronic Chemical Co., Ltd. Examples of the ultraviolet-transmitting black dye include "SOC-L-0123" manufactured by Orient Chemical Industries.

[0139] The content of the colorant in the pressure-sensitive adhesive composition (A) is, for example, about 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the pressure-sensitive adhesive composition (A), and may be appropriately set according to the type of the colorant, the color tone and light transmittance of the pressure-sensitive adhesive layer (A), etc. The colorant may be added as a solution or dispersion dissolved or dispersed in an appropriate solvent.

[0140] The pressure-sensitive adhesive composition (A) may contain, as other optional components, various additives common in the field of pressure-sensitive adhesives, such as tackifier resins (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based tackifier resins), viscosity modifiers (e.g., thickeners), leveling agents, antioxidants, plasticizers, fillers, stabilizers, preservatives, anti-aging agents, etc., as required. Since such various additives are those known in the art and can be used by conventional methods and are not particularly characteristic of the present invention, detailed description thereof will be omitted.

[0141] Note that the pressure-sensitive adhesive composition (A) can exhibit good adhesive strength without using the above-described tackifier resin. Therefore, in some embodiments, the content of the tackifier resin in the pressure-sensitive adhesive layer (A) or the pressure-sensitive adhesive composition (A) can be, for example, less than 10 parts by weight, further less than 5 parts by weight, based on 100 parts by weight of the monomer component. The content of the tackifier resin may be less than 1 part by weight (e.g., less than 0.5 part by weight), or may be less than 0.1 part by weight (0 part by weight or more and less than 0.1 part by weight). The pressure-sensitive adhesive layer (A) or the pressure-sensitive adhesive composition (A) may not contain a tackifier resin.

[0142] The adhesive layer (A) is preferably a cured product of the adhesive composition (A), which is formed by a cured product with a benzophenone structure remaining. This benzophenone structure can form a crosslinked structure by irradiation with a high-pressure mercury lamp to cure the adhesive layer (A). The adhesive layer (A) before curing is in a semi-cured state with high fluidity and exhibits excellent step absorption properties. Therefore, when the adhesive layer (A) of the photocurable adhesive sheet of the present invention is bonded to a display panel in which optical semiconductor elements (LED chips) are densely arranged, it can sufficiently follow the fine steps between the optical semiconductor elements (LED chips) and adhere closely without leaving air bubbles and without gaps. On the other hand, the cured adhesive layer (A) exhibits excellent reworkability. Therefore, the cured adhesive layer (A) can be easily peeled off from the optical semiconductor elements of the display panel and is also difficult to remain on the display panel. Thus, according to the adhesive layer (A) formed from the adhesive composition (A), it is possible to suitably achieve both excellent step absorption properties and reworkability.

[0143] In addition, by controlling the irradiation amount of the high-pressure mercury lamp irradiating the adhesive layer (A), it is also possible to suppress the occurrence of lack of adhesive during cutting of the laminate containing the adhesive layer (A) as a sealing material, the protrusion or sagging of the adhesive layer from the end during storage, and improve the processability.

[0144] The method for producing the adhesive layer (A) is not particularly limited. For example, it can be produced by irradiating the adhesive composition (A) with active energy rays and / or performing heat drying, etc. Specifically, the adhesive composition (A) is applied (coated) on a substrate or a release liner, and if necessary, dried, cured, or dried and cured.

[0145] In addition, a known coating method may be used for the application (coating) of the adhesive composition (A). For example, coaters such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, and a direct coater may be used.

[0146] When the pressure-sensitive adhesive composition (A) is cured by irradiation with active energy rays, it is preferably carried out 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 pressure-sensitive adhesive layer (A). As the active energy rays for forming the pressure-sensitive adhesive layer (A), ultraviolet rays are preferable, and ultraviolet rays that do not contain a component having a wavelength of less than 300 nm, preferably less than 350 nm, or that contain a small amount of such a wavelength component are more preferable.

[0147] When the pressure-sensitive adhesive composition (A) contains a BP polymer (A) and an ethylenically unsaturated compound (B), the pressure-sensitive adhesive layer (A) may contain a BP polymer (A) and a polymer (E) derived from the ethylenically unsaturated compound (B). In this embodiment, the pressure-sensitive adhesive composition (A) may be a composition in which the ethylenically unsaturated compound (B) does not contain an ethylenically unsaturated BP. According to the pressure-sensitive adhesive composition (A) having such a composition, a pressure-sensitive adhesive layer (A) containing a BP polymer (A) and a polymer (E) derived from an ethylenically unsaturated compound (B), and the polymer (E) being a polymer having no benzophenone structure (sometimes referred to as a [non-BP polymer]) can be produced.

[0148] On one 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 the monomer components, the pressure-sensitive adhesive layer (A) contains two or more polymers having different monomer compositions, and at least one of the two or more polymers may be a polymer having a benzophenone structure in the side chain (sometimes referred to as "BP polymer (A')"). The pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer containing 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 can be formed by using a pressure-sensitive adhesive composition containing an ethylenically unsaturated compound having no benzophenone structure and polymerizing the ethylenically unsaturated compound. The BP polymer (A') may be, for example, the BP polymer (A) contained in the pressure-sensitive adhesive composition (A), or a modified product thereof, or may be formed by copolymerizing an ethylenically unsaturated BP contained in the pressure-sensitive adhesive composition (A) with another ethylenically unsaturated compound. The two or more polymers may or may not be chemically bonded. The pressure-sensitive adhesive layer (A) according to some embodiments may contain at least one BP polymer in a form not chemically bonded to a polymer other than the BP polymer.

[0149] Irradiation of active energy rays for curing the pressure-sensitive adhesive composition (A) is preferably performed so as to react ethylenically unsaturated groups and leave the benzophenone structure. As the pressure-sensitive adhesive composition (A), a pressure-sensitive adhesive composition containing a BP polymer (A) and an ethylenically unsaturated compound (B) can be preferably used. As a light source for curing the pressure-sensitive adhesive composition (A) to form a photocrosslinkable pressure-sensitive adhesive, a light source capable of irradiating ultraviolet rays containing no component having a wavelength of less than 300 nm, preferably less than 350 nm, or having a small amount of such a wavelength component, such as the above-mentioned black light or UV-LED lamp, can be preferably employed.

[0150] In a preferred embodiment of the present invention, the maximum value of the transmittance of the adhesive layer (A) at a wavelength of 200 to 400 nm (preferably 330 to 400 nm) is greater than the maximum value of the transmittance at a wavelength of 400 to 700 nm. By sealing the fine step between the metal wiring layer and the optical semiconductor element (LED chip) of the self-luminous display device (mini / micro LED display device) without gaps with the adhesive layer (A) having excellent light-shielding properties for visible light, reflection by the metal wiring or the like is prevented, color mixing of the optical semiconductor element (LED chip) is prevented, and the contrast of the image is improved. On the other hand, the adhesive layer (A) having a high transmittance in the ultraviolet region (wavelength 200 to 400 nm, preferably 330 to 400 nm) forms a crosslinked structure by irradiating with a high-pressure mercury lamp and curing, thereby improving the reworkability, being easily peeled from the optical semiconductor element of the display panel, and being less likely to remain on the display panel.

[0151] Further, in a preferred embodiment of the present invention, the maximum value of the transmittance of the adhesive layer of the present invention at a wavelength 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.

[0152] Further, in a preferred embodiment of the present invention, the average transmittance of the adhesive layer of the present invention at a wavelength of 200 to 400 nm (preferably 330 to 400 nm) is greater than the average transmittance at a wavelength of 400 to 700 nm. The average transmittance of the adhesive layer of the present invention at a wavelength 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.

[0153] The adhesive layer (A) preferably contains, per 1 g of the adhesive layer, a benzophenone structure in an amount of, for example, approximately 0.1 mg or more in terms of 4-benzoylphenyl acrylate. Hereinafter, the weight of the benzophenone structure contained per 1 g of the adhesive layer of the present invention 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 enhancing reworkability by photocuring), the BP equivalent of the adhesive layer is usually suitably 0.3 mg / g or more, may be 0.5 mg / g or more, may be 1 mg / g or more, may be 5 mg / g or more, may be 10 mg / g or more, or may be 20 mg / g or more. Also, from the viewpoints of the impact resistance of the joint portion by the photocured product and the suppression of strain in the photocured product, the BP equivalent of the adhesive layer is usually suitably 100 mg / g or less, may be 80 mg / g or less, may be 60 mg / g or less, may be 40 mg / g or less, may be 25 mg / g or less, or may be 15 mg / g or less.

[0154] The high-pressure mercury lamp irradiation conditions of the adhesive layer of the present invention are not particularly limited, but preferably include ultraviolet rays having a wavelength of 200 to 280 nm. The UV-LED irradiation conditions of the adhesive layer of the present invention are not particularly limited, but preferably include ultraviolet rays having a wavelength of 350 nm or more and do not include or include less ultraviolet rays having a wavelength of 200 to 280 nm, and a metal halide lamp, a chemical lamp, or a black light can also be used. Also, regarding the irradiation energy, irradiation time, and irradiation method of the radiation for curing, they can be appropriately set as long as they do not unduly affect the adherend. For example, the irradiation amount (integrated light amount) is preferably 1000 mJ / cm 2 ~10000 mJ / cm 2 and more preferably 2000 mJ / cm 2 ~4000 mJ / cm 2 and even more preferably 3000 mJ / cm 2 .

[0155] [VOC emission amount] The VOC (volatile organic compound) emission amount of the pressure-sensitive adhesive layer of the present invention is not particularly limited. The VOC emission amount may be, for example, 5000 μg / g or less, 3000 μg / g or less, or 1000 μg / g or less. In some embodiments, the VOC emission amount of the pressure-sensitive adhesive layer of the present invention is preferably 500 μg / g or less, more preferably 300 μg / g or less, and even more preferably 100 μg / g or less. A pressure-sensitive adhesive layer with a low VOC emission amount has a low odor and is preferable from the perspective of environmental hygiene. The fact that the pressure-sensitive adhesive layer of the present invention has a low VOC emission amount is also preferable from the perspectives of suppressing foaming caused by volatile organic compounds (VOCs) in the pressure-sensitive adhesive layer and low contamination. The VOC emission amount of the pressure-sensitive adhesive layer of the present invention is measured by the following method using an appropriate amount (for example, about 1 mg to 2 mg) of the pressure-sensitive adhesive layer as a measurement sample. Note that the thickness of the measurement sample is preferably 1 mm or less.

[0156] (Gel fraction) The gel fraction of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but from the perspectives of the cohesiveness of the pressure-sensitive adhesive layer and the handleability of the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer, etc., it is usually appropriate to be 5% or more, preferably 15% or more, and may be 25% or more or 35% or more. In principle, the gel fraction of the pressure-sensitive adhesive layer of the present invention is 100% or less. Also, from the perspective of the step absorption property with respect to the surface shape of the adherend, the gel fraction of the pressure-sensitive adhesive layer of the present invention is preferably less than 85%, and may be less than 70%, less than 55%, or less than 40%.

[0157] The gel fraction is measured by the following method. That is, about 0.5 g of the 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 1 week, then dried, and the weight W2 of the ethyl acetate-insoluble matter is measured. W1 and W2 are substituted into the following formula: Gel fraction (%) = W2 / W1 × 100; to calculate the gel fraction. As the porous PTFE sheet, a product named "Nitoflon NTF1122" manufactured by Nitto Denko Corporation or its equivalent can be used.

[0158] In some embodiments of the adhesive layer of the present invention, using a high-pressure mercury lamp, the illuminance is 300 mW / cm 2 , and the gel fraction of the photocured product obtained by irradiating ultraviolet rays under the condition of an integrated light quantity of 10000 mJ / cm 2 may be, for example, 70% or more, preferably 90% or more, may be 95% or more, and may be 98% or more. In principle, the gel fraction of the photocured product is 100% or less. The gel fraction is measured by the above method. The gel fraction of the adhesive layer of the present invention can be adjusted by the composition of the adhesive composition (A) (for example, 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), the adhesive composition (A), the curing conditions (heating conditions, ultraviolet irradiation conditions) of the adhesive layer of the present invention, etc.

[0159] The glass transition temperature (Tg) of the adhesive layer of the present invention 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 above Tg is higher than 20°C, the adhesive force cannot be exhibited at room temperature.

[0160] The above Tg is not particularly limited, but for example, using the adhesive layer as a measurement sample, it can be measured in accordance with JIS K 7121 by differential scanning calorimetry (DSC). Specifically, for example, as a measurement device, using the device named "Q-2000" manufactured by TA instruments, it can be measured under the condition of a heating rate of 10°C / min from -80°C to 80°C.

[0161] The thickness of the adhesive layer of the present invention is not particularly limited and may be appropriately set so as to sufficiently seal the optical semiconductor elements arranged on the display panel described later. For example, the thickness of the adhesive layer of the present invention 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 optical semiconductor element. By setting the above thickness to 1.0 times or more, the adhesive layer easily follows the step, and the step absorbability is improved. Further, by setting the above thickness to 4.0 or less, the reworkability of the adhesive layer is improved.

[0162] The adhesive layer (A) can be photocrosslinked, for example, by irradiating ultraviolet rays containing a wavelength component capable of exciting the benzophenone structure. It is preferable to use a high-pressure mercury lamp as a light source capable of irradiating ultraviolet rays containing a component having a wavelength of less than 300 nm, for example, 200 to 280 nm. The light irradiated by the above light source may contain a component having a wavelength of 300 nm or more.

[0163] In addition, examples of light sources capable of irradiating ultraviolet rays that do not contain a wavelength component capable of exciting the benzophenone structure (for example, a component having a wavelength of less than 300 nm, preferably less than 350 nm) or that contain a small amount of the wavelength component include black lights, UV-LED lamps, and the like. These light sources can be preferably adopted as light sources for promoting the reaction (polymerization reaction or curing reaction) of ethylenically unsaturated groups by light irradiation performed in the presence of the benzophenone structure. In ultraviolet irradiation for reacting ethylenically unsaturated groups, the above-mentioned photopolymerization initiator can be used to promote the reaction.

[0164] The pressure-sensitive adhesive layer of the present invention may have a composition that substantially does not contain a photopolymerization initiator that absorbs light with a wavelength of 300 nm or more and generates radicals, and for example, may have a composition that substantially does not contain a photopolymerization initiator that absorbs visible light with a wavelength of 380 nm or more (particularly 400 nm or more) and generates radicals. This can be advantageous from the viewpoint of the optical properties of the pressure-sensitive adhesive layer of the present invention. Note that not containing a photopolymerization initiator that absorbs light with a wavelength of 300 nm or more and generates radicals means not containing the photopolymerization initiator in a form capable of generating the above radicals (a form having a site cleaved by the above light), and it may be acceptable to contain cleavage residues of the photopolymerization initiator. The pressure-sensitive adhesive layer according to a preferred embodiment of the present invention substantially does not contain a photopolymerization initiator containing a phosphorus element in the molecule. The pressure-sensitive adhesive layer disclosed herein may be one that substantially does not contain either a photopolymerization initiator containing a phosphorus element in the molecule or cleavage residues of the photopolymerization initiator.

[0165] As described above, the photocurable pressure-sensitive adhesive sheet of the present invention may be a pressure-sensitive adhesive sheet with a substrate. Examples of such a substrate include various optical films such as plastic films, antireflection (AR) films, polarizing plates, and retardation plates. Examples of materials such as the above plastic films include plastic materials such as 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, cyclic olefin polymers such as the trade name "Arton" (manufactured by JSR Corporation), and the trade name "Zeonoa" (manufactured by Zeon Corporation, Japan). These plastic materials may be used alone or in combination of two or more.

[0166] The base material is preferably transparent. The total light transmittance (in accordance with JIS K7361-1) of the base material in the visible light wavelength region is not particularly limited, but is preferably 85% or more, more preferably 88% or more. Further, the haze (in accordance with JIS K7136) of the base material is not particularly limited, but is preferably 1.5% or less, more preferably 1.0% or less. Examples of such a transparent base material include a PET film and an unoriented film such as the product name "Arton" and the product name "Zeonoa".

[0167] The thickness of the base material is not particularly limited, but is preferably 12 to 75 μm. Note that the base material may have either a single-layer or a multi-layer form. Further, on the surface of the base material, known and commonly used surface treatments such as an antireflection treatment (AR treatment), an antiglare treatment or other antireflection treatments, a physical treatment such as a corona discharge treatment or a plasma treatment, and a chemical treatment such as an undercoat treatment may be appropriately applied.

[0168] As described above, the photocurable pressure-sensitive adhesive sheet of the present invention may have another pressure-sensitive adhesive layer (a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer of the present invention). The other pressure-sensitive adhesive layer is not particularly limited, and examples thereof include a pressure-sensitive adhesive layer formed from a known or commonly used pressure-sensitive adhesive such as a urethane-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyamide-based pressure-sensitive adhesive, an epoxy-based pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, and a fluorine-based pressure-sensitive adhesive. Note that the pressure-sensitive adhesives may be used alone or in combination of two or more.

[0169] Further, the photocurable pressure-sensitive adhesive sheet of the present invention may have other layers (for example, an intermediate layer, an undercoat layer, etc.) within a range not impairing the effects of the present invention, in addition to the pressure-sensitive adhesive layer, the base material, and the other pressure-sensitive adhesive layer of the present invention.

[0170] The photocurable pressure-sensitive adhesive sheet of the present invention may have a release film (separator) provided on the adhesive surface until use. The form in which the adhesive surface of the photocurable pressure-sensitive adhesive sheet of the present invention is protected by the release film is not particularly limited, but may be a form in which each adhesive surface is protected by two release films, or by being wound in a roll shape, with one release film having release surfaces on both sides, and each adhesive surface being protected. The release film is used as a protective material for the adhesive layer and is peeled off when sticking to an adherend. In the photocurable pressure-sensitive adhesive sheet of the present invention, the release film also serves as a support for the adhesive layer. Note that the release film is not necessarily provided.

[0171] The release film is not particularly limited. For example, a release film obtained by subjecting the surface of a film substrate such as a resin film or paper to a release treatment, or a release film made of a low-adhesion material such as a fluoropolymer (such as polytetrafluoroethylene) or a polyolefin resin (such as polyethylene or polypropylene) can be used. For the above-mentioned release treatment, for example, a release treatment agent such as a silicone-based or long-chain alkyl-based release treatment agent can be used. In some embodiments, a resin film subjected to a release treatment can be preferably adopted as the release film.

[0172] The thickness (total thickness) of the photocurable pressure-sensitive adhesive sheet of the present invention 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 setting the above thickness to 10 μm or more, the adhesive layer of the present invention can easily follow the stepped portion, and the step absorption property can be improved. Note that the thickness of the photocurable pressure-sensitive adhesive sheet (A) does not include the thickness of the release film.

[0173] Since the photocurable pressure-sensitive adhesive sheet of the present invention has the adhesive layer of the present invention, it has excellent step absorption property before curing. For example, in addition to a step of 5 to 10 μm, it also has excellent step absorption property for a high step exceeding 40 μm. Furthermore, it also has step absorption property for a high step exceeding 80 μm.

[0174] In addition, since the photocurable pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer of the present invention, after irradiation with a high-pressure mercury lamp, it cures and shrinks, has excellent reworkability, can be easily peeled off from the display panel, and is difficult to remain on the display panel. In addition, since the photocurable pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer of the present invention, the pressure-sensitive adhesive layer cures and shrinks due to ultraviolet rays contained in external light or light emitted from a blue light semiconductor element, and the pressure-sensitive adhesive layer (sealing material) can be prevented from peeling off from the display panel.

[0175] In addition, since the photocurable pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer of the present invention, by controlling the irradiation amount of the high-pressure mercury lamp, it has excellent processability, suppresses glue shortage during cutting, and the pressure-sensitive adhesive layer from protruding or sagging from the end during storage, and furthermore, the adhesive reliability can also be made excellent.

[0176] <Optical semiconductor device, self-emitting display device, image display device> The optical semiconductor device of the present invention includes a substrate, one or more optical semiconductor elements disposed on the substrate, and the photocurable pressure-sensitive adhesive sheet of the present invention, and the photocurable pressure-sensitive adhesive sheet seals the optical semiconductor element. The optical semiconductor device of the present invention is preferably a self-emitting display device. The image display device of the present invention preferably includes the self-emitting display device of the present invention.

[0177] The optical semiconductor device (self-emitting display device) of the present invention arranges a large number of minute optical semiconductor elements on a wiring substrate, and selectively emits light from each optical semiconductor element by light emission control means connected thereto, so that visual information such as characters, images, and moving images can be directly displayed on the display screen by the blinking of each optical semiconductor element. Examples of the self-emitting display device include a mini / micro LED display device and an organic EL (electroluminescence) display device. The photocurable pressure-sensitive adhesive sheet of the present invention is particularly preferably used in the manufacture of a mini / micro LED display device.

[0178] FIG. 3 is a schematic diagram (cross-sectional view) showing an embodiment of the self-emitting display device (mini / micro LED display device) of the present invention. In FIG. 3, a mini / micro LED display device 20 includes a display panel in which a plurality of optical semiconductor elements (LED chips) 4 are arranged on one side of a substrate 2 via a metal wiring layer 3, an adhesive layer 1 laminated on the display panel to seal the metal wiring layer 3 and the plurality of optical semiconductor elements 4, and a base material (cover member) S5 laminated on the upper part (image display side) of the adhesive layer 1. The base material S5 is not particularly limited, but can be made of the same material as the above-mentioned "base material".

[0179] In the mini / micro LED display device 20 of the present embodiment, a metal wiring layer 3 for sending a light emission control signal to each optical semiconductor element 4 is laminated on the substrate 2 of the display panel. Each optical semiconductor element 4 that emits light of each color of red (R), green (G), and blue (B) is alternately arranged on the substrate 2 of the display panel via the metal wiring layer 3. The metal wiring layer 3 is formed of a metal such as copper, reflects the light emission of each optical semiconductor element 4, and reduces the visibility of the image. In addition, the light emitted by each optical semiconductor element 5 of each RGB color is mixed, and the contrast is reduced.

[0180] In the mini / micro LED display device 20 of the present embodiment, each optical semiconductor element 4 arranged on the display panel is sealed by the adhesive layer 1. The adhesive layer 1 is constituted by the adhesive layer of the present invention. The adhesive layer 1 sufficiently follows the fine steps between the plurality of optical semiconductor elements 4 and is sealed without gaps.

[0181] When the adhesive layer 1 contains a colorant, it has sufficient light shielding properties in the visible light region. When the fine steps between the optical semiconductor elements 4 are sealed without gaps by the adhesive layer 1 having high light shielding properties, reflection by the metal wiring layer 3 can be prevented, color mixing between the optical semiconductor elements 4 can be prevented, and the contrast can be improved.

[0182] The self-luminous display device (mini / micro LED display device) of this embodiment may include optical members other than the display panel, the adhesive layer, and the 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, an optical compensation film, and the like. The optical members also include members (such as a design film, a decorative film, and a surface protection plate) that play a role in decoration and protection while maintaining the visibility of the display device or the input device.

[0183] 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 an adhesive layer of the photocurable adhesive sheet of the present invention on a display panel having a plurality of optical semiconductor elements arranged on one side of a substrate, and encapsulating the optical semiconductor elements with the adhesive layer.

[0184] Self-luminous display devices have problems such as optical semiconductor elements not lighting up, being different in color, missing, being misaligned, etc., resulting in reduced yields. In addition, when sealing the display panel, mistakes such as wrinkles, contamination with foreign matter, and air bubbles can occur. When such reduced yields and sealing mistakes occur, the sealing material is peeled off and removed from the display panel and reused, a process known as rework.

[0185] The photocurable adhesive sheet of the present invention can improve reworkability by curing and shrinking the adhesive layer of the present invention by irradiating it with a high-pressure mercury lamp. Therefore, when a yield reduction or sealing error occurs in a self-luminous display device such as a mini / micro LED display device of the present invention, the adhesive layer (sealant) of the present invention can be easily peeled off from the substrate on the display panel or the optical semiconductor element by irradiating the adhesive layer (sealant) of the present invention with a high-pressure mercury lamp, and little of the adhesive layer (sealant) of the present invention remains.

[0186] FIG. 4 is a schematic diagram (cross-sectional view) showing a process for implementing an embodiment of the rework of the self-luminous display device (mini / micro LED display device) of the present invention. In the present embodiment, as shown in FIG. 4(a), the photocurable adhesive sheet 11 of the present invention and a display panel in which a plurality of optical semiconductor elements (LED chips) 4 are arranged via a metal wiring layer 3 on one side of the substrate 2 are used.

[0187] In the present embodiment, the photocurable adhesive sheet 11 is composed of an adhesive layer 1 and a base material (cover member) S5. In the present embodiment, the photocurable adhesive sheet 11 has a base material S5, but the base material S5 may not be provided. The base material S5 is not particularly limited, but can be composed of the same material as the above-mentioned "base material", and may be a release film (separator).

[0188] Next, as shown in FIG. 4(b), the adhesive layer 1 of the photocurable adhesive sheet 11 is laminated on the surface of the display panel on which a plurality of optical semiconductor elements are arranged, and the optical semiconductor element 4 and the metal wiring layer 3 are sealed with the adhesive layer 1. The lamination can be performed by a known method, for example, under heating and pressurizing conditions using an autoclave. The adhesive layer 1 of the photocurable adhesive sheet 11 has high fluidity and excellent step absorption properties. Therefore, the adhesive layer 1 is sealed so as to fill the step between the metal wiring layer 3 and the plurality of optical semiconductor elements 4 without gaps.

[0189] In the manufactured self-luminous display device 20, since the curing shrinkage of the adhesive layer 1 due to external light or light contained in the blue optical semiconductor element does not proceed, peeling of the adhesive layer 1 (sealing material) hardly occurs in the use environment, and the durability is excellent.

[0190] When a yield reduction such as non-lighting, color difference, missing, or misalignment of the optical semiconductor element or a sealing error occurs in the manufactured self-luminous display device 20, as shown in FIG. 4(c), the adhesive layer 1 is irradiated with radiation U from a high-pressure mercury lamp to cause curing shrinkage. By irradiating with a high-pressure mercury lamp, the adhesive layer 1 cures and shrinks, the peeling force with respect to the substrate 2 and the optical semiconductor element 4 of the display panel decreases, and the reworkability is improved.

[0191] Next, as shown in FIGS. 4(d) and 4(e), the adhesive layer 1 that has been cured and shrunk by irradiation with a high-pressure mercury lamp is peeled off from the substrate 2 of the display panel and the optical semiconductor element 4. Since the cured and shrunk adhesive layer 1 is excellent in reworkability, it can be easily peeled off from the substrate 2 of the display panel and the optical semiconductor element 4, and it is difficult to leave residues.

[0192] The peeled display panel can be repaired for defective non-light-emitting optical semiconductor elements and reused as necessary. Also, in a self-luminous display device shipped as a qualified product, when a failure such as non-light emission of the optical semiconductor element occurs in the usage environment, it is also possible to peel off the photocurable adhesive sheet and perform repairs by the same operations as in FIGS. 4(c) to 4(e).

[0193] The radiation irradiated by the high-pressure mercury lamp preferably includes ultraviolet rays having a wavelength of less than 300 nm, and more preferably includes ultraviolet rays having a wavelength of 200 to 280 nm. That is, the adhesive layer of the present invention preferably cures and shrinks by irradiation with ultraviolet rays having a wavelength of 200 to 280 nm. Furthermore, the adhesive layer of the present invention preferably cures and shrinks by irradiation with ultraviolet rays having a wavelength of 200 to 280 nm and is difficult to cure and shrink by ultraviolet rays having a wavelength of 300 nm or more, preferably ultraviolet rays having a wavelength of 350 nm or more. Such a configuration is such that the adhesive layer of the present invention cures and shrinks by a high-pressure mercury lamp, which is a light source including radiation having a wavelength of 200 to 280 nm not contained in external light or light emitted from a blue optical semiconductor element, improving the reworkability. On the other hand, since curing and shrinking do not proceed due to radiation having a wavelength of 350 nm or more contained in external light or light emitted from a blue optical semiconductor element, it is preferable in that peeling of the adhesive layer (sealing material) can be prevented in the usage environment of the self-luminous display device.

[0194] Regarding the irradiation time and irradiation method of the high-pressure mercury lamp, they can be appropriately set as long as the adhesive layer 1 can be cured without unduly affecting the display panel and the adhesive layer 1 is cured to exhibit sufficient reworkability. For example, the irradiation amount (integrated light amount) of ultraviolet rays is preferably 1000 mJ / cm 2 ~10000 mJ / cm 2and more preferably 2000 mJ / cm 2 ~ 4000 mJ / cm 2 and even more preferably 3000 mJ / cm 2 .

[0195] Also, as another embodiment, by controlling the irradiation time and irradiation method of the high-pressure mercury lamp to be less than the above, the adhesive layer 1 has improved processability, and gluing failure during cutting and bleeding or sagging of the adhesive layer from the end during storage are suppressed. Further, the adhesive layer 1 can suppress the generation of gases such as carbon dioxide due to heating of the display panel, prevent the generation of bubbles, and also improve the adhesion reliability. The irradiation time and irradiation method of the high-pressure mercury lamp in this embodiment can be appropriately set as long as they do not have an adverse effect on the display panel and the adhesive layer 1 is cured to exhibit sufficient processability.

Examples

[0196] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these examples.

[0197] [Example 1] (Preparation of prepolymer) Into a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirring device, as monomer components, 100 parts of n-butyl acrylate (BA), 15.9 parts of cyclohexyl acrylate (CHA), 45.3 parts by weight of 2-hydroxyethyl acrylate (2HEA), 4.2 parts of 4-acryloyloxybenzophenone (ABP), and 202.7 parts of methyl ethyl ketone (MEK) as a polymerization solvent were charged, and 0.5 part of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added, and solution polymerization was carried out under a nitrogen atmosphere to obtain a solution containing an acrylic prepolymer with an Mw of 300,000.

[0198] (Preparation of adhesive composition) To the solution containing the acrylic prepolymer obtained above, 1 part of Coronate L (trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation) was added per 100 parts of the monomer component used in the preparation of the solution on a solid content basis, and they were uniformly mixed to prepare a solvent-based pressure-sensitive adhesive composition.

[0199] (Preparation of Adhesive Sheet) The solvent-based pressure-sensitive adhesive composition prepared above was applied to the release surface of a 38-μm-thick release film (MRF#38, manufactured by Mitsubishi Rayon Co., Ltd.) having one side of the polyester film as the release surface, and dried at 130°C for 3 minutes to form an adhesive sheet with a thickness of 50 μm. The release surface of a 38-μm-thick release film (MRE#38, manufactured by Mitsubishi Rayon Co., Ltd.) was laminated on this adhesive layer for protection, and a photocurable adhesive sheet 1 with an adhesive layer of about 50 μm thickness sandwiched between the above release films was obtained in the form of a substrate-free double-sided adhesive sheet.

[0200] [Example 2] A photocurable adhesive sheet 2 with an adhesive layer of about 50 μm thickness sandwiched between release films was obtained in the form of a substrate-free double-sided adhesive sheet in the same manner as in Example 1, except that 7.5 parts of cyclohexyl acrylate (CHA) and 12.5 parts of 4-acryloyloxybenzophenone (ABP) were blended.

[0201] [Example 3] (Preparation of Adhesive Composition) To the solution containing the acrylic prepolymer obtained in Example 1, 1 part of Coronate L (trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation) and 5.2 parts of Pigment Dispersion Liquid 9256BLACK (pigment weight fraction: 20 wt%; manufactured by Tokushi Co., Ltd.) were added per 100 parts of the monomer component used in the preparation of the solution on a solid content basis, and they were uniformly mixed to prepare a solvent-based black pressure-sensitive adhesive composition. (Preparation of Adhesive Sheet) A photocurable adhesive sheet 3 with an adhesive layer of about 50 μm thickness sandwiched between release films was obtained in the form of a substrate-free double-sided adhesive sheet in the same manner as in Example 1, except that the solvent-based black pressure-sensitive adhesive composition obtained above was used.

[0202] [Example 4] (Preparation of prepolymer) A solution containing an acrylic prepolymer was obtained in the same manner as in Example 1, except that 7.5 parts of cyclohexyl acrylate (CHA) and 12.5 parts of 4-acryloyloxybenzophenone (ABP) were blended. (Preparation of pressure-sensitive adhesive composition) To the solution containing the acrylic prepolymer obtained above, 1 part of Coronate L (trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation) and 5.2 parts of Pigment Dispersion Liquid 9256BLACK (pigment weight fraction: 20 wt%; manufactured by Toxiki Co., Ltd.) were added per 100 parts of the monomer component used in the preparation of the solution, and they were uniformly mixed to prepare a solvent-based black pressure-sensitive adhesive composition. (Preparation of pressure-sensitive adhesive sheet) A photocurable pressure-sensitive adhesive sheet 4 in which an adhesive layer having a thickness of about 50 μm was sandwiched between release films was obtained in the form of a substrate-free double-sided pressure-sensitive adhesive sheet in the same manner as in Example 1, except that the solvent-based black pressure-sensitive adhesive composition obtained above was used.

[0203] [Comparative Example 1] A pressure-sensitive adhesive sheet 5 in which an adhesive layer having a thickness of about 50 μm was sandwiched between release films was obtained in the form of a substrate-free double-sided pressure-sensitive adhesive sheet in the same manner as in Example 1, except that 4-acryloyloxybenzophenone (ABP) was not blended.

[0204] [Comparative Example 2] (Preparation of prepolymer) Into a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 100 parts of n-butyl acrylate (BA), 20 parts of cyclohexyl acrylate (CHA), and 45 parts of 2-hydroxyethyl acrylate (2HEA) were charged as monomer components, 200 parts of ethyl acetate was charged as a polymerization solvent, and 0.5 part of 2,2'-azobisisobutyronitrile (AIBN) was added as a thermal polymerization initiator, and solution polymerization was carried out under a nitrogen atmosphere to obtain an acrylic polymer solution.

[0205] (Preparation of pressure-sensitive adhesive composition) To the solution containing the acrylic polymer obtained above, 5 parts of 2-methacryloyloxyethyl isocyanate (MOI) and 0.025 part of dibutyltin dilaurate were added per 100 parts of the monomer component used for preparing the solution, and the mixture was stirred at 50 °C for 7 hours under an air atmosphere to cause an addition reaction of MOI to the above polymer, thereby obtaining a polymer solution having a carbon-carbon double bond. To the solution of the above polymer, 1 part of Coronate L was added per 100 parts of the polymer in the solution on a solid content basis, and the mixture was uniformly mixed to prepare a solvent-type pressure-sensitive adhesive composition.

[0206] (Preparation of Adhesive Sheet) The solvent-type pressure-sensitive adhesive composition prepared above was applied to the release surface of a 38-μm-thick release film (manufactured by Mitsubishi Rayon Co., Ltd., MRF#38) having one side of a polyester film as the release surface, and dried at 130 °C for 3 minutes to form an adhesive sheet having a thickness of 150 μm. The release surface of a 38-μm-thick release film (manufactured by Mitsubishi Rayon Co., Ltd., MRE#38) was laminated on this adhesive layer for protection, and a photocurable adhesive sheet 6 having an adhesive layer with a thickness of about 150 μm sandwiched between the above release films was obtained in the form of a substrate-free double-sided adhesive sheet.

[0207] (Evaluation) Using the adhesive sheets obtained in the above Examples and Comparative Examples, the following evaluations were conducted. The evaluation methods are shown below. The results are shown in Table 1.

[0208] [Evaluation of Storage Elastic Modulus] Regarding the shear storage elastic modulus G’ before irradiation, it was evaluated using ARES GII of TA Instruments. An adhesive sheet laminated to a thickness of about 1 mm was punched out into a φ8 mm size, and the shear storage elastic modulus G’ at 25 °C and 85 °C when measured from -50 °C to 150 °C at an initial strain of 1%, a frequency of 1 Hz, and a heating rate of 10 °C / min was read, and taken as the shear storage elastic modulus G’ (G’b25, G’b85) before curing. The tensile storage modulus E’ after high-pressure mercury lamp irradiation was evaluated using an RSA GII from TA Instruments. For the adhesive sheet sandwiched between release films, a high-pressure mercury lamp was used to irradiate it so that the integrated light quantity reached 3000 mJ / cm 2 Then, the irradiated samples were laminated to a thickness of approximately 0.2 mm, cut into 5 mm widths, and the tensile storage modulus E’ at 25 °C and 85 °C were read when measured from -50 °C to 150 °C with an initial length of 20 mm, an initial strain of 0.1%, and a heating rate of 10 °C / min. These values were designated as the tensile storage modulus E’ (E’a25, E’a85) after high-pressure mercury lamp irradiation. This integrated light quantity is the measured value obtained 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. Regarding the shear storage modulus G’ after UV-LED irradiation, for the adhesive sheet sandwiched between release films, a UV-LED was used to irradiate it so that the integrated light quantity reached 800 mJ / cm 2 (for 1 minute). Then, the irradiated samples were laminated to a thickness of approximately 1 mm, punched into φ8 mm, and evaluated in the same manner as before curing. These values were designated as the shear storage modulus G’ (G’a25, G’a85) after UV-LED irradiation. This integrated light quantity is the measured value obtained using an industrial UV checker (manufactured by Topcon Corporation, product name: UVR-T1, light-receiving unit type UD-T40) with a peak sensitivity wavelength of approximately 410 nm. Note that since the adhesive sheet of Comparative Example 1 does not exhibit photocurability, the storage moduli G’ and E’ after curing were not evaluated.

[0209] [Evaluation of 180° peel force] The 180° peel force was measured according to JIS Z 0237. Specifically, one side of the release film of the adhesive sheet sandwiched between release films was peeled off and adhered to a PET substrate (product name "T912E75(UE80)", manufactured by Mitsubishi Chemical Corporation). It was cut into 20 mm widths, the other release film was peeled off, and it was adhered to an acrylic plate. The pasting method was one round trip with a 2 kg roller. After more than 15 minutes had passed since pasting, it was peeled at 180°, and the 180° peel force (N / 20 mm) before radiation irradiation was measured. The pulling speed was 300 mm / min. The 180° peel strength (N / 20 mm) after radiation exposure was evaluated in the same manner as above after at least 15 minutes had elapsed after irradiation under each of the following irradiation conditions. · High-pressure mercury lamp: Integrated light quantity 3000 mJ / cm 2 · UV-LED: Integrated light quantity 4800 mJ / cm 2 (6 minutes)

[0210] [Evaluation of transmittance] The release film on one side was peeled off from the adhesive sheet, and non-alkali glass was bonded to the exposed surface. Then, the release film on the other side was peeled off from the adhesive sheet to obtain a sample in which the adhesive sheet was bonded onto the non-alkali glass plate. The total light transmittance was measured using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., product name "HN-150") in accordance with the method specified in JIS K7361.

[0211] [Evaluation of adhesive residue] The adherend after the above 180° peel strength test was visually observed, and those with adhesive attachment were evaluated as "with adhesive residue", and those without attachment were evaluated as "without adhesive residue".

[0212]

Table 1

[0213] It can be seen that in Examples 1 to 4 and Comparative Example 2, which are photocurable adhesive sheets, the storage modulus increased and the 180° peel strength decreased after irradiation with a high-pressure mercury lamp, and no adhesive residue was observed, indicating that the reworkability was improved. On the other hand, in Comparative Example 1, which is an adhesive sheet that does not exhibit photocurability, adhesive residue was observed, indicating that the reworkability was inferior. In addition, the photocurable adhesive sheets of Examples 1 to 4 show little decrease in the 180° peel strength after UV-LED irradiation, and it is difficult for curing shrinkage to progress with external light or the light of a blue light semiconductor element, indicating excellent light resistance and durability, making it difficult to peel from the adherend. On the other hand, it can be seen that the photocurable adhesive sheet of Comparative Example 2 shows a significant decrease in the 180° peel strength after UV-LED irradiation, and curing shrinkage progresses with external light or the light of a blue light semiconductor element, making it easy to peel from the adherend.

[0214] The variations of the present invention are appended below. 〔Appendix 1〕A photocurable adhesive sheet having an adhesive layer that cures by radiation irradiation, wherein the adhesive layer is characterized in that the 180° peel strength after high-pressure mercury lamp irradiation is 11 N / 20 mm or less. 〔Appendix 2〕The photocurable adhesive sheet according to Appendix 1, wherein the change rate of the 180° peel strength before and after UV-LED irradiation of the adhesive layer is within 10%. 〔Appendix 3〕The photocurable adhesive sheet according to Appendix 1 or 2, wherein the adhesive layer has a tensile storage modulus (E’a25) at 25°C after high-pressure mercury lamp irradiation of 400 kPa or more. 〔Appendix 4〕The photocurable adhesive sheet according to any one of Appendices 1 to 3, wherein the maximum value of the transmittance of the adhesive layer at a wavelength of 200 to 400 nm is 5% or more. 〔Appendix 5〕The photocurable adhesive sheet according to any one of Appendices 1 to 4, wherein the ratio (kPa / μm) of the tensile storage modulus (E’a25: kPa) at 25°C after high-pressure mercury lamp irradiation to the thickness (μm) of the adhesive layer is 1 to 50. 〔Appendix 6〕The photocurable adhesive sheet according to any one of Appendices 1 to 5, wherein the light irradiated by the high-pressure mercury lamp contains radiation having a wavelength of 200 to 280 nm. 〔Appendix 7〕The photocurable adhesive sheet according to any one of Appendices 2 to 6, wherein the light irradiated by the UV-LED is radiation having a wavelength of 350 nm or more. 〔Appendix 8〕Comprising a substrate, one or more light semiconductor elements disposed on the substrate, and the photocurable adhesive sheet according to any one of Appendices 1 to 7, An optical semiconductor device in which the photocurable adhesive sheet seals the optical semiconductor element. 〔Appendix 9〕The optical semiconductor device according to Appendix 8, which is a self-luminous display device. 〔Appendix 10〕An image display device including the self-luminous display device according to Appendix 9. 〔Appendix 11〕A method for peeling the photocurable adhesive sheet from the substrate and one or more optical semiconductor elements disposed on the substrate of the optical semiconductor device according to any one of Appendices 8 to 10, a step of irradiating the photocurable adhesive sheet with radiation including light having a wavelength of 200 to 280 nm, and a step of peeling the cured photocurable adhesive sheet from the substrate and one or more optical semiconductor elements disposed on the substrate. 〔Appendix 12〕The peeling method according to Appendix 11, wherein the radiation including light having a wavelength of 200 to 280 nm is radiation by irradiation with a high-pressure mercury lamp.

Explanation of Signs

[0215] 10 Photocurable adhesive sheet 1 Adhesive layer S1, S2 Release film 11 Photocurable adhesive sheet S3 Base material S4 Release film 20 Self-luminous display device (mini / micro LED display device) 2 Substrate 3 Metal wiring layer 4 Optical semiconductor element (LED chip) S5 Base material (cover member)

Claims

1. having an adhesive layer that cures upon irradiation with radiation, as monomer components constituting the adhesive composition forming the adhesive layer, including a compound having an ethylenically unsaturated group and a benzophenone structure in the molecule, and a hydroxyl group-containing monomer, The adhesive layer is a photocurable adhesive sheet characterized in that the 180° peel strength after irradiation with a high-pressure mercury lamp is 11 N / 20 mm or less.

2. The adhesive layer is the photocurable adhesive sheet according to claim 1, wherein the change rate of the 180° peel strength before and after UV-LED irradiation is within 10%.

3. The photocurable adhesive sheet according to claim 2, wherein the light irradiated with the UV-LED is radiation having a wavelength of 350 nm or more.

4. The adhesive layer is the photocurable adhesive sheet according to any one of claims 1 to 3, wherein the tensile storage modulus (E’a25) at 25°C after irradiation with a high-pressure mercury lamp is 400 kPa or more.

5. The photocurable adhesive sheet according to any one of claims 1 to 4, wherein the maximum value of the transmittance of the adhesive layer at a wavelength of 200 to 400 nm is 5% or more.

6. The adhesive layer is the photocurable adhesive sheet according to any one of claims 1 to 5, wherein the ratio (kPa / μm) of the tensile storage modulus (E’a25: kPa) at 25°C after irradiation with a high-pressure mercury lamp to the thickness (μm) is 1 to 50.

7. The photocurable adhesive sheet according to any one of claims 1 to 6, wherein the light irradiated with the high-pressure mercury lamp contains radiation having a wavelength of 200 to 280 nm.

8. A substrate, one or more optical semiconductor elements disposed on the substrate, and the photocurable adhesive sheet according to any one of claims 1 to 7, The photocurable adhesive sheet seals the optical semiconductor element, an optical semiconductor device.

9. The semiconductor optical device according to claim 8, which is a self-luminous display device.

10. An image display device including the self-luminous display device according to claim 9.

11. A method of peeling the photocurable adhesive sheet from the substrate and one or more semiconductor optical elements disposed on the substrate of the semiconductor optical device according to any one of claims 8 to 10, comprising: irradiating the photocurable adhesive sheet with radiation including light having a wavelength of 200 to 280 nm, and peeling the cured photocurable adhesive sheet from the substrate and one or more semiconductor optical elements disposed on the substrate.

12. The peeling method according to claim 11, wherein the radiation including light having a wavelength of 200 to 280 nm is radiation by irradiation with a high-pressure mercury lamp.

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