CN116096828A - Photocurable adhesive sheet - Google Patents

Photocurable adhesive sheet Download PDF

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Publication number
CN116096828A
CN116096828A CN202180052956.4A CN202180052956A CN116096828A CN 116096828 A CN116096828 A CN 116096828A CN 202180052956 A CN202180052956 A CN 202180052956A CN 116096828 A CN116096828 A CN 116096828A
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China
Prior art keywords
adhesive layer
weight
crosslinking agent
adhesive sheet
polymer
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Pending
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CN202180052956.4A
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Chinese (zh)
Inventor
浅井量子
福富秀平
仲野武史
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Nitto Denko Corp
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Nitto Denko Corp
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Priority claimed from JP2021080519A external-priority patent/JP2022039945A/en
Application filed by Nitto Denko Corp filed Critical Nitto Denko Corp
Publication of CN116096828A publication Critical patent/CN116096828A/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
    • C09J151/06—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C09J201/02—Adhesives based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups
    • C09J201/06—Adhesives based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups containing oxygen atoms
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/33—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being semiconductor devices, e.g. diodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/52—Encapsulations
    • H01L33/56—Materials, e.g. epoxy or silicone resin
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/02—Details
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/20—Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive itself
    • C09J2301/21—Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive itself the adhesive layer being formed by alternating adhesive areas of different nature
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/312—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier parameters being the characterizing feature
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/416—Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00

Abstract

The present invention provides an adhesive sheet which is suitable for manufacturing self-luminous display devices such as mini/micro LED display devices with improved contrast and which has excellent level difference absorbability and processability, and which has a function of preventing reflection of metal wiring and the like. The photocurable pressure-sensitive adhesive sheet of the present invention is characterized by comprising a pressure-sensitive adhesive layer that is cured by irradiation with radiation, wherein the pressure-sensitive adhesive layer comprises a colorant, the maximum value of the transmittance at a wavelength of 200 to 400nm of the pressure-sensitive adhesive layer is greater than the maximum value of the transmittance at a wavelength of 400 to 700nm, the storage modulus (G ' b 85) of the pressure-sensitive adhesive layer before curing at 85 ℃ is lower than 65kPa, and the storage modulus (G ' a 10) of the pressure-sensitive adhesive layer after curing at 10 ℃ and the storage modulus (G ' b 85) of the pressure-sensitive adhesive layer before curing at 85 ℃ satisfy the following relational expression (1). 3.3< G 'a10/G' b85 (1).

Description

Photocurable adhesive sheet
Technical Field
The present invention relates to a photocurable pressure-sensitive adhesive sheet. More specifically, the present invention relates to a photocurable pressure-sensitive adhesive sheet suitable for sealing a light-emitting element of a self-luminous display device such as a mini/micro LED.
Background
In recent years, as a next-generation display device, a self-luminous display device typified by a Mini/micro LED display device (Mini/Micro Light Emitting Diode Display) has been designed. As a basic configuration of a mini/micro LED display device, a substrate in which a large number of micro LED light emitting elements (LED chips) are densely arranged is used as a display panel, the LED chips 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.
Some types of self-luminous display devices such as mini/micro LED display devices include a white backlight type, a white light-emitting color filter type, and an RGB type, and in the white light-emitting color filter type and the RGB type, a black colored adhesive may be used as a sealing material (see, for example, patent documents 1 to 3).
This is because the black adhesive agent contributes to prevention of color mixing and improvement of contrast by embedding the RGB LED chips arranged on the substrate of the display panel, and can prevent reflection of metal wiring, metal oxide such as ITO, and the like arranged on the substrate of the display panel.
In a mini/micro LED display device, LED chips are densely spread on a substrate, a large number of fine level differences exist in gaps between the LED chips, and a sealing material used in the mini/micro LED display device is required to have excellent level difference absorption (also referred to as "level difference following property") which is a property of filling these level differences. Therefore, in order to improve the level difference absorbency, the black adhesive needs to be designed so as to exhibit high fluidity.
On the other hand, the adhesive exhibiting high fluidity has a problem of reduced workability such as shape stability and handling property, although the difference in level absorbency is excellent. For example, a laminate having an adhesive layer exhibiting high fluidity is likely to suffer from a shortage of adhesive during cutting, and an overflow or sagging of the adhesive layer from the end during storage, and foreign matter may adhere to the overflowed adhesive layer, resulting in contamination of the process.
As an adhesive that combines the level difference absorbability and processability, a photocurable adhesive (mixed adhesive) is known (for example, see patent document 4). For mixed adhesives, there are the following advantages: first, the fluidity is high, a semi-cured state excellent in level difference absorptivity is produced, the level difference is sufficiently followed, and then the curing is completed by irradiation with light, whereby the workability can be improved.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open publication No. 2019-204905
Patent document 2: japanese patent application laid-open No. 2017-203810
Patent document 3: japanese patent application laid-open No. 2018-523854
Patent document 4: international publication WO2016/170875
Disclosure of Invention
Problems to be solved by the invention
However, for example, when a mixed binder is colored by mixing carbon black or the like, light cannot pass through the binder, and thus there is a problem that curing is suppressed and it is difficult to improve workability.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an adhesive sheet suitable for manufacturing a self-luminous display device such as a mini/micro LED display device having an improved function of preventing reflection of metal wiring or the like and an improved contrast, and having excellent level difference absorbability and workability.
Solution for solving the problem
As a result of intensive studies to achieve the above object, the inventors have found that an adhesive layer of a photocurable adhesive sheet is colored so as to exhibit absorption in the visible light region but high transmittance in the ultraviolet region, thereby improving the function of preventing reflection of metal wiring and the like and the contrast in a self-luminous display device, and achieving both excellent level difference absorption and workability. The present invention has been completed based on these findings.
The 1 st aspect of the present invention provides a photocurable adhesive sheet. That is, the photocurable adhesive sheet according to the 1 st aspect of the present invention includes an adhesive layer that is cured by irradiation with radiation. In the photocurable adhesive sheet according to the 1 st aspect of the present invention, the adhesive layer before curing is in a semi-cured state with high fluidity, and exhibits excellent level difference absorbability. Therefore, when the light emitting device is attached to a display panel in which light emitting elements (LED chips) are arranged at high density, the light emitting device sufficiently follows a fine height difference between the light emitting elements (LED chips), and the light emitting device is attached to the display panel without leaving bubbles and gaps. On the other hand, the adhesive layer after curing exhibits excellent workability. Therefore, the occurrence of a shortage of adhesive can be suppressed when cutting a laminate including the cured adhesive layer, and the occurrence of overflow and sagging of the adhesive layer from the end portion can be suppressed when keeping the laminate.
In the photocurable pressure-sensitive adhesive sheet of the 1 st aspect of the present invention, the maximum value of the transmittance at a wavelength of 200 to 400nm of the pressure-sensitive adhesive layer is larger than the maximum value of the transmittance at a wavelength of 400 to 700 nm. The adhesive layer has high absorption to visible light (wavelength 400-700 nm) and excellent light shielding property. The structure in which the pressure-sensitive adhesive layer is excellent in light-shielding properties against visible light is preferable from the viewpoint of: the adhesive layer filled in the fine level difference between the LED chips without gaps prevents reflection due to metal wiring or the like on the display panel, prevents color mixing of the arranged light emitting elements (LED chips), and improves contrast. On the other hand, the pressure-sensitive adhesive layer has high transmittance to ultraviolet rays (wavelength 200 to 400 nm). The structure in which the pressure-sensitive adhesive layer has excellent ultraviolet light transmittance is preferable in that the pressure-sensitive adhesive layer is irradiated with ultraviolet light to undergo a curing reaction and the workability of the pressure-sensitive adhesive layer is improved. That is, the structure in which the maximum value of the transmittance at a wavelength of 200 to 400nm of the pressure-sensitive adhesive layer is larger than the maximum value of the transmittance at a wavelength of 400 to 700nm is preferable in view of the excellent light shielding property against visible light and the curing reaction by ultraviolet irradiation.
The pressure-sensitive adhesive layer in the photocurable pressure-sensitive adhesive sheet in the 1 st aspect of the present invention contains a colorant. The colorant is preferably a colorant having a maximum value of transmittance at a wavelength of 200 to 400nm that is larger than a maximum value of transmittance at a wavelength of 400 to 700 nm. This configuration is preferable in that the maximum value of transmittance at a wavelength of 200 to 400nm is larger than the maximum value of transmittance at a wavelength of 400 to 700nm, which is achieved by the pressure-sensitive adhesive layer.
In the photocurable adhesive sheet according to the 1 st aspect of the present invention, the storage modulus (G' b 85) of the adhesive layer before curing at 85℃is less than 65kPa. Such a constitution is preferable in that the adhesive layer before curing exhibits excellent level difference absorbency.
In the photocurable adhesive sheet according to the 1 st aspect of the present invention, the storage modulus (G 'a 10) of the adhesive layer after curing at 10 ℃ and the storage modulus (G' b 85) of the adhesive layer before curing at 85 ℃ satisfy the following relational expression (1).
3.3<G'a10/G'b85 (1)
This configuration is preferable in that the adhesive layer before curing exhibits excellent level difference absorbency and the adhesive layer after curing exhibits excellent workability.
In the photocurable adhesive sheet according to the 1 st aspect of the present invention, the curing by irradiation with the aforementioned radiation is preferably based on a cumulative light quantity of 3000mJ/cm 2 Is cured by ultraviolet irradiation. This configuration is preferable in view of the fact that the adhesive layer is cured by ultraviolet irradiation and exhibits excellent workability.
In the photocurable adhesive sheet according to the 1 st aspect of the present invention, the storage modulus (G' a 10) of the cured adhesive layer at 10℃is preferably 90kPa or more. This configuration is preferable in that the adhesive layer after curing exhibits excellent workability.
In the photocurable pressure-sensitive adhesive sheet according to the 1 st aspect of the present invention, the pressure-sensitive adhesive layer preferably contains a base polymer, a crosslinking agent and a photopolymerization initiator. In this configuration, the base polymer preferably contains an acrylic polymer. In this case, the crosslinking agent preferably contains a polyfunctional (meth) acrylate. These structures are preferable in view of the fact that the adhesive layer is cured by forming a crosslinked structure by the reaction of a crosslinking agent and a photopolymerization initiator by irradiation of radiation, and thus exhibits excellent processability. In this configuration, the adhesive layer constitutes a mixed adhesive, and the base polymer is semi-cured to such an extent that the level difference absorbency is excellent.
In the photocurable pressure-sensitive adhesive sheet according to the 1 st aspect of the present invention, the pressure-sensitive adhesive layer preferably has the following composition: the adhesive layer is formed of the base polymer and has 2 opposed main surfaces, and when the adhesive layer of the single layer is divided into two parts in the thickness direction, the concentration of the crosslinking agent and/or the photopolymerization initiator in the region to which one of the 2 main surfaces, i.e., the 1 st main surface, belongs is different from the concentration of the crosslinking agent and/or the photopolymerization initiator in the region to which the other 2 main surface belongs. In this configuration, the pressure-sensitive adhesive layer of the single layer preferably has a concentration gradient of the crosslinking agent and/or the photopolymerization initiator in the thickness direction.
The photocurable pressure-sensitive adhesive sheet of these embodiments is preferably produced by a method comprising the following steps.
An adhesive layer forming a single layer formed of the aforementioned base polymer,
the aforementioned adhesive layer is cured and,
preparing a solution of the crosslinking agent and/or the photopolymerization initiator,
applying the solution to one surface of the cured adhesive layer, allowing the crosslinking agent and/or the photopolymerization initiator contained in the solution to penetrate from the one surface of the adhesive layer in the thickness direction,
The adhesive layer is dried.
In the above-described configuration, the solution of the crosslinking agent and/or the photopolymerization initiator is applied to one surface of the adhesive layer and allowed to permeate, thereby generating a concentration difference between the crosslinking agent and/or the photopolymerization initiator on the front surface and the back surface of the adhesive layer. This configuration is preferable in terms of achieving excellent level difference absorbency of the adhesive layer before curing and excellent workability of the adhesive layer after curing.
In the photocurable pressure-sensitive adhesive sheet according to the 1 st aspect of the present invention, the pressure-sensitive adhesive layer preferably contains a polymer having a benzophenone structure in a side chain. In this structure, the adhesive layer is preferably a cured product of an adhesive composition containing an ethylenically unsaturated compound and a polymer having a benzophenone structure in a side chain. This configuration is preferable in that the adhesive layer before curing exhibits excellent level difference absorbability, and the benzophenone structure is cured by ultraviolet irradiation to form a crosslinked structure, thereby achieving excellent processability.
Further, a 2 nd aspect of the present invention provides a self-luminous display device comprising: a display panel in which a plurality of light-emitting elements are arranged on one surface of a substrate, and the photocurable adhesive sheet according to the 1 st aspect of the present invention, wherein the light-emitting elements of the display panel are sealed with an adhesive layer of the photocurable adhesive sheet, and the adhesive layer is cured. In the self-luminous display device according to the 2 nd aspect of the present invention, the display panel may be an LED panel in which a plurality of LED chips are arranged on one surface of a substrate. This configuration is preferable in terms of: in the self-luminous display device according to the 2 nd aspect of the present invention, the adhesive layer having excellent light shielding properties and being filled in a fine level difference between light emitting elements (LED chips) without gaps can prevent reflection of metal wiring and the like on a substrate, prevent color mixing of RGB, and improve contrast.
The self-luminous display device according to the 2 nd aspect of the present invention can be manufactured by a method including the following steps.
Laminating an adhesive layer of the photocurable adhesive sheet of the 1 st side of the present invention on a display panel having a plurality of light-emitting elements arranged on one side of a substrate, and sealing the light-emitting elements with the adhesive layer; and
and a step of curing the adhesive layer by irradiation with radiation.
Since the adhesive layer before curing has excellent level difference absorptivity, it sufficiently follows the fine level difference between light emitting elements, and adheres without leaving bubbles and gaps. The adhesive layer is cured by irradiation with radiation, and thus has excellent workability.
The radiation is preferably ultraviolet rays which the adhesive layer transmits.
ADVANTAGEOUS EFFECTS OF INVENTION
The photocurable pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer having high light-shielding properties against visible light and excellent level difference absorptivity, and therefore is used for manufacturing a self-luminous display device, so that the level difference between a plurality of light-emitting elements is filled without gaps, reflection from metal wiring is prevented, color mixing between the plurality of light-emitting elements is suppressed, and contrast is improved. In addition, by curing the adhesive layer having excellent ultraviolet ray transmittance by irradiation with radiation, workability is improved, and occurrence of a shortage of adhesive can be suppressed during cutting processing, and occurrence of overflow and sagging of the adhesive layer from the end portion can be suppressed during storage. Therefore, when the photocurable pressure-sensitive adhesive sheet of the present invention is used for the production of a self-luminous display device, a self-luminous display device having an improved function of preventing reflection of metal wiring and the like and an improved contrast can be produced efficiently.
Drawings
Fig. 1 is a view (cross-sectional view) schematically showing one embodiment of the photocurable adhesive sheet of the present invention.
Fig. 2 is a diagram (cross-sectional view) schematically showing a process for carrying out one embodiment of the method for producing a photocurable pressure-sensitive adhesive sheet in accordance with the present invention.
Fig. 3 is a view (cross-sectional view) schematically showing one embodiment of the photocurable adhesive sheet of the present invention.
Fig. 4 is a schematic view (cross-sectional view) showing one embodiment of a self-luminous display device (mini/micro LED display device) of the present invention.
Fig. 5 is a schematic view (cross-sectional view) showing a process for implementing one embodiment of a method for manufacturing a self-luminous display device (mini/micro LED display device) of the present invention.
Detailed Description
Embodiments of the present invention will be described with reference to the drawings, as necessary, but the present invention is not limited thereto and is merely illustrative.
[ Photocurable pressure-sensitive adhesive sheet ]
The photocurable adhesive sheet according to the 1 st aspect of the present invention comprises an adhesive layer cured by irradiation with radiation, wherein the adhesive layer comprises a colorant, the maximum value of transmittance at a wavelength of 200 to 400nm of the adhesive layer is larger than the maximum value of transmittance at a wavelength of 400 to 700nm, the storage modulus (G ' b 85) of the adhesive layer before curing at 85 ℃ is lower than 65kPa, and the storage modulus (G ' a 10) of the adhesive layer after curing at 10 ℃ and the storage modulus (G ' b 85) of the adhesive layer at 85 ℃ before curing satisfy the following relational expression (1).
3.3<G'a10/G'b85 (1)
In the present specification, the photocurable adhesive sheet in the 1 st side of the present invention may be simply referred to as "photocurable adhesive sheet a". In the present specification, the pressure-sensitive adhesive layers satisfying the following (a) to (d) are sometimes referred to as "pressure-sensitive adhesive layer a".
(a) Curing by irradiation with radiation.
(b) The maximum value of the transmittance at the wavelength of 200 to 400nm is larger than the maximum value of the transmittance at the wavelength of 400 to 700 nm.
(c) The storage modulus (G' b 85) at 85℃before curing is less than 65kPa.
(d) The storage modulus (G 'a 10) at 10℃after curing and the storage modulus (G' b 85) at 85℃before curing satisfy the following relational expression (1).
3.3<G'a10/G'b85 (1)
The "adhesive sheet" is considered to include the meaning of "adhesive tape". That is, the photocurable adhesive sheet a may be an adhesive tape having a tape-like form.
The form of the photocurable pressure-sensitive adhesive sheet a is not particularly limited as long as it has a pressure-sensitive adhesive surface formed on the surface of the pressure-sensitive adhesive layer a. The photocurable pressure-sensitive adhesive sheet a may be a single-sided pressure-sensitive adhesive sheet having only one side as a pressure-sensitive adhesive surface, or may be a double-sided pressure-sensitive adhesive sheet having both sides as pressure-sensitive adhesive surfaces. In the case where the photocurable adhesive sheet a is a double-sided adhesive sheet, the photocurable adhesive sheet a may have a configuration in which two adhesive surfaces are provided by the adhesive layer a, or may have a configuration in which one adhesive surface is provided by the adhesive layer a and the other adhesive surface is provided by an adhesive layer (other adhesive layer) other than the adhesive layer a. From the viewpoint of bonding the adherends to each other, a double-sided adhesive sheet is preferable, and a double-sided adhesive sheet having both sides of the sheet on the surface of the adhesive layer a is more preferable.
The photocurable adhesive sheet a may be an adhesive sheet having no base material (base material layer), that is, a so-called "base material-free type" adhesive sheet (sometimes referred to as "base material-free adhesive sheet"), or an adhesive sheet having a base material (sometimes referred to as "base material-provided adhesive sheet"). Examples of the substrate-free pressure-sensitive adhesive sheet in the present invention include: a double-sided adhesive sheet composed of only the adhesive layer a, and a double-sided adhesive sheet formed of the adhesive layer a and other adhesive layers (adhesive layers other than the adhesive layer a). Examples of the pressure-sensitive adhesive sheet with a base material in the present invention include: a single-sided adhesive sheet having an adhesive layer a on one side of a substrate, a double-sided adhesive sheet having an adhesive layer a on both sides of a substrate, and a double-sided adhesive sheet having an adhesive layer a on one side of a substrate and another adhesive layer on the other side.
Among the above, from the viewpoint of improvement of optical properties, a base-free pressure-sensitive adhesive sheet is preferable, and a base-free double-sided pressure-sensitive adhesive sheet (base-free double-sided pressure-sensitive adhesive sheet) composed only of the pressure-sensitive adhesive layer a is more preferable. In addition, when the adhesive sheet a is an adhesive sheet having a base material, the adhesive sheet a is preferably a double-sided adhesive sheet having an adhesive layer a on both sides of the base material (double-sided adhesive sheet with base material) from the viewpoint of workability, although not particularly limited.
The "base material (base material layer)" refers to a portion that is adhered to an adherend (optical member or the like) together with the adhesive layer when the photocurable adhesive sheet a is used for (adhered to) the adherend, and does not include a release film (release film) that is peeled off when the adhesive sheet is used for (adhered to) the adherend.
The photocurable adhesive sheet a may be a base-material-attached adhesive sheet as described above. Examples of such a substrate include various optical films such as plastic films, anti-reflection (AR) films, polarizing plates, and retardation plates. Examples of the raw material of the plastic film include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonates, triacetyl cellulose (TAC), polysulfones, polyarylates, polyimides, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, cyclic olefin polymers such as "Arton" (available from JSR corporation), and cyclic olefin polymers such as "ZEONOR" (available from cyclic olefin polymers, available from japanese patent No. Weng Zhushi). It should be noted that these plastic materials may be used alone or in combination of 2 or more.
The substrate is preferably transparent. The total light transmittance of the substrate in the visible light wavelength region (according to JIS K7361-1) is not particularly limited, and is preferably 85% or more, more preferably 88% or more. The haze (according to 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 transparent substrates include PET films, unoriented films such as "Arton" and "ZEONOR".
The thickness of the base material is not particularly limited, and is preferably 12 to 75. Mu.m. The substrate may have any of a single layer and a plurality of layers. The surface of the substrate may be subjected to a known and conventional surface treatment such as an antireflection treatment (AR treatment), an antireflection treatment such as an antiglare treatment, a physical treatment such as a corona discharge treatment or a plasma treatment, and a chemical treatment such as a primer treatment.
The photocurable adhesive sheet a may have other adhesive layers (adhesive layers other than the adhesive layer a) as described above. The other adhesive layer is not particularly limited, and examples thereof include adhesive layers formed of a known and customary adhesive such as urethane-based adhesive, acrylic-based adhesive, rubber-based adhesive, silicone-based adhesive, polyester-based adhesive, polyamide-based adhesive, epoxy-based adhesive, vinyl alkyl ether-based adhesive, and fluorine-based adhesive. The above-mentioned binders may be used singly or in combination of 2 or more.
The photocurable pressure-sensitive adhesive sheet a may have other layers (e.g., an intermediate layer, an undercoat layer, etc.) in addition to the pressure-sensitive adhesive layer a, the base material, and other pressure-sensitive adhesive layers, as long as the effects of the present invention are not impaired.
The photocurable pressure-sensitive adhesive sheet a may be provided with a release film (release film) on the pressure-sensitive adhesive surface until the time of use. The form of protecting the adhesive surface of the photocurable adhesive sheet a by the release film is not particularly limited, and each adhesive surface may be protected by 2 release films, or may be protected by 1 release film having both surfaces as release surfaces by winding into a roll. The release film is used as a protective material for an adhesive layer, and is peeled off when adhered to an adherend. In the photocurable pressure-sensitive adhesive sheet a, the release film also functions as a support for the pressure-sensitive adhesive layer. The release film may not be provided.
Fig. 1 is a view (cross-sectional view) schematically showing one embodiment of the photocurable adhesive sheet a of the present invention. In fig. 1, 1A is a photocurable pressure-sensitive adhesive sheet in accordance with the present invention, 10 is a pressure-sensitive adhesive layer, and S1 and S2 are supports (including a separator).
The thickness (total thickness) of the photocurable pressure-sensitive adhesive sheet A is not particularly limited, but is preferably 10 μm to 1mm, more preferably 100 μm to 500 μm, and still more preferably 150 μm to 350 μm. By making the thickness 10 μm or more, the pressure-sensitive adhesive layer a easily follows the level difference portion, and the level difference absorbency can be improved. The thickness of the photocurable adhesive sheet a does not include the thickness of the release film.
The photocurable pressure-sensitive adhesive sheet a has light absorbency to visible light because of the pressure-sensitive adhesive layer a. The total light transmittance of the photocurable pressure-sensitive adhesive sheet a is, for example, 80% or less, or 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.
Since the photocurable adhesive sheet a has the adhesive layer a, it has excellent level difference absorbability before curing. For example, the level difference absorption is excellent even for a relatively high level difference exceeding 40 μm in addition to a level difference of 5 to 10. Mu.m. Further, the film has a level difference absorbency even for a level difference of a height exceeding 80. Mu.m.
Further, since the photocurable pressure-sensitive adhesive sheet a has the pressure-sensitive adhesive layer a, it has excellent workability after curing, and can suppress the lack of adhesive at the time of cutting processing, and the overflow and sagging of the pressure-sensitive adhesive layer from the end during storage.
Further, since the photocurable pressure-sensitive adhesive sheet a has the pressure-sensitive adhesive layer a, the adhesion reliability is also excellent.
(adhesive layer A)
The adhesive layer a is cured by irradiation with radiation. For example, when the photocurable pressure-sensitive adhesive sheet a is adhered to an adherend and then irradiated with radiation, the pressure-sensitive adhesive layer a is cured. The adhesive layer a before curing is in a state of high fluidity, and is excellent in level difference absorption, and for example, a fine level difference between a metal wiring layer and a light emitting element (LED chip) of a self-light emitting display device (mini/micro LED display device) can be sealed without a gap. In addition, workability of the cured adhesive layer a after irradiation with radiation is improved, and it is possible to suppress shortage of adhesive during cutting processing, and overflow and sagging of the adhesive layer from the end during storage.
Examples of the radiation for curing include ionizing radiation such as α rays, β rays, γ rays, X rays, neutron rays, and electron rays, ultraviolet rays, and the like. Since the adhesive layer a exhibits ultraviolet ray transmittance, ultraviolet rays are preferable. More preferably, ultraviolet rays having a wavelength of 200 to 400nm, and still more preferably, ultraviolet rays having a wavelength of 330 to 400 nm. As the light source for ultraviolet irradiation, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light lamp, or an LED can be used. In additionThe irradiation energy, irradiation time, and irradiation method of the radiation for curing can be appropriately set as long as the adhesive layer a can be cured without adversely affecting the adherend. For example, when ultraviolet rays are used as the curing radiation, the irradiation amount (cumulative light amount) is preferably 1000mJ/cm 2 ～10000mJ/cm 2 More preferably 2000mJ/cm 2 ～4000mJ/cm 2 Further preferably 3000mJ/cm 2 。
(storage modulus)
The storage modulus (G' b 85) of the adhesive layer A before curing at 85℃is not particularly limited, and is, for example, preferably less than 65kPa, more preferably 60kPa or less, still more preferably 55kPa or less, particularly preferably 50kPa or less, and further may be 45kPa or less. Such a configuration is preferable in terms of achieving excellent level difference absorbency of the adhesive layer a before curing. Further, G' b85 is not particularly limited, but is preferably 5kPa or more, more preferably 10kPa or more, and further preferably 15kPa or more from the viewpoint of handling property and handleability. The storage modulus (G' b 85) of the adhesive layer a before curing at 85 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 1 st crosslinking agent), the Mw, tg, weight fraction of BP polymer, the composition of monomer components constituting BP polymer and ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The storage modulus (G' a 10) of the cured adhesive layer A at 10℃is not particularly limited, and is, for example, preferably 90kPa or more, more preferably 100kPa or more, more preferably 110kPa or more, more preferably 120kPa or more, more preferably 130kPa or more, more preferably more than 146kPa, more preferably 180kPa or more, more preferably 200kPa or more, particularly preferably 250kPa or more, and further may be 300kPa or more, or 350kPa or more. Such a configuration is preferable in terms of achieving excellent workability of the cured adhesive layer a. Further, G' a10 is not particularly limited, but is, for example, 5000kPa or less, preferably 2500kPa or less, more preferably 1000kPa or less from the viewpoint of adhesion reliability. The storage modulus (G' a 10) of the cured adhesive layer a at 10 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 2 nd crosslinking agent), the Mw, tg, BP equivalent of the BP polymer (a), the weight fraction of the BP polymer, the composition of monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The ratio (G 'a10/G' b 85) of the storage modulus (G 'a 10) at 10 ℃ of the cured adhesive layer a to the storage modulus (G' b 85) at 85 ℃ of the adhesive layer a before curing is not particularly limited, and is preferably, for example, greater than 3.3, more preferably 3.4 or more, still more preferably 3.5 or more, particularly preferably 3.6 or more, and further may be 3.7 or more, 3.8 or more, 3.9 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, or 11 or more. Such a configuration is preferable in view of the excellent level difference absorbability of the adhesive layer a before curing and the excellent workability of the adhesive layer a after curing. The G 'a10/G' b85 is not particularly limited, but is preferably 100 or less, more preferably 50 or less, and further preferably 30 or less from the viewpoints of handling property, and adhesion reliability. The ratio (G 'a10/G' b 85) of the storage modulus (G 'a 10) at 10 ℃ of the cured adhesive layer a to the storage modulus (G' b 85) at 85 ℃ of the adhesive layer a before curing can be adjusted, for example, by the composition (for example, the molecular weight, the amount used, the monomer composition, the kind and amount of functional groups, the kind, amount and ratio of the crosslinking agent (particularly, the 1 st and 2 nd crosslinking agents), the Mw, tg, BP equivalent of the BP polymer, the weight fraction of the BP polymer, the composition of monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of the crosslinking agent, and the like of the mixed adhesive composition to be described later for forming the adhesive layer a.
The storage modulus (G' b 10) of the adhesive layer A before curing at 10℃is not particularly limited, but is preferably, for example, 10kPa or more, more preferably 50kPa or more, still more preferably 70kPa or more, or may be 90kPa or more, 100kPa or more, from the viewpoints of handleability and handleability. Further, G' b10 is not particularly limited, but is, for example, 5000kPa or less, preferably 2500kPa or less, more preferably 1000kPa or less from the viewpoint of adhesion reliability. The storage modulus (G' b 10) of the adhesive layer a before curing at 10 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 1 st crosslinking agent), the Mw, tg, weight fraction of BP polymer, the composition of monomer components constituting BP polymer and ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The storage modulus (G' a 85) of the cured adhesive layer A at 85℃is not particularly limited, but is preferably, for example, 10kPa or more, preferably 20kPa or more, more preferably 30kPa or more, from the viewpoints of handleability and handleability. In addition, G' a85 is not particularly limited, and is, for example, 1000kPa or less, preferably 500kPa or less, more preferably 200kPa or less, from the viewpoint of adhesion reliability. The storage modulus (G' a 85) of the cured adhesive layer a at 85 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 2 nd crosslinking agent), the Mw, tg, BP equivalent of the BP polymer, the weight fraction of the BP polymer, the composition of monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The storage modulus (G' a 25) of the cured adhesive layer A at 25℃is not particularly limited, and is, for example, preferably 70kPa or more, more preferably more than 100kPa, still more preferably 150kPa or more, and still more preferably 170kPa or more. Such a configuration is preferable in terms of achieving excellent workability of the cured adhesive layer a. In addition, G' a25 is not particularly limited, but is, for example, 5000kPa or less, preferably 2500kPa or less, and more preferably 1000kPa or less from the viewpoint of adhesion reliability. The storage modulus (G' a 25) of the cured adhesive layer a at 25 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 2 nd crosslinking agent), the Mw, tg, BP equivalent of the BP polymer, the weight fraction of the BP polymer, the composition of monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The storage modulus (G' b 25) of the adhesive layer A before curing at 25℃is not particularly limited, and is, for example, 300kPa or less, preferably 250kPa or less, more preferably 200kPa or less. Such a configuration is preferable in terms of achieving excellent level difference absorbency of the adhesive layer a before curing. In addition, G' b25 is not particularly limited, but is, for example, 10kPa or more, preferably 30kPa or more, and more preferably 50kPa or more from the viewpoint of adhesion reliability. The storage modulus (G' b 25) of the adhesive layer a before curing at 25 ℃ can be adjusted, for example, by the composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 1 st crosslinking agent), the Mw, tg, weight fraction of BP polymer, the composition of monomer components constituting BP polymer and ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent) of the mixed adhesive composition to be described later for forming the adhesive layer a.
The ratio (G 'a25/G' b 85) of the storage modulus (G 'a 25) at 10 ℃ of the cured adhesive layer a to the storage modulus (G' b 85) at 85 ℃ of the adhesive layer a before curing is not particularly limited, and is, for example, preferably 0.3 or more, more preferably 0.5 or more, more preferably 1 or more, more preferably more than 3, preferably 3.5 or more, and more preferably 4 or more. Such a configuration is preferable in view of the excellent level difference absorbability of the adhesive layer a before curing and the excellent workability of the adhesive layer a after curing. The G 'a25/G' b85 is not particularly limited, but is, for example, 100 or less, preferably 50 or less, and more preferably 30 or less from the viewpoints of handling property, and adhesion reliability. The ratio (G 'a25/G' b 85) of the storage modulus (G 'a 25) at 10 ℃ of the cured adhesive layer a to the storage modulus (G' b 85) at 85 ℃ of the adhesive layer a before curing can be adjusted, for example, by the composition (for example, the molecular weight, the amount used, the monomer composition, the kind and amount of functional groups, the kind, amount and ratio of the crosslinking agent (particularly, the 1 st and 2 nd crosslinking agents), the Mw, tg, BP equivalent of the BP polymer, the weight fraction of the BP polymer, the composition of monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of the crosslinking agent, and the like of the mixed adhesive composition to be described later for forming the adhesive layer a.
The curing conditions in the "cured adhesive layer a" are not particularly limited, and ultraviolet rays that the adhesive layer a exhibits permeability are preferable. More preferably, ultraviolet rays having a wavelength of 200 to 400nm, and still more preferably, ultraviolet rays having a wavelength of 330 to 400 nm. As the light source for ultraviolet irradiation, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light lamp, or an LED can be used. The irradiation energy, irradiation time, and irradiation method of the curing radiation can be appropriately set as long as the adhesive layer a can be cured without adversely affecting the adherend. For example, when ultraviolet rays are used as the curing radiation, the irradiation amount (cumulative light amount) is preferably 1000mJ/cm 2 ～10000mJ/cm 2 More preferably 2000mJ/cm 2 ～4000mJ/cm 2 Further preferably 3000mJ/cm 2 。
The storage modulus is a value measured by dynamic viscoelasticity measurement.
(other Properties of adhesive layer A)
The gel fraction of the adhesive layer a before curing is 50 to 90 wt%, preferably 50 to 80 wt%, and more preferably 50 to 70 wt%. When the gel fraction is 90 wt% or less, the cohesive force of the adhesive layer a becomes small to some extent, and the adhesive layer a becomes soft, so that the adhesive layer becomes easy to follow the level difference portion, and excellent level difference absorbency can be obtained. On the other hand, when the gel fraction is 50% by weight or more, problems such as excessive softening of the pressure-sensitive adhesive layer, deterioration of handling properties and handling properties of the pressure-sensitive adhesive sheet can be suppressed, and occurrence of bubbles and floating can be suppressed in a high-temperature environment and a high-temperature and high-humidity environment, thereby improving the bonding reliability. The gel fraction can be controlled by, for example, the type and content (amount) of the crosslinking agent.
The gel fraction (ratio of solvent-insoluble components) can be determined as ethyl acetate-insoluble components. Specifically, the content of insoluble components after immersing the adhesive layer in ethyl acetate at room temperature (23 ℃) for 7 days was determined as the weight fraction (unit: weight%) of the sample before immersion. More specifically, the gel fraction is a value calculated by the following "gel fraction measurement method".
(method for measuring gel fraction)
The adhesive layer was taken at about 1g and its weight was measured, and this weight was taken as "weight of the adhesive layer before impregnation". Next, the collected adhesive layer was immersed in 40g of ethyl acetate for 7 days, and then all the ethyl acetate-insoluble components (insoluble portions) were collected, and the total insoluble portions thus collected were dried at 130 ℃ for 2 hours, and the weight was measured after removal of ethyl acetate, and the "dry weight of insoluble portions" (weight of the adhesive layer after immersion) was used. Then, the obtained numerical value is substituted into the following equation to calculate.
Gel fraction (wt%) = [ (dry weight of insoluble portion)/(weight of adhesive layer before impregnation) ]×100
The gel fraction of the adhesive layer a before curing can be adjusted, for example, by the composition of the mixed adhesive composition (for example, the molecular weight, the amount of use, the monomer composition, the kind and amount of functional groups of the base polymer, the kind and amount of crosslinking agent (particularly, the 1 st crosslinking agent), the Mw, tg of the BP polymer (a), the weight fraction of the BP polymer, the composition of the monomer components constituting the BP polymer and the ethylenically unsaturated compound, the kind and amount of functional groups, the kind and amount of crosslinking agent), the curing conditions (heating conditions, radiation irradiation conditions) and the like, which will be described later, for forming the adhesive layer a.
The glass transition temperature (Tg) of the adhesive layer A before curing is not particularly limited, but is preferably-60 to 20 ℃, more preferably-40 to 10 ℃, and even more preferably-30 to 0 ℃. When the Tg is higher than 20 ℃, the adhesive force cannot be developed at room temperature.
The Tg is not particularly limited, and the pressure-sensitive adhesive layer may be measured by Differential Scanning Calorimetry (DSC) in accordance with JIS K7121, for example, as a sample for measurement. Specifically, for example, the measurement can be performed at a temperature of-80℃to 80℃and a temperature rise rate of 10℃per minute using a device name "Q-2000" manufactured by TA instruments, inc. as a measurement device.
The thickness of the adhesive layer a is not particularly limited, and may be appropriately set so that light-emitting elements to be arranged on a display panel described later can be sufficiently sealed. For example, the thickness of the adhesive layer a is adjusted to be 1.0 to 4.0 times, preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and even more preferably 1.3 to 2.0 times the height of the light-emitting element. By setting the thickness to 1.0 times or more, the adhesive layer a easily follows the level difference, and the level difference absorbency improves. In addition, by setting the thickness to 4.0 or less, deformation of the adhesive layer a is less likely to occur, and workability is improved.
The thickness of the pressure-sensitive adhesive layer A may be, for example, about 10 to 500. Mu.m, or 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. The thickness of the adhesive layer A may be 400 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. By making the thickness 10 μm or more, the pressure-sensitive adhesive layer a easily follows the level difference portion, and the level difference absorbency is improved. In addition, by setting the thickness to 500 μm or less, deformation of the adhesive layer a is less likely to occur, and workability is improved.
The maximum value of the transmittance at a wavelength of 200 to 400nm (preferably, a wavelength of 330 to 400 nm) of the adhesive layer a is larger than the maximum value of the transmittance at a wavelength of 400 to 700 nm.
The pressure-sensitive adhesive layer A has a lower transmittance to visible light (wavelength 400 to 700 nm) than in the ultraviolet region (wavelength 200 to 400nm, preferably wavelength 330 to 400 nm). The adhesive layer a having excellent light-shielding properties against visible light seals a fine level difference between a metal wiring layer and a light-emitting element (LED chip) of a self-luminous display device (mini/micro LED display device) without a gap, thereby preventing reflection due to the metal wiring or the like, preventing color mixing of the light-emitting element (LED chip), and improving contrast of an image.
On the other hand, the pressure-sensitive adhesive layer a has a higher transmittance in the ultraviolet region (wavelength of 200 to 400nm, preferably 330 to 400 nm) than that of visible light, and can be cured by irradiation with ultraviolet light. The workability of the adhesive layer A cured by ultraviolet irradiation is improved, and the adhesive layer can be prevented from being damaged during cutting processing, and from overflowing and sagging from the end during storage.
In the present specification, the "maximum value of transmittance at a wavelength of 200 to 400 nm" means the highest transmittance in the range of the region of 200 to 400 nm. For example, when there is a maximum value of transmittance in a wavelength range of 200 to 400nm, the maximum value becomes the maximum value of transmittance. When the maximum transmittance does not exist in the wavelength range of 200 to 400nm, the higher transmittance of the transmittance at the wavelength of 200nm or 400nm becomes the maximum. The same applies to "maximum transmittance at a wavelength of 330 to 400 nm" and "maximum transmittance at a wavelength of 400 to 700 nm".
The maximum value of the transmittance of the pressure-sensitive adhesive layer a at a wavelength of 400 to 700nm (visible light range) may be, for example, 80% or less, or 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less.
The pressure-sensitive adhesive layer A preferably has an average transmittance at a wavelength of 200 to 400nm (preferably 330 to 400 nm) that is greater than an average transmittance at a wavelength of 400 to 700 nm. The average transmittance of the pressure-sensitive adhesive layer a at a wavelength of 400 to 700nm (visible light range) may be, for example, 80% or less, or 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less.
The adhesive layer a exhibits excellent light-shielding properties against visible light, and therefore, even when a metal adherend is laminated on the adhesive layer a, reflection and gloss of the metal surface can be prevented. The reflectance in the visible light region of 5 ° regular reflection when the metal adherend is laminated on the pressure-sensitive adhesive layer a is preferably 50% or less, more preferably 30% or less, still more preferably 15% or less, and particularly preferably 10% or less. The glossiness when the metal adherend is laminated on the adhesive layer a (based on JIS Z8741-1997) is preferably 100% or less, more preferably 80% or less, still more preferably 60% or less, particularly preferably 50% or less.
The metal adherends include copper, aluminum, stainless steel, and the like.
(colorant)
The adhesive layer a contains a colorant. The colorant is preferably a colorant having a maximum value of transmittance at a wavelength of 200 to 400nm (preferably, a wavelength of 330 to 400 nm) which is larger than a maximum value of transmittance at a wavelength of 400 to 700nm (hereinafter, may be referred to as "colorant (A)").
The structure in which the maximum value of the transmittance at a wavelength of 200 to 400nm (preferably 330 to 400 nm) of the pressure-sensitive adhesive layer a is larger than the maximum value of the transmittance at a wavelength of 400 to 700nm is not particularly limited, and is preferably achieved by including the colorant a.
The maximum value of the transmittance of the colorant (including the colorant a) at a wavelength of 400 to 700nm (visible light range) is, for example, 80% or less, or may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.
The average transmittance of the colorant (including the colorant A) at a wavelength of 200 to 400nm (preferably, at a wavelength of 330 to 400 nm) is preferably larger than the average transmittance at a wavelength of 400 to 700 nm. The average transmittance of the colorant (including the colorant a) at a wavelength of 400 to 700nm (visible light range) is, for example, 80% or less, or may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.
The transmittance of the colorant (including the colorant a) can be measured by using a solution or dispersion in which the colorant is diluted with an appropriate solvent such as Tetrahydrofuran (THF) or a dispersion medium (an organic solvent having a small absorption in the range of 200 to 700 nm) so that the transmittance at a wavelength of 400nm is about 50 to 60%.
The colorant (including the colorant a) may be a dye or a pigment as long as it can be dissolved or dispersed in the adhesive layer a. Dyes are preferred from the viewpoint that low haze can be achieved even with a small amount of addition, no sedimentation is possible as in pigments, and uniform distribution is easy. In addition, pigments are also preferred in terms of high color rendering properties even when added in small amounts. When pigments are used as colorants, it is preferred that the conductivity be low or not. In addition, when a dye is used, it is preferably used in combination with an antioxidant or the like.
Examples of the ultraviolet-transmitting BLACK pigment include "9050BLACK", "9256BLACK", "9170BLACK", "UVBK-0001", mitsubishi Materials Electronic Chemicals co., ltd. Examples of the ultraviolet-transmitting black dye include "SOC-L-0123" manufactured by Ltd, orient Chemical Industries Co.
The content of the colorant (including the colorant a) in the pressure-sensitive adhesive layer a may be, for example, about 0.01 to 20 parts by weight, preferably about 0.1 to 10 parts by weight, based on 100 parts by weight of the pressure-sensitive adhesive layer a, and may be appropriately set according to the type of the colorant, the color tone of the pressure-sensitive adhesive layer a, the light transmittance, and the like. The colorant may be added as a solution or dispersion in which it is dissolved or dispersed in an appropriate solvent.
(Mixed adhesive composition)
The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer a is not particularly limited as long as the above-mentioned properties (a) to (d) are satisfied, and a mixed pressure-sensitive adhesive composition containing a colorant (preferably, a colorant a) is preferable.
The hybrid adhesive is an adhesive that is stepwise cured by compounding 2 kinds of polymerization initiators, crosslinking agents, or having crosslinkable functional groups (in this specification, the polymerization initiators, crosslinking agents, and crosslinkable functional groups are sometimes referred to as "initiators") that differ in curing initiation conditions such as heat and light.
In the mixed adhesive, first, one of the initiators (in this specification, sometimes referred to as "1 st initiator") is brought into a semi-cured state having high fluidity and excellent level difference absorptivity, so that the level difference is sufficiently followed, and then light is irradiated, and curing is terminated by the other of the initiators (in this specification, sometimes referred to as "2 nd initiator"), whereby the workability can be improved.
The mixed adhesive composition constituting the adhesive layer a is not particularly limited, and typically contains a base polymer, a crosslinking agent, and a photopolymerization initiator. Here, the base polymer is a polymer cured by the 1 st initiator, and the crosslinking agent and the photopolymerization initiator correspond to the 2 nd initiator.
The base polymer is not particularly limited as long as it is a material having adhesiveness that can be used for optical applications. For example, any one of the acrylic polymer contained in the acrylic adhesive layer as a base polymer, the rubber polymer contained in the rubber adhesive layer (natural rubber adhesive layer, synthetic rubber adhesive layer, etc.), the silicone polymer contained in the silicone adhesive layer as a base polymer, the polyester polymer contained in the polyester adhesive layer as a base polymer, the urethane polymer contained in the urethane adhesive layer as a base polymer, the polyamide polymer contained in the polyamide adhesive layer as a base polymer, the epoxy polymer contained in the epoxy adhesive layer as a base polymer, the vinyl alkyl ether polymer contained in the vinyl alkyl ether adhesive layer as a base polymer, the fluorine polymer contained in the fluorine adhesive layer as a base polymer, etc. may be appropriately selected and used, and these polymers may be used alone or in combination of 2 or more. From the viewpoints of processability, durability, and the like, an acrylic polymer is preferably used. The acrylic polymer is not particularly limited, but is preferably a homopolymer or copolymer of a monomer containing an alkyl (meth) acrylate as a main component. Here, the expression "(meth) acrylic acid" is used as meaning either or both of "acrylic acid" and "methacrylic acid", and the same applies in other cases. In the present invention, the term acrylic polymer is used in the sense of comprising other monomers copolymerizable therewith in addition to the above-mentioned alkyl (meth) acrylate.
The acrylic polymer preferably contains, as the most main monomer unit in terms of weight ratio, a monomer unit derived from an alkyl acrylate having a linear or branched alkyl group and/or an alkyl methacrylate having a linear or branched alkyl group.
Examples of the alkyl (meth) acrylate having a linear or branched alkyl group as a monomer unit for forming the acrylic polymer include alkyl (meth) acrylate having a linear or branched alkyl group as a monomer component for forming the acrylic polymer, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, isobutyl (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, and octadecyl (meth) acrylate Alkyl (meth) acrylates having a linear or branched alkyl group having 1 to 20 carbon atoms, such as isostearyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate. As the alkyl (meth) acrylate used for the acrylic polymer, one type of alkyl (meth) acrylate may be used, or two or more types of alkyl (meth) acrylates may be used. In the present embodiment, as the alkyl (meth) acrylate used for the acrylic polymer, at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate and isostearyl acrylate is preferably used.
The ratio of the monomer unit derived from the alkyl (meth) acrylate having a linear or branched alkyl group in the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, still more preferably 80% by weight or more, still more preferably 90% by weight or more. That is, the ratio of the alkyl (meth) acrylate in the monomer component composition of the raw material for forming the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more.
The acrylic polymer may contain a monomer unit derived from an alicyclic monomer. Examples of the alicyclic monomer used for forming the monomer unit of the acrylic polymer, that is, the alicyclic monomer contained in the monomer component used for forming the acrylic polymer include cycloalkyl (meth) acrylate, a (meth) acrylate having a bicyclic hydrocarbon ring, and a (meth) acrylate having a hydrocarbon ring of three or more rings. Examples of cycloalkyl (meth) acrylates include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate. Examples of the (meth) acrylic acid ester having a bicyclic hydrocarbon ring include bornyl (meth) acrylate and isobornyl (meth) acrylate. Examples of the (meth) acrylic acid ester having a hydrocarbon ring of three or more rings include dicyclopentyl (meth) acrylate, dicyclopentyloxyethyl (meth) acrylate, tricyclopentyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, and 2-ethyl-2-adamantyl (meth) acrylate. As the alicyclic monomer used for the acrylic polymer, one type of alicyclic monomer may be used, or two or more types of alicyclic monomers may be used. In the present embodiment, as the alicyclic monomer for the acrylic polymer, at least one selected from the group consisting of cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate and isobornyl methacrylate is preferably used.
From the viewpoint of achieving a suitable flexibility in the base polymer formed by including the acrylic polymer, the ratio of the monomer unit derived from the alicyclic monomer in the acrylic polymer is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, and still more preferably 12 to 40% by weight. In addition, in some embodiments of the present invention, the acrylic polymer may contain no monomer unit derived from an alicyclic monomer.
The aforementioned acrylic polymer may contain monomer units derived from hydroxyl-containing monomers. The hydroxyl group-containing monomer is a monomer having at least one hydroxyl group in the monomer unit. When the acrylic polymer in the base polymer contains a hydroxyl group-containing monomer unit, adhesiveness and proper cohesive force are easily obtained in the base polymer. In addition, the hydroxyl group can also be a reaction point with a crosslinking agent described later.
Examples of the hydroxyl group-containing monomer used for forming the monomer unit of the acrylic polymer, that is, the hydroxyl group-containing monomer contained in the monomer component used for forming the acrylic polymer include hydroxyl group-containing (meth) acrylates, vinyl alcohols and allyl alcohols. Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate. As the hydroxyl group-containing monomer used for the acrylic polymer, one type of hydroxyl group-containing monomer may be used, or two or more types of hydroxyl group-containing monomers may be used. In the present embodiment, as the hydroxyl group-containing monomer for the acrylic polymer, at least one selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate and 4-hydroxybutyl methacrylate is preferably used.
The ratio of the monomer unit derived from the hydroxyl group-containing monomer in the acrylic polymer is preferably 1% by weight or more, more preferably 2% by weight or more, more preferably 3% by weight or more, more preferably 7% by weight or more, more preferably 10% by weight or more, more preferably 15% by weight or more. The ratio of the monomer unit derived from the hydroxyl group-containing monomer in the acrylic polymer is preferably 35% by weight or less, more preferably 30% by weight or less. These structures related to the ratio of the hydroxyl group-containing monomer are suitable for achieving adhesion and proper cohesion in the base polymer formed by including the acrylic polymer.
The aforementioned acrylic polymer may contain monomer units derived from a nitrogen atom-containing monomer. The nitrogen atom-containing monomer is a monomer having at least one nitrogen atom in the monomer unit. When the acrylic polymer in the base polymer contains a monomer unit containing a nitrogen atom, hardness and good adhesion reliability can be easily obtained in the base polymer.
Examples of the nitrogen atom-containing monomer used for forming the monomer unit of the acrylic polymer include N-vinyl cyclic amides and (meth) acrylamides.
As the N-vinyl cyclic amide as the nitrogen atom-containing monomer, for example, an N-vinyl cyclic amide represented by the general formula (1) can be used.
Figure BDA0004096359830000231
Here, in the general formula (1), R 1 An organic group having a valence of 2, specifically- (CH) 2 ) n -. n is an integer of 2 to 7 (preferably 2, 3 or 4).
Examples of the N-vinyl cyclic amide include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1, 3-oxazin-2-one, and N-vinyl-3, 5-morpholindione.
Examples of the (meth) acrylamides as the nitrogen atom-containing monomer include (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N-octyl (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, and N, N-diisopropyl (meth) acrylamide. As the nitrogen atom-containing monomer used for the acrylic polymer, one type of nitrogen atom-containing monomer may be used, or two or more types of nitrogen atom-containing monomers may be used. In this embodiment, as the nitrogen atom-containing monomer used for the acrylic polymer, N-vinyl-2-pyrrolidone is preferably used.
From the viewpoint of achieving moderate hardness and adhesiveness in the base polymer formed by including the acrylic polymer, the ratio of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is preferably 1% by weight or more, more preferably 3% by weight or more, and still more preferably 5% by weight or more. In addition, from the viewpoint of suppressing the formation of excessive hardening in the base polymer formed by including the acrylic polymer and achieving good adhesion reliability, the ratio of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is preferably 30% by weight or less, more preferably 25% by weight or less. In addition, in some embodiments of the present invention, the aforementioned acrylic polymer may also be free of monomer units derived from nitrogen atom-containing monomers.
The aforementioned acrylic polymer may contain monomer units derived from carboxyl group-containing monomers. The carboxyl group-containing monomer is a monomer having at least one carboxyl group in a monomer unit. When the acrylic polymer in the base polymer contains a carboxyl group-containing monomer unit, good adhesion reliability may be obtained in the base polymer. In addition, the carboxyl group can also be a reaction point with a crosslinking agent described later.
Examples of the carboxyl group-containing monomer used for forming the monomer unit of the acrylic polymer, that is, the carboxyl group-containing monomer contained in the monomer component used for forming the acrylic polymer include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. As the carboxyl group-containing monomer used for the acrylic polymer, one type of carboxyl group-containing monomer may be used, or two or more types of carboxyl group-containing monomers may be used. In the present embodiment, acrylic acid is preferably used as the carboxyl group-containing monomer for the acrylic polymer.
The ratio of the monomer unit derived from the carboxyl group-containing monomer in the acrylic polymer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, from the viewpoint of ensuring good adhesion reliability by obtaining the contribution of the interaction of the polar group with the carboxyl group when the polar group is present on the surface of the adherend in the base polymer formed by containing the acrylic polymer. In addition, from the viewpoint of suppressing the formation of excessive hardening in the base polymer formed by including the acrylic polymer and achieving good adhesion reliability, the ratio of the monomer unit derived from the carboxyl group-containing monomer in the acrylic polymer is preferably 20% by weight or less, more preferably 15% by weight or less. In addition, the acrylic polymer may contain substantially no carboxyl group-containing monomer as its constituent monomer unit from the viewpoint of metal corrosion resistance and the like. Substantially free of carboxyl group-containing monomers means that the carboxyl group-containing monomers are not used intentionally, and it can be said that the carboxyl group-containing monomers are substantially not used when they are preferably 0.05% by weight or less (for example, 0 to 0.05% by weight), more preferably 0.01% by weight or less (for example, 0 to 0.01% by weight), and still more preferably 0.001% by weight or less (for example, 0 to 0.001% by weight).
The acrylic polymer may be a partial polymer of a mixture of monomer components constituting the acrylic polymer. The acrylic polymer may be a polymer obtained by adding the remaining monomer components to a part of a mixture of the monomer components constituting a part of the acrylic polymer. The "partial polymer of the mixture of monomer components" refers to a composition in which 1 or 2 or more monomer components constituting the monomer components are partially polymerized.
The aforementioned base polymer may contain a crosslinking agent. The base polymer has a crosslinked structure by the crosslinking agent, and thus the viscosity is increased, the shape stability is improved, and the adhesive layer a is easily formed. Examples of the crosslinking agent include polyfunctional (meth) acrylates and thermosetting crosslinking agents as a copolymerizable crosslinking agent (photocurable crosslinking agent) for the acrylic polymer. The base polymer may have a crosslinked structure derived from only a polyfunctional (meth) acrylate, may have a crosslinked structure derived from only a thermosetting crosslinking agent, and may have a crosslinked structure derived from both a polyfunctional (meth) acrylate and a thermosetting crosslinking agent.
The crosslinking agent is a crosslinking agent (crosslinking agent 1) constituting the 1 st initiator in the case where the adhesive layer a of the present invention is composed of the mixed adhesive composition. That is, the base polymer having a crosslinked structure derived from the 1 st crosslinking agent is in a semi-cured state with high fluidity, and exhibits excellent level difference absorbency.
Examples of the polyfunctional (meth) acrylate as the copolymerizable crosslinking agent (photocurable crosslinking agent) include 1, 6-hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, and vinyl (meth) acrylate. As the polyfunctional (meth) acrylate used for the acrylic polymer, one polyfunctional (meth) acrylate may be used, or two or more polyfunctional (meth) acrylates may be used. In the present embodiment, as the polyfunctional (meth) acrylate for the acrylic polymer, at least one selected from the group consisting of 1, 6-hexanediol diacrylate, dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, and polypropylene glycol diacrylate is preferably used.
The ratio of the monomer unit derived from the polyfunctional (meth) acrylate in the acrylic polymer is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, still more preferably 0.03% by weight or more, and still more preferably 0.05% by weight or more. The ratio of the monomer units derived from the polyfunctional (meth) acrylate in the acrylic polymer is preferably 1% by weight or less, more preferably 0.5% by weight or less. These structures related to the ratio of the polyfunctional (meth) acrylate are suitable for achieving moderate hardness, adhesiveness, shape stability, and excellent level difference absorbability in the base polymer formed by including the acrylic polymer.
Examples of the thermosetting crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. The base polymer may contain one kind of the thermosetting crosslinking agent, or may contain two or more kinds of the thermosetting crosslinking agents. At least one selected from the group consisting of isocyanate-based crosslinkers and epoxy-based crosslinkers is preferably used.
Examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Examples of the lower aliphatic polyisocyanates include 1, 2-ethylene diisocyanate, 1, 4-butylene diisocyanate and 1, 6-hexamethylene diisocyanate. Examples of the alicyclic polyisocyanate include cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated xylene diisocyanate. Examples of the aromatic polyisocyanates include 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 4' -diphenylmethane diisocyanate and xylylene diisocyanate. Examples of the isocyanate-based crosslinking agent include trimethylolpropane/toluene diisocyanate adduct (trade name "CORONATE L", manufactured by japan polyurethane industry Co., ltd.), trimethylolpropane/hexamethylene diisocyanate adduct (trade name "CORONATE HL", manufactured by japan polyurethane industry Co., ltd.), and trimethylolpropane/xylylene diisocyanate adduct (trade name "TAKENATE D-110N", manufactured by mitsunobu chemical Co., ltd.).
Examples of the epoxy-based crosslinking agent (polyfunctional epoxy compound) include N, N' -tetraglycidyl-m-xylylenediamine, diglycidyl aniline, 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. Further, as the epoxy-based crosslinking agent, epoxy-based resins having two or more epoxy groups can be mentioned. In addition, as the epoxy-based crosslinking agent, commercially available products such as "tetra d C" (manufactured by mitsubishi gas chemical Co., ltd.) are also included.
When the thermosetting crosslinking agent as described above is contained for crosslinking the base polymers, the content of the thermosetting crosslinking agent in the base polymer is preferably 0.001 parts by weight or more, more preferably 0.01 parts by weight or more based on 100 parts by weight of the total amount of the monomer components constituting the base polymer, from the viewpoints of improving the shape stability of the base polymer, facilitating the formation of the adhesive layer a, achieving sufficient adhesion reliability to an adherend, and excellent level difference absorbability. Further, from the viewpoint of exhibiting moderate flexibility, achieving good adhesion and excellent level difference absorbency in the base polymer, the content of the thermosetting crosslinking agent is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, relative to 100 parts by weight of the total amount of the monomer components constituting the base polymer.
When the base polymer contains the acrylic polymer as described above as a binder, the content of the acrylic polymer in the base polymer is, for example, 85 to 100% by weight.
The base polymer may contain a polymerization initiator in addition to a monomer and a crosslinking agent for forming an acrylic polymer. Examples of the polymerization initiator include photopolymerization initiators and thermal polymerization initiators. The base polymer may contain one kind of polymerization initiator or two or more kinds of polymerization initiators.
The polymerization initiator is a polymerization initiator (1 st polymerization initiator) constituting the 1 st initiator when the adhesive layer a of the present invention is formed from the mixed adhesive composition.
Examples of the photopolymerization initiator include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α -ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzil photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, and thioxanthone photopolymerization initiators. Examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2, 2-dimethoxy-1, 2-diphenylethane-1-one. Examples of the acetophenone photopolymerization initiator include 2, 2-diethoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone and 4- (t-butyl) dichloroacetophenone. Examples of the α -ketol photopolymerization initiator include 2-methyl-2-hydroxyphenylacetone and 1- [4- (2-hydroxyethyl) phenyl ] -2-methylpropan-1-one. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photo-polymerization initiator for photoactive oximes include 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl) -oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzil photopolymerization initiator include benzil. Examples of the benzophenone photopolymerization initiator include benzophenone, benzoyl benzoic acid, 3' -dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of the ketal photopolymerization initiator include benzildimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone and dodecylthioxanthone.
The amount of the photopolymerization initiator used is not particularly limited, and is preferably 0.001 to 1 part by weight, more preferably 0.01 to 0.50 part by weight, based on 100 parts by weight of all monomer units of the acrylic polymer (the total amount of monomer components constituting the acrylic polymer).
Examples of the thermal polymerization initiator include azo-based polymerization initiators, peroxide-based polymerization initiators, and redox-based polymerization initiators. As the azo-based polymerization initiator, examples thereof include 2,2 '-Azobisisobutyronitrile (AIBN), 2' -azobis-2-methylbutyronitrile (AMBN), dimethyl 2,2 '-azobis (2-methylpropionate), 4' -azobis-4-cyanovaleric acid, and 2,2 '-azobis (4-methoxy-2, 4-dimethylvaleronitrile), 2' -azobis (2, 4-dimethylvaleronitrile), 1 '-azobis (cyclohexane-1-carbonitrile), 2' -azobis (2, 4-trimethylpentane), and the like. Examples of the peroxide-based polymerization initiator include benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1-bis (t-butyl peroxide) -3, 5-trimethylcyclohexane, and 1, 1-bis (t-butyl peroxide) cyclododecane.
The amount of the thermal polymerization initiator used is not particularly limited, but is preferably 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight, based on 100 parts by weight of all monomer units of the acrylic polymer (the total amount of monomer components constituting the acrylic polymer).
The crosslinking agent contained in the mixed adhesive composition constituting the adhesive layer a includes a polyfunctional (meth) acrylate as the copolymerizable crosslinking agent (photocurable crosslinking agent). The crosslinking agent is a crosslinking agent (crosslinking agent 2) constituting the initiator 2 in the case where the adhesive layer a of the present invention is composed of the mixed adhesive composition. That is, the base polymer cured by the 2 nd crosslinking agent realizes excellent processability.
The content of the polyfunctional (meth) acrylate as the 2 nd crosslinking agent is not particularly limited, but is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, more preferably 2 parts by weight or more, and still more preferably 4 parts by weight or more, based on 100 parts by weight of the base polymer, from the viewpoint of imparting excellent processability to the cured base polymer. The content of the polyfunctional (meth) acrylate is preferably 60 parts by weight or less, more preferably 40 parts by weight or less, based on 100 parts by weight of the base polymer. These configurations related to the content of the polyfunctional (meth) acrylate as the 2 nd crosslinking agent are suitable for achieving excellent processability by curing the base polymer formed by containing the acrylic polymer.
The photopolymerization initiator contained in the mixed adhesive composition constituting the adhesive layer a may be the same as the photopolymerization initiator described above. The photopolymerization initiator is a polymerization initiator (polymerization initiator 2) constituting the initiator 2 in the case where the adhesive layer a of the present invention is composed of the mixed adhesive composition. That is, the base polymer cured by the photopolymerization initiator as the 2 nd polymerization initiator achieves excellent processability.
The content of the photopolymerization initiator as the 2 nd polymerization initiator is not particularly limited, but is preferably 0 to 2 parts by weight, more preferably 0.005 to 1.5 parts by weight, based on 100 parts by weight of the base polymer, from the viewpoint of imparting excellent processability to the cured base polymer. These configurations related to the content of the photopolymerization initiator as the 2 nd polymerization initiator are suitable for achieving excellent processability by curing the base polymer formed by including the acrylic polymer.
The mixed adhesive composition constituting the adhesive layer a may further contain additives such as ultraviolet absorbers, rust inhibitors, antistatic agents, crosslinking accelerators, silane coupling agents, tackifying resins, aging inhibitors, fillers, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, polyols, solvents, and the like, as necessary. Examples of the tackifying resin include rosin derivatives, polyterpene resins, petroleum resins, and oil-soluble phenols.
The mixed adhesive composition constituting the adhesive layer a may contain a silane coupling agent within a range that does not impair the effects of the present invention. When the adhesive layer a contains a silane coupling agent, the adhesion reliability to glass (especially, adhesion reliability to glass in a high-temperature and high-humidity environment) is preferably improved.
The silane coupling agent is not particularly limited, and examples thereof include gamma-glycidoxypropyl trimethoxysilane, gamma-glycidoxypropyl triethoxysilane, gamma-aminopropyl trimethoxysilane, and N-phenyl-aminopropyl trimethoxysilane. Among them, gamma-glycidoxypropyl trimethoxysilane is preferable. Further, as a commercial product, for example, a trade name "KBM-403" (manufactured by Xinyue chemical Co., ltd.) is cited. The silane coupling agent may be used alone or in combination of 2 or more.
The content of the silane coupling agent in the mixed adhesive composition constituting the adhesive layer a is not particularly limited, but is preferably 0.01 to 1 part by weight, more preferably 0.03 to 0.5 part by weight, based on 100 parts by weight of the base polymer.
The mixed adhesive composition constituting the adhesive layer a may contain a polyol within a range that does not impair the effects of the present invention. When the adhesive layer a contains a polyol, for example, a crosslinked structure based on the 1 st crosslinking agent (particularly the thermosetting crosslinking agent) is formed, and it is preferable that the level difference absorption is improved.
The polyol is not particularly limited, and examples thereof include polyester polyols, polycarbonate polyols, polyacrylic polyols, polyether polyols, epoxy polyols, polyolefin polyols, polyether ester polyols, and the like. Further, as a commercial product, for example, trade name "Adeka polyether EPD-300" (manufactured by ADEKA corporation) is cited. The polyhydric alcohol may be used alone or in combination of 2 or more.
The content of the polyol in the mixed adhesive composition constituting the adhesive layer a is not particularly limited, but is preferably 0.01 to 1 part by weight, more preferably 0.03 to 0.5 part by weight, based on 100 parts by weight of the base polymer.
In addition, a solvent may be contained in the mixed adhesive composition constituting the adhesive layer a. The solvent is not particularly limited, and examples thereof include: esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; organic solvents such as ketones including methyl ethyl ketone and methyl isobutyl ketone. The solvent may be used alone or in combination of 2 or more.
The method for forming the pressure-sensitive adhesive layer a is not particularly limited, and as embodiment 1, there is mentioned: coating (coating) the aforementioned mixed adhesive composition on a support and drying and curing the resulting adhesive layer; the mixed adhesive is applied (coated) onto a support, and the obtained adhesive layer is irradiated with active energy rays to be cured. If necessary, the heat drying may be further performed.
The drying and curing, irradiation with active energy rays, and heat drying are required to select conditions under which only the curing by the crosslinking agent and the polymerization initiator constituting the 1 st initiator is performed, and the curing reaction by the crosslinking agent and the photopolymerization initiator constituting the 2 nd initiator is not performed or suppressed.
The support is not particularly limited, and a plastic film is preferable. Examples of the raw material of the plastic film include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonates, triacetyl cellulose (TAC), polysulfones, polyarylates, polyimides, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, cyclic olefin polymers such as "Arton" (available from JSR corporation), and cyclic olefin polymers such as "ZEONOR" (available from cyclic olefin polymers, available from japanese patent No. Weng Zhushi). It should be noted that only one kind of these plastic materials may be used, or two or more kinds may be used.
The support may be a release sheet. The release sheet is not particularly limited, and examples thereof include plastic films surface-treated with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide.
The mixed adhesive composition may be applied (coated) by a known coating method, and examples thereof include a gravure roll coater, a reverse roll coater, a roll lick coater, a dip roll coater, a bar coater, a blade coater, a spray coater, a comma coater, a direct coater, and the like.
The drying and curing temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and still more preferably 60 to 170 ℃. The drying and curing time may be a suitable time, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.
Examples of the active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron rays, ultraviolet rays, and the like, and ultraviolet rays having transparency of the adhesive layer a are particularly preferable. That is, the adhesive layer a has high light-shielding properties against visible light and high transmittance against ultraviolet rays, and thus the base polymer can be cured by ultraviolet rays. The irradiation energy, irradiation time, irradiation method, and the like of the active energy ray are not particularly limited, and may be appropriately set so as to have a desired viscosity and viscoelasticity depending on the thickness of the adhesive layer a, and the like.
When the adhesive layer is to be photo-cured by the active energy rays and/or ultraviolet radiation described later on the main surface of the formed adhesive layer which does not face the support, it is preferable to further laminate the adhesive layer with another support (including a release sheet) in order to block oxygen which inhibits photo-curing.
In addition, as another preferred embodiment 2 of the method for forming the adhesive layer a, a method including the following steps is exemplified.
(1) An adhesive layer forming a single layer formed of the aforementioned base polymer.
(2) The adhesive layer is cured.
(3) A solution of the crosslinking agent and/or the photopolymerization initiator is prepared.
(4) The solution is applied to one surface of the cured adhesive layer, and the crosslinking agent and/or the photopolymerization initiator contained in the solution is allowed to penetrate from the one surface of the adhesive layer in the thickness direction.
(5) The adhesive layer is dried.
By forming the adhesive layer a according to embodiment 2, the curing reaction by the crosslinking agent and the polymerization initiator constituting the 1 st initiator and the curing reaction by the crosslinking agent and the photopolymerization initiator constituting the 2 nd initiator can be separated from each other, and therefore, it is no longer necessary to select curing reaction conditions under which only the curing by the crosslinking agent and the polymerization initiator constituting the 1 st initiator is performed, and the degree of freedom in combination of the crosslinking agent and the polymerization initiator constituting the 1 st initiator with the crosslinking agent and the polymerization initiator constituting the 2 nd initiator is significantly improved.
In addition, by separating the curing reaction of the crosslinking agent and the polymerization initiator constituting the 1 st initiator from the curing reaction of the crosslinking agent and the photopolymerization initiator constituting the 2 nd initiator, the level difference absorbability of the base polymer obtained by curing the 1 st initiator and the workability of the base polymer cured by the 2 nd initiator can be easily adjusted, and the ease of design and the degree of freedom of the photocurable adhesive sheet a having the adhesive layer a with both the more excellent level difference absorbability and workability can be remarkably improved.
Fig. 2 is a view (sectional view) schematically showing a process for carrying out embodiment 2 of the method for producing the photocurable adhesive sheet a.
In fig. 2 (a), first, an adhesive layer 10a made of a base polymer is formed on a support S1.
In the adhesive layer forming step, first, a base polymer, to which a crosslinking agent and a photopolymerization initiator constituting the 2 nd initiator are not added, is applied (coated) on the support S1. As the support, the same support as that of embodiment 1 can be used.
The base polymer may be coated (applied) by a known coating method, and examples thereof include a gravure roll coater, a reverse roll coater, a roll-lick coater, a dip roll coater, a bar coater, a blade coater, a spray coater, a comma coater, a direct coater, and the like.
When the adhesive layer is to be photo-cured by active energy rays and/or ultraviolet radiation or the like in the adhesive layer curing step described later, it is preferable to further laminate the main surface of the adhesive layer 10a which does not face the support S1 with another support S2 (including a release sheet) in order to block oxygen which inhibits photo-curing.
Next, the pressure-sensitive adhesive layer 10a is cured (pressure-sensitive adhesive layer curing step). In fig. 2 (b), 10b is an adhesive layer obtained by curing the adhesive layer 10 a. The method for curing the pressure-sensitive adhesive layer 10a is not particularly limited, and examples thereof include: heating the adhesive layer 10a; the adhesive layer 10a is cured by irradiation with active energy rays. If necessary, the heat drying may be further performed. The specific curing conditions are the same as those in embodiment 1.
In the adhesive layer curing step, since the adhesive layer is dried, cured by irradiation with active energy rays, and heated, and does not contain the crosslinking agent and photopolymerization initiator constituting the 2 nd initiator, any conditions can be used as long as the curing is performed by the crosslinking agent and polymerization initiator constituting the 1 st initiator, and the degree of freedom is extremely high as compared with embodiment 1.
The conditions for curing the adhesive layer 10a may be appropriately selected so that the adhesive layer 10b has desired physical properties according to the embodiment. For example, the heating temperature, time, or the irradiation amount of the active energy ray may be appropriately set so that the adhesive layer 10b exhibits high fluidity and excellent level difference absorbability.
Fig. 2 (b) shows an embodiment in which the adhesive layer 10a is cured by irradiating the adhesive layer 10a with ultraviolet rays U. The adhesive layer 10a constituting the adhesive layer a has high light-shielding properties against visible light and high transmittance against ultraviolet rays, and is therefore curable by ultraviolet rays U.
The ultraviolet ray U may directly irradiate the adhesive layer 10a, but is preferably irradiated through the support in order to block oxygen that inhibits curing by ultraviolet ray irradiation. Fig. 2 (b) shows an embodiment in which ultraviolet rays are irradiated to the adhesive layer 10a through the support S2. When ultraviolet light is irradiated through the support, another support S2 (including a release sheet) is bonded to the main surface of the pressure-sensitive adhesive layer 10a opposite to the main surface facing the support S1, and ultraviolet light is irradiated through the support. The illuminance and time of the ultraviolet irradiation are appropriately set according to the composition of the base polymer, the thickness of the adhesive layer, and the like. The ultraviolet irradiation may be performed by a high-pressure mercury lamp, a low-pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light lamp, an LED, or the like.
Next, as shown in fig. 2 (c), the support S2 is peeled off and removed, and then the solution 14 of the crosslinking agent 11 and/or the photopolymerization initiator 12 is applied to the one surface of the adhesive layer 10b (solution application step). Here, the crosslinking agent 11 and the photopolymerization initiator 12 are a crosslinking agent and a photopolymerization initiator constituting the 2 nd initiator.
The solution 14 may contain a solvent, or may contain no solvent when the crosslinking agent 11 functions as a solvent. Fig. 2 (c) shows an embodiment in which the solution 14 is a solution in which the crosslinking agent 11 and/or the photopolymerization initiator 12 are dissolved in the solvent 13.
The solvent 13 is not particularly limited as long as it can dissolve the crosslinking agent 11 and/or the photopolymerization initiator 12 and can swell the adhesive layer 10b, but is preferably a nonaqueous solvent because the aqueous solvent has poor wettability to the adhesive layer and the additive is difficult to permeate. The nonaqueous solvent is not particularly limited, and examples thereof include: esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, and the like; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alicyclic ketones such as cyclopentanone and cyclohexanone; aliphatic hydrocarbons such as hexane, heptane, octane, etc.; alicyclic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as chloroform, methylene chloride, and 1, 2-dichloroethane; ethers such as diethyl ether, dimethoxyethane, tetrahydrofuran, and dioxane; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; nitriles such as acetonitrile, propionitrile, and benzonitrile; alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol are preferably esters, aromatic hydrocarbons, ketones, and alcohols. The solvent may be used alone or in combination of 1 or more than 2.
The concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the solution 14 may be appropriately set, and may be selected from the range of, for example, 0.1 to 100 wt%, preferably 0.1 to 80 wt%, more preferably 1 to 70 wt%, more preferably 1.5 to 60 wt%, more preferably 3 to 50 wt%, and still more preferably 5 to 40 wt%. When the concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the solution 14 falls within this range, the crosslinking agent 11 and/or the photopolymerization initiator 12 can be dissolved and the adhesive layer 10b can be sufficiently swelled.
The concentration of the crosslinking agent 11 in the solution 14 may be appropriately set, and may be selected from a range of, for example, 0.1 to 100 wt%, for example, 95 wt% or less (for example, 1 to 95 wt%, 1 to 90 wt%, 1 to 85 wt%, 1 to 80 wt%, 1 to 60 wt%, etc.), for example, 1 wt% or more (for example, 1 to 95 wt%, 2 to 95 wt%). When the concentration of the crosslinking agent is higher than the above range, the crosslinking agent 11 may bleed out or a distribution deviation may occur from the viewpoint of coating uniformity. When the concentration is less than the above range, the solvent needs to be more than necessary, and there are cases where the adhesive properties are lowered by the residual solvent, the adhesive swells more than necessary, and the appearance is impaired (referred to as surface irregularities).
The application (coating) of the solution 14 to the adhesive layer 10b may be performed by a known coating method, and examples thereof include a gravure roll coater, a reverse roll coater, a roll lick coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, a direct coater, and the like.
The amount of the solution 14 applied to the pressure-sensitive adhesive layer 10b may be appropriately set, and may be, for example, from 1 to 1000. Mu.g/cm 2 Preferably 1 to 500. Mu.g/cm 2 More preferably 1 to 300. Mu.g/cm 2 Further preferably 1 to 100. Mu.g/cm 2 Is selected from the range of (2). When the coating amount of the solution 14 is within this range, the crosslinking agent 11 and/or the photopolymerization initiator 12 can be dissolved andthe crosslinking agent 11 and/or the photopolymerization initiator 12 are sufficiently provided to the adhesive layer 10 b.
After the solution 14 is applied to the adhesive layer 10b, the crosslinking agent 11 and/or the photopolymerization initiator 12 may be allowed to permeate by standing as needed. The standing time is not particularly limited, and may be appropriately selected from, for example, 15 minutes or less, and may be selected from, for example, a range of 1 second to 10 minutes, preferably 5 seconds to 5 minutes. The standing temperature may be about room temperature (10 to 30 ℃). When left standing under the above conditions, the crosslinking agent 11 and/or the photopolymerization initiator 12 can be sufficiently permeated in the adhesive layer 10 b.
The surface of the adhesive layer 10b is swollen by penetrating the solution 14, and in this process, the crosslinking agent 11 and/or the photopolymerization initiator 12 in the solution 14 penetrate in the thickness direction within the adhesive layer 10b (solution penetration process). This state is shown in fig. 2 (d). The crosslinking agent 11 and/or the photopolymerization initiator 12 penetrate in the adhesive layer 10b in a dissolved state. Therefore, the crosslinking agent 11 and/or the photopolymerization initiator 12 becomes in a "dissolved" state in the adhesive layer 10 b.
In addition, the crosslinking agent 11 and/or the photopolymerization initiator 12 can form a concentration gradient in the thickness direction during permeation in the adhesive layer 10 b. Therefore, the concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 on the side coated with the solution 14 may be higher than that on the opposite side. This state is shown in fig. 2 (d).
Then, the adhesive layer 10b is dried, whereby the adhesive layer 10 shown in fig. 2 (e) can be obtained (drying step). When the solution 14 contains the solvent 13, the solvent 13 is evaporated by the drying step. Through the drying process, the adhesive layer 10b returns to a state similar to that before swelling. At the time point when the adhesive layer 10b is dried, permeation of the crosslinking agent 11 and/or the photopolymerization initiator 12 into the adhesive layer 10b is stopped, and the concentration gradient of the crosslinking agent 11 and/or the photopolymerization initiator 12 is fixed.
The heating and drying temperature in the drying step is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and still more preferably 60 to 170 ℃. The drying time may be a suitable time, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes. By drying under the above conditions, the adhesive layer 10 can return to a state similar to that before coating.
Further, a standing time for further homogenizing the crosslinking agent and the adhesive layer may be set as needed. The standing time is not particularly limited, and may be appropriately selected from, for example, 30 days or less, for example, 1 hour to 15 days, and preferably 24 hours to 10 days. By standing, the crosslinking agent of the adhesive layer 10 and the adhesive layer are stabilized, and variation in characteristic evaluation can be suppressed.
The photocurable adhesive sheet 1B shown in fig. 2 (e) is one of embodiments of a photocurable adhesive sheet a including an adhesive layer 10, and the adhesive layer 10 is composed of a mixed adhesive composition including a base polymer, a crosslinking agent 11, and a photopolymerization initiator 12.
In embodiment 2, the base polymer contains a 1 st crosslinking agent and a 1 st polymerization initiator as a 1 st initiator, and the adhesive layer curing step is curing based on the reaction of the 1 st crosslinking agent and the 1 st polymerization initiator, and the crosslinking agent 11 and the photopolymerization initiator 12 become the 2 nd initiator.
After the adhesive layer curing step, both or either of the 1 st crosslinking agent and the 1 st polymerization initiator may remain. In this case, only either the 2 nd crosslinking agent or the 2 nd polymerization initiator may be used as the crosslinking agent 11 and the photopolymerization initiator 12, and it is preferable to use only the 2 nd crosslinking agent (crosslinking agent 11). However, both the 2 nd crosslinking agent and the 2 nd polymerization initiator may be used.
In embodiment 2, the degree of freedom in combination of the 1 st initiator and the 2 nd initiator is very wide. That is, the combination of the polymerization initiators is not limited, and for example, a combination in which both the 1 st initiator and the 2 nd initiator are photopolymerization initiators, a combination in which the 1 st initiator is a thermal polymerization initiator and the 2 nd initiator is a photopolymerization initiator, and the like can be freely selected. In addition, in the case where both the 1 st initiator and the 2 nd initiator are combinations of photopolymerization initiators, the light absorption wavelength bands of both photopolymerization initiators may be repeated or approximated. Furthermore, a combination of the same polymerization initiator as the 1 st initiator and the 2 nd initiator, which is not possible in the conventional mixed pressure-sensitive adhesive sheet, is also possible.
The combination of the crosslinking agents is not limited, and the 1 st initiator and the 2 nd initiator may be the same crosslinking agent.
Fig. 3 (a) is a cross-sectional view showing one embodiment of the photocurable adhesive sheet a of the present invention, and fig. 3 (b) is a cross-sectional view showing another embodiment of the photocurable adhesive sheet a of the present invention.
Referring to fig. 3 (a), the photocurable adhesive sheet 1C according to one embodiment of the present invention is composed of an adhesive layer 10 and a support S1, wherein one surface of the adhesive layer 10, namely, the 1 st main surface 10A, is not bonded to the support, and the support S1 is composed of a release sheet bonded to the other surface of the adhesive layer 10, namely, the 2 nd main surface 10B.
Referring to fig. 3 (B), the photocurable adhesive sheet 1D according to one embodiment of the present invention comprises an adhesive layer 10, a 1 st support S2 formed of a release sheet bonded to one surface of the adhesive layer 10, namely, the 1 st main surface 10A, and a 2 nd support S1 formed of a release sheet bonded to the other surface of the adhesive layer 10, namely, the 2 nd main surface 10B. The photocurable adhesive sheet 1D can be obtained by bonding the support S2 to the 1 st principal surface 10A of the photocurable adhesive sheet 1C.
In fig. 3 (a) and (b), a broken line X-X' is a line equally dividing the adhesive layer 10 into two parts in the thickness direction. When the thickness of the adhesive layer 10 is not uniform, the broken line X-X' is a line dividing the thickness 2 at each point equally.
In fig. 3, the adhesive layer 10 is a single layer formed of a base polymer and having 2 opposed main faces (a 1 st main face and a 2 nd main face). The adhesive layer 10 can be formed by the method of embodiment 2 described above, and corresponds to the adhesive layer 10 of fig. 2.
The adhesive layer being a "single layer" means not a laminated structure. For example, a structure in which an adhesive layer formed of a base polymer is formed and an adhesive layer formed of the same base polymer is further formed thereon is a laminated structure, not a single layer. Similarly, a structure in which an adhesive layer made of a base polymer containing a crosslinking agent and/or a photopolymerization initiator is formed, and further an adhesive layer made of a base polymer in which a crosslinking agent and/or a photopolymerization initiator are dissolved at different concentrations is formed thereon, is a laminated structure, and is not a single layer.
The thickness of the pressure-sensitive adhesive layer 10 is not particularly limited, but is usually 5 μm to 500. Mu.m, preferably 5 μm to 400. Mu.m, and more preferably 5 μm to 350. Mu.m. When the thickness of the adhesive layer 10 is within this range, it is preferable to form a concentration gradient of the crosslinking agent and/or the photopolymerization initiator in the thickness direction of the adhesive layer 10.
Regarding the crosslinking agent 11 and/or the photopolymerization initiator 12, the crosslinking agent 11 and/or the photopolymerization initiator 12 is permeated in the adhesive layer 10 through the aforementioned solution coating process, solution permeation process, and drying process, so that a concentration gradient of the crosslinking agent 11 and/or the photopolymerization initiator 12 may be generated in the thickness direction of the adhesive layer 10 as shown in fig. 3. Therefore, when dividing the single adhesive layer 10 into two parts in the thickness direction, the concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the region to which the 1 st principal surface 10A belongs is different from the concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the region to which the other 2 nd principal surface 10B belongs in one of the 2 principal surfaces. The case where the crosslinking agent 11 and/or the photopolymerization initiator 12 are not present in the region of lower concentration (concentration of 0) is also included in the scope of the present invention.
When the concentration of the region to which the 1 st main surface belongs and the concentration of the region to which the 2 nd main surface belongs also have a concentration gradient in the respective regions, the average concentration of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the respective regions is referred to.
Fig. 3 (a) shows the following embodiment: the concentration of the crosslinking agent 11 and/or photopolymerization initiator 12 in the region where the 1 st principal surface 10A belongs to is higher than the concentration of the crosslinking agent 11 and/or photopolymerization initiator 12 in the region where the 2 nd principal surface 10B belongs to on the support S1, and can be obtained by: the solution of the crosslinking agent 11 and/or the photopolymerization initiator 12 is applied to the 1 st main surface 10A, and the crosslinking agent 11 and/or the photopolymerization initiator 12 penetrates into the adhesive layer 10 in a dissolved state over the entire depth in the thickness direction from the 1 st main surface 10A.
The adhesive layer 10 generates a concentration gradient of the crosslinking agent 11 and/or the photopolymerization initiator 12 in the thickness direction, and as a result, when the adhesive layer 10 is cured, a difference in crosslinking density can be generated between the front surface and the back surface. That is, in fig. 3, the region to which the main surface 10A belongs may generate a higher crosslink density than the region to which the main surface 10B belongs. This configuration is preferable in view of improving the flexibility, for example, in the case where the photocurable pressure-sensitive adhesive sheet a is used as a flexible image display device in which one side of the main surface 10A is bent outward. That is, when the flexible display is bent, a tensile stress is applied to the outside and a compressive stress is applied to the inside, and the stress on the outside is stronger than the stress on the inside. Therefore, by disposing the main surface 10A of the adhesive layer 10 on the outer side when bending the flexible display, the durability against bending can be improved.
As another embodiment 3 of the mixed adhesive composition constituting the adhesive layer a, an adhesive composition containing a polymer having a benzophenone structure in a side chain (hereinafter, sometimes referred to as "BP polymer") is exemplified (hereinafter, sometimes referred to as "BP type mixed adhesive composition"). The "benzophenone structure" acts as the 2 nd initiator in the hybrid adhesive.
As a preferable example of the BP polymer, an acrylic polymer having a benzophenone structure in a side chain can be cited. The BP polymer is preferably a polymer substantially free of ethylenically unsaturated groups.
In the present specification, "benzophenone structure" means a general formula: ar (Ar) 1 -(C＝O)-Ar 2 -; or-Ar 3 -(C＝O)-Ar 2 -the diaryl ketone structure shown. Here, ar in the above formula 1 Selected from phenyl optionally having substituents. Ar in the above formula 2 、Ar 3 Each independently selected from optionally substituted phenylene groups. Ar (Ar) 2 And Ar is a group 3 May be the same or different. The benzophenone structure can be excited by irradiation of ultraviolet rays, and in this excited state, hydrogen radicals can be extracted from other molecules or other parts of the molecules.
The adhesive layer formed from the BP type hybrid adhesive composition contains a polymer having a benzophenone structure in a side chain (BP polymer), and thus can form a crosslinked structure by exciting the benzophenone structure by utilizing the abstraction reaction of the hydrogen radical. The polymer having a benzophenone structure in a side chain is preferably represented by the general formula: ar (Ar) 1 -(C＝O)-Ar 2 Ar in 1 Is phenyl optionally substituted, and Ar 2 A polymer having a benzophenone structure in a side chain which is a phenylene group optionally having a substituent. Ar as described above 1 And Ar is a group 2 When at least one of (a) has 1 or more substituents, the substituents may each be independently selected from the group consisting of an alkoxy group (e.g., an alkoxy group having 1 to 3 carbon atoms, preferably a methoxy group), a halogen atom (e.g., F, cl, br, etc., preferably Cl or Br), a hydroxyl group, an amino group, and a carboxyl group.
The BP polymer may have a side chain directly bonded to the main chain as described above, or may have a side chain bonded to the main chain via one or two or more of an ester bond, an oxyalkylene structure, and the like. Suitable examples of the BP polymer include polymers containing a repeating unit derived from a compound having an ethylenically unsaturated group and a benzophenone structure in the molecule (hereinafter sometimes referred to as "ethylenically unsaturated BP"). The repeating unit may be a polymerized residue obtained by reacting an ethylenically unsaturated group of the corresponding ethylenically unsaturated BP.
Examples of the ethylenically unsaturated BP include: optionally substituted acryloxybenzophenone such as 4-acryloxybenzophenone, 4-acryloxy4 ' -methoxybenzophenone, 4-acryloxyethoxy-4 ' -methoxybenzophenone, 4-acryloxy4 ' -bromobenzophenone, and 2-hydroxy-4-acryloxybenzophenone; acryloxyalkoxybenzophenone optionally having a substituent such as 4- [ (2-acryloyloxy) ethoxy ] benzophenone and 4- [ (2-acryloyloxy) ethoxy ] -4' -bromobenzophenone; methacryloxybenzophenone optionally having a substituent such as 4-methacryloxybenzophenone, 4-methacryloxy4 ' -methoxybenzophenone, 4-methacryloxy4 ' -bromobenzophenone, 4-methacryloxyethoxy-4 ' -bromobenzophenone, and 2-hydroxy-4-methacryloxybenzophenone; methacryloxyalkoxybenzophenone optionally having a substituent such as 4- [ (2-methacryloxyoxy) ethoxy ] benzophenone and 4- [ (2-methacryloxyoxy) ethoxy ] -4' -methoxybenzophenone; vinyl benzophenones optionally having substituents such as 4-vinyl benzophenone, 4 '-bromo-3-vinyl benzophenone and 2-hydroxy-4-methoxy-4' -vinyl benzophenone, etc., but are not limited thereto. The ethylenically unsaturated BP may be used singly or in combination for the preparation of the BP polymer. As the ethylenically unsaturated BP, commercially available ones can be used, and further, it can be synthesized by a known method. From the viewpoint of reactivity and the like, an ethylenically unsaturated BP having a (meth) acryloyl group, that is, an ethylenically unsaturated BP belonging to an acrylic monomer can be preferably used.
The BP polymer may be a copolymer having a repeating unit derived from an ethylenically unsaturated BP and a repeating unit derived from an ethylenically unsaturated compound (hereinafter also referred to as "other ethylenically unsaturated compound") which is not an ethylenically unsaturated BP. Such BP polymer may be a copolymer comprising the monomer components of the above-mentioned ethylenically unsaturated BP and the above-mentioned other ethylenically unsaturated compounds. The BP polymer may be a copolymer obtained by copolymerizing a partial polymer (prepolymer) of a monomer mixture composed only of the other ethylenically unsaturated compound with the ethylenically unsaturated BP. As the other ethylenically unsaturated compound, one or two or more types of acrylic monomers can be preferably used. As a preferable example of the BP polymer, an acrylic BP polymer in which more than 50 wt% (preferably more than 70 wt%, for example more than 90 wt%) of the monomer components constituting the BP polymer is an acrylic monomer is exemplified.
As the acrylic monomer of the other ethylenically unsaturated compound, the same monomer as the alkyl acrylate having a linear or branched alkyl group constituting the monomer unit of the acrylic polymer can be used. The monomer component constituting the BP polymer may contain, as the other ethylenically unsaturated compound, one or more selected from the group consisting of alicyclic monomers, hydroxyl group-containing monomers, nitrogen atom-containing monomers and carboxyl group-containing monomers constituting the monomer unit of the acrylic polymer.
The BP type hybrid adhesive composition may be a photocurable acrylic adhesive composition in which more than 50 wt% (preferably more than 70 wt%, for example, more than 90 wt%) of the total monomer components constituting the composition is an acrylic monomer. The photocurable acrylic adhesive composition is photocured to form an acrylic photocurable product.
The weight average molecular weight (Mw) of the BP polymer is not particularly limited, and may be, for example, 0.5X10 4 ～500×10 4 Left and right. The Mw of the BP polymer is usually 1X 10 from the viewpoints of the cohesiveness of the adhesive layer A, the handleability of the photocurable adhesive sheet A, etc 4 The above is suitable, preferably 5X 10 4 The above can be 10×10 4 The above may be 15×10 4 The above may be 20×10 4 The above. In addition, from the viewpoint of the level difference absorbency of the adhesive layer a, the Mw of the BP polymer is usually 200×10 4 The following are suitable, preferably 150X 10 4 Hereinafter, it may be 100X 10 4 The following may be 70×10 4 Hereinafter, 50×10 may be used 4 The following is given.
The weight average molecular weight (Mw) of the polymer refers to a value in terms of standard polystyrene obtained by Gel Permeation Chromatography (GPC). As a GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgelGMH-H (S), manufactured by Tosoh Co., ltd.) may be used.
The glass transition temperature (Tg) of the BP polymer is not particularly limited. The BP polymer may have a Tg of, for example, from-80℃to 150℃or lower, from-80℃to 50℃or lower, or from-80℃to 10℃or lower. From the viewpoint of the high level difference absorbency of the adhesive layer a, the Tg of the BP polymer is preferably lower than 0 ℃, preferably-10 ℃ or lower, and may be-20 ℃ or lower, or may be-30 ℃ or lower, or may be-40 ℃ or lower, or may be-50 ℃ or lower. Further, from the viewpoint of improving the cohesiveness of the adhesive layer a and the processability after photocuring, the Tg of the BP polymer is usually at least-75 ℃, or at least-70 ℃. In some embodiments, the BP polymer may have a Tg of-55deg.C or greater, or-45deg.C or greater. The Tg of the BP polymer can be adjusted by the kind and amount of the monomer components constituting the BP polymer.
The glass transition temperature (Tg) of a polymer is a glass transition temperature obtained by Fox expression based on the composition of monomer components constituting the polymer. The Fox formula is a relational expression between Tg of the copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg＝Σ(Wi/Tgi)
In the above Fox formula, tg represents the glass transition temperature (unit: K) of the copolymer, wi represents the weight fraction (copolymerization ratio based on weight) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of the homopolymer of the monomer i.
The glass transition temperature of the homopolymer used for calculation of Tg was a value described in known data. 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 DEG C
N-butyl acrylate: -55 DEG C
Isostearyl acrylate: -18 DEG C
Methyl methacrylate: 105 DEG C
Methyl acrylate: 8 DEG C
Cyclohexyl acrylate: 15 DEG C
N-vinyl-2-pyrrolidone: 54 DEG C
2-hydroxyethyl acrylate: -15 DEG C
4-hydroxybutyl acrylate: -40 DEG C
Isobornyl acrylate: 94 DEG C
Acrylic acid: 106 DEG C
Methacrylic acid: 228 DEG C
For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3 rd edition, john Wiley & Sons, inc., 1989) are used. In the case where a plurality of values are described in this document, the highest value is used. For the monomer having a glass transition temperature of the homopolymer, which is not described in the Polymer Handbook, a value obtained by a measurement method described in Japanese patent application laid-open No. 2007-51271 is used. The nominal value of the glass transition temperature may be used for a polymer provided by the manufacturer or the like.
The BP polymer is preferably: for example, the benzophenone structure in terms of 4-benzoylphenyl acrylate is contained in an amount of about 0.5mg or more per 1g of the polymer. Hereinafter, the value obtained by converting the number of benzophenone structures contained in each 1g of BP polymer into the converted amount of 4-benzoylphenyl acrylate is sometimes referred to as BP equivalent of BP polymer (unit: mg/g). For example, the BP equivalent of the polymer was calculated to be 10mg/g when 40. Mu. Mol of the benzophenone structure was contained in each 1 g.
From the viewpoint of obtaining a higher photocuring effect (for example, an effect of improving workability by photocuring), in some embodiments, it is preferable that the BP equivalent weight of the BP polymer is generally 0.11mg/g or more, and may be 0.5mg/g or more, and may be 1mg/g or more, and may be 5mg/g or more, and may be 8mg/g or more, and may be 10mg/g or more, and may be 15mg/g or more, and may be 20mg/g or more. In some embodiments, the BP equivalent of the BP polymer is usually 100mg/g or less, preferably 80mg/g or less, preferably 60mg/g or less, preferably 40mg/g or less, preferably 25mg/g or less, preferably 15mg/g or less, from the viewpoint of improving the impact resistance and peel strength of the joint portion formed by the photocurable substance. The BP equivalent of the BP polymer can be adjusted by the composition of the monomer components constituting the BP polymer.
Further, from the viewpoint of reducing the peeling force by photocuring, and performing reworking and maintenance, the BP equivalent is preferably 50mg/g or more, or may be 100mg/g or more.
The weight ratio of the BP polymer in the entire BP type hybrid adhesive composition, that is, the weight fraction of the BP polymer in the BP type hybrid adhesive composition is not particularly limited, and may be set so that the level difference absorbability of the adhesive layer a is appropriately balanced with the processability of the photocurable product thereof. In some embodiments, the weight fraction of the BP polymer may be, for example, 1 wt% or more, and is usually 5 wt% or more, and may be 10 wt% or more, 15 wt% or more, 25 wt% or more, 35 wt% or more, 45 wt% or more, or 55 wt% or more, as appropriate. When the weight fraction of the BP polymer is increased, the aforementioned G 'a10/G' b85 tends to be increased.
The BP polymer may be used in a proportion of substantially 100% by weight (for example, 99.5% by weight or more) in the BP-type mixed adhesive composition. In addition, in some embodiments, the weight fraction of BP polymer in the BP type hybrid adhesive composition may be, for example, less than 99 wt%, less than 95 wt%, less than 85 wt%, less than 70 wt%, less than 50 wt%, or less than 40 wt% from the viewpoint of the ease of adhesive performance.
It is preferable that the benzophenone structure is contained in an amount of, for example, about 0.1mg or more per 1g of the BP-type mixed adhesive composition in terms of 4-benzoylphenyl acrylate. Hereinafter, the weight of 4-benzoylphenyl acrylate having a benzophenone structure per 1g of the BP-type mixed adhesive composition may be referred to as BP equivalent (unit: mg/g) of the BP-type mixed adhesive composition. From the viewpoint of obtaining a higher photocuring effect (for example, an effect of improving workability by photocuring), in some embodiments, the BP equivalent weight of the BP type hybrid adhesive composition is generally 0.3mg/g or more, and may be 0.5mg/g or more, may be 1mg/g or more, may be 5mg/g or more, may be 10mg/g or more, or may be 20mg/g or more. In some embodiments, the BP equivalent of the BP-type hybrid adhesive composition is usually 100mg/g or less, preferably 80mg/g or less, preferably 60mg/g or less, preferably 40mg/g or less, preferably 25mg/g or less, preferably 15mg/g or less, from the viewpoints of impact resistance of the joint portion based on the photocurable substance and suppression of strain in the photocurable substance.
The aforementioned BP-type hybrid adhesive composition may be an adhesive composition comprising an ethylenically unsaturated compound and a BP polymer. The BP type mixed adhesive composition may be an acrylic 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 the adhesive composition is an acrylic monomer.
As the ethylenically unsaturated compound, the same compound as the alkyl acrylate having a linear or branched alkyl group, the alicyclic monomer, the hydroxyl group-containing monomer, the nitrogen atom-containing monomer, the carboxyl group-containing monomer, and the polyfunctional (meth) acrylate constituting the monomer unit of the acrylic polymer can be used.
The ethylenically unsaturated compound may contain alkyl acrylate at a ratio of 40% by weight or more. The ratio of the alkyl acrylate to the monomer component may be, for example, 50% by weight or more, 60% by weight or more, or 65% by weight or more. In addition, from the viewpoint of improving the cohesive property of the adhesive layer a, the ratio of the alkyl acrylate to the ethylenically unsaturated compound is usually 99.5% by weight or less, and may be 95% by weight or less, 85% by weight or less, 70% by weight or less, or 60% by weight or less.
The amount of alicyclic monomer used is not particularly limited, and may be, for example, 1 wt% or more, 3 wt% or more, or 5 wt% or more of the total monomer components. In one embodiment, the alicyclic monomer may be used in an amount of 10% by weight or more, or 15% by weight or more of the total monomer components. The upper limit of the amount of the alicyclic monomer to be used is preferably 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, an alicyclic monomer may not be used as the above-mentioned ethylenically unsaturated compound.
The amount of the nitrogen atom-containing monomer to be used is not particularly limited, and may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, and further 5% by weight or more or 7% by weight or more of the total monomer components. In one embodiment, the amount of the nitrogen atom-containing monomer used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer components. The amount of the nitrogen atom-containing monomer used is, for example, preferably 40% by weight or less, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less, based on the total monomer components. In another embodiment, the amount of the nitrogen atom-containing monomer used may be 20% by weight or less, for example, or 15% by weight or less of the total monomer components. Alternatively, a nitrogen atom-containing monomer may not be used as the ethylenically unsaturated compound.
The amount of the hydroxyl group-containing monomer used is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, or 5% by weight or more, or 10% by weight or more of the total monomer components. In some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer components, and may be 30% by weight or less, 25% by weight or less, or 20% by weight or less, from the viewpoint of suppressing water absorption of the BP type hybrid adhesive composition or the adhesive layer a. In another embodiment, the amount of the hydroxyl group-containing monomer used may be, for example, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer components. Alternatively, hydroxyl group-containing monomers may not be used as the above-mentioned ethylenically unsaturated compounds.
The amount of the carboxyl group-containing monomer used is not particularly limited, and the ratio of the carboxyl group-containing monomer to the total monomer components may be, for example, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less (for example, less than 0.1% by weight). The BP-type hybrid adhesive composition may also be substantially free of carboxyl group-containing monomers as its constituent monomer components. By substantially free of carboxyl group containing monomers is meant herein that at least no carboxyl group containing monomer is used intentionally. This may be advantageous from the viewpoint of metal corrosion resistance of the adhesive layer a formed of the BP type mixed adhesive composition and its photo-cured product, and the like.
The amount of the polyfunctional (meth) acrylate used is not particularly limited, and may be less than 5.0% by weight of the total monomer components constituting the BP-type hybrid adhesive composition. This can prevent the formation of an excessive crosslinked structure during the formation of the adhesive layer a (i.e., at a stage before photo-curing), and can improve the level difference absorbability of the adhesive layer a. The amount of the polyfunctional (meth) acrylate used may be, for example, 4.0 wt% or less, 3.0 wt% or less, 2.0 wt% or less, 1.0 wt% or less, 0.5 wt% or less, or 0.3 wt% or less of the total monomer components. Polyfunctional (meth) acrylates may not be used. In some embodiments, the amount of the polyfunctional (meth) acrylate used may be, for example, 0.001 wt% or more, 0.005 wt% or more, 0.01 wt% or more, or 0.03 wt% or more, based on the total monomer components, from the viewpoint of imparting appropriate cohesiveness to the adhesive layer a. Alternatively, polyfunctional (meth) acrylates may not be used as the above-mentioned ethylenically unsaturated compounds.
The weight ratio of the BP polymer to the total amount of the BP polymer and the ethylenically unsaturated compound contained in the BP-type hybrid adhesive composition is not particularly limited, and may be set so that the level difference absorbability of the adhesive layer a formed from the adhesive composition and the processability of the photocurable product thereof are appropriately balanced. In some embodiments, the weight fraction of the BP polymer may be, for example, 0.5 wt% or more, usually 1 wt% or more, preferably 1.5 wt% or more, more preferably 5 wt% or more, and from the viewpoint of improving the effect of photocuring, may be 10 wt% or more, 15 wt% or more, 25 wt% or more, 35 wt% or more, 45 wt% or more, or 55 wt% or more. In addition, in some embodiments, the weight ratio of the BP polymer in the above total amount may be, for example, less than 99 wt%, less than 95 wt%, less than 85 wt%, less than 70 wt%, less than 50 wt%, or less than 40 wt%, from the viewpoint of ease of preparation of the adhesive composition, coatability, and the like.
The ratio of the weight of the organic solvent to the weight of the entire BP type hybrid adhesive composition may be, for example, 30 wt% or less, advantageously 20 wt% or less, preferably 10 wt% or less, more preferably 5 wt% or less. In some embodiments, the weight ratio of the organic solvent may be 3 wt% or less, may be 1 wt% or less, may be 0.5 wt% or less, may be 0.1 wt% or less, may be 0.05 wt% or less, or may be substantially free of the organic solvent.
From the viewpoint of the coatability in the normal temperature region, the viscosity of the BP-type mixed adhesive composition (BH-type viscometer, no.5 spindle, measurement at 10rpm at a measurement temperature of 30 ℃ C. The same applies hereinafter) is preferably 1000 Pa.s or less, more preferably 100 Pa.s or less, and still more preferably 50 Pa.s or less. The viscosity of the BP-type hybrid adhesive composition may be, for example, 30 pas or less, 20 pas or less, 10 pas or less, or 5 pas or less. The lower limit of the viscosity of the BP type mixed adhesive composition is not particularly limited, but is usually 0.1pa·s or more, or may be 0.5pa·s or more, or may be 1pa·s or more, from the viewpoint of suppressing shrinkage cavity of the adhesive composition in the coating range and overflow of the adhesive composition at the outer edge of the coating range.
The aforementioned BP type hybrid adhesive composition may contain at least a compound having 1 ethylenically unsaturated group (i.e., a monofunctional monomer) as the aforementioned ethylenically unsaturated compound. The monofunctional monomer may be used by selecting a corresponding compound from the examples of the above-mentioned ethylenically unsaturated compounds. The monofunctional monomer may be used singly or in combination of two or more.
The weight ratio of the monofunctional monomer in the total amount of the BP polymer and the ethylenically unsaturated compound may be, for example, 1% by weight or more, 5% by weight or more, or 15% by weight or more. In some embodiments, the weight ratio of the monofunctional monomer may be 25 wt% or more, may be 35 wt% or more, or may be 45 wt% or more from the viewpoint of ease of preparation, coatability, and the like of the BP type hybrid adhesive composition. The weight ratio of the monofunctional monomer in the total amount may be, for example, 99% by weight or less, and is usually 95% by weight or less, preferably 85% by weight or less, 75% by weight or less, 65% by weight or less, 55% by weight or less, or 45% by weight or less.
In the case where the BP-type hybrid adhesive composition contains a monofunctional monomer, the glass transition temperature (Tg) obtained by Fox formula based on the composition of the monofunctional monomer is not particularly limited, and may be, for example, from-80℃to 250 ℃. From the viewpoint of compatibility of the polymer derived from the monofunctional monomer with other components, the Tg based on the composition of the monofunctional monomer is generally preferably 150 ℃ or less, may be 100 ℃ or less, may be 70 ℃ or less, may be 50 ℃ or less, or may be 30 ℃ or less. In some embodiments, from the viewpoint of the level difference absorbency of the adhesive layer a, the Tg based on the composition of the monofunctional monomer is preferably lower than 0 ℃, more preferably-10 ℃ or lower, may be-20 ℃ or lower, may be-30 ℃ or lower, or may be-40 ℃ or lower. In addition, from the viewpoints of cohesiveness of the adhesive layer a and workability after photocuring, tg based on the composition of the monofunctional monomer is usually favorably-60 ℃ or higher, and may be-54 ℃ or higher, may be-50 ℃ or higher, may be-45 ℃ or higher, may be-35 ℃ or higher, or may be-25 ℃ or higher. The Tg may be adjusted by the compounds used as monofunctional monomers and the ratio of the amounts used.
In a BP-type hybrid adhesive composition comprising a BP polymer and a monofunctional monomer, an adhesive layer A formed from the adhesive composition, and a photo-cured product thereof, tg of the BP polymer (hereinafter referred to as "Tg" A ". ) Tg of monomer composition with monofunctional monomer (hereinafter referred to as "Tg B1 ". ) Can pass Tg B1 [℃]-Tg A [℃]Calculated Tg difference [. Degree.C [. Degree.](hereinafter also referred to asIs ΔTg. ) For example, the temperature is set in a range of-50 ℃ to 70 ℃. From the standpoint of compatibility of the adhesive layer a with its photocurable substance, it may be advantageous that the absolute value of the Tg difference is not excessively large. In some embodiments, ΔTg may be, for example, at least-10deg.C, preferably at least 0deg.C, at least 7deg.C, at least 10deg.C, at least 20deg.C, or at least 30deg.C.
The BP type hybrid adhesive composition may contain at least a compound having 2 or more ethylenically unsaturated groups (i.e., a polyfunctional monomer) as the ethylenically unsaturated compound. The polyfunctional monomer may be used singly or in combination of two or more from the above examples of the polyfunctional monomer. The amount of the polyfunctional monomer used may be set in the same manner as the ratio of the polyfunctional (meth) acrylate to the total monomer components constituting the adhesive composition.
In the embodiment in which the monofunctional monomer and the polyfunctional monomer are used in combination as the ethylenically unsaturated compound, the weight ratio of the monofunctional monomer to the ethylenically unsaturated compound may be, for example, 1% by weight or more, and usually 25% by weight or more, and it is appropriate that the weight ratio is 50% by weight or more, 75% by weight or more, 95% by weight or more, or 99% by weight or more. The weight ratio of the monofunctional monomer to the ethylenically unsaturated compound may be, for example, 99.9% by weight or less, or 99.8% by weight or less.
In the BP-type hybrid adhesive composition, the ethylenically unsaturated compound may be contained in the form of a partial polymer or may be contained in the form of an unreacted monomer in the entire amount. The adhesive composition of a preferred embodiment comprises an ethylenically unsaturated compound in the form of a partially polymerized form. The polymerization method in partially polymerizing the ethylenically unsaturated compound is not particularly limited, and for example, it can be appropriately selected and used: photopolymerization by irradiation with light such as ultraviolet light; radiation polymerization by irradiation with radiation such as beta rays and gamma rays; thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization; and various polymerization methods known in the prior art. From the viewpoint of efficiency and simplicity, photopolymerization is preferably used. With photopolymerization, the polymerization conversion (monomer conversion) can be easily controlled by polymerization conditions such as the irradiation amount (light amount) of light.
The polymerization conversion of the ethylenically unsaturated compound in the partial polymer is not particularly limited. The polymerization conversion is usually about 50% by weight or less, preferably about 40% by weight or less (for example, about 35% by weight or less) from the viewpoint of ease of preparation of the adhesive composition, coatability, and the like. The lower limit of the polymerization conversion is not particularly limited, and is typically about 1% by weight or more, and usually about 5% by weight or more is suitable.
The BP-type hybrid adhesive composition comprising a partial polymer of an olefinically unsaturated compound can be obtained, for example, by: the entire amount of the monomer mixture containing the ethylenically unsaturated compound used in the preparation of the adhesive composition is partially polymerized by a suitable polymerization method, such as photopolymerization. In addition, the BP-type hybrid adhesive composition comprising a partial polymer of an ethylenically unsaturated compound may also be a mixture of a partial polymer of a monomer mixture comprising a portion of the ethylenically unsaturated compound used in the preparation of the adhesive composition with the remaining ethylenically unsaturated compound or a partial polymer thereof. In the present specification, "complete polymer" means that the polymerization conversion is higher than 95% by weight.
The partial polymer may be produced, for example, by irradiating an ethylenically unsaturated compound with ultraviolet rays. When the preparation of the partial polymer is performed in the presence of the BP polymer, the irradiation condition of ultraviolet rays is set so that the ethylenically unsaturated group is reacted and the benzophenone structure is not excited by light, whereby an adhesive composition comprising the partial polymer of the ethylenically unsaturated compound and the BP polymer can be obtained. As the light source, a light source capable of irradiating ultraviolet rays containing no component having a wavelength of less than 300nm or a small amount of the component having the wavelength, such as the above-mentioned black light lamp or UV-LED lamp, can be preferably used.
Alternatively, the adhesive composition may be prepared by preparing a partial polymer of the ethylenically unsaturated compound in advance, and then mixing the partial polymer with the BP polymer. When the partially polymerized product is produced by irradiating ultraviolet rays to an ethylenically unsaturated compound in the absence of a component containing a benzophenone structure, both a light source that does not excite the benzophenone structure and an excited light source can be used as the ultraviolet source.
In preparing the partial polymer of the ethylenically unsaturated compound, the reaction of the ethylenically unsaturated groups can be promoted by using a photopolymerization initiator. As the photopolymerization initiator, ketal-based photopolymerization initiator, acetophenone-based photopolymerization initiator, benzoin ether-based photopolymerization initiator, acylphosphine oxide-based photopolymerization initiator, α -ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzil-based photopolymerization initiator, benzophenone-based photopolymerization initiator, alkylbenzene-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, and the like can be used. A photopolymerization initiator that absorbs light having a wavelength of 300nm or more (for example, light having a wavelength of 300nm or more and 500nm or less) to generate radicals can be preferably used. The photopolymerization initiator may be used alone or in combination of 2 or more.
The BP-type hybrid adhesive composition may contain a photopolymerization initiator, if necessary, for the purpose of improving or imparting photocurability and the like. As the photopolymerization initiator, ketal-based photopolymerization initiator, acetophenone-based photopolymerization initiator, benzoin ether-based photopolymerization initiator, acylphosphine oxide-based photopolymerization initiator, α -ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzil-based photopolymerization initiator, benzophenone-based photopolymerization initiator, alkylbenzene-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, and the like can be used. The photopolymerization initiator may be used alone or in combination of 2 or more.
Specific examples of ketal-based photopolymerization initiators include: 2, 2-dimethoxy-1, 2-diphenylethan-1-one, and the like.
Specific examples of the acetophenone photopolymerization initiator include: 1-hydroxycyclohexyl-phenyl-ketone, 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, and the like.
Specific examples of the benzoin ether photopolymerization initiator include: benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and anisoin methyl ether.
Specific examples of the acylphosphine oxide-based photopolymerization initiator include: bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2, 4-di-n-butoxyphenylphosphine oxide, 2,4, 6-trimethylbenzoyl diphenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2, 4-trimethylpentylphosphine oxide, and the like.
Specific examples of the α -ketol photopolymerization initiator include: 2-methyl-2-hydroxy propiophenone, 1- [4- (2-hydroxyethyl) phenyl ] -2-methylpropan-1-one, and the like.
Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride and the like.
Specific examples of the photo-polymerization initiator for photoactive oximes include 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl) -oxime and the like.
Specific examples of the benzoin-based photopolymerization initiator include benzoin and the like.
Specific examples of the benzil-based photopolymerization initiator include benzil and the like.
Specific examples of the benzophenone-based photopolymerization initiator include: benzoyl benzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α -hydroxycyclohexyl phenyl ketone, and the like.
Specific examples of the thioxanthone photopolymerization initiator include: thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-dichlorothioxanthone, 2, 4-diethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone, dodecylthioxanthone, and the like.
As the photopolymerization initiator contained in the BP type hybrid adhesive composition, a photopolymerization initiator that absorbs light having a wavelength of 300nm or more (for example, light having a wavelength of 300nm or more and 500nm or less) to generate radicals can be preferably used. The photopolymerization initiator may be used alone or in combination of 2 or more. In some embodiments, a photopolymerization initiator containing no phosphorus element in the molecule may be preferably used. The BP type hybrid adhesive composition may be substantially free of a photopolymerization initiator containing a phosphorus element in the molecule.
The content of the photopolymerization initiator in the BP type hybrid adhesive composition is not particularly limited, and may be set so as to appropriately exhibit a desired effect. In some embodiments, the content of the photopolymerization initiator may be, for example, about 0.005 parts by weight or more, and usually 0.01 parts by weight or more, preferably 0.05 parts by weight or more, 0.10 parts by weight or more, 0.15 parts by weight or more, or 0.20 parts by weight or more, based on 100 parts by weight of the monomer components constituting the BP type hybrid adhesive composition. By increasing the content of the photopolymerization initiator, the photocurability of the BP type hybrid adhesive composition is improved. The content of the photopolymerization initiator is usually 5 parts by weight or less, preferably 2 parts by weight or less, and may be 1 part by weight or less, 0.7 part by weight or less, or 0.5 part by weight or less, based on 100 parts by weight of the monomer components constituting the BP type hybrid adhesive composition. From the viewpoint of suppressing gelation of the BP type hybrid adhesive composition, etc., it may be advantageous that the content of the photopolymerization initiator is not excessive.
The BP-type hybrid pressure-sensitive adhesive composition may be blended with, for example, a known crosslinking agent such as an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, a melamine-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a hydrazine-based crosslinking agent, or an amine-based crosslinking agent, as necessary. As crosslinking agent, peroxides may also be used. These crosslinking agents may be used singly or in combination of 1 or more than 2. The adhesive layer a formed from the BP type hybrid adhesive composition containing a crosslinking agent preferably contains the crosslinking agent mainly in a form after the crosslinking reaction. By using the crosslinking agent, the cohesive force or the like of the adhesive layer a can be appropriately adjusted.
The amount of the crosslinking agent used (the total amount of the 2 or more crosslinking agents used) is not particularly limited. The amount of the crosslinking agent used is usually about 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.50 parts by weight or less, 0.30 parts by weight or less, or 0.20 parts by weight or less, based on 100 parts by weight of the monomer components constituting the BP type mixed adhesive composition, from the viewpoint of achieving an adhesive that exhibits well balanced adhesive properties such as adhesive force and cohesive force. The lower limit of the amount of the crosslinking agent to be used is not particularly limited, and may be more than 0 parts by weight based on 100 parts by weight of the monomer components constituting the BP-type hybrid adhesive composition. In some embodiments, the crosslinking agent may be used in an amount of, for example, 0.001 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.10 parts by weight or more, based on 100 parts by weight of the monomer components constituting the BP type hybrid adhesive composition.
The BP-type hybrid adhesive composition may contain various conventionally known chain transfer agents. As the chain transfer agent, thiols such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycollic acid, and α -thioglycerol can be used. Alternatively, a chain transfer agent (non-sulfur chain transfer agent) having no sulfur atom may be used. Specific examples of the non-sulfur chain transfer agent include: anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenes such as alpha-pinene and terpinolene; styrenes such as alpha-methylstyrene, alpha-methylstyrene dimer, etc.; compounds having a benzylidene group such as dibenzylidene acetone, cinnamyl alcohol, and cinnamaldehyde; hydroquinones such as hydroquinone and 1, 4-dihydroxynaphthalene; quinone 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 diphenyl benzene and triphenyl benzene; etc. The chain transfer agent may be used alone or in combination of 1 or more than 2. When the chain transfer agent is used, the amount thereof may be, for example, about 0.01 to 1 part by weight based on 100 parts by weight of the monomer component. It may also be preferably carried out without using a chain transfer agent.
As other components that may be contained in the BP type hybrid adhesive composition, a silane coupling agent may be mentioned. By using the silane coupling agent, the peel strength to an adherend (for example, a glass plate) can be improved. In addition, the adhesive layer a may contain a silane coupling agent. The adhesive layer a containing the silane coupling agent can be suitably formed using a BP type hybrid adhesive composition containing the silane coupling agent. The silane coupling agent may be used alone or in combination of 1 or more than 2.
The BP type mixed adhesive composition may contain, as other optional components, various additives conventionally used in the adhesive field such as tackifying resins (for example, rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based and the like), viscosity modifiers (for example, tackifiers), leveling agents, antioxidants, plasticizers, fillers, stabilizers, preservatives, anti-aging agents and the like, as required. As such various additives, conventionally known ones can be used by a conventional method, and since the present invention is not particularly characterized, detailed description thereof is omitted.
The BP type mixed adhesive composition can exhibit good adhesion without using the tackifying resin. Accordingly, in some embodiments, the content of the tackifying resin in the adhesive layer or the adhesive composition may be set to, for example, less than 10 parts by weight, and further less than 5 parts by weight, relative to 100 parts by weight of the monomer component. The content of the tackifier resin may be less than 1 part by weight (for example, less than 0.5 part by weight), or less than 0.1 part by weight (0 part by weight or more and less than 0.1 part by weight). The adhesive layer or the adhesive composition may not contain a tackifying resin.
By curing the BP type mixed adhesive composition, an adhesive layer a containing a BP polymer (hereinafter, sometimes referred to as "BP type adhesive layer a") can be formed. The curing of the BP type hybrid adhesive composition is preferably performed so that the ethylenically unsaturated groups contained in the adhesive composition react and the benzophenone structure contained in the BP type hybrid adhesive composition remains. The curing may be preferably performed by irradiation with active energy rays. The active energy ray used for forming the adhesive layer a is preferably ultraviolet ray, and more preferably ultraviolet ray containing no component having a wavelength of less than 300nm or less.
The BP type adhesive layer a was produced using the BP type mixed adhesive composition described above. The BP-type adhesive layer a may comprise a BP polymer and a polymer derived from an ethylenically unsaturated compound. In some preferred embodiments, the aforementioned BP-type hybrid adhesive composition may be a composition in which the aforementioned olefinically unsaturated compound is free of olefinically unsaturated BP. According to the BP type hybrid adhesive composition of such composition, a BP type adhesive layer a comprising a BP polymer and a polymer derived from an ethylenically unsaturated compound, which is a non-BP polymer, can be produced.
The method for producing the BP type adhesive layer a by the BP type mixed adhesive composition can be carried out by the following method: in the adhesive layer forming step and the adhesive layer curing step in embodiment 2 described above, a BP type mixed adhesive composition is used instead of the base polymer.
As for the curing conditions in the adhesive layer curing step of the present embodiment, in order to react the above-mentioned ethylenically unsaturated groups and leave a benzophenone structure, a light source capable of irradiating ultraviolet rays containing no component having a wavelength of less than 300nm or a small amount of the component having the wavelength, such as a black light lamp or a UV-LED lamp, may be preferably used.
< self-luminous display device >
The self-luminous display device according to the 2 nd aspect of the present invention is a display device as follows: a large number of light emitting elements are arranged on a wiring board, and each light emitting element selectively emits light by a light emission control means connected thereto, whereby visual information such as characters, images, and videos is directly displayed on a display screen by blinking of each light emitting element. Examples of the self-luminous display device include a mini/micro LED display device and an organic EL (electro luminescence) display device. The photocurable adhesive sheet a according to the invention as defined in the 1 st aspect is particularly suitable for use in the manufacture of mini/micro LED display devices.
Fig. 4 is a schematic view (cross-sectional view) showing an embodiment of a self-luminous display device (mini/micro LED display device) according to the 2 nd side of the present invention.
In fig. 4, the mini/micro LED display device 2A is constituted by: a display panel in which a plurality of LED chips 23 are arranged on one surface of a substrate 21 via a metal wiring layer 22, an adhesive layer 20 which is laminated on the display panel and seals the metal wiring layer 22 and the plurality of LED chips 23, and a cover member 24 which is laminated on an upper portion (image display side) of the adhesive layer 20. The cover member 24 is not particularly limited, and may be made of the same material as the "base material" described above.
In the mini/micro LED display device 2A of the present embodiment, a metal wiring layer 22 for supplying a light emission control signal to each LED chip 23 is laminated on a substrate 21 of a display panel. The LED chips 23 that emit light of red (R), green (G), and blue (B) are alternately arranged on the substrate 21 of the display panel through the metal wiring layers 22. The metal wiring layer 22 is made of a metal such as copper, and reflects the light emitted from each LED chip 23 to reduce the visibility of the image. In addition, the light emitted from each LED chip 23 of each color of RGB is mixed, and the contrast is lowered.
In the mini/micro LED display device 2A of the present embodiment, each LED chip 23 arranged on the display panel is sealed with the adhesive layer 20. The adhesive layer 20 is composed of a cured product of the adhesive layer a of the present invention. The adhesive layer 20 sufficiently follows the fine level difference between the plurality of LED chips 23, and seals without gaps.
The adhesive layer 20 has sufficient light-shielding properties in the visible light region. Since the fine level difference between the LED chips 23 is sealed with the pressure-sensitive adhesive layer 20 having high light-shielding properties without gaps, reflection by the metal wiring layer 22 can be prevented, color mixing between the LED chips 23 can be prevented, and contrast can be improved.
In addition, the adhesive layer 20 is a cured product of the adhesive layer a, and thus is excellent in workability. Therefore, the adhesive layer 20 can be prevented from overflowing and sagging from the end portion during the dicing process and storage of the mini/micro LED display device 2A of the present embodiment.
The self-luminous display device (mini/micro LED display device) of the present embodiment may include an optical member other than the display panel, the adhesive layer, and the cover member. The optical member is not particularly limited, and examples thereof include a polarizing plate, a retardation plate, an antireflection film, a viewing angle adjusting film, and an optical compensation film. The optical member also includes a member (an exterior film, a decorative film, a surface protection plate, etc.) that retains the visibility of the display device and the input device and plays a role of decoration and protection.
The self-luminous display device (mini/micro LED display device) of the present embodiment is not particularly limited, and is preferably manufactured by a method including the following steps.
(1) And a step of laminating an adhesive layer A of a photocurable adhesive sheet A on a display panel having a plurality of light-emitting elements arranged on one surface of a substrate, and sealing the light-emitting elements with the adhesive layer A.
(2) And a step of curing the adhesive layer by irradiation with radiation.
Fig. 5 is a diagram schematically showing a process of one embodiment of a method for manufacturing a self-luminous display device (mini/micro LED display device) according to the 2 nd side of the present invention. In the present embodiment, as shown in fig. 5 (a), the photocurable adhesive sheet 1E on the 2 nd side of the present invention and a display panel in which a plurality of light-emitting elements (LED chips) 23 are arranged on one surface of a substrate 21 via a metal wiring layer 22 are used.
In this embodiment, the photocurable adhesive sheet 1E is composed of the adhesive layer 10 and the cover member 24 which can be produced by the method for producing the photocurable adhesive sheet a according to embodiment 2 of the present invention. The adhesive layer 10 has a structure in which a crosslinking agent 11 and a photopolymerization initiator 12 are dissolved in a base polymer. A mode in which only one of the crosslinking agent 11 and the photopolymerization initiator 12 is dissolved in the adhesive layer 10 is also included in the present embodiment. In the present embodiment, there is a concentration gradient of the crosslinking agent 11 and the photopolymerization initiator 12 in the thickness direction from the main surface 10A where the adhesive layer 10 contacts the support S3.
In the present embodiment, the photocurable adhesive sheet 1E has the cover member 24, but the cover member 24 may be omitted. The cover member 24 is not particularly limited, and may be formed of the same material as the "base material" described above, or may be a release film (separator).
Next, as shown in fig. 5 (B), the main surface 10B of the cover member 24 is not laminated in the adhesive layer 10 in which the photocurable adhesive sheet 1E is laminated on the surface of the display panel on which the plurality of LED chips are arranged, and the LED chips 23 and the metal wiring layer 22 are sealed with the adhesive layer 10. The lamination may be performed by a known method, for example, under heating and pressurizing conditions using an autoclave. The pressure-sensitive adhesive layer 10 of the photocurable pressure-sensitive adhesive sheet 1E has high fluidity and exhibits excellent level difference absorbency. Therefore, the adhesive layer 10 seals so as to fill the height difference between the metal wiring layer 22 and the plurality of LED chips 23 without gaps.
Next, as shown in fig. 5 (c), the adhesive layer 10 is irradiated with radiation to be cured. Upon irradiation with radiation, the photopolymerization initiator 12 decomposes and generates radicals, ions, or the like, which initiate polymerization/crosslinking reactions of the crosslinking agent 12. The radiation is not particularly limited as long as the pressure-sensitive adhesive layer 10 is cured, and ultraviolet rays that allow the pressure-sensitive adhesive layer 10 to exhibit permeability are preferable. That is, the adhesive layer 10 has high light-shielding properties against visible light and high transmittance against ultraviolet rays, and thus the adhesive layer 10 can be cured by ultraviolet rays. Fig. 5 (c) shows an embodiment in which the adhesive layer 10 is cured by irradiation with ultraviolet rays U.
The ultraviolet light is preferably ultraviolet light having a wavelength of 200 to 400nm, more preferably 330 to 400 nm. In the case where the pressure-sensitive adhesive layer 10 is composed of the BP type pressure-sensitive adhesive layer a, the pressure-sensitive adhesive layer may be cured by irradiation with ultraviolet rays containing a wavelength component capable of exciting a benzophenone structure, and specifically, a light source capable of irradiation with ultraviolet rays containing a component having a wavelength of less than 300nm is preferably used.
As the light source for ultraviolet irradiation, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a microwave excitation lamp, a metal halide lamp, a chemical lamp, a black light lamp, or an LED can be used. In addition, the irradiation time and irradiation method of the ultraviolet rays are not limited to those of the display panel as long as the adhesive layer 10 can be curedThe adhesive layer 10 is cured to exhibit sufficient workability, and can be appropriately set. For example, the irradiation amount (cumulative light amount) of ultraviolet rays is preferably 1000mJ/cm 2 ～10000mJ/cm 2 More preferably 2000mJ/cm 2 ～4000mJ/cm 2 Further preferably 3000mJ/cm 2 。
By curing the adhesive layer 10, as shown in fig. 5 (d), a self-luminous display device (mini/micro LED display device) 2B can be obtained. In fig. 5 (d), the adhesive layer 20 is an adhesive layer obtained by curing the adhesive layer 10. The self-luminous display device (mini/micro LED display device) 2B is an embodiment showing an example of the self-luminous display device (mini/micro LED display device) of the 2 nd side of the present invention.
By curing the adhesive layer 10, the crosslinking agent 11 is crosslinked/polymerized to form a crosslinked structure 11', forming the adhesive layer 20. The workability of the adhesive layer 20 is improved, and the adhesive shortage during cutting processing and the overflow and sagging of the adhesive layer from the end during storage can be suppressed. In addition, the pressure-sensitive adhesive layer 20 can suppress the generation of gas such as carbon dioxide caused by heating of the display panel, prevent the generation of bubbles, and improve the bonding reliability.
In the embodiment of fig. 5 (d), the cross-linking density of the main surface of the adhesive layer 20 on the side contacting the support S3 is higher than that on the opposite side. This configuration is preferable in view of improving the flexibility when a self-luminous display device (mini/micro LED display device) is used as a flexible image display device that is bent outward, for example.
That is, when the flexible display is bent, a tensile stress is applied to the outside and a compressive stress is applied to the inside, and the stress on the outside is stronger than the stress on the inside. Therefore, by disposing the upper portion (image display side) of the adhesive layer 20 on the outer side when bending the flexible display, durability against bending can be improved.
Examples
The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
(preparation of prepolymer)
67 parts by weight of Butyl Acrylate (BA), 14 parts by weight of cyclohexyl acrylate (CHA), 19 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.09 parts by weight of a photopolymerization initiator (trade name "Irgacure 184" manufactured by BASF corporation) and 0.09 parts by weight of a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF corporation) were put into a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, and nitrogen was introduced thereinto, followed by stirring for nitrogen substitution for about 1 hour. Then, at 5mW/cm 2 Irradiating UVA for polymerization, and adjusting the reaction rate to 5-15% to obtain the acrylic prepolymer solution A.
(preparation of adhesive composition)
To the acrylic prepolymer solution A (100 parts by weight of the total amount of the prepolymer) thus obtained, 9 parts by weight of 2-hydroxyethyl acrylate (HEA), 8 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.02 part by weight of dipentaerythritol hexaacrylate (trade name "KAYARAD DPHA" manufactured by Sanremo Industrial Co., ltd.), 0.35 part by weight of a silane coupling agent (3-glycidoxypropyl trimethoxysilane, trade name "KBM-403" manufactured by Xinyue chemical Co., ltd.) and 0.45 part by weight of a photopolymerization initiator (Irgacure 651 "manufactured by BASF) were added to obtain an adhesive composition B.
(preparation of black adhesive composition)
To 100 parts by weight of the above-mentioned adhesive composition B, 5.8 parts by weight of a 20% dispersion (9256 BLACK, manufactured by TOKUSHIKI) of a BLACK pigment and 0.2 part by weight of an additional photopolymerization initiator (Irgacure 651, manufactured by BASF corporation) were added to obtain a BLACK adhesive composition C.
(production of adhesive sheet)
The black adhesive composition C prepared above was applied to the release surface of a release film R1 (trade name "mrf#38" manufactured by mitsubishi resin co.) having a thickness of 38 μm, which was a release surface, on one side of the polyester film, and the release film R2 (manufactured by mitsubishi resin co., mre#38), which was a release surface, on one side of the polyester film was covered to block air. From a single of the laminateOn the side, a black light lamp (trade name FL15BL, manufactured by Toshiba Co., ltd.) was used at an illuminance of 5mW/cm 2 Cumulative light quantity 1300mJ/cm 2 Ultraviolet rays are irradiated on the condition of (2). Thus, an adhesive sheet D having an adhesive layer of about 50 μm thick sandwiched between the release films R1, R2 was obtained as a base-free double-sided adhesive sheet as a cured product of the black adhesive composition C.
The illuminance value of the black light lamp was measured by an industrial UV inspection device (product name: UVR-T1, model UD-T36 of light receiving unit, manufactured by TOPCON Co., ltd.) having a peak sensitivity wavelength of about 350 nm.
(production of photocurable pressure-sensitive adhesive sheet)
The release film R2 of the adhesive sheet D was peeled off, and a solution (target Wet coating thickness 15 μm) obtained by dissolving a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF) in trimethylolpropane triacrylate (TMPTA) so as to be 5% by weight was applied by a bar coater of Wire work Rod type #7 manufactured by RD Specialties corporation. After coating, the coating was heated in an oven at 110℃for 2 minutes. Then, the adhesive face was protected again with a release film R2, and a photocurable adhesive sheet E including an adhesive layer in which TMPTA and a photopolymerization initiator were dissolved was obtained in the form of a base-free double-sided adhesive sheet.
Example 2
(preparation of solvent type Black adhesive composition)
60 parts by weight of N-Butyl Acrylate (BA), 6 parts by weight of cyclohexyl acrylate (CHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), 1 part by weight of isostearyl acrylate (iSTA), 15 parts by weight of 4-hydroxybutyl acrylate (4 HBA), 0.125 part by weight of alpha-thioglycerol as a chain transfer agent and 122 parts by weight of ethyl acetate as a polymerization solvent as monomer components were charged into a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, and 0.2 part by weight of 2,2' -Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was charged to conduct solution polymerization under a nitrogen atmosphere, thereby obtaining a solution containing an acrylic polymer having Mw of about 50 ten thousand.
To 100 parts of the monomer component used in the preparation of the above-obtained solution, 0.22 parts by weight of a polymerization initiator (Irgacure 651, manufactured by BASF corporation), 0.27 parts by weight of an isocyanate-based crosslinking agent (trimethylolpropane/xylylene diisocyanate adduct, manufactured by Mitsui chemical Co., ltd., trade name "TAKENATE D-110N", solid content concentration 75%), 2.2 parts by weight of dipentaerythritol hexaacrylate (manufactured by Sanchiku chemical Co., ltd., trade name "KAYARAD DPHA"), 1 part by weight of polypropylene glycol #400 diacrylate (manufactured by Sanchiku chemical Co., ltd.), 0.33 parts by silane coupling agent (3-glycidoxypropyl trimethoxysilane, manufactured by Xinshi chemical Co., ltd., trade name "KBM-403"), 0.3 parts by antioxidant (manufactured by BASF corporation, trade name "IRGANOX 1135"), 0.18 parts by weight of polyether polyol (manufactured by ADEKA, trade name "ADEKA Polyether EPD-300"), and 20% BLACK pigment dispersion (manufactured by KHICK, BLACK binder) were added to obtain a BLACK adhesive composition.
(production of photocurable pressure-sensitive adhesive sheet)
A release film (MRF#38, manufactured by Mitsubishi resin Co., ltd.) having a thickness of 38 μm and having one side of 2 sheets of polyester film as a release surface was prepared. The solvent type black adhesive composition prepared above was applied to the release surface of the 1 st release film, and dried at 60℃for 3 minutes, followed by drying at 120℃for 3 minutes, to form a photocurable adhesive layer having a thickness of 134. Mu.m. The release surface of the 2 nd release film was bonded to the pressure-sensitive adhesive layer and protected, and a photocurable pressure-sensitive adhesive sheet was obtained as a base-free double-sided pressure-sensitive adhesive sheet.
Example 3
(preparation of adhesive composition)
An acrylic copolymer having a benzophenone structure in the side chain (trade name "acrresin A260UV", manufactured by BASF Co., ltd., tg: -39 ℃ C., mw: 19X 10) was charged into a detachable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet pipe 4 BP equivalent: 2 mg/g) 50 parts by weight, butyl Acrylate (BA) 26 parts by weight, N-vinyl-2-pyrrolidone (NVP) 8 parts by weight, isobornyl acrylate (IBXA) 16 parts by weight, and a photopolymerization initiator (manufactured by BASF corporation under the trade name "Irgacure184 ") 0.2 parts by weight, and mixed to prepare an adhesive composition.
(preparation of black adhesive composition)
To 100 parts by weight of the above-mentioned adhesive composition, 2 parts by weight of a 20% dispersion (9256 BLACK manufactured by TOKUSHIKI) of a BLACK pigment was added to prepare a BLACK adhesive composition.
(production of photocurable pressure-sensitive adhesive sheet)
The black adhesive composition prepared as described above was applied to the release surface of a release film R1 (trade name "mrf#38" manufactured by mitsubishi resin co.) having a thickness of 38 μm, which was a release surface, on one side of the polyester film, and the release film R2 (manufactured by mitsubishi resin co., ltd., mre#38), which was a release surface, on one side of the polyester film, was covered to block air. From one side of the laminate, a black light lamp (trade name FL15BL, manufactured by Toshiba Co., ltd.) was used at an illuminance of 5mW/cm 2 Cumulative light quantity 1300mJ/cm 2 Ultraviolet rays are irradiated on the condition of (2). Thus, a photocurable adhesive sheet in which an adhesive layer having a thickness of about 104 μm as a cured product of the black adhesive composition was sandwiched between the release films R1 and R2 was obtained as a substrate-free double-sided adhesive sheet.
Example 4
(preparation of black adhesive composition)
To 100 parts by weight of the adhesive composition B prepared in example 1, 4 parts by weight of a 20% dispersion (9256 BLACK by TOKUSHIKI) of a BLACK pigment and 0.2 part by weight of an additional photopolymerization initiator (Irgacure 651 by BASF) were added, and 1 part of 4-acryloxybenzophenone by Ark Pharmm were added to obtain a BLACK adhesive composition.
(production of photocurable pressure-sensitive adhesive sheet)
The black adhesive composition prepared as described above was applied to the release surface of a release film R1 (trade name "mrf#38" manufactured by mitsubishi resin co.) having a thickness of 38 μm, which was a release surface, on one side of the polyester film, and the release film R2 (manufactured by mitsubishi resin co., ltd., mre#38), which was a release surface, on one side of the polyester film, was covered to block air. From one side of the laminate, a black light lamp (trade name FL15BL, manufactured by Toshiba Co., ltd.) was used at an illuminance of 5mW/cm 2 Cumulative light quantity 1300mJ/cm 2 Ultraviolet rays are irradiated on the condition of (2). Thus, an adhesive sheet having an adhesive layer of about 100 μm thick, which is a cured product of the black adhesive composition, sandwiched between the release films R1 and R2 was obtained as a base-free double-sided adhesive sheet.
The illuminance value of the black light lamp was measured by an industrial UV inspection device (product name: UVR-T1, model UD-T36 of light receiving unit, manufactured by TOPCON Co., ltd.) having a peak sensitivity wavelength of about 350 nm.
Example 5
A photocurable adhesive sheet was produced in the same manner as in example 4 except that 2 parts of 4-acryloxybenzophenone was used.
Reference example 1
(preparation of adhesive composition)
To the acrylic prepolymer solution a obtained in example 1 (the total amount of the prepolymer was set to 100 parts by weight), 9 parts by weight of 2-hydroxyethyl acrylate (HEA), 8 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.45 part by weight of a polymerization initiator (manufactured by BASF corporation, "Irgacure 651"), and 1 part by weight of nano silica (manufactured by Japan Aerosil co., ltd., trade name "R976S") were added to obtain an adhesive composition.
(preparation of black adhesive composition)
To 100 parts by weight of the above-mentioned adhesive composition, 5.8 parts by weight of a 20% dispersion (9256 BLACK, manufactured by TOKUSHIKI) of a BLACK pigment and 0.2 part by weight of an additional photopolymerization initiator (Irgacure 651, manufactured by BASF) were added to obtain a BLACK adhesive composition.
(production of adhesive sheet)
The black adhesive composition prepared as described above was applied to the release surface of a release film R1 (trade name "mrf#38" manufactured by mitsubishi resin co.) having a thickness of 38 μm, which was a release surface, on one side of the polyester film, and the release film R2 (manufactured by mitsubishi resin co., mre#38), which was a release surface, was covered on one side of the polyester film, was blocked from air. From one side of the laminate, a black light lamp (trade name FL15BL, manufactured by Toshiba Co., ltd.) was used at an illuminance of 5mW/cm 2 Cumulative light quantity 1300mJ/cm 2 Ultraviolet rays are irradiated on the condition of (2). Thus, an adhesive sheet having an adhesive layer of about 100 μm thick, which is a cured product of the black adhesive composition, sandwiched between the release films R1 and R2 was obtained as a base-free double-sided adhesive sheet. The obtained adhesive sheet did not show photo-curability.
Reference example 2
An adhesive sheet was obtained in the same manner as in reference example 1, except that the amount of nano silica used was 3 parts by weight.
Reference example 3
A pressure-sensitive adhesive sheet was obtained in the same manner as in reference example 1, except that the amount of nano silica used was 5 parts by weight.
Reference example 4
A pressure-sensitive adhesive sheet was obtained in the same manner as in reference example 1, except that the amount of nano silica used was 7 parts by weight.
The purpose of reference examples 1 to 4 was to verify the storage modulus and the ratio thereof for both the level difference followability and the workability, and to evaluate the storage modulus by changing the amount of nano silica used by using an adhesive sheet that does not exhibit photo-curability.
Comparative example 1
(production of adhesive sheet)
The adhesive composition B prepared in example 1 was applied to the release surface of a release film R1 (trade name "MRF#38" manufactured by Mitsubishi resin Co., ltd.) having a thickness of 38 μm, which was a release surface, on one side of the polyester film, and a release film R2 (MRE#38 manufactured by Mitsubishi resin Co., ltd.) having a release surface on one side of the polyester film was covered to block air. From one side of the laminate, a black light lamp (trade name FL15BL, manufactured by Toshiba Co., ltd.) was used at an illuminance of 5mW/cm 2 Cumulative light quantity 1300mJ/cm 2 Ultraviolet rays are irradiated on the condition of (2). Thus, an adhesive sheet having an adhesive layer of about 50 μm thick, which is a cured product of the adhesive composition B, sandwiched between the release films R1 and R2 was obtained as a base-free double-sided adhesive sheet.
(production of photocurable pressure-sensitive adhesive sheet)
The release film R2 of the adhesive sheet was peeled off, and a solution (target Wet coating thickness 15 μm) obtained by dissolving a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF) in trimethylolpropane triacrylate (TMPTA) so as to be 5% by weight was applied by a bar coater of Wire work Rod type #7 manufactured by RD Specialties corporation. After coating, the coating was heated in an oven at 110℃for 2 minutes. Then, the adhesive surface was protected again with a release film R2, and a photocurable adhesive sheet including an adhesive layer in which TMPTA and a photopolymerization initiator were dissolved was obtained in the form of a base-free double-sided adhesive sheet.
Comparative example 2
The adhesive sheet D obtained in example 1 was used as the adhesive sheet of comparative example 2. The adhesive sheet D does not exhibit photo-curability.
(evaluation)
The following evaluations were performed using the adhesive sheets obtained in the above examples, reference examples and comparative examples. The evaluation method is shown below. The results are shown in Table 1.
[ evaluation of transmittance ]
And a release film having one surface peeled from the adhesive sheet, wherein an alkali-free glass is bonded to the exposed surface. Then, the other surface of the release film was peeled off from the adhesive sheet to obtain a sample having the adhesive sheet bonded to an alkali-free glass plate.
The total light transmittance was measured by a haze meter (trade name "HN-150", manufactured by Toku Kogyo Co., ltd.) according to the method defined in JIS K7361.
[ evaluation of storage modulus ]
Evaluation was performed using ARES GII from TA Instruments.
The adhesive sheet laminated to a thickness of about 1mm was sandwiched by 8mm parallel plates, and the storage modulus G ' at 10 ℃, 25 ℃ and 85 ℃ as the storage modulus G ' (G ' b10, G ' b25, G ' b 85) before curing was read when measured from-50 ℃ to 100 ℃ at an initial strain of 1%, a frequency of 1Hz, and a heating rate of 5 ℃/min.
Regarding the storage modulus G' after curing, the cumulative light amount was 3000mJ/cm 2 In (2) a sheet laminate obtained by irradiating a pressure-sensitive adhesive sheet sandwiched between release films with a high-pressure mercury lampThe thickness was about 1mm, and the storage modulus G '(G' a10, G 'a25, G' a 85) after curing was evaluated in the same manner as described above.
The cumulative light amount was measured by an industrial UV measuring device (trade name: UVR-T1, model UD-T36 of light receiving unit, manufactured by TOPCON Co., ltd.) having a peak sensitivity wavelength of about 350 nm.
Since the adhesive sheets of reference examples 1 to 4 and comparative example 2 did not exhibit photocurability, the storage modulus G' after curing was not evaluated.
[ evaluation of level-difference following Property ]
(production of concave-convex adherend)
A laminate of a TAC film (thickness: 60 μm) and an adhesive (thickness: 20 μm) was bonded to a 45mm X50 mm glass plate, and then CO was used 2 A TAC film and an adherend A having an adhesive layer formed into a lattice-like concave-convex shape were obtained by performing a linear etching process with a longitudinal direction of 150 μm pitch and a transverse direction of 225 μm pitch in a range of 10mm X10 mm in the center by a laser beam (wavelength: 10.6 μm/laser beam diameter: good).
The present adherend a mimics an LED panel in which a plurality of LED films are arranged on a substrate.
(production of adhesive sheet)
The pressure-sensitive adhesive sheets prepared in examples 1 and 3 and reference examples 1 to 4 and comparative examples 1 and 2 were laminated to have a thickness of about 200. Mu.m. The adhesive sheet produced in example 2 was laminated to about 250. Mu.m. The release film on one side of the laminated pressure-sensitive adhesive sheet was peeled off, and a PET film having a thickness of 75 μm was bonded to the exposed surface.
(vacuum lamination)
The adhesive surface exposed by peeling the release film on the other surface of the laminated adhesive sheet obtained above was bonded to the processed surface of the adherend a with accuracy within the processing range in which the adhesive sheet can completely cover the adherend a using a vacuum bonding apparatus (manufactured by CRIMB Products, SE340 aaH), and samples for evaluation were obtained, each of which was formed of a PET film, a laminated adhesive sheet, and the adherend a. Further, autoclave treatment (60 minutes at 50 ℃ C./0.5 MPa) was performed to seal the substrates.
(evaluation of level-difference following Property)
In the above-described evaluation sample, the area of the white portion was calculated by photographing with a fixed-point camera by utilizing the property that the processed portion of the adherend a was recognized as being transparent and the portion that could not be traced was recognized as being white when the pressure-sensitive adhesive sheet could follow the pattern portion of the concave-convex shape, and the level difference following property was evaluated.
Area of white part at the time of evaluation of level difference following property (%) =100- { []Area of white part before bonding =1 cm 2 ]×100}
[ evaluation of processability ]
(production of laminate for evaluation of processability)
The release film of the laminated adhesive sheet produced in the step of evaluating the level difference following property was peeled off and bonded to a fr-4 substrate (thickness: 1.2 mm) made of MISUMI Corporation. After autoclave treatment (15 minutes at 50 ℃ C./0.5 MPa), examples 1 to 3 and comparative example 1, which showed photo-curability, were irradiated with ultraviolet light. The irradiation conditions of the ultraviolet rays were set to a high-pressure mercury lamp and the cumulative light amount was 3000mJ/cm 2 . The cumulative light amount is a measured value based on an industrial UV inspection device (trade name: UVR-T1, model UD-T36 of light receiving unit manufactured by TOPCON Co., ltd.) having a peak sensitivity wavelength of about 350 nm.
(processing)
The laminate for workability evaluation obtained above was cut using DTF6450 manufactured by Disco corporation. The cutting conditions were blade type P1A861 (abrasive grain # 400), spindle 30krpm, speed 30mm/s, and cooling water 1L/min.
(evaluation of processability)
The cut end portions were observed from the laminated adhesive sheet side by a solid microscope, and workability was evaluated by the amount of glue overflow from the cut end portions. The evaluation criteria were set as follows.
○：0～150μm
△：150～200μm
X: 200 μm or more
[ evaluation of reflectivity ]
A plate was produced by laminating an aluminum foil on a black acrylic plate. The release films on one side of the adhesive sheets produced in examples 1 to 3 and comparative examples 1 and 2 were peeled off, and a PET film having a thickness of 75 μm was bonded to the exposed surface. The other release films were peeled off, and the exposed adhesive surface was laminated on the aluminum foil side of the plate to obtain a sample. For the obtained sample, a reflectance (%) of a visible light region regularly reflected by 5 ° was measured by setting a PET film as a light source side in a spectrophotometer U4100 (manufactured by Hitachi High-Technologies Corporation).
TABLE 1
Figure BDA0004096359830000671
Examples 1 to 5, which are photocurable adhesive sheets, show excellent level-difference following property (level-difference absorbing property) and workability. As is clear from reference examples 1 to 4 and comparative example 2, when the storage modulus at 85 ℃ before curing is lower than 65kPa, the level difference following property (level difference absorbency) is improved. It is also clear from reference examples 1 to 4 that the region where the storage modulus (G ' b 85) at 85℃before curing was lower than 65kPa and the ratio (G ' a10/G ' b 85) of the storage modulus (G ' a 10) at 10℃after curing to the storage modulus (G ' b 85) at 85℃before curing was higher than 3.3 exhibited excellent level-difference followability (level-difference absorbency) and workability. Since the adhesive sheets of reference examples 1 to 4 did not exhibit photocurability, the ratio (G 'b10/G' b 85) of the storage modulus (G 'b 10) at 10 ℃ before curing to the storage modulus (G' b 85) at 85 ℃ before curing was used for evaluation.
Comparative example 1, which is a photocurable pressure-sensitive adhesive sheet, exhibits excellent level-difference following property (level-difference absorbing property) and workability, but does not contain a black pigment, and thus has a high reflectance.
The following applies to the variations of the present invention.
[ appendix 1] A photocurable adhesive sheet comprising an adhesive layer cured by irradiation of radiation,
The aforementioned adhesive layer comprises a colorant and,
the maximum value of the transmittance of the adhesive layer at a wavelength of 200 to 400nm is larger than the maximum value of the transmittance at a wavelength of 400 to 700nm,
the storage modulus (G' b 85) of the adhesive layer before curing at 85 ℃ is lower than 65kPa,
the storage modulus (G 'a 10) of the cured adhesive layer at 10 ℃ and the storage modulus (G' b 85) of the adhesive layer before curing at 85 ℃ satisfy the following relational expression (1).
3.3<G'a10/G'b85 (1)
The photocurable pressure-sensitive adhesive sheet according to appendix 2, wherein the colorant is a colorant having a maximum value of transmittance at a wavelength of 200 to 400nm greater than a maximum value of transmittance at a wavelength of 400 to 700 nm.
[ additionally remembered 3 ]]The photocurable adhesive sheet according to any one of supplementary notes 1 and 2, wherein the curing by irradiation with the aforementioned radiation is based on a cumulative light amount of 3000mJ/cm 2 Is cured by ultraviolet irradiation.
[ additional note 4] the photocurable adhesive sheet according to any one of additional notes 1 to 3, wherein the cured adhesive layer has a storage modulus (G' a 10) of 90kPa or more at 10 ℃.
[ additional note 5] the photocurable adhesive sheet according to any one of additional notes 1 to 4, wherein the adhesive layer contains a base polymer, a crosslinking agent and a photopolymerization initiator.
The photocurable pressure-sensitive adhesive sheet according to appendix 6, wherein the base polymer contains an acrylic polymer.
[ additional note 7] the photocurable adhesive sheet according to additional note 5 or 6, wherein the crosslinking agent contains a polyfunctional (meth) acrylate.
[ additional note 8] the photocurable adhesive sheet according to any one of additional notes 5 to 7, wherein the adhesive layer is a single layer formed of the base polymer and having 2 main faces facing each other,
when the single adhesive layer is divided into two parts in the thickness direction,
The concentration of the crosslinking agent and/or the photopolymerization initiator in the region to which the 1 st main surface belongs is different from the concentration of the crosslinking agent and/or the photopolymerization initiator in the region to which the other 2 nd main surface belongs in one of the 2 main surfaces.
The photocurable adhesive sheet according to appendix 9, wherein the pressure-sensitive adhesive layer of the single layer has a concentration gradient of the crosslinking agent and/or the photopolymerization initiator in the thickness direction.
[ additional note 10] the method for producing a photocurable pressure-sensitive adhesive sheet in accordance with additional note 8 or 9, comprising the steps of:
an adhesive layer forming a single layer formed of the aforementioned base polymer,
The aforementioned adhesive layer is cured and,
preparing a solution of the crosslinking agent and/or the photopolymerization initiator,
applying the solution to one surface of the cured adhesive layer, allowing the crosslinking agent and/or the photopolymerization initiator contained in the solution to penetrate from the one surface of the adhesive layer in the thickness direction,
the adhesive layer is dried.
The photocurable pressure-sensitive adhesive sheet according to any one of supplementary notes 11 to 4, wherein the pressure-sensitive adhesive layer contains a polymer having a benzophenone structure in a side chain.
The photocurable pressure-sensitive adhesive sheet according to item 11, wherein the pressure-sensitive adhesive layer is a cured product of a pressure-sensitive adhesive composition containing an ethylenically unsaturated compound and a polymer having a benzophenone structure in a side chain.
[ additional note 13] a self-luminous display device comprising:
display panel having a plurality of light emitting elements arranged on one surface of substrate, and method for manufacturing the same
The photocurable adhesive sheet according to any one of supplementary notes 1 to 9, 11, and 12,
the light emitting element of the display panel is sealed with the adhesive layer of the photocurable adhesive sheet,
the aforementioned adhesive layer is cured.
The self-luminous display device according to item 14, wherein the display panel is an LED panel in which a plurality of LED chips are arranged on one surface of a substrate.
The method for manufacturing a self-luminous display device according to any one of supplementary notes 13 and 14, comprising the steps of:
a step of laminating an adhesive layer of the photocurable adhesive sheet according to any one of claims 1 to 9, 11 and 12 on a display panel having a plurality of light-emitting elements arranged on one surface of a substrate, and sealing the light-emitting elements with the adhesive layer; and
and a step of curing the adhesive layer by irradiation with radiation.
The method according to item 15, wherein the radiation is ultraviolet.
Industrial applicability
The photocurable pressure-sensitive adhesive sheet of the present invention is suitable for sealing a light-emitting element of a self-luminous display device such as a mini/micro LED.
Description of the reference numerals
1A to 1E photocurable pressure-sensitive adhesive sheet
10. Adhesive layer
10a to 10c adhesive layers
11. Crosslinking agent
12. Photopolymerization initiator
13. Solvent(s)
14. Solution
2A, 2B self-luminous display device (Mini/micro LED display device)
20. Adhesive layer
21. Substrate board
22. Metal wiring layer
23. Luminous element (LED chip)
24. Covering member
S1, S2 support (Release film)

Claims (16)

1. A photocurable pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer cured by irradiation with radiation,
The adhesive layer may comprise a colorant and,
the maximum value of the transmittance of the adhesive layer at a wavelength of 200 to 400nm is larger than the maximum value of the transmittance at a wavelength of 400 to 700nm,
the storage modulus (G' b 85) of the adhesive layer before curing at 85 ℃ is lower than 65kPa,
the storage modulus (G 'a 10) of the adhesive layer after curing at 10 ℃ and the storage modulus (G' b 85) of the adhesive layer before curing at 85 ℃ satisfy the following relational expression (1),
3.3<G'a10/G'b85 (1)。
2. the photocurable adhesive sheet according to claim 1, wherein the colorant is a colorant having a maximum value of transmittance at a wavelength of 200 to 400nm that is greater than a maximum value of transmittance at a wavelength of 400 to 700 nm.
3. The photocurable adhesive sheet according to claim 1 or 2, wherein the curing based on irradiation with radiation is based on a cumulative light amount of 3000mJ/cm 2 Is cured by ultraviolet irradiation.
4. The photocurable adhesive sheet according to any one of claims 1-3, wherein the cured adhesive layer has a storage modulus (G' a 10) of 90kPa or more at 10 ℃.
5. The photocurable adhesive sheet according to any one of claims 1-4, wherein the adhesive layer contains a base polymer, a crosslinking agent, and a photopolymerization initiator.
6. The photocurable adhesive sheet according to claim 5, wherein the base polymer contains an acrylic polymer.
7. The photocurable adhesive sheet according to claim 5 or 6, wherein the crosslinking agent contains a polyfunctional (meth) acrylate.
8. The photocurable adhesive sheet according to any one of claims 5-7, wherein the adhesive layer is a single layer formed from the base polymer having 2 opposing major faces,
when the single adhesive layer is divided into two parts in the thickness direction,
The concentration of the crosslinking agent and/or the photopolymerization initiator in one of the 2 main faces, that is, the region to which the 1 st main face belongs, is different from the concentration of the crosslinking agent and/or the photopolymerization initiator in the other one, that is, the region to which the 2 nd main face belongs.
9. The photocurable adhesive sheet according to claim 8, wherein the adhesive layer of the single layer has a concentration gradient of the crosslinking agent and/or the photopolymerization initiator in a thickness direction.
10. A method for producing the photocurable adhesive sheet according to claim 8 or 9, comprising the steps of:
an adhesive layer forming a single layer formed of the base polymer,
The layer of adhesive is allowed to cure,
preparing a solution of the crosslinking agent and/or the photopolymerization initiator,
applying the solution to one side of the cured adhesive layer, allowing the crosslinking agent and/or the photopolymerization initiator contained in the solution to penetrate from the one side of the adhesive layer in the thickness direction,
the adhesive layer is dried.
11. The photocurable adhesive sheet according to any one of claims 1-4, wherein the adhesive layer comprises a polymer having a benzophenone structure in a side chain.
12. The photocurable adhesive sheet according to claim 11, wherein the adhesive layer is a cured product of an adhesive composition containing an ethylenically unsaturated compound and a polymer having a benzophenone structure in a side chain.
13. A self-luminous display device, comprising:
display panel having a plurality of light emitting elements arranged on one surface of substrate, and method for manufacturing the same
The photocurable adhesive sheet according to any one of claim 1-9, 11 and 12,
the light emitting element of the display panel is sealed by the adhesive layer of the photocurable adhesive sheet,
the adhesive layer is cured.
14. The self-luminous display device according to claim 13, wherein the display panel is an LED panel in which a plurality of LED chips are arranged on one side of a substrate.
15. A method of manufacturing the self-luminous display device according to claim 13 or 14, comprising the steps of:
laminating the adhesive layer of the photocurable adhesive sheet according to any one of claims 1 to 9, 11 and 12 on a display panel having a plurality of light-emitting elements arranged on one surface of a substrate, and sealing the light-emitting elements with the adhesive layer; and
and a step of curing the adhesive layer by irradiation with radiation.
16. The method of manufacturing according to claim 15, wherein the radiation is ultraviolet.
CN202180052956.4A 2020-08-28 2021-08-24 Photocurable adhesive sheet Pending CN116096828A (en)

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PCT/JP2021/030986 WO2022045130A1 (en) 2020-08-28 2021-08-24 Photocurable adhesive sheet

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WO2023074556A1 (en) * 2021-10-27 2023-05-04 日東電工株式会社 Optical pressure-sensitive adhesive sheet

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