Polymerization method and method for curing adhesive

Abstract

Provided is a polymerization method applied for the curing or production of an adhesive. The polymerization method includes subjecting an object to be treated, which contains a monomer having a radically polymerizable functional group and / or a polymer having a radically polymerizable functional group, to an active energy line irradiation treatment including a heating / active energy line (AEL) treatment in which the object is irradiated with AEL while being subjected to heating.

Description

Polymerization method and adhesive curing method

[0001] The present invention relates to a polymerization method and a method for curing a pressure-sensitive adhesive using the polymerization method. This application claims priority to Japanese Patent Application No. 2023-163143, filed on September 26, 2023, the entire contents of which are incorporated herein by reference.

[0002] Generally, adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are soft solids (viscoelastic bodies) at temperatures near room temperature and easily adhere to adherends under pressure. Because of their ease of application to adherends, adhesives are widely used in a variety of fields in the form of supported adhesive sheets having an adhesive layer on a support, or in the form of supportless adhesive sheets without a support. Some such adhesives are used by adhering to an adherend and are removed from the adherend after their adhesive purpose is completed. For example, in the backgrinding process in which the backside of a semiconductor wafer is ground to a desired thickness, adhesive sheets are used to temporarily fix the semiconductor wafer to a processing table and to protect the surface opposite the grinding surface (e.g., Patent Document 1).

[0003] Japanese Patent Application Publication No. 2017-212441

[0004] Pressure-sensitive adhesive sheets used in applications where they are peeled and removed from an adherend are required to exhibit good adhesion while adhering to the adherend, and to be easily peelable from the adherend after their intended purpose has been fulfilled. Pressure-sensitive adhesives with such properties can be used that maintain a certain adhesive strength during adhesion and fixation while being able to reduce their peel strength at an appropriate time. Examples of pressure-sensitive adhesives that can reduce the peel strength include UV-curable pressure-sensitive adhesives that contain a component having a radically polymerizable functional group and a photopolymerization initiator, and that cure when irradiated with UV light through reaction (polymerization) of the radically polymerizable functional group. These UV-irradiation-peelable pressure-sensitive adhesives are known, and are designed to reduce their peel strength by UV irradiation after application to an adherend. However, UV-irradiation-peelable pressure-sensitive adhesives can sometimes cause contamination of the adherend surface after peeling due to adhesive residue (glue residue), for example, when applied to an adherend having an uneven or stepped surface, or when applied to such an adherend and then subjected to a heating process after UV irradiation and then peeled from the adherend.

[0005] The present inventors believed that improving the curability of active energy ray-peelable pressure-sensitive adhesives, such as ultraviolet radiation-peelable pressure-sensitive adhesives, could reduce contamination of the adherend surface, and conducted extensive research into methods for curing active energy ray-peelable pressure-sensitive adhesives. As a result, they found that by subjecting an active energy ray-peelable pressure-sensitive adhesive containing a component having a radically polymerizable functional group to a specific treatment, the reaction rate of the radically polymerizable functional group can be improved, resulting in better curing of the pressure-sensitive adhesive. They also found that the specific treatment is useful in the production of pressure-sensitive adhesives, and thus completed the present invention.

[0006] This specification provides a polymerization method applicable to the curing or production of pressure-sensitive adhesives. The polymerization method includes subjecting a processing object containing at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment, including a heating / AEL treatment, in which the processing object is irradiated with active energy rays (hereinafter, sometimes referred to as "AEL") while applying heat. The active energy ray irradiation treatment including the heating / AEL treatment can improve the reaction rate of the radically polymerizable functional groups contained in the processing object, and can further reduce the amount of residual radically polymerizable functional groups compared to, for example, when only active energy ray irradiation is performed. The active energy rays can be non-thermal energy rays such as ultraviolet rays or electron beams. The technology disclosed herein can be preferably implemented in an embodiment in which the active energy rays irradiated while applying heat in the heating / AEL treatment are ultraviolet (UV) rays, i.e., in an embodiment in which the heating / AEL treatment is a "heating / UV treatment." In this embodiment, the active energy ray irradiation treatment including the heating / AEL treatment can be an active energy ray irradiation treatment including a heating / UV treatment (for example, a UV irradiation treatment including a heating / UV treatment).

[0007] The treatment object may be a pressure-sensitive adhesive forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet. The method disclosed herein can improve the reactivity of radically polymerizable functional groups contained in the pressure-sensitive adhesive, thereby enabling the pressure-sensitive adhesive to be cured more effectively. The method disclosed herein can be applied, for example, to a pressure-sensitive adhesive having a Young's modulus [MPa] of 0.005 MPa or more before being subjected to an active energy ray irradiation treatment including a heating / AEL treatment, thereby enabling the pressure-sensitive adhesive to be cured more effectively. In some embodiments, the active energy ray irradiation treatment including a heating / AEL treatment is preferably performed so that the Young's modulus [MPa] of the cured product obtained by subjecting the treatment object to the active energy ray irradiation treatment including a heating / AEL treatment is 1.2 times or more the Young's modulus [MPa] of the cured product obtained by irradiating the treatment object with active energy rays under the same conditions except that heat is not applied to the treatment object.

[0008] In some embodiments, the PSA sheet has a peel force reduction rate calculated by the following formula of greater than 20%. The method disclosed herein can be preferably applied to the polymerization of radically polymerizable functional groups contained in a PSA exhibiting such properties: Peel force reduction rate [%] = (1 - F1 / F0) x ​​100 (where F0 is the initial peel force [N / 20 mm] of the PSA sheet relative to a glass plate, and F1 is the post-treatment peel force [N / 20 mm] measured after the PSA sheet is attached to a glass plate and subjected to an active energy ray irradiation treatment including the heating / AEL treatment.)

[0009] In some embodiments, the object to be treated includes a radically polymerizable functional group containing a carbon-carbon double bond as the radically polymerizable functional group. In such embodiments, the active energy ray irradiation treatment including the heating / AEL treatment can be carried out so that, in measurement of the amount of carbon-carbon double bonds based on peak intensity ratios in microscopic Raman analysis, the amount of carbon-carbon double bonds remaining in a cured product obtained by subjecting the object to the active energy ray irradiation treatment including the heating / AEL treatment is 5% or more less than the amount of carbon-carbon double bonds remaining in a cured product obtained by irradiating the object to be treated with active energy rays under the same conditions except for not heating the object to be treated. This allows the object to be cured more effectively.

[0010] This specification also provides a method for producing a pressure-sensitive adhesive sheet. The method for producing the pressure-sensitive adhesive sheet includes subjecting a pressure-sensitive adhesive containing at least one of a monomer and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment, including a heating / AEL treatment (e.g., a heating / UV treatment) in which the pressure-sensitive adhesive is irradiated with active energy rays (AEL) while being heated. The active energy ray irradiation treatment including the heating / AEL treatment can, for example, more effectively cure the pressure-sensitive adhesive than when the pressure-sensitive adhesive is subjected to only an active energy ray irradiation treatment. The production method can produce a pressure-sensitive adhesive sheet having such a well-cured pressure-sensitive adhesive (a product cured by the active energy ray irradiation). Such a pressure-sensitive adhesive sheet can exhibit excellent non-contamination properties (e.g., no adhesive residue) on the surface of an adherend.

[0011] This specification also provides a method for curing a pressure-sensitive adhesive. The curing method includes subjecting a pressure-sensitive adhesive containing at least one of a monomer and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment (e.g., a heating / UV treatment) in which the pressure-sensitive adhesive is heated while being irradiated with active energy rays (AEL). The curing method can cure the pressure-sensitive adhesive more effectively than, for example, when the pressure-sensitive adhesive is subjected to only an active energy ray irradiation treatment.

[0012] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0013] 1 is a cross-sectional view schematically showing an example of an adhesive sheet.

[0014] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic to clearly explain the present invention and do not necessarily accurately represent the size or scale of the actual product provided.

[0015] In this specification, the "base polymer" of a PSA refers to the main rubbery polymer component contained in the PSA. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, unless otherwise specified, the "main component" refers to a component that accounts for more than 50% by weight.

[0016] In this specification, the term "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule. In this specification, the acrylic polymer is defined as a polymer containing a monomer unit derived from an acrylic monomer.

[0017] Furthermore, in this specification, "acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl group" refers to an acryloyl group and a methacryloyl group in a comprehensive sense. Therefore, the concept of acrylic monomer here can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" refers to acrylic acid and methacrylic acid in a comprehensive sense, and "(meth)acrylate" refers to acrylate and methacrylate in a comprehensive sense. The same applies to other similar terms.

[0018] In this specification, the term "radically polymerizable functional group" refers to a functional group that can be radically polymerized under appropriate conditions. Representative examples of radically polymerizable functional groups include ethylenically unsaturated groups such as acryloyl, methacryloyl, vinyl, and allyl groups.

[0019] In this specification, "active energy rays" refers to energy rays having energy capable of inducing chemical reactions such as polymerization reactions, crosslinking reactions, and decomposition of initiators. Examples of active energy rays referred to here include light and radiation (typically ionizing radiation). Specific examples of active energy rays include ultraviolet rays, visible light rays, infrared rays, X-rays, gamma rays, electron beams, and neutron beams. Furthermore, in this specification, the term "non-thermal energy rays" among active energy rays is a concept that does not include infrared rays, and specific examples include ultraviolet rays, visible light rays (typically light with a wavelength of 780 nm to 380 nm), X-rays, gamma rays, electron beams, and neutron beams.

[0020] In this specification, "weight" may be read as "mass." For example, "% by weight" may be read as "% by mass," and "parts by weight" may be read as "parts by mass."

[0021] <Heating / AEL Treatment> This specification discloses a polymerization method that includes subjecting a processing object containing a component having a radically polymerizable functional group to an active energy ray irradiation treatment, including a heating / AEL treatment, in which heat is applied to the object while irradiating the object with active energy rays (AEL). The object to be subjected to the heating / AEL treatment (hereinafter also referred to as the "processing object") contains, as the component having the radically polymerizable functional group, at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group. The processing object may contain, as the component having the radically polymerizable functional group, a monomer having a radically polymerizable functional group, a polymer having a radically polymerizable functional group, or both. The processing object may further contain, in addition to at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group, a polymer not having a radically polymerizable functional group.

[0022] The active energy ray irradiation in the active energy ray irradiation treatment including the heating / AEL treatment can be carried out by selecting an appropriate light source from among known light sources depending on the composition of the object to be treated (e.g., the presence or absence and type of photopolymerization initiator, as described below) and the intended use. For example, in an embodiment in which the active energy ray irradiation treatment including the heating / AEL treatment includes ultraviolet (UV) irradiation, examples of known light sources that can be used for the UV irradiation include, but are not limited to, high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, UV LED light sources, etc. In some embodiments, it is preferable to cover the object to be treated with a resin film (e.g., a polyethylene terephthalate (PET) film) or the like and irradiate the active energy ray through the resin film. This can prevent or suppress oxygen-induced inhibition of the reaction of the radically polymerizable functional group. As another means for preventing or suppressing reaction inhibition by oxygen, for example, active energy ray irradiation may be carried out under an inert gas atmosphere.

[0023] The illuminance and time of active energy ray irradiation can be appropriately set so as to obtain a desired treatment effect. Although not particularly limited, the active energy ray irradiation time in the active energy ray irradiation treatment including the heating / AEL treatment is, from the viewpoint of productivity and the like, suitably, for example, 1 hour or less, advantageously 30 minutes or less, preferably 10 minutes or less, and more preferably 5 minutes or less. From the viewpoint of ease of control of the heating / AEL treatment and the like, the active energy ray irradiation time is usually suitably 1 second or more, preferably 5 seconds or more, and may be, for example, 10 seconds or more, 30 seconds or more, or 1 minute or more. Furthermore, in an embodiment in which the active energy ray irradiation treatment including the heating / AEL treatment includes UV irradiation (for example, an embodiment in which the heating / AEL treatment is a heating / UV treatment), the integrated light amount supplied to the treatment object by the UV irradiation is, for example, 10 mJ / cm ２ More than 10000mJ / cm ２ In some embodiments, the integrated light dose can be set appropriately within a range of, for example, 100 mJ / cm. ２ Above, 300mJ / cm ２ or more than 500 mJ / cm ２or more, and 7000 mJ / cm ２ Below, 5000mJ / cm ２ Below, 2500mJ / cm ２ Below, 1000mJ / cm ２ or less than 800 mJ / cm ２ It can be as follows:

[0024] In the technology disclosed herein (which may include polymerization methods, pressure-sensitive adhesive curing methods, pressure-sensitive adhesive manufacturing methods, pressure-sensitive adhesive sheet manufacturing methods, etc.; the same applies hereinafter unless otherwise specified), the phrase "irradiating with active energy rays while applying heat" in the heating / AEL treatment refers to applying other heating means to the object to be treated in addition to the active energy ray irradiation. Therefore, the concept of "other heating means" (hereinafter also referred to as "external heating means") does not include temperature increases in the object to be treated that are solely due to the active energy ray irradiation (e.g., radiation from an active energy ray source, temperature increases due to heat generated by the reaction of radically polymerizable functional groups due to the active energy ray irradiation, etc.). The external heating means may be one type that applies heat to the object to be treated by one or more of thermal conduction, convection, and radiation, either singly or in combination. Specific examples of external heating means include, but are not limited to, hot plates, hot air heaters, infrared heaters, etc. In some embodiments, external heating means other than infrared heaters may be used to avoid competition with the active energy rays irradiated during the heating / AEL treatment.

[0025] The heating temperature and heating time by the external heating means can be appropriately set so as to obtain the desired treatment effect. The heating temperature can be, for example, 30°C or higher. From the viewpoint of obtaining a higher effect, it is advantageous to set it to 35°C or higher, preferably 40°C or higher (e.g., above 40°C), more preferably 45°C or higher, and may be 50°C or higher, or may be 55°C or higher. Furthermore, the heating temperature can be, for example, 200°C or lower, and is usually suitably 150°C or lower, and can be, for example, 100°C or lower, 90°C or lower, 80°C or lower, or 70°C or lower. Here, the heating temperature by the external heating means refers to the temperature applied to the treatment object by the external heating means alone. The heating temperature is usually understood to be the set temperature of the device used for external heating (e.g., a hot plate). When the set temperature of the equipment cannot be determined, a 50 μm-thick PET film can be heated instead of the object to be treated using only the external heating means (i.e., without irradiating it with active energy rays), the temperature of the PET film can be measured, and the measured temperature can be used as the heating temperature by the external heating means. From the viewpoint of productivity, etc., the heating time is suitably, for example, 1 hour or less, advantageously 30 minutes or less, preferably 10 minutes or less, and more preferably 5 minutes or less. From the viewpoint of ease of control of the heating / AEL treatment, etc., the heating time is usually suitably 1 second or more, preferably 5 seconds or more, and may be, for example, 10 seconds or more, 30 seconds or more, or 1 minute or more.

[0026] In the technology disclosed herein, the time for performing the heating / AEL treatment, i.e., the time for simultaneously performing heating by an external heating means and irradiating with active energy rays, can be appropriately set so as to obtain the desired treatment effect. In some embodiments, the time for performing the heating / AEL treatment is, for example, suitably 1 hour or less, advantageously 30 minutes or less, preferably 10 minutes or less, and more preferably 5 minutes or less, from the viewpoint of productivity, etc. Furthermore, the time for performing the heating / AEL treatment is usually suitably 1 second or more, preferably 5 seconds or more, from the viewpoint of ease of control of the heating / AEL treatment, etc., and may be, for example, 10 seconds or more, 30 seconds or more, or 1 minute or more.

[0027] In some embodiments of the technology disclosed herein, the active energy ray irradiation treatment including the heating / AEL treatment may include a treatment in which only active energy ray irradiation (preferably non-thermal energy ray irradiation, for example, UV irradiation) is performed on the treatment object before and / or after the heating / AEL treatment, either consecutively with the heating / AEL treatment or at an interval from the heating / AEL treatment. The "active energy ray irradiation time in the active energy ray irradiation treatment including the heating / AEL treatment" exemplified above refers to the time during which at least the active energy ray is irradiated on the treatment object, and may be the total time of the time during which heating by an external heating means and active energy ray irradiation are performed simultaneously (i.e., the heating / AEL treatment time) and the time during which only active energy ray irradiation is performed. The above-mentioned examples of the "active energy ray irradiation time in the active energy ray irradiation treatment including the heating / AEL treatment" may also be applied to the examples of the heating / AEL treatment time of the treatment object. Similarly, the "integrated amount of light supplied to the treatment object in the active energy ray irradiation treatment including the heating / AEL treatment" exemplified above may be the sum of the integrated amount of light supplied to the treatment object during the time when heating by the external heating means and active energy ray irradiation are performed simultaneously (i.e., by the heating / AEL treatment) and the integrated amount of light supplied to the treatment object during the time when only active energy ray irradiation is performed. Each of the examples of "integrated amount of light supplied to the treatment object by the UV irradiation in an aspect where the active energy ray irradiation treatment including the heating / AEL treatment includes UV irradiation" above may also be applied to the examples of integrated amount of light supplied to the treatment object during the time when the heating / UV treatment is performed as the heating / AEL treatment (i.e., by the heating / UV treatment).

[0028] Furthermore, in the technology disclosed herein, it is not prohibited to subject the object to heating alone before and / or after the heating / AEL treatment, either consecutively with the heating / AEL treatment or at an interval therebetween. For example, the active energy ray irradiation treatment including the heating / AEL treatment may be performed in such a manner that the object to be treated is continuously heated for a predetermined time while irradiating it with active energy rays once or twice or more times during the predetermined time. The heating time exemplified above is the time during which the object to be treated is at least heated, and may be the total time of the time during which heating by an external heating means and active energy ray irradiation are performed simultaneously (heating / AEL treatment time) and the time during which only heating is performed.

[0029] (Amount of Carbon-Carbon Double Bonds) In some embodiments of the technology disclosed herein, the treatment object may be a treatment object that includes a radically polymerizable functional group containing a carbon-carbon double bond as the radically polymerizable functional group. In such embodiments, the active energy ray irradiation treatment including the heating / AEL treatment is performed such that, in a measurement of the amount of carbon-carbon double bonds (C=C amount) based on a peak intensity ratio in a microscopic Raman analysis, the amount of carbon-carbon double bonds D1 remaining in a cured product obtained by subjecting the treatment object to the active energy ray irradiation treatment including the heating / AEL treatment is equal to or greater than the amount of carbon-carbon double bonds D1 remaining in a cured product obtained by irradiating the treatment object with active energy rays under the same conditions except for not heating the treatment object (hereinafter also referred to as the "control amount of carbon-carbon double bonds") Ｒ This indicates that, compared with the active energy ray irradiation treatment without external heating, the active energy ray irradiation treatment including heating / AEL treatment causes the carbon-carbon double bonds in the treatment object to react at a higher reaction rate, and the amount of residual C=C is further reduced. The carbon-carbon double bond amount D1 can be calculated by, for example, comparing the control carbon-carbon double bond amount D1 Ｒ That is, the carbon-carbon double bond amount D1 is preferably 5% or more less than the control carbon-carbon double bond amount D1 ＲWhen converted into a relative value with respect to 100%, the relative value (hereinafter also referred to as "relative carbon-carbon double bond amount") is preferably 95% or less. From the viewpoint of better exerting the effects of the active energy ray irradiation treatment including the heating / AEL treatment, in some embodiments, the relative carbon-carbon double bond amount is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, and may be 75% or less, 70% or less, or 65% or less. The lower limit of the relative carbon-carbon double bond amount is not particularly limited and may be 0%, typically 5% or more, 10% or more, 20% or more, or 30% or more. Carbon-carbon double bond amount D1 and control carbon-carbon double bond amount D1 Ｒ is determined by the method described in the Examples below.

[0030] According to the technology disclosed herein, by subjecting the object to be treated to an active energy ray irradiation treatment including a heating / AEL treatment, it is possible to improve the reaction rate of the radical polymerizable functional groups contained in the object to be treated, compared to when the object to be treated is irradiated with active energy rays under the same conditions except that the object is not heated. The reason for obtaining such an effect is not particularly limited, but it is thought that by simultaneously performing heating by an external heating means and active energy ray irradiation in the heating / AEL treatment, the fluidity of the object to be treated and the mobility of the radical polymerizable functional groups and the polymer having the radical polymerizable functional groups (preferably the side chains of the polymer) within the object to be treated are improved, which contributes to the improvement of the reaction rate.

[0031] <Curing Pressure-Sensitive Adhesive> The polymerization method disclosed herein can be used, for example, as a method for curing a pressure-sensitive adhesive. The pressure-sensitive adhesive contains at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group, and thus has active energy ray curability. By applying a method including subjecting such a pressure-sensitive adhesive to an active energy ray irradiation treatment including a heating / AEL treatment, the reaction rate of the radically polymerizable functional group contained in the pressure-sensitive adhesive can be increased, resulting in better curing. The pressure-sensitive adhesive can be, for example, a pressure-sensitive adhesive that constitutes a pressure-sensitive adhesive sheet. The technology disclosed herein can be preferably implemented in an embodiment in which the pressure-sensitive adhesive to be treated is a pressure-sensitive adhesive that forms a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet.

[0032] The PSA sheet may be a substrate-attached PSA sheet having the PSA layer on one or both sides of a non-releasable substrate (support substrate), or may be a substrate-less PSA sheet (i.e., a PSA sheet without a non-releasable substrate; typically, a PSA sheet consisting of a PSA layer) in which the PSA layer is held by a release liner. The concept of PSA sheet here may include what are called PSA tapes, PSA labels, PSA films, etc. The PSA sheet disclosed herein may be in the form of a roll or sheets. Alternatively, it may be a PSA sheet processed into various shapes.

[0033] An example of the cross-sectional structure of a PSA sheet is shown in Figure 1. As shown in Figure 1, PSA sheet 1 has an adhesive surface 1A and is in the form of a single-sided PSA sheet in which a PSA layer 20 is provided on one surface 10A of a sheet-like base material layer (supporting substrate) 10. The PSA sheet 1 is used by attaching the surface 20A of the PSA layer 20, which is the adhesive surface 1A, to an adherend. The back surface 10B of the base material layer 10 (the surface opposite to the one surface 10A) also serves as the back surface 1B of the PSA sheet 1 and constitutes the outer surface of the PSA sheet 1. Before use (i.e., before attachment to an adherend), the PSA sheet 1 may be in the form of a release-liner-attached PSA sheet 50 in which the adhesive surface 1A is protected by a release liner 30, the side of which facing at least the PSA layer 20 serves as a release surface. Alternatively, the adhesive sheet may be in a form in which the other surface (back surface) 10B of the base layer 10 is the release surface, and when the adhesive sheet 1 is rolled up, the adhesive layer 20 abuts against the back surface, thereby protecting its surface (adhesive surface 1A).

[0034] The release liner is not particularly limited, and examples thereof include release liners in which the surface of a liner substrate such as a resin film or paper has been release-treated, and release liners made of low-adhesion materials such as fluorine-based polymers (e.g., polytetrafluoroethylene) and polyolefin-based resins (e.g., polyethylene and polypropylene). For the release treatment, for example, a silicone-based or long-chain alkyl-based release treating agent can be used. In some embodiments, a release-treated resin film can be preferably used as the release liner.

[0035] (Polymer) In embodiments in which the object to be treated is a pressure-sensitive adhesive, the type of pressure-sensitive adhesive is not particularly limited. The pressure-sensitive adhesive may contain one or more of various rubber-like polymers that can be used in the field of pressure-sensitive adhesives, such as acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-based polymers. The polymer may be used as a base polymer in the pressure-sensitive adhesive and function as a structural polymer that shapes the pressure-sensitive adhesive. From the viewpoint of ease of adjusting the content of radically polymerizable functional groups, the technology disclosed herein is preferably applied to the curing of pressure-sensitive adhesives that contain acrylic polymers as the base polymer (acrylic pressure-sensitive adhesives). The following mainly describes embodiments in which the object to be treated is an acrylic pressure-sensitive adhesive, but it is not intended to limit the object to be treated in the technology disclosed herein to acrylic pressure-sensitive adhesives.

[0036] (Acrylic Polymer) In some embodiments, the acrylic polymer is an acrylic polymer in which more than 50% by weight of the monomer components constituting the polymer is an acrylic monomer. The proportion of the acrylic monomer in the monomer components is suitably 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 85% by weight or more, and may be, for example, 90% by weight or more. The upper limit of the proportion of the acrylic monomer in the monomer components constituting the acrylic polymer is 100% by weight, and the proportion of the acrylic monomer may be, for example, 98% by weight or less, 95% by weight or less, or 92% by weight or less, from the viewpoint of obtaining the effect of using a non-acrylic monomer. The acrylic monomer may be used alone or in combination of two or more.

[0037] In some preferred embodiments, the monomer component includes an alkoxy group-containing (meth)acrylate. Acrylic polymers containing an alkoxy group-containing (meth)acrylate as a monomer component are likely to provide good adhesion in the initial stage (i.e., before heating / AEL treatment) and to produce a pressure-sensitive adhesive layer that can effectively reduce peel strength through heating / AEL treatment. Furthermore, in embodiments in which the treatment target contains a polymer and a monomer (hereinafter, sometimes referred to as a "compounded monomer" to distinguish it from the monomer component used in synthesizing the polymer), good compatibility with the monomer (e.g., a polyfunctional monomer, as described below) is likely to be achieved. The alkoxy group-containing (meth)acrylate can be used alone or in combination of two or more. The acrylic polymer containing an alkoxy group-containing (meth)acrylate as a monomer component may be a polymer without a radically polymerizable functional group or a polymer with a radically polymerizable functional group.

[0038] Examples of alkoxy group-containing (meth)acrylates include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; and alkoxy(poly)alkylene glycol (meth)acrylates such as methoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, ethoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate. Of these, alkoxyalkyl (meth)acrylates are preferred, and among these, alkoxyalkyl (meth)acrylates having an alkoxy group with 1 to 4 carbon atoms (e.g., 1, 2, or 3 carbon atoms) are more preferred, with methoxyethyl (meth)acrylate being particularly preferred.

[0039] The content of the alkoxy group-containing (meth)acrylate in the monomer component constituting the acrylic polymer is not particularly limited. From the viewpoint of effectively obtaining the effects of using the alkoxy group-containing (meth)acrylate, the content of the alkoxy group-containing (meth)acrylate in the monomer component is usually about 1 wt% or more, for example, 10 wt% or more, 30 wt% or more, or 50 wt% or more. In some embodiments, from the viewpoint of adhesive properties such as adhesive strength and compatibility with the blended monomer, the content of the alkoxy group-containing (meth)acrylate in the monomer component is, for example, more than 50 wt%, preferably 60 wt% or more, more preferably 70 wt% or more, and even more preferably 80 wt% or more. The upper limit of the content of the alkoxy group-containing (meth)acrylate in the monomer component is 100 wt%. From the viewpoint of obtaining the effects of other copolymerizable monomers, such as functional group-containing monomers, in some embodiments, the content of the alkoxy group-containing (meth)acrylate is advantageously approximately 99 wt% or less, and may be 95 wt% or less, 93 wt% or less, or 90 wt% or less. In other embodiments, the content of the alkoxy group-containing (meth)acrylate may be approximately 80 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 50 wt% or less (e.g., less than 50 wt%), 30 wt% or less, 10 wt% or less, 5 wt% or less, 1 wt% or less, or 0.1 wt% or less. The monomer component may be substantially free of alkoxy group-containing (meth)acrylate.

[0040] In some other embodiments, the monomer component constituting the acrylic polymer may include a chain alkyl(meth)acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Hereinafter, a chain alkyl(meth)acrylate having an alkyl group having X to Y carbon atoms at the ester terminal will be referred to as "C Ｘ－ＹIn this specification, the term "chain alkyl (meth)acrylate" is used to mean both straight chain and branched chain. The chain alkyl (meth)acrylates can be used singly or in combination of two or more.

[0041] C １－２０ Non-limiting examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate. (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and the like.

[0042] C is a monomer component constituting an acrylic polymer. １－２０ In some embodiments using alkyl (meth)acrylates, C １－２０ As the alkyl (meth)acrylate, at least C ４－２０ It is preferable to use alkyl (meth)acrylate, and at least C ４－１８ It is more preferred to use alkyl (meth)acrylates. １－２０ As the alkyl (meth)acrylate, C ４－８ It is preferable to use alkyl (meth)acrylate. ４－８The use of alkyl acrylates is more preferred. ４－８ The alkyl (meth)acrylates can be used alone or in combination of two or more. ４－８ The use of alkyl (meth)acrylate tends to make it easier to obtain good adhesive properties (adhesive strength, etc.). For example, an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the monomer component is preferred, and an acrylic polymer containing at least 2EHA is particularly preferred. １－２０ In some other embodiments using alkyl (meth)acrylates, C ７－１２ Alkyl (meth)acrylates are preferably used. ７－１２ The alkyl (meth)acrylates can be used alone or in combination of two or more. ７－１２ Examples of alkyl (meth)acrylates include C ７－１０ Alkyl acrylates are preferred, C ７－９ Alkyl acrylate is more preferred, C ８ Alkyl acrylates are more preferred.

[0043] C is a monomer component constituting an acrylic polymer. １－２０ In the embodiment in which alkyl (meth)acrylate is used, １－２０ The content of alkyl (meth)acrylate is not particularly limited. １－２０ In order to effectively obtain the effect of using alkyl (meth)acrylate, in some embodiments, C １－２０ The content of alkyl (meth)acrylate is usually about 1% by weight or more, and may be, for example, 10% by weight or more, 30% by weight or more, 50% by weight or more (e.g., more than 50% by weight), 60% by weight or more, 70% by weight or more, or 80% by weight or more. １－２０ The upper limit of the content of alkyl (meth)acrylate is 100% by weight. In some embodiments, in order to obtain the effect of other copolymerizable monomers such as functional group-containing monomers, １－２０The content of alkyl (meth)acrylate is advantageously about 99% by weight or less, and may be 95% by weight or less, 93% by weight or less, 90% by weight or less, 70% by weight or less, 50% by weight or less (e.g., less than 50% by weight), 30% by weight or less, 10% by weight or less, 5% by weight or less, 1% by weight or less, or 0.1% by weight or less. １－２０ The monomer component may be substantially free of alkyl (meth)acrylate. １－２０ The range of the content of alkyl (meth)acrylate is １－２０ The above-mentioned C included in the concept of alkyl (meth)acrylate ４－２０ Alkyl (meth)acrylate, C ４－１８ Alkyl (meth)acrylate, C ４－８ Alkyl (meth)acrylate, C ４－８ Alkyl acrylate, C ７－１２ Alkyl (meth)acrylate, C ７－１０ Alkyl acrylate, C ７－９ Alkyl acrylate, C ８ The content of each of the alkyl acrylate, BA, and 2EHA may be within a range.

[0044] In some embodiments, the monomer components constituting the acrylic polymer preferably include other monomers besides the alkoxyalkyl (meth)acrylate and linear alkyl (meth)acrylate. Such other monomers may be monomers (copolymerizable monomers) copolymerizable with the alkoxyalkyl (meth)acrylate and linear alkyl (meth)acrylate. Suitable examples of the other monomers include monomers having polar groups (e.g., carboxyl groups, hydroxyl groups, nitrogen-containing rings, etc.). Monomers having polar groups can be useful for introducing reactive sites with the crosslinking agent described below or for increasing the cohesive strength of the adhesive. Furthermore, monomers having polar groups can be used, for example, to introduce radically polymerizable functional groups (e.g., ethylenically unsaturated groups) into the polymer. The other monomers can be used alone or in combination of two or more.

[0045] Non-limiting specific examples of the other monomers include: Carboxy group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride, etc. Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloyl phosphate, etc. Epoxy group-containing monomers: for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl (meth)acrylate glycidyl ether, allyl glycidyl ether, (meth)acrylic acid glycidyl ether, etc. Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile, etc. Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate, etc.Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-monoalkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-hydroxyalkyl(meth)acrylamides such as N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and others, such as N,N-dimethylaminopropyl(meth)acrylamide, alkoxydiacetone(meth)acrylamide, vinylformamide, and vinylacetamide. Amino group-containing monomers, for example, aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate.Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine Examples of suitable monomers include N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and N-vinylpyridazine (e.g., lactams such as N-vinyl-2-caprolactam). Monomers having a succinimide skeleton include N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyhexamethylenesuccinimide. Maleimides include N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide. Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc. Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Alkoxysilyl group-containing monomers: for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane. Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether. Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc. Olefins: for example, ethylene, butadiene, isoprene, isobutylene, etc. (Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, etc. (Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. Other examples include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols.

[0046] When such other monomers are used, the amount used is not particularly limited, but is suitably 0.01 wt% or more of the total monomer components. From the viewpoint of better demonstrating the effects of using the other monomers, the amount used of the other monomers may be 0.1 wt% or more, or even 0.5 wt% or more of the total monomer components. Furthermore, from the viewpoint of easily balancing the adhesive properties, the amount used of the other monomers is suitably 50 wt% or less (e.g., less than 50 wt%) of the total monomer components, and preferably 40 wt% or less.

[0047] In some embodiments, the monomer component constituting the acrylic polymer may contain a monomer having a nitrogen atom. The use of a monomer having a nitrogen atom can increase the cohesive strength of the PSA and favorably improve the adhesive strength. The monomer having a nitrogen atom can be used alone or in combination of two or more. A suitable example of the monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring. The monomer having a nitrogen atom and the monomer having a nitrogen atom-containing ring can be those exemplified above, and for example, a monomer represented by the general formula (1): In the general formula (1), N-vinyl cyclic amides represented by the formula: 1 is a divalent organic group, specifically -(CH2) ｎ n is an integer of 2 to 7 (preferably 2, 3, or 4). Of these, N-vinyl-2-pyrrolidone (NVP) can be preferably used. Other suitable examples of the monomer having a nitrogen atom include N,N-dialkyl(meth)acrylamides such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; N-monoalkyl(meth)acrylamides such as N-isopropyl(meth)acrylamide; N-hydroxyalkyl(meth)acrylamides such as N-(2-hydroxyethyl)acrylamide (HEAA); N-acryloylmorpholine (ACMO); alkoxydiacetone(meth)acrylamide; vinylformamide; vinylacetamide; and the like. Of these, NVP, HEAA, and ACMO are more preferred.

[0048] The amount of the nitrogen-containing monomer (preferably a monomer having a nitrogen-containing ring) used is not particularly limited and may be, for example, 1% by weight or more, or 3% by weight or more, of the total monomer components. In some embodiments, the amount of the nitrogen-containing monomer used in the monomer components is preferably 5% by weight or more, more preferably 7% by weight or more, and even more preferably 9% by weight or more. In other embodiments, the amount of the nitrogen-containing monomer used in the monomer components may be 10% by weight or more, 12% by weight or more, or 15% by weight or more. Furthermore, the amount of the nitrogen-containing monomer used is suitably, for example, 40% by weight or less, or may be 35% by weight or less, 30% by weight or less, or 25% by weight or less, of the total monomer components. In some embodiments, the amount of the nitrogen-containing monomer used may be, for example, 20% by weight or less, 18% by weight or less, 15% by weight or less, or 12% by weight or less, of the total monomer components.

[0049] In some embodiments, the monomer component may include a hydroxyl group-containing monomer. Use of a hydroxyl group-containing monomer can adjust the cohesive strength and crosslink density of the PSA, thereby improving adhesive strength. Hydroxyl group-containing monomers can also be preferably used as a means for introducing radically polymerizable functional groups (e.g., ethylenically unsaturated groups) into the polymer. Examples of hydroxyl group-containing monomers that can be used include those exemplified above, and preferred examples include hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). One type of hydroxyl group-containing monomer can be used alone, or two or more types can be used in combination.

[0050] When a hydroxyl group-containing monomer is used, the amount used is not particularly limited, and may be, for example, 0.01 wt% or more, 0.1 wt% or more, or 0.5 wt% or more of the total monomer components. In some embodiments, the amount of the hydroxyl group-containing monomer used is 1 wt% or more, more preferably 2 wt% or more, or even 3 wt% or more of the total monomer components. In some preferred embodiments, the amount of the hydroxyl group-containing monomer used is 5 wt% or more, more preferably 7 wt% or more, even more preferably 10 wt% or more, and particularly preferably 12 wt% or more of the total monomer components. Such an amount of the hydroxyl group-containing monomer is suitable when the hydroxyl group-containing monomer is used as a means of introducing a radically polymerizable functional group into the polymer. In some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40 wt% or less of the total monomer components, preferably 30 wt% or less, more preferably 20 wt% or less, and may be 15 wt% or less, 10 wt% or less, or 7 wt% or less.

[0051] In some preferred embodiments, the monomer component of the acrylic polymer uses a monomer having a nitrogen atom (for example, an amide group-containing monomer such as (meth)acrylamide, or a monomer having a nitrogen atom-containing ring such as NVP or ACMO) in combination with a hydroxyl group-containing monomer (for example, HEA, 4HBA) as a monomer having a polar group (polar group-containing monomer). This allows for a good balance between adhesive strength and cohesive strength. In an embodiment in which a monomer having a nitrogen atom and a hydroxyl group-containing monomer are used in combination, the amount A of the monomer having a nitrogen atom is Ｎ and the amount A of hydroxyl group-containing monomer ＯＨ Weight ratio (A Ｎ / A ＯＨ ) is not particularly limited, and may be, for example, 0.1 or more, 0.5 or more, 1.0 or more, 1.2 or more, 1.5 or more, or 1.8 or more. Ｎ / A ＯＨ ) may be, for example, 10 or less, 5 or less, 3 or less, or 2.5 or less.

[0052] In some embodiments, the monomer component may include a carboxyl group-containing monomer. Suitable examples of the carboxyl group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA). The carboxyl group-containing monomer may be used alone or in combination of two or more. For example, AA and MAA may be used in combination.

[0053] In embodiments where a carboxyl group-containing monomer is used, the amount used may be, for example, 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.3 wt% or more, or 0.5 wt% or more of the total monomer components. Furthermore, the amount used of the carboxyl group-containing monomer may be, for example, 15 wt% or less, 10 wt% or less, 5 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less (e.g., less than 1 wt%) of the total monomer components. The monomer components may be substantially free of a carboxyl group-containing monomer.

[0054] Furthermore, when an acrylic polymer having a radically polymerizable functional group (e.g., an ethylenically unsaturated group) described below is used as the polymer, it is preferable to use, as the other monomer, a monomer having a functional group (functional group A) that can react with a functional group (functional group B) of a compound having a radically polymerizable functional group described below. In this embodiment, the type of the other monomer is determined depending on the type of compound. Examples of other monomers having functional group A include carboxyl group-containing monomers, epoxy group-containing monomers, hydroxyl group-containing monomers, and isocyanate group-containing monomers, with hydroxyl group-containing monomers being particularly preferred. By using a hydroxyl group-containing monomer as the other monomer, the acrylic polymer has a hydroxyl group. On the other hand, by using, for example, an isocyanate group-containing monomer as the compound having a radically polymerizable functional group, the hydroxyl group of the acrylic polymer reacts with the isocyanate group of the compound, and a radically polymerizable functional group derived from the compound is introduced into the acrylic polymer.

[0055] Furthermore, when another monomer is used for the purpose of reacting with a compound having a radically polymerizable functional group, the amount of the other monomer (preferably a hydroxyl group-containing monomer) is suitably about 1 wt% or more of the total monomer components, preferably about 5 wt% or more, more preferably about 10 wt% or more, and may be about 12 wt% or more, from the viewpoint of the thermosetting property of the adhesive and adhesive properties such as cohesive strength. Furthermore, from the viewpoint of maintaining good adhesive properties such as adhesive strength, the amount of the other monomer is suitably about 40 wt% or less of the total monomer components, preferably about 30 wt% or less, more preferably about 25 wt% or less, and may be about 20 wt% or less (e.g., 15 wt% or less).

[0056] The acrylic polymer may contain, as another monomer component, a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. The use of a polyfunctional monomer as a monomer component can enhance the cohesive strength of the pressure-sensitive adhesive. The polyfunctional monomer can be used as a crosslinking agent. The polyfunctional monomer is not particularly limited, and, for example, a suitable one from among those exemplified as blended monomers contained in the pressure-sensitive adhesive layer described below can be used alone or in combination of two or more.

[0057] The amount of polyfunctional monomer used is not particularly limited and can be appropriately set so as to achieve the purpose of using the polyfunctional monomer. The amount of polyfunctional monomer used can be approximately 3% by weight or less of the above-mentioned monomer components, preferably approximately 2% by weight or less, and more preferably approximately 1% by weight or less (for example, approximately 0.5% by weight or less). When using a polyfunctional monomer, the lower limit of the amount used is not particularly limited as long as it is greater than 0% by weight. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of polyfunctional monomer used to approximately 0.001% by weight or more (for example, approximately 0.01% by weight or more) of the monomer components.

[0058] The method for obtaining the polymer (e.g., acrylic polymer) contained in the pressure-sensitive adhesive to be treated is not particularly limited, and various polymerization methods known as synthesis techniques in the field of pressure-sensitive adhesives, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization can be preferably employed. The monomer supply method for solution polymerization can be appropriately selected from a batch charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, and the like. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

[0059] The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixed solvent of two or more selected from aromatic compounds (typically aromatic hydrocarbons) such as toluene, acetate esters such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane, halogenated alkanes such as 1,2-dichloroethane, lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol, ethers such as tert-butyl methyl ether, and ketones such as methyl ethyl ketone can be used.

[0060] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method.For example, thermal polymerization initiators such as azo-based polymerization initiators, peroxide-based polymerization initiators, redox-based polymerization initiators formed by a combination of peroxide and a reducing agent, and substituted ethane-based polymerization initiators, as well as those described below as photopolymerization initiators that can be contained in the pressure-sensitive adhesive layer, can be mentioned.The polymerization initiator can be used alone or in combination of two or more.

[0061] The amount of the polymerization initiator used is not particularly limited and may be a normal amount depending on the polymerization method, polymerization mode, etc. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, e.g., about 0.01 to 1 part by weight) of the polymerization initiator can be used per 100 parts by weight of all monomer components to be polymerized.

[0062] (Polymer Having Radically Polymerizable Functional Groups) In some embodiments, the pressure-sensitive adhesive to be treated contains a polymer having a radically polymerizable functional group (e.g., an ethylenically unsaturated group such as an acryloyl group, a methacryloyl group, a vinyl group, or an allyl group). The technology disclosed herein can be applied to a pressure-sensitive adhesive containing a polymer having a radically polymerizable functional group to help improve curing of the pressure-sensitive adhesive. This can provide one or more of the effects obtained by curing the pressure-sensitive adhesive (e.g., one or more of the following effects: reduced peel force (easier peeling), increased Young's modulus, reduced amount of remaining radically polymerizable functional groups, suppression of adhesive residue, etc.).

[0063] In some embodiments, the polymer having a radical polymerizable functional group may be, for example, a polymer having an ethylenically unsaturated group (preferably, a polymer having an ethylenically unsaturated group in a side chain). As the monomer component of the polymer having an ethylenically unsaturated group, one or more of the monomer components exemplified for the polymer above may be used within the above content range.

[0064] The amount of ethylenically unsaturated groups in the polymer having ethylenically unsaturated groups is not particularly limited, and is suitably 0.01 mmol per gram of polymer (hereinafter also referred to as mmol / g) or more, and may be 0.1 mmol / g or more, or may be 0.5 mmol / g or more, from the viewpoint of thermosetting properties, etc. The amount of ethylenically unsaturated groups in the polymer is suitably 10.0 mmol / g or less, and may be 5.0 mmol / g or less, 3.0 mmol / g or less, 2.5 mmol / g or less, or may be 2.0 mmol / g or less.

[0065] The amount of ethylenically unsaturated groups in a polymer, for example, when the ethylenically unsaturated groups are (meth)acryloyl groups, is measured by the following method. First, 0.25 mg of the polymer to be measured is dissolved in 50 mL of THF (tetrahydrofuran), and 15 mL of methanol is added to obtain a solution. Next, 10 mL of 4N aqueous sodium hydroxide is added to the solution to obtain a mixed solution. Next, the mixed solution is stirred at a liquid temperature of 40°C for 2 hours. Further, 10.2 mL of 4N methanesulfonic acid solution is added to the mixed solution and stirred. 5 mL of demineralized water is added to the mixture, followed by 2 mL of methanol to prepare a measurement solution. The content of (meth)acrylic acid in the measurement solution is measured by HPLC (High Performance Liquid Chromatography) (absolute calibration curve method), and the content of ethylenically unsaturated groups is calculated. (HPLC measurement conditions) Column: Phenomenex Synergi 4μ Polar-RP 80A (4.6 mm × 250 mm) Column temperature: 40°C Flow rate: 1.0 mL / min Detector wavelength: 210 nm Eluent: THF (for HPLC) 55 / buffer water (containing 0.2% phosphoric acid and 0.2% triethylamine) 45 Aqueous solution injection volume: 5 μL

[0066] An example of a method for measuring the content of ethylenically unsaturated groups other than (meth)acryloyl groups is a method for measuring the bromine number in accordance with JIS K2605: 1996. In this measurement method, the content of ethylenically unsaturated groups other than (meth)acryloyl groups is determined by converting the number of grams of bromine (Br) added to 100 g of the polymer to be measured into the number of moles of bromine (Br) added to 1 g of the polymer.

[0067] The method for introducing a radically polymerizable functional group into a polymer is not particularly limited. For example, a method can be preferably adopted in which a compound having a radically polymerizable functional group and a functional group (functional group B) capable of reacting with the functional group (functional group A) introduced into the acrylic polymer by copolymerization is reacted (typically by condensation or addition reaction) so as not to lose the radically polymerizable functional group. Examples of combinations of functional group A and functional group B include a combination of a carboxy group and an epoxy group, a combination of a carboxy group and an aziridyl group, and a combination of a hydroxyl group and an isocyanate group. Among these, from the viewpoint of reaction traceability, a combination of a hydroxyl group and an isocyanate group is preferred. From the viewpoint of polymer design, etc., a combination in which the acrylic polymer has a hydroxyl group and the compound has an isocyanate group is particularly preferred.

[0068] The compound having the radically polymerizable functional group (e.g., an ethylenically unsaturated group) may have a functional group B that can react with functional group A, as described above. Suitable examples of such compounds include the isocyanate group-containing monomers (isocyanate group-containing compounds) exemplified as other monomers that can be used in the polymerization of acrylic polymers. Of these, 2-(meth)acryloyloxyethyl isocyanate is more preferred. An acrylic polymer having a radically polymerizable functional group can be obtained by reacting the isocyanate group of the isocyanate group-containing compound having a radically polymerizable functional group with the hydroxyl group of the acrylic polymer to form a bond (specifically, a urethane bond).

[0069] The amount of the compound having the radical polymerizable functional group (for example, an isocyanate group-containing monomer) to be added is not particularly limited, but from the viewpoint of reactivity with the functional group A (for example, a hydroxyl group) in the polymer, it is preferable to add the compound having the radical polymerizable functional group in an amount of 100 moles (M Ａ ) and the moles of functional group B (isocyanate group) (M Ｂ ) and the molar ratio (M Ａ / M Ｂ ) can be set to be in the range of about 0.5 to 2 (for example, 1 to 1.5).

[0070] In embodiments in which a polymer having a radically polymerizable functional group (e.g., an ethylenically unsaturated group) is used as the polymer, the content of the polymer having a radically polymerizable functional group in the adhesive layer is not particularly limited. In some embodiments, the amount of the polymer having a radically polymerizable functional group used is suitably approximately 10% by weight or more of the total polymer (specifically, base polymer) contained in the adhesive layer, and may be about 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, 90% by weight or more, 95% by weight or more, or 99 to 100% by weight. In some embodiments, the base polymer contained in the adhesive layer may consist essentially of the polymer having a radically polymerizable functional group.

[0071] In some embodiments, the polymer used is a polymer substantially free of radically polymerizable functional groups, for example, a polymer substantially free of ethylenically unsaturated groups such as acryloyl groups, methacryloyl groups, vinyl groups, and allyl groups (the amount of ethylenically unsaturated groups is less than 0.01 mmol / g). The amount of such polymer used is suitably approximately 10% by weight or more of the total polymer (specifically, base polymer) contained in the pressure-sensitive adhesive layer, and may be about 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, 90% by weight or more, 95% by weight or more, or 99 to 100% by weight. In some embodiments, the base polymer contained in the pressure-sensitive adhesive layer may be substantially composed of a polymer substantially free of ethylenically unsaturated groups.

[0072] The molecular weight of the polymer (for example, an acrylic polymer having or not having a radically polymerizable functional group) is not particularly limited and can be set within an appropriate range depending on the required performance, etc. The weight average molecular weight (Mw) of the polymer is about 1 × 10 ４ It is appropriate that the ratio is equal to or greater than 10×10. ４ By using a polymer having a Mw of a predetermined value or more, a good balance between cohesive strength and adhesive strength can be achieved. In some embodiments, the Mw is 20 × 10 ４ or more, 30 × 10４ More than that is fine, about 40 x 10 ４ More than that is fine, about 50 x 10 ４ or more, for example, about 55×10 ４ The upper limit of the Mw of the polymer is not particularly limited, and may be, for example, about 1000×10 ４ It may be less than or equal to approximately 100×10 ４ Here, Mw refers to a value calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, a model "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) may be used.

[0073] (Monomer) In some embodiments, the pressure-sensitive adhesive layer preferably contains a monomer (compounded monomer) in addition to the polymer. The monomer has a radically polymerizable functional group (typically, an ethylenically unsaturated group). By incorporating the monomer into the pressure-sensitive adhesive layer, at least a portion of the radically polymerizable functional group of the monomer is contained in the pressure-sensitive adhesive layer in an unreacted (pre-reaction) state. The technology disclosed herein can be applied to pressure-sensitive adhesives containing the monomer to help improve curing of the pressure-sensitive adhesive. This can provide the effects obtained by curing the pressure-sensitive adhesive (e.g., one or more effects such as reduced peel force (easy peeling), increased Young's modulus, reduced amount of remaining radically polymerizable functional groups, and suppression of adhesive residue). The above-mentioned monomers can be used alone or in combination of two or more.

[0074] Examples of radically polymerizable functional groups possessed by the above-mentioned monomers include, but are not limited to, ethylenically unsaturated groups such as acryloyl, methacryloyl, vinyl, and allyl groups. Preferred examples of ethylenically unsaturated groups include acryloyl and methacryloyl groups. Of these, acryloyl groups are preferred. Hereinafter, compounds having acryloyl and / or methacryloyl groups may be referred to as acrylic monomers. Furthermore, compounds having vinyl groups may be referred to as vinyl monomers.

[0075] Although not particularly limited, it is appropriate to use a monomer having a molecular weight of 100 or more. In some preferred embodiments, the molecular weight of the monomer may be, for example, 150 or more, 250 or more, 300 or more, 350 or more, 400 or more, 450 or more, or 500 or more. The molecular weight of the monomer is usually approximately 100,000 or less, for example, approximately 10,000 or less (e.g., less than 10,000) is appropriate, and 5,000 or less (e.g., less than 5,000) is preferable, and may be 1,500 or less, 1,000 or less (e.g., less than 1,000), 800 or less, or 600 or less. The use of a monomer having a molecular weight within the above range can be advantageous, for example, in terms of the preparation and coatability of the pressure-sensitive adhesive composition. The above molecular weight is the manufacturer's nominal value or a molecular weight calculated from the molecular structure. For the above-mentioned monomers having a molecular weight equal to or greater than a predetermined value, the value of the weight average molecular weight (Mw) calculated in terms of standard polystyrene obtained by GPC may be used.

[0076] In some preferred embodiments, the monomer used is one that exhibits a weight loss rate of 1% or less (specifically, 1.0% or less) at 180°C in TGA (thermogravimetric analysis) at a temperature increase of 10°C / min. By using a heat-resistant monomer (hereinafter also referred to as a "heat-resistant monomer") that exhibits a weight loss rate of 1% or less at 180°C, the pressure-sensitive adhesive layer exhibits easy peelability due to the inclusion of the monomer (e.g., easy peelability by active energy ray irradiation treatment that may include heating / AEL treatment; hereinafter also referred to as "easy active energy ray peelability") while suppressing outgassing during heating. By using the heat-resistant monomer, for example, it is possible to achieve both easy peelability with active energy ray and reduced outgassing. From the viewpoint of reducing outgassing, in some preferred embodiments, the weight loss rate of the heat-resistant monomer at 180°C is 0.9% or less, more preferably 0.8% or less, even more preferably 0.7% or less, particularly preferably 0.6% or less, and may even be 0.5% or less. The lower limit of the weight loss rate of the heat-resistant monomer when heated to 180°C is theoretically 0%, and in practice may be 0.1% or more, 0.2% or more, or 0.3% or more. As the heat-resistant monomer, trimethylolpropane triacrylate (TMPTA, weight loss rate when reaching 180°C: 1%) and dipentaerythritol hexaacrylate (DPHA, weight loss rate when reaching 180°C: 0.5%) are preferably used. The heat-resistant monomer may be used alone or in combination of two or more.

[0077] Specifically, the weight loss rate of the monomer upon heating at 180°C can be measured using a differential thermal analyzer (manufactured by TA Instruments, trade name "Discovery TGA") under measurement conditions of a temperature increase rate of 10°C / min, an air atmosphere, and a flow rate of 25 mL / min.

[0078] In some preferred embodiments, a polyfunctional monomer is used as the monomer. In this specification, the term "polyfunctional monomer" refers to a compound having two or more radically polymerizable functional groups (typically ethylenically unsaturated groups) in one molecule, and includes compounds known as oligomers. Hereinafter, a compound having two or more acryloyl groups and / or methacryloyl groups may be referred to as a polyfunctional acrylic monomer. Furthermore, a compound having two or more vinyl groups may be referred to as a polyfunctional vinyl monomer.

[0079] In some preferred embodiments, the number of radically polymerizable functional groups contained in one molecule of the polyfunctional monomer may be 3 or more, preferably 4 or more, more preferably 5 or more, and may even be 6 or more. The greater the number of radically polymerizable functional groups in the polyfunctional monomer, the easier it tends to be to obtain releasability. For example, curability by active energy ray irradiation treatment, which may include heating / AEL treatment, tends to be good, and easy releasability by active energy ray irradiation tends to be easily obtained. Furthermore, polyfunctional monomers with a greater number of radically polymerizable functional groups (functional groups) can obtain easy releasability with a relatively small amount of use. This also leads to a reduction in the amount of outgassing derived from the polyfunctional monomer, which is advantageous. The upper limit of the number of radically polymerizable functional groups in one molecule of the polyfunctional monomer is not limited to a specific range and may be, for example, 50 or less, 40 or less, 30 or less, 20 or less, or 15 or less. In some embodiments, the number of radically polymerizable functional groups in one molecule of the polyfunctional monomer may be, for example, 10 or less, 8 or less, or 6 or less. Polyfunctional monomers having the above number of radically polymerizable functional groups tend to easily achieve both good adhesion and easy peelability, and also tend to have excellent storage stability.

[0080] As the polyfunctional monomer, various polyfunctional acrylate monomers or polyfunctional vinyl monomers having two or more radically polymerizable functional groups can be used. Among them, polyfunctional acrylate monomers can be preferably used. Although not particularly limited, polyfunctional acrylate monomers tend to be compatible and easily exhibit desired properties when used in combination with acrylic polymers. The polyfunctional acrylate monomers and polyfunctional vinyl monomers can each be used alone or in combination of two or more.

[0081] Examples of polyfunctional monomers include 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, allyl (meth)acrylate, alkylene oxide-modified bisphenol A di(meth)acrylate, alkylene oxide-modified neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dimethylol dicyclopentadi(meth)acrylate, vinyl (meth)acrylate, and divinylbenzene. Bifunctional monomers: trifunctional monomers such as trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, glycerin propoxy triacrylate, tetramethylolmethane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; and tetrafunctional monomers such as pentaerythritol alkoxy tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate. pentafunctional monomers such as sorbitol penta(meth)acrylate and dipentaerythritol penta(meth)acrylate; hexafunctional monomers such as dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, alkylene oxide-modified hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate; and di- or higher functional monomers such as epoxy acrylate, polyester acrylate and urethane acrylate. Of these, preferred examples include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate and dipentaerythritol hexa(meth)acrylate.Among these, dipentaerythritol hexa(meth)acrylate is particularly preferred.

[0082] In embodiments in which a polyfunctional monomer is contained in the pressure-sensitive adhesive layer, the content of the polyfunctional monomer in the pressure-sensitive adhesive layer is not particularly limited. In some embodiments, the content of the polyfunctional monomer may be approximately 1 part by weight or more, or may be 3 parts by weight or more, relative to 100 parts by weight of the polymer (specifically, the base polymer, preferably an acrylic polymer) contained in the pressure-sensitive adhesive layer. The appropriate amount of the polyfunctional monomer may vary depending on its molecular weight, the number of functional groups, etc., but in some preferred embodiments, from the viewpoint of improving peelability, the content of the polyfunctional monomer is 5 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, or even 9 parts by weight or more, more preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 15 parts by weight or more, even more preferably 20 parts by weight or more, and even more preferably 25 parts by weight or more. The upper limit of the content of the polyfunctional monomer in the pressure-sensitive adhesive layer is not particularly limited and can be set to achieve the desired adhesive properties. In some embodiments, from the viewpoint of compatibility with the polymer (specifically, the base polymer, for example, an acrylic polymer), the amount of the polyfunctional monomer relative to 100 parts by weight of the polymer is suitably approximately 200 parts by weight or less, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, and even more preferably 140 parts by weight or less, and may be 120 parts by weight or less, or may be 90 parts by weight or less. In some preferred embodiments, the amount of the polyfunctional monomer relative to 100 parts by weight of the polymer may be 70 parts by weight or less, 50 parts by weight or less (e.g., less than 50 parts by weight), 45 parts by weight or less (e.g., less than 45 parts by weight), 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less (e.g., less than 20 parts by weight), 18 parts by weight or less, 15 parts by weight or less, or 12 parts by weight or less.

[0083] In embodiments in which a polyfunctional monomer is used as the monomer, the amount of the polyfunctional monomer relative to the total amount of the monomers is not particularly limited. In some embodiments, from the viewpoint of effectively exerting the effect of containing the polyfunctional monomer, the amount of the polyfunctional monomer is suitably approximately 10 wt% or more of the total amount of the monomers, preferably 30 wt% or more, more preferably about 50 wt% or more (e.g., more than 50 wt%), even more preferably 70 wt% or more, even more preferably 90 wt% or more, particularly preferably 95 wt% or more, and may be 99 to 100 wt%. In some embodiments, the monomer contained in the pressure-sensitive adhesive composition may essentially consist of the polyfunctional monomer.

[0084] Alternatively, one or more monofunctional monomers containing one radically polymerizable functional group per molecule may be used as the monomer. Known monofunctional acrylate monomers and vinyl monomers may be used as the monofunctional monomer. For example, one or more of the acrylate monomers (alkoxy group-containing (meth)acrylates, linear alkyl (meth)acrylates, etc.) exemplified as the monomer components of the polymer may be used.

[0085] In embodiments in which the pressure-sensitive adhesive layer contains the monomer, the content of the monomer in the pressure-sensitive adhesive layer is not particularly limited. In some embodiments, the content of the monomer may be approximately 1 part by weight or more, or may be 3 parts by weight or more, relative to 100 parts by weight of the polymer (specifically, the base polymer, preferably an acrylic polymer) contained in the pressure-sensitive adhesive layer. The appropriate amount of the monomer may vary depending on its molecular weight, the number of functional groups, etc., but in some preferred embodiments, the content of the monomer is 5 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, or 9 parts by weight or more, more preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 15 parts by weight or more, even more preferably 20 parts by weight or more, and even more preferably 25 parts by weight or more, from the viewpoint of easily enhancing the effect obtained by curing the pressure-sensitive adhesive with active energy rays (e.g., the effect of making the pressure-sensitive adhesive more easily peelable with active energy rays). The upper limit of the content of the monomer in the pressure-sensitive adhesive layer is not particularly limited and can be set to achieve the desired adhesive properties. In some embodiments, from the viewpoint of compatibility with the polymer (specifically, the base polymer, for example, an acrylic polymer), the amount of the monomer relative to 100 parts by weight of the polymer is suitably approximately 200 parts by weight or less, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, and even more preferably 140 parts by weight or less, and may be 120 parts by weight or less, or may be 90 parts by weight or less. In some preferred embodiments, the amount of the monomer relative to 100 parts by weight of the polymer may be 70 parts by weight or less, 50 parts by weight or less (e.g., less than 50 parts by weight), 45 parts by weight or less (e.g., less than 45 parts by weight), 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less (e.g., less than 20 parts by weight), 18 parts by weight or less, 15 parts by weight or less, or 12 parts by weight or less.

[0086] (Photopolymerization initiator) In some embodiments, the pressure-sensitive adhesive layer contains a photopolymerization initiator. Here, the photopolymerization initiator refers to a polymerization initiator that generates radicals by, for example, decomposing itself when irradiated with active energy rays such as ultraviolet rays. By including the photopolymerization initiator in the pressure-sensitive adhesive layer, when the pressure-sensitive adhesive layer is irradiated with active energy rays, for example, in an embodiment in which the pressure-sensitive adhesive layer contains radically polymerizable functional groups, the photopolymerization initiator reacts with the radically polymerizable functional groups in the pressure-sensitive adhesive layer to harden, thereby reducing the adhesive strength and achieving easy peelability. The photopolymerization initiator may be suitably selected from, for example, ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, oxime ester-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, alkylphenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and the like, and one or more of these may be used.

[0087] Specific examples of ketal-based photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one (for example, trade name "Omnirad 651", manufactured by IGM Resins B.V.), etc. Specific examples of acetophenone-based photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone (for example, trade name "Omnirad 184", manufactured by IGM Resins B.V.), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and methoxyacetophenone. Specific examples of benzoin ether-based photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, as well as substituted benzoin ethers such as anisole methyl ether. Specific examples of acylphosphine oxide-based photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Specific examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. Specific examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride, etc. Specific examples of photoactive oxime photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, etc. Specific examples of benzoin photopolymerization initiators include benzoin, etc. Specific examples of benzyl photopolymerization initiators include benzyl, etc.Specific examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, etc. Specific examples of thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

[0088] The amount of photopolymerization initiator contained in the pressure-sensitive adhesive layer is not particularly limited. In some embodiments, the content of the photopolymerization initiator in the pressure-sensitive adhesive layer is suitably 0.1 parts by weight or more relative to 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the pressure-sensitive adhesive layer, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, even more preferably 0.4 parts by weight or more, particularly preferably 0.5 parts by weight or more, and may be 0.6 parts by weight or more, or even 0.7 parts by weight or more. The higher the content of the photopolymerization initiator, the higher the frequency of collision between the photopolymerization initiator and the radically polymerizable functional group, and the more likely the curing reaction will proceed. In addition, in some embodiments, the amount of photopolymerization initiator relative to 100 parts by weight of the polymer may be, for example, about 10 parts by weight or less, or may be approximately 5 parts by weight or less. In some preferred embodiments, the amount of photopolymerization initiator per 100 parts by weight of the polymer is suitably 3 parts by weight or less (e.g., less than 3 parts by weight), preferably 2.5 parts by weight or less, more preferably 2.0 parts by weight or less, even more preferably 1.5 parts by weight or less, particularly preferably less than 1.2 parts by weight (e.g., 1.1 parts by weight or less), and may be 1.0 parts by weight or less (e.g., less than 1.0 part by weight), 0.9 parts by weight or less, 0.8 parts by weight or less, 0.7 parts by weight or less, or 0.6 parts by weight or less. By setting the total amount of photopolymerization initiator within a predetermined range, a pressure-sensitive adhesive having efficient active energy ray curability can be preferably realized while maintaining adhesive properties such as adhesive strength and storage stability.

[0089] Although not particularly limited, in some preferred embodiments, the total proportion of the above-mentioned polymer (specifically, the base polymer, for example, an acrylic polymer), the above-mentioned monomer (for example, a polyfunctional acrylic monomer), and the photopolymerization initiator in the entire pressure-sensitive adhesive layer is, from the viewpoint of better exerting the effects of applying the technology disclosed herein, suitably 50% by weight or more (for example, more than 50% by weight and 100% by weight or less), preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and may be 95% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99 to 100% by weight).

[0090] (Crosslinking Agent) The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer may contain a crosslinking agent as needed, mainly for the purpose of crosslinking within the pressure-sensitive adhesive layer or between the pressure-sensitive adhesive layer and its adjacent surface. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer in a form after crosslinking reaction. The use of a crosslinking agent allows the cohesive strength of the pressure-sensitive adhesive layer to be appropriately adjusted.

[0091] The type of crosslinking agent is not particularly limited, and can be selected from conventionally known crosslinking agents so that the crosslinking agent exerts an appropriate crosslinking function within the pressure-sensitive adhesive layer, for example, depending on the composition of the pressure-sensitive adhesive. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These crosslinking agents can be used alone or in combination of two or more. From the viewpoint of achieving a good balance between adhesiveness and cohesive strength, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and carbodiimide-based crosslinking agents are preferred, with isocyanate-based crosslinking agents being particularly preferred.

[0092] The isocyanate crosslinking agent may be a polyfunctional isocyanate compound having two or more functionalities, such as aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. Examples of commercially available products include isocyanate adducts such as a trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), a trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL"), an isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"), and a trimethylolpropane / xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, Inc., trade name "Takenate D-110N").

[0093] As the epoxy-based crosslinking agent, those having two or more epoxy groups per molecule can be used without particular limitation. Epoxy-based crosslinking agents having three to five epoxy groups per molecule are preferred. Specific examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy-based crosslinking agents include "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., "Epicron CR-5L" manufactured by DIC Corporation, "Denacol EX-512" manufactured by Nagase ChemteX Corporation, and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

[0094] As the oxazoline-based crosslinking agent, any agent having one or more oxazoline groups per molecule can be used without particular limitation. Examples of aziridine-based crosslinking agents include trimethylolpropane tris[3-(1-aziridinyl)propionate] and trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)]. As the carbodiimide-based crosslinking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used.

[0095] In some embodiments, an isocyanate-based crosslinking agent is used as the crosslinking agent. The isocyanate-based crosslinking agent can easily form a PSA with good peelability while exhibiting a balanced adhesive property, such as adhesive strength and cohesive strength. The isocyanate-based crosslinking agent can be used alone or in combination with two or more. Although not particularly limited, when an isocyanate-based crosslinking agent is used, the amount used is preferably less than 3 parts by weight per 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the PSA layer. By limiting the amount of isocyanate-based crosslinking agent used, the crosslink density of the PSA to be treated can be appropriately suppressed, and at such a crosslink density, the effect of curing the PSA with active energy rays using the technology disclosed herein can be more effectively achieved. From this perspective, in some preferred embodiments, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the polymer is 2 parts by weight or less, more preferably 1.5 parts by weight or less, even more preferably 1.0 parts by weight or less, even more preferably 0.8 parts by weight or less, and particularly preferably 0.6 parts by weight or less. By limiting the amount of isocyanate-based crosslinking agent used, sufficient adhesive strength tends to be easily obtained.In addition, the amount of isocyanate-based crosslinking agent used can be, for example, 0.01 parts by weight or more relative to 100 parts by weight of the polymer, and in some preferred embodiments, it may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more.By appropriately setting the amount of isocyanate-based crosslinking agent used within the above range, it is possible to preferably obtain a pressure-sensitive adhesive that exhibits well-balanced adhesive properties such as adhesive strength and cohesive strength while preferably achieving the effects of the technology disclosed herein.

[0096] When a crosslinking agent is used, the amount of crosslinking agent used may be greater than 0 parts by weight relative to 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the adhesive layer, from the viewpoint of realizing an adhesive that exhibits well-balanced adhesive properties such as adhesive strength and cohesive strength. For example, the amount may be 0.001 parts by weight or more, or even 0.01 parts by weight or more. In some preferred embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the polymer may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or even 0.5 parts by weight or more. The upper limit of the amount of crosslinking agent used may vary depending on the type of crosslinking agent used, and is not limited to a specific range, but is preferably limited to a predetermined amount or less. By limiting the amount of crosslinking agent used, the crosslink density of the adhesive to be treated is appropriately suppressed. At such a crosslink density, the effect of curing the adhesive with active energy rays using the technology disclosed herein can be more effectively exhibited. For example, the amount of crosslinking agent used is suitably less than 10 parts by weight per 100 parts by weight of the polymer, and in some embodiments, it is preferably less than 5 parts by weight, and may be less than 3 parts by weight. In some embodiments, the amount of crosslinking agent used is suitably less than 1 part by weight per 100 parts by weight of the polymer, and is preferably 0.9 parts by weight or less, and may be 0.8 parts by weight or less, 0.7 parts by weight or less, 0.6 parts by weight or less, or 0.5 parts by weight or less. By limiting the amount of crosslinking agent used, sufficient adhesive strength tends to be obtained.

[0097] A crosslinking catalyst may be used to more effectively promote the crosslinking reaction. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, nursem ferric, butyltin oxide, and dioctyltin dilaurate. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used may be, for example, approximately 0.0001 parts by weight or more, approximately 0.001 parts by weight or more, or approximately 0.005 parts by weight or more, relative to 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the pressure-sensitive adhesive layer, and may be approximately 1 part by weight or less, approximately 0.1 parts by weight or less, or approximately 0.05 parts by weight or less.

[0098] The PSA composition used to form the PSA layer may optionally contain a compound that undergoes keto-enol tautomerization as a crosslinking retarder. For example, a compound that undergoes keto-enol tautomerization may be preferably used in a PSA composition containing an isocyanate-based crosslinking agent or a PSA composition that can be used with an isocyanate-based crosslinking agent. This can have the effect of extending the pot life of the PSA composition. Various β-dicarbonyl compounds can be used as the compound that undergoes keto-enol tautomerization. Specific examples include β-diketones such as acetylacetone and 2,4-hexanedione; acetoacetate esters such as methyl acetoacetate and ethyl acetoacetate; propionyl acetate esters such as ethyl propionyl acetate; isobutyryl acetate esters such as ethyl isobutyryl acetate; and malonate esters such as methyl malonate and ethyl malonate. Among these, acetylacetone and acetoacetate esters are particularly preferred. The compounds that undergo keto-enol tautomerization may be used alone or in combination of two or more. The amount of the compound that undergoes keto-enol tautomerization used may be, for example, 0.1 parts by weight or more and 20 parts by weight or less, and suitably 0.5 parts by weight or more and 15 parts by weight or less, relative to 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the pressure-sensitive adhesive layer, and can be, for example, 1 part by weight or more and 10 parts by weight or less, or may be 1 part by weight or more and 5 parts by weight or less.

[0099] (Other Components) The pressure-sensitive adhesive layer may optionally contain various additives commonly used in the field of pressure-sensitive adhesives, such as tackifiers, silane coupling agents, release force modifiers (such as surfactants), viscosity modifiers (e.g., thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, and antioxidants. These various additives can be conventionally used and do not particularly characterize the present invention, so detailed description is omitted. The technology disclosed herein can achieve desired adhesive properties, such as adhesive strength, without the use of a tackifier. In some embodiments, the content of the tackifier in the pressure-sensitive adhesive layer can be, for example, less than 10 parts by weight, or even less than 5 parts by weight, per 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the pressure-sensitive adhesive layer. The content of the tackifier may be less than 1 part by weight (e.g., less than 0.5 parts by weight) or less than 0.1 parts by weight (0 parts by weight or more but less than 0.1 parts by weight). The pressure-sensitive adhesive layer may not contain a tackifier.

[0100] (Formation of Pressure-Sensitive Adhesive (Layer)) A pressure-sensitive adhesive to be treated can be formed by a conventionally known method. For example, a pressure-sensitive adhesive composition can be applied (e.g., coated) to an appropriate surface, followed by an appropriate treatment to make the surface non-fluid, thereby forming a layer (pressure-sensitive adhesive layer). Only one method for making the pressure-sensitive adhesive composition non-fluid (e.g., drying, crosslinking, polymerization, cooling, etc.) may be applied, or two or more methods may be applied simultaneously or in multiple stages. In the case of a solvent-based pressure-sensitive adhesive composition, the pressure-sensitive adhesive can typically be formed by drying (preferably further crosslinking) the composition.

[0101] For example, in the case of a substrateless double-sided PSA sheet, a method can be used in which a PSA composition is applied to a surface (release surface) having releasability, and then the PSA composition is immobilized to form a PSA layer on the surface. In the case of a PSA sheet with a substrate, a method can be used in which a PSA composition is directly applied (typically coated) to the substrate, and then immobilized to form a PSA layer (direct method). Alternatively, a method can be used in which a PSA composition applied to a surface (release surface) having releasability is immobilized to form a PSA layer on the surface, and then the PSA layer is transferred to the substrate (transfer method). The release surface can be the surface of a release liner, the back surface of a release-treated substrate, or the like. While the PSA layer disclosed herein is typically formed continuously, it is not limited to this form and may be formed in a regular or random pattern, such as dots or stripes.

[0102] The form of the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive (layer) is not particularly limited, and may be, for example, an aqueous pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, an active energy ray-curable pressure-sensitive adhesive composition, etc. Here, the aqueous pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive in a solvent (aqueous solvent) whose main component is water. The concept of the aqueous pressure-sensitive adhesive composition here may include those referred to as water-dispersed pressure-sensitive adhesive compositions (compositions in which the pressure-sensitive adhesive is dispersed in water), water-soluble pressure-sensitive adhesive compositions (compositions in which the pressure-sensitive adhesive is dissolved in water), etc. Furthermore, the solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive in an organic solvent. The solvent contained in the solvent-based pressure-sensitive adhesive composition can be appropriately selected from conventionally known organic solvents. For example, any one solvent selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; and ketones such as methyl ethyl ketone; or a mixed solvent of two or more thereof can be used.

[0103] The pressure-sensitive adhesive composition can be applied using a known or conventional coater, such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, die coater, bar coater, knife coater, or spray coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction and improving production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature is not particularly limited, but can be, for example, about 40 to 100°C, and is usually preferably about 60 to 80°C. After drying, the pressure-sensitive adhesive composition may be further aged for the purposes of adjusting component migration within the pressure-sensitive adhesive layer, promoting the crosslinking reaction, and alleviating distortion that may exist within the substrate or pressure-sensitive adhesive layer.

[0104] (Thickness of Pressure-Sensitive Adhesive Layer) The thickness of the pressure-sensitive adhesive layer is not particularly limited. The thickness of the pressure-sensitive adhesive layer is typically 1 μm or more, and may be 2 μm or more, or 3 μm or more. The thicker the pressure-sensitive adhesive layer, the more its adhesive strength to the adherend tends to improve. In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is 5 μm or more, or may be 10 μm or more, or may be 15 μm or more, or may be 20 μm or more, or may be 25 μm or more. The upper limit of the thickness of the pressure-sensitive adhesive layer is suitably, for example, about 200 μm or less, or may be 100 μm or less (e.g., less than 100 μm), or may be 50 μm or less. Limiting the thickness of the pressure-sensitive adhesive layer within a predetermined range tends to prevent adhesive residue due to cohesive failure and to facilitate easy peeling. In addition, a thin pressure-sensitive adhesive layer is advantageous in terms of thinning the pressure-sensitive adhesive sheet and tends to have excellent conformability to the adherend. In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is 40 μm or less, or may be 30 μm or less.

[0105] (Substrate Layer) In an embodiment in which the method disclosed herein is applied to the curing of a pressure-sensitive adhesive forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet may include a substrate layer. Various sheet-like substrates can be used as the substrate (layer) supporting (backing) the pressure-sensitive adhesive layer. Examples of the substrate include resin films, paper, cloth (woven fabric, nonwoven fabric, etc.), rubber sheets, foam sheets, metal foils, and composites thereof. Examples of resin films include polyolefin films; polyester films; vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluororesin films; cellophane; and the like. Non-limiting examples of polyester films include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Other examples of resin films include resin films formed from one or more engineering plastics (which may be super engineering plastics) such as polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyarylate resins, polyamideimide resins, and polyimide resins. The use of engineering plastics is preferred from the viewpoint of heat resistance.

[0106] In some preferred embodiments, a resin film having a predetermined rigidity (strength) and excellent processability and handling properties is used as the substrate (layer). Among these, from the viewpoint of heat resistance, polyester films, polyamide resin films, and engineering plastic films (e.g., polyimide resin films, etc.) are preferred as the resin film substrate. In this specification, the term "resin film" typically refers to a non-porous film, and typically refers to a resin film that is substantially bubble-free (void-free). Therefore, the above-mentioned resin film is a concept that is distinct from foam films and nonwoven fabrics. The density of the resin film that can be used as the substrate is approximately 0.85 to 1.50 g / cm. ３ (e.g., 0.90 g / cm ３ ~1.20 g / cm ３ , typically 0.92 g / cm ３ ~1.05g / cm ３The resin film may have a single layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

[0107] The substrate layer (e.g., a resin film) may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, antiblocking agents, etc. The amount of additives to be added is not particularly limited and can be set appropriately depending on the application, etc.

[0108] The method for producing the resin film is not particularly limited, and any conventionally known resin film forming method such as extrusion molding, inflation molding, T-die casting, or calendar roll molding can be appropriately employed.

[0109] The substrate layer may be substantially composed of a resin film. Alternatively, the substrate layer may include an auxiliary layer in addition to the resin film. Examples of the auxiliary layer include an optical property adjusting layer (e.g., a coloring layer or an anti-reflection layer), a printing layer or a laminating layer for imparting a desired appearance, an antistatic layer, an undercoat layer, a release layer, or other surface treatment layer.

[0110] The thickness of the base layer is not particularly limited and can be selected appropriately depending on the purpose, but generally can be 1 to 500 μm. From the viewpoints of processability, handleability, workability, etc., the thickness of the base layer is suitably 2 μm or more (for example, 3 μm or more, typically 5 μm or more), and may be approximately 7 μm or more, or may be 10 μm or more. Furthermore, the thickness of the base layer is suitably approximately 200 μm or less, and from the viewpoint of weight reduction and thinning, it is preferably approximately 100 μm or less, more preferably approximately 50 μm or less, and may be 30 μm or less, 20 μm or less, or 15 μm or less. As the thickness of the base layer decreases, the flexibility of the PSA sheet and its ability to follow the surface shape of the adherend tend to improve.

[0111] The surface of the substrate layer facing the pressure-sensitive adhesive layer may be subjected to a conventionally known surface treatment, such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer, as necessary. Such surface treatments may be intended to improve the adhesion between the substrate layer and the pressure-sensitive adhesive layer, in other words, the anchoring ability of the pressure-sensitive adhesive layer to the substrate layer. The composition of the primer is not particularly limited and can be appropriately selected from known primers. The thickness of the primer layer is not particularly limited, but is suitably about 0.01 μm to 1 μm, for example, and preferably about 0.1 μm to 1 μm. The back surface of the substrate layer may be subjected to the various surface treatments described above or a surface treatment such as an antistatic treatment.

[0112] (Total Thickness of Pressure-Sensitive Adhesive Sheet) The total thickness of the pressure-sensitive adhesive sheet (which may include the pressure-sensitive adhesive layer and the base layer, but does not include the release liner) is not particularly limited, and is suitably in the range of approximately 5 to 1,000 μm. The total thickness of the pressure-sensitive adhesive sheet may be 10 μm or more, 15 μm or more, or 20 μm or more, from the viewpoints of adhesive properties, handleability, etc. In some embodiments, the total thickness of the pressure-sensitive adhesive sheet may be 30 μm or more, 40 μm or more, or 50 μm or more. Furthermore, from the viewpoints of weight reduction and thinning, in some embodiments, the total thickness of the pressure-sensitive adhesive sheet is 500 μm or less, or may be 300 μm or less. In some preferred embodiments, the total thickness of the pressure-sensitive adhesive sheet is 100 μm or less (e.g., less than 100 μm), more preferably 80 μm or less, or may be 70 μm or less. Reducing the thickness of the pressure-sensitive adhesive sheet is advantageous in terms of thinning, miniaturization, weight reduction, resource conservation, etc.

[0113] (Young's Modulus) In embodiments in which the method disclosed herein is applied to the curing of a pressure-sensitive adhesive, the Young's modulus of the pressure-sensitive adhesive before the active energy ray irradiation treatment including the heating / AEL treatment, i.e., the initial Young's modulus Y0 [MPa], is not particularly limited and can be appropriately selected so as to obtain the desired properties (e.g., the peel strength of a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive) according to the intended use of the pressure-sensitive adhesive. In some embodiments, the initial Young's modulus may be, for example, 0.001 MPa or more. From the viewpoint of the cohesiveness of the pressure-sensitive adhesive and the processability of a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive, it is appropriate to be 0.005 MPa or more, preferably 0.01 MPa or more, more preferably 0.05 MPa or more, and may be 0.08 MPa or more, or even 0.1 MPa or more. In some embodiments, the initial Young's modulus Y0 of the pressure-sensitive adhesive may be 0.5 MPa or more, 1.0 MPa or more, 3.0 MPa or more, or 5.0 MPa or more. The initial Young's modulus Y0 of the pressure-sensitive adhesive may be, for example, 50 MPa or less, and from the viewpoint of initial adhesiveness, etc., it is appropriate to be 25 MPa or less, advantageously 15 MPa or less, and is preferably 10 MPa or less or 7.0 MPa or less, and may be 5.0 MPa or less, 3.0 MPa or less, or 1.0 MPa or less or 0.5 MPa or less (e.g., less than 0.5 MPa). The technology disclosed herein can be applied to a pressure-sensitive adhesive having an initial Young's modulus Y0 that satisfies any of the above-mentioned upper and / or lower limits, and can suitably exert the effect of curing the pressure-sensitive adhesive (e.g., increasing the Young's modulus).

[0114] The method disclosed herein is typically carried out so that the Young's modulus of the pressure-sensitive adhesive after the active energy ray irradiation treatment including the heating / AEL treatment, i.e., the post-treatment Young's modulus Y1 [MPa], is higher than the initial Young's modulus Y0 [MPa] of the pressure-sensitive adhesive, i.e., so that the Young's modulus increase ratio calculated from the initial Young's modulus Y0 [MPa] and the post-treatment Young's modulus Y1 [MPa] using the following formula is greater than 1.0: Young's modulus increase ratio=(Y1 / Y0)

[0115] In some embodiments, the Young's modulus increase ratio is suitably 1.5 or more, and from the viewpoint of better curing the PSA, it is advantageously 2.0 or more, preferably 10 or more, or may be 30 or more, or may be 50 or more. In some embodiments, for example, from the viewpoint of making the PSA easier to peel by the active energy ray irradiation treatment, the Young's modulus increase ratio is suitably 70 or more, advantageously 100 or more, preferably 150 or more, or may be 200 or more, 300 or more, or 400 or more, or may be 500 or more, or 600 or more. The upper limit of the Young's modulus increase ratio is not particularly limited. From the viewpoint of easily exhibiting appropriate adhesiveness initially, in some embodiments, the Young's modulus increase ratio of the PSA may be, for example, approximately 10,000 or less, 5,000 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less.

[0116] In the technology disclosed herein, the Young's modulus Y1 [MPa] of the pressure-sensitive adhesive after treatment is not particularly limited and can be appropriately selected so that the cured product (cured pressure-sensitive adhesive) obtained by the treatment exhibits the desired properties depending on the purpose. The Young's modulus Y1 after treatment may be, for example, 0.005 MPa or more, 0.01 MPa or more, 0.05 MPa or more, 0.1 MPa or more, 0.5 MPa or more, or 1.0 MPa or more. In some embodiments, from the viewpoint of making the pressure-sensitive adhesive easier to peel by the active energy ray irradiation treatment, the Young's modulus Y1 after treatment may be, for example, 3.0 MPa or more, advantageously 5.0 MPa or more, preferably 10 MPa or more, 15 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more, 50 MPa or more, 60 MPa or more, or 70 MPa or more, or 90 MPa or more, or 110 MPa or more. In some embodiments, the Young's modulus Y1 after treatment is suitably, for example, 2000 MPa or less, preferably 1000 MPa or less, and more preferably 500 MPa or less. Having a post-treatment Young's modulus Y1 that is not too high can be advantageous, for example, from the viewpoint of avoiding an excessive decrease in peel strength after treatment and maintaining the PSA sheet on the adherend until the desired peel timing. In some embodiments, the post-treatment Young's modulus Y1 may be, for example, 300 MPa or less, 200 MPa or less, 150 MPa or less, 100 MPa or less, or 75 MPa or less.

[0117] The initial Young's modulus Y0 of a pressure-sensitive adhesive is determined from a stress-strain curve (SS curve) under conditions of 23°C, 50% RH, and a tensile speed of 50 mm / min. The post-treatment Young's modulus Y1 of a pressure-sensitive adhesive is determined by performing the same measurement as for the initial Young's modulus Y0 on the pressure-sensitive adhesive (cured pressure-sensitive adhesive) after active energy ray irradiation treatment, including heating / AEL treatment. More specifically, the Young's moduli Y0 and Y1 are measured by the method described in the Examples below. Based on the contents of this specification, the initial Young's modulus Y0 can be adjusted by appropriately selecting the type of polymer contained in the pressure-sensitive adhesive (monomer composition, etc.), whether or not a photopolymerization initiator is contained, and whether or not other components that may be contained in the pressure-sensitive adhesive (e.g., polyfunctional monomers, crosslinking agents, etc.) are contained, their types, and contents. Based on the contents of this specification, the post-treatment Young's modulus Y1 can be achieved and adjusted by appropriately selecting the same factors as those used to adjust the initial Young's modulus Y0 described above, and the conditions of the active energy ray irradiation treatment, including heating / AEL treatment, as needed.

[0118] According to the technology disclosed herein, by subjecting a pressure-sensitive adhesive to an active energy ray irradiation treatment including the heating / AEL treatment, a higher Young's modulus [MPa] can be achieved compared to a case where the pressure-sensitive adhesive is subjected to an active energy ray irradiation treatment under the same conditions except for not applying heat to the pressure-sensitive adhesive (i.e., the same conditions except for not using the external heating means described above). In some embodiments, the Young's modulus Y1 [MPa] after treatment of a cured product (cured pressure-sensitive adhesive) obtained by subjecting a pressure-sensitive adhesive to an active energy ray irradiation treatment including the heating / AEL treatment is, for example, the Young's modulus Y1 [MPa] of a cured product obtained by subjecting the pressure-sensitive adhesive to an active energy ray irradiation treatment under the same conditions except for not applying heat to the pressure-sensitive adhesive. Ｒ The Young's modulus Y1 after treatment may be 1.05 times or more, preferably 1.1 times or more or 1.2 times or more, more preferably 1.3 times or more or 1.4 times or more, and may be 1.5 times or more, 1.6 times or more, or 1.7 times or more of the Young's modulus Y1 [MPa]. Ｒ It may be 100 times or less, 50 times or less, or 30 times or less, or may be 10 times or less, 5 times or less, or 3 times or less.

[0119] (Peel Force) In embodiments in which the methods disclosed herein are applied to the curing of a PSA forming a PSA layer of a PSA sheet, the peel force of the PSA sheet before the PSA is subjected to an active energy ray irradiation treatment including a heating / AEL treatment, i.e., the initial peel force F0, is not particularly limited and can be, for example, within a range of about 0.5 N / 20 mm to 50 N / 20 mm. In some embodiments, the initial peel force F0 can be, for example, 0.8 N / 20 mm or more, 1.0 N / 20 mm or more, or more than 1.0 N / 20 mm, or 1.5 N / 20 mm or more. From the viewpoint of easily obtaining better adhesion (e.g., adherend retention performance), in some embodiments, the initial peel force F0 is advantageously 2.0 N / 20 mm or more, 2.0 N / 20 mm or more, or 4.0 N / 20 mm or more, and is preferably 5.0 N / 20 mm or more, 8.0 N / 20 mm or more, or 10 N / 20 mm or more, and may be 12 N / 20 mm or more, or may be 15 N / 20 mm or more. In some embodiments, the initial peel force F0 may be, for example, 30 N / 20 mm or less, 20 N / 20 mm or less, 15 N / 20 mm or less, 10 N / 20 mm or less, 5.0 N / 20 mm or less, or 3.0 N / 20 mm or less. The initial peel force F0 refers to the peel strength (peel force) against a glass plate measured under the conditions of a peel angle of 180 degrees and a speed of 300 mm / min in an environment of 23 ° C. More specifically, the initial peel force F0 is measured by the method described in the Examples below. Based on the contents of this specification, the initial peel force F0 can be adjusted by appropriately selecting the type of polymer contained in the pressure-sensitive adhesive (monomer composition, etc.), whether or not a photopolymerization initiator is contained, and whether or not other components that may be contained in the pressure-sensitive adhesive (e.g., polyfunctional monomers, crosslinking agents, etc.) are contained, and the type and amount thereof.

[0120] The peel strength of the PSA sheet after the PSA has been subjected to an active energy ray irradiation treatment including heating / AEL treatment, i.e., the post-treatment peel strength F1, is not particularly limited and can be, for example, within a range of about 0.5 N / 20 mm to 50 N / 20 mm. In some embodiments, the active energy ray irradiation treatment can be a treatment that reduces the peel strength of the PSA sheet. In such embodiments, the post-treatment peel strength F1 is suitably, for example, 5.0 N / 20 mm or less, advantageously 3.0 N / 20 mm or less or less than 3.0 N / 20 mm, preferably 2.0 N / 20 mm or less, and more preferably 1.0 N / 20 mm or less. In some embodiments where a higher level of easy releasability is required after treatment, the post-treatment peel force F1 may be, for example, less than 1.0 N / 20 mm, preferably 0.8 N / 20 mm or less, more preferably 0.6 N / 20 mm or less, and even more preferably 0.5 N / 20 mm or less, and may be 0.4 N / 20 mm or less, 0.3 N / 20 mm or less, 0.2 N / 20 mm or less, or less than 0.2 N / 20 mm. In some embodiments, the lower limit of the post-treatment peel force F1 may be 0.0 N / 20 mm. In other embodiments, the post-treatment peel force F1 may be, for example, 0.01 N / 20 mm or more, or 0.05 N / 20 mm or more. A post-treatment peel force F1 that is not too low can be advantageous, for example, from the perspective of maintaining the PSA sheet on the adherend until the desired release timing after treatment. In some embodiments, the post-treatment peel force F1 may be 0.1 N / 20 mm or more, 0.2 N / 20 mm or more, 0.3 N / 20 mm or more, or 0.4 N / 20 mm or more. The post-treatment peel force F1 refers to the peel strength (peel force) measured under an environment of 23°C and 50% RH after being attached to a glass plate and subjected to an active energy ray irradiation treatment including a heating / AEL treatment. More specifically, the post-treatment peel force F1 is measured by the method described in the Examples below. Based on the description of this specification, the post-treatment peel force F1 can be achieved and adjusted by appropriately selecting the same factors as those used to adjust the initial peel force F0 described above, and the conditions of the active energy ray irradiation treatment including a heating / AEL treatment, as needed.

[0121] The PSA sheet may be configured so that its peel strength is reduced by curing the PSA using the method disclosed herein. The method disclosed herein can be applied, for example, to a PSA sheet whose peel strength reduction rate, calculated from the initial peel strength F0 and the post-treatment peel strength F1 using the following formula: Peel Strength Reduction Rate [%] = (1 - F1 / F0) x ​​100, is greater than 0%. In some embodiments, the peel strength reduction rate may be, for example, 5% or greater or 10% or greater, suitably greater than 20% (e.g., greater than 30%), advantageously greater than 40%, preferably greater than 50%, and may be 60% or greater, 70% or greater, 80% or greater, 85% or greater, 90% or greater, 95% or greater, or 97% or greater. In some embodiments, the peel strength reduction rate is preferably less than 99.9%. A PSA sheet having a peel force reduction rate of less than 99.9% exhibits the desired ease of releasability from an adherend while maintaining adhesion to the adherend after active energy ray irradiation treatment, including heating / AEL treatment. This makes it easier to maintain the PSA sheet on the adherend until the desired release timing. For example, it prevents the PSA sheet from spontaneously peeling from the adherend before the desired release timing after active energy ray irradiation treatment, including heating / AEL treatment, and the resulting defects. From this perspective, in some embodiments, the peel force reduction rate may be 99.8% or less, or 99.5% or less, or less than 99.5%.

[0122] (Gel Fraction) In embodiments in which the method disclosed herein is applied to the curing of a pressure-sensitive adhesive, the gel fraction of the pressure-sensitive adhesive prior to the active energy ray irradiation treatment, including the heating / AEL treatment, i.e., the initial gel fraction G0, is not particularly limited. From the viewpoint of easily achieving both the curability (e.g., the easy peelability due to the treatment) resulting from the active energy ray irradiation treatment, including the heating / AEL treatment, and good adhesion prior to the treatment, in some embodiments, the initial gel fraction G0 is suitably, for example, 90% or less or 85% or less, preferably 80% or less, and may be 75% or less, 70% or less, or 65% or less. Furthermore, the initial gel fraction G0 of the pressure-sensitive adhesive may be 0% or more than 0% (e.g., 1% or more). From the viewpoint of the handleability and processability of the pressure-sensitive adhesive sheet, in some embodiments, the initial gel fraction G0 of the pressure-sensitive adhesive is suitably 5% or more, and advantageously 10% or more or 20% or more. From the viewpoint of making it easier to obtain appropriate cohesion and holding power, it is preferably 30% or more, more preferably 40% or more, and may be 50% or more, or may be 60% or more.

[0123] The technology disclosed herein is preferably carried out so that the gel fraction increase (G1-G0) calculated from the initial gel fraction G0 [%] and the post-treatment gel fraction G1 [%] is greater than 0%, i.e., so that the gel fraction of the PSA increases as a result of the active energy ray irradiation treatment including the heating / AEL treatment. The post-treatment gel fraction G1 is the gel fraction of the PSA after the active energy ray irradiation treatment including the heating / AEL treatment. In some embodiments, the gel fraction increase is suitably 5% or more. From the viewpoint of easily exerting the effect of the active energy ray irradiation treatment including the heating / AEL treatment to improve releasability, the gel fraction increase is preferably 10% or more, more preferably 13% or more, and may be, for example, 16% or more, 20% or more, 25% or more, or 30% or more. The upper limit of the gel fraction increase is 100%. The increase in gel fraction may be, for example, 99% or less, 98% or less, 95% or less, 90% or less, or 80% or less. In some embodiments, from the viewpoint of favorably achieving both initial adhesiveness and easy releasability after treatment, the increase in gel fraction is, for example, suitably 70% or less, preferably 60% or less, or may be 50% or less, or may be 40% or less.

[0124] The post-treatment gel fraction G1 of the PSA is not particularly limited and may be, for example, within the range of 20% to 100%, 40% to 100%, or 60% to 100%. From the viewpoint of the ease of releasability of the PSA sheet after active energy ray irradiation treatment including heating / AEL treatment, in some embodiments, the post-treatment gel fraction G1 is suitably 70% or more (e.g., greater than 70%), advantageously 80% or more, preferably 83% or more, more preferably 85% or more, or even 88% or more, or even 90% or more. In some preferred embodiments, the post-treatment gel fraction G1 may be, for example, greater than 90%, 93% or more, 94% or more, 95% or more, 96% or more, or 97% or more, or even greater than 97%. In embodiments in which the post-treatment gel fraction G1 is relatively high, it is particularly meaningful to apply the techniques disclosed herein (e.g., by active energy ray irradiation treatment including heating / AEL treatment) to increase the reaction rate of the radically polymerizable functional groups. The upper limit of the post-treatment gel fraction G1 is 100%, and is typically less than 100%. In some embodiments, from the viewpoint of maintaining the PSA sheet on the adherend until the desired timing of peeling, the post-treatment gel fraction G1 is suitably, for example, 99.8% or less, preferably 99.5% or less, or may be 99% or less, or may be 98% or less.

[0125] The initial gel fraction G0 and the post-treatment gel fraction G1 are determined as the weight percentages of the ethyl acetate-insoluble components of the pressure-sensitive adhesive at the initial stage and after treatment, respectively. More specifically, the initial gel fraction G0 and the post-treatment gel fraction G1 are measured by the method described in the Examples below. Based on the contents of this specification, the initial gel fraction G0 can be adjusted by appropriately selecting the type of polymer (monomer composition, etc.) contained in the pressure-sensitive adhesive, the presence or absence of a photopolymerization initiator, and the presence, type, and content of other components that may be contained in the pressure-sensitive adhesive (e.g., polyfunctional monomers, crosslinking agents, etc.). The post-treatment gel fraction G1 can be achieved and adjusted based on the contents of this specification, if necessary, by appropriately selecting factors similar to those used to adjust the initial Young's modulus Y1 described above, and the conditions of the active energy ray irradiation treatment, including the heating / AEL treatment.

[0126] <Application to Pressure-Sensitive Adhesive Production> The polymerization method disclosed herein can also be used to produce a pressure-sensitive adhesive. The polymerization method disclosed herein can be carried out, for example, by subjecting a processing object containing at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment, thereby reacting the radically polymerizable functional group and producing a pressure-sensitive adhesive from the processing object. The processing object can be understood as an active energy ray-curable pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive by an active energy ray irradiation treatment including a heating / AEL treatment. From the standpoint of ease of application, the active energy ray-curable pressure-sensitive adhesive composition is preferably in a liquid form before being subjected to an active energy ray irradiation treatment including a heating / AEL treatment. Therefore, this specification provides a method for producing a pressure-sensitive adhesive, which includes subjecting a liquid pressure-sensitive adhesive composition containing at least one of a monomer and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment.

[0127] Applying the polymerization method disclosed herein to the production of a pressure-sensitive adhesive can provide a method for producing a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive. The method for producing the pressure-sensitive adhesive sheet can include: coating a film of a treatment target (preferably a liquid active energy ray-curable pressure-sensitive adhesive composition) containing at least one of a monomer and a polymer having a radically polymerizable functional group; and forming a pressure-sensitive adhesive layer from the pressure-sensitive adhesive composition by subjecting the pressure-sensitive adhesive composition to an active energy ray irradiation treatment, including a heating / AEL treatment, in which the pressure-sensitive adhesive composition is irradiated with active energy rays (AEL) while being heated. In a pressure-sensitive adhesive sheet produced by this method, the Young's modulus of the pressure-sensitive adhesive layer can be, for example, 0.005 MPa or more, preferably 0.01 MPa to 50 MPa, and more preferably 0.05 MPa to 10 MPa. The gel fraction of the pressure-sensitive adhesive layer can be, for example, 1% or more, preferably 5% to 99.9%, and more preferably 20% to 99%.

[0128] In an embodiment in which the polymerization method disclosed herein is applied to the production of a pressure-sensitive adhesive, the pressure-sensitive adhesive composition (subject to be treated) to be subjected to an active energy ray irradiation treatment including a heating / AEL treatment may be an object to be treated that includes a polymer (e.g., an acrylic polymer) with or without a radically polymerizable functional group and a monomer (radical polymerizable monomer) with a radically polymerizable functional group, and may further include a photopolymerization initiator. Examples of "polymers with radically polymerizable functional groups" that may be included in the pressure-sensitive adhesive composition as the object to be treated can be found in the examples of polymers with radically polymerizable functional groups that may be included in the pressure-sensitive adhesive described above regarding the embodiment in which the polymerization method disclosed herein is used to cure the pressure-sensitive adhesive. Examples of "polymers without radically polymerizable functional groups" that may be included in the pressure-sensitive adhesive composition as the object to be treated can be found in the examples of polymers without radically polymerizable functional groups that may be included in the pressure-sensitive adhesive described above regarding the embodiment in which the polymerization method disclosed herein is used to cure the pressure-sensitive adhesive. The polymer without radically polymerizable functional groups may be included in the pressure-sensitive adhesive composition as the object to be treated in the form of a partial polymer of the polymer. Furthermore, as examples of radical polymerizable monomers that can be contained in the pressure-sensitive adhesive composition as the treatment target, reference can be made to the examples of radical polymerizable monomers (compounded monomers) that can be contained in the pressure-sensitive adhesive in the above-mentioned explanation of the embodiment in which the polymerization method disclosed herein is used to harden the pressure-sensitive adhesive.

[0129] As will be understood from the above description and the examples described below, the matters disclosed by this specification include the following. [1] A polymerization method applied to the curing or production of a pressure-sensitive adhesive, comprising: subjecting a processing object containing at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment in which active energy ray (AEL) is irradiated while applying heat to the processing object. [2] The polymerization method according to [1] above, wherein the active energy ray is a non-thermal energy ray. [3] The polymerization method according to [1] or [2] above, wherein the active energy ray is ultraviolet (UV) light. [4] The polymerization method according to any of [1] to [3] above, wherein the processing object further contains a photopolymerization initiator. [5] The polymerization method according to any of [1] to [4] above, wherein the processing object is a pressure-sensitive adhesive forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet. [6] The polymerization method according to [5] above, wherein the pressure-sensitive adhesive has a Young's modulus [MPa] of 0.005 MPa or more before being subjected to the active energy ray irradiation treatment including the heating / AEL treatment. [7] The polymerization method according to [5] or [6] above, wherein the active energy ray irradiation treatment including the heating / AEL treatment is carried out so that the Young's modulus [MPa] of a cured product obtained by subjecting the treatment object to the active energy ray irradiation treatment including the heating / AEL treatment is 1.2 times or more the Young's modulus [MPa] of a cured product obtained by irradiating the treatment object with active energy rays under the same conditions except that heat is not applied to the treatment object. [8] The polymerization method according to any of [5] to [7] above, wherein the pressure-sensitive adhesive sheet has a peel force reduction rate of more than 20%, calculated by the following formula: Peel strength reduction rate [%] = (1 - F1 / F0) x ​​100 (wherein F0 is the initial peel strength [N / 20 mm] of the pressure-sensitive adhesive sheet relative to a glass plate, and F1 is the post-treatment peel strength [N / 20 mm] measured after the pressure-sensitive adhesive sheet is attached to a glass plate and subjected to an active energy ray irradiation treatment including the heating / AEL treatment.) [9] The polymerization method according to any one of [5] to [8] above, wherein the pressure-sensitive adhesive has a gel fraction of 1% or more before being subjected to an active energy ray irradiation treatment including the heating / AEL treatment.

[10] The polymerization method according to any one of [1] to [4] above, wherein the object to be treated is a liquid pressure-sensitive adhesive composition.

[11] The polymerization method according to any one of [1] to

[10] above, wherein the object to be treated comprises a radically polymerizable functional group containing a carbon-carbon double bond as the radically polymerizable functional group, and the active energy ray irradiation treatment including the heating / AEL treatment is carried out so that, in carbon-carbon double bond amount measurement based on peak intensity ratios in microscopic Raman analysis, the amount of carbon-carbon double bonds remaining in a cured product obtained by subjecting the object to the active energy ray irradiation treatment including the heating / AEL treatment is 5% or more less than the amount of carbon-carbon double bonds remaining in a cured product obtained by irradiating the object with active energy rays under the same conditions except for not heating the object to be treated.

[12] A method for producing a pressure-sensitive adhesive sheet, comprising subjecting a pressure-sensitive adhesive containing at least one of a monomer and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment in which the pressure-sensitive adhesive is irradiated with active energy rays (AEL) while being heated.

[13] A method for curing a pressure-sensitive adhesive, comprising: subjecting a pressure-sensitive adhesive containing at least one of a monomer and a polymer having a radical polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment in which the pressure-sensitive adhesive is irradiated with active energy rays (AEL) while heating the pressure-sensitive adhesive.

[14] A method for producing a pressure-sensitive adhesive, comprising subjecting a liquid pressure-sensitive adhesive composition containing at least one of a monomer and a polymer having a radical polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment in which the pressure-sensitive adhesive composition is irradiated with active energy rays (AEL) while applying heat to the pressure-sensitive adhesive composition.

[15] A method for producing a pressure-sensitive adhesive, comprising: coating a liquid pressure-sensitive adhesive composition containing at least one of a monomer and a polymer having a radical polymerizable functional group in the form of a film; and subjecting the film-like pressure-sensitive adhesive composition to an active energy ray irradiation treatment including a heating / AEL treatment in which the film-like pressure-sensitive adhesive composition is irradiated with active energy rays (AEL) while applying heat to the pressure-sensitive adhesive composition, thereby forming a pressure-sensitive adhesive layer from the film-like pressure-sensitive adhesive composition.

[0130] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0131] <Preparation of Pressure-Sensitive Adhesive Sheet> A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was charged with 100 parts of a monomer mixture containing methoxyethyl acrylate (MEA), acryloylmorpholine (ACMO), and hydroxyethyl acrylate (HEA) in a molar ratio of 80:20:20, and 65 parts of toluene as a polymerization solvent. 0.2 parts of benzoyl peroxide was added as a thermal polymerization initiator, and a polymerization reaction (solution polymerization) was carried out for 6 hours at 61 ° C. under a nitrogen atmosphere to obtain a solution containing acrylic polymer a. To this solution of acrylic polymer a, methacryloyloxyethyl isocyanate (MOI) in an amount equivalent to 16 moles relative to 20 moles of HEA used as a raw material for the acrylic polymer a was added, and an addition reaction treatment was carried out in an air stream at 50 ° C. for 48 hours to obtain a solution of acrylic polymer A having a methacryloyl group at the side chain end.

[0132] To the solution of the acrylic polymer A, 10 parts of dipentaerythritol hexaacrylate (DPHA) as a polyfunctional monomer, 0.3 parts of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E"; hereinafter referred to as "crosslinking agent CL1"), and 0.8 parts of a photoinitiator (trade name "Omnirad 651" manufactured by IGM Resins B.V.; hereinafter referred to as "Omni.651") were added per 100 parts of the acrylic polymer A, and the mixture was mixed uniformly to prepare a pressure-sensitive adhesive composition.

[0133] The pressure-sensitive adhesive composition obtained above was applied to the release surface of a commercially available PET release liner and dried at 80°C for 5 minutes to form a 30 μm thick pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer was laminated to one side of a 50 μm thick PET film (product "Lumirror S10", manufactured by Toray Industries, Inc.) used as a substrate, and aging was carried out at 50°C for 3 days to obtain a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet with substrate) S1. The adhesive surface of the pressure-sensitive adhesive sheet S1 was protected by the PET release liner used to form the pressure-sensitive adhesive layer.

[0134] The pressure-sensitive adhesive composition was also applied to the release surface of a commercially available PET release liner and dried at 80°C for 5 minutes to form a 30 µm thick pressure-sensitive adhesive layer. The release surface of a commercially available PET release liner was then bonded to this pressure-sensitive adhesive layer, and aging was carried out at 50°C for 3 days to obtain a pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet) S2. The pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet S2 was protected by the PET release liner used to form the pressure-sensitive adhesive layer and the PET release liner bonded to it after drying.

[0135] <Adhesive Treatment> (Example 1) An adhesive sheet having an adhesive layer or an evaluation sample prepared using the adhesive sheet was placed on a hot plate adjusted to 40°C, and subjected to a heating / AEL treatment (heating / UV treatment) in which UV light was irradiated under the following conditions while heat was applied using the hot plate. [UV Irradiation Conditions] UV Irradiator: Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810" Light source: high-pressure mercury lamp (characteristic wavelength 365 nm) Irradiation amount: cumulative light amount 600 mJ / cm ２ (Illuminance 2.5mW / cm ２ , irradiation time 240 seconds)

[0136] Example 2 Heating / AEL treatment (heating / UV treatment) was carried out in the same manner as in Example 1, except that a hot plate adjusted to 60° C. was used.

[0137] Comparative Example 1 A UV irradiation treatment was carried out under the same conditions as in Example 1, except that a non-operating hot plate (surface temperature: 25° C.) was used.

[0138] <Evaluation Method> (Peel Strength) The pressure-sensitive adhesive sheet S1 before treatment according to each example was cut together with the release liner to a size of 20 mm wide and 100 mm long. Under an environment of 23°C and 50% RH, the release liner was removed, and the exposed adhesive surface was bonded to an alkali glass plate (manufactured by Matsunami Glass Industry Co., Ltd., 1.35 mm thick, blue plate edge polished) as an adherend by rolling a 2 kg roller back and forth once. The adherend with the pressure-sensitive adhesive sheet attached was left to stand for 6 hours and used as an evaluation sample. The evaluation sample was placed in a tensile tester under an environment of 23°C and 50% RH, and the pressure-sensitive adhesive sheet was peeled from the adherend at a peel angle of 180° and a peel speed of 300 mm / min to measure the peel strength (initial peel strength) F0 [N / 20 mm width].

[0139] Furthermore, evaluation samples prepared in the same manner as above were subjected to the treatment according to each example (heating / UV treatment in the Examples, UV irradiation treatment in Comparative Example 1), and then, in the same manner as in the measurement of the initial peel force F0, the peel strength (post-treatment peel force) F1 [N / 20 mm width] was measured when the PSA sheet was peeled from the adherend under conditions of a peel angle of 180° and a peel speed of 300 mm / min in an environment of 23°C and 50% RH. Note that when performing the treatment according to each example above, the evaluation sample was placed on the hot plate with the alkali glass plate side facing down.

[0140] The obtained initial peel force F0 [N / 20 mm] and post-treatment peel force F1 [N / 20 mm] were substituted into the following formula to calculate the peel force reduction rate [%]: Peel force reduction rate [%] = (1 - F1 / F0) x ​​100

[0141] The PSA sheet to be evaluated may be backed with a resin film as needed before being used to prepare the evaluation sample. For example, if the PSA sheet to be evaluated is a double-sided PSA sheet, the non-measurement side may be backed with a resin film before measurement. Various resin films can be used as the backing resin film, with suitable examples including polyimide (PI) film and polyethylene terephthalate (PET) film. The thickness of the resin film is preferably approximately 10 μm to 100 μm, and preferably approximately 25 μm to 75 μm. A tensile tester such as Shimadzu's "EZ-S 500N" or an equivalent can be used.

[0142] (Young's Modulus) Before treatment according to each example, the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) S2 was cut together with the release liner to a size of 80 mm wide and 30 mm long. One release liner was removed from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was wound up on the other release liner in the longitudinal direction so as to prevent air bubbles from being trapped, thereby preparing a rod-shaped sample having a length of 30 mm. The rod-shaped sample was set in a tensile tester (manufactured by ORIENTEC, product name "RTC-1150A") and pulled under conditions of a measurement temperature of 23°C, a chuck distance of 10 mm, and a pulling speed of 50 mm / min. The initial elastic modulus was determined from the rise of the obtained stress-strain curve (S-S curve), and this was designated as the initial (pre-treatment) Young's modulus Y0 [MPa] of the pressure-sensitive adhesive layer.

[0143] Furthermore, the pressure-sensitive adhesive sheet (adhesive layer) S2 was subjected to the treatment according to each example (heating / UV treatment in the Examples, UV irradiation treatment in Comparative Example 1), and then a rod-shaped sample was prepared using the treated pressure-sensitive adhesive sheet S2 in the same manner as in the measurement of the initial Young's modulus Y0. The rod-shaped sample was pulled under conditions of a measurement temperature of 23°C, a chuck distance of 10 mm, and a tensile speed of 50 mm / min, and the initial elastic modulus was determined from the rise of the obtained stress-strain curve (S-S curve), which was designated as the post-treatment Young's modulus Y1 [MPa] of the pressure-sensitive adhesive layer. Furthermore, the values ​​of the post-treatment Young's modulus Y1 in Examples 1 and 2 were converted to a relative value, with the value of the post-treatment Young's modulus Y1 in Comparative Example 1 being set to 100.

[0144] The initial Young's modulus Y0 [MPa] and the post-treatment Young's modulus Y1 [MPa] obtained for each example were substituted into the following formula to calculate the Young's modulus increase ratio: Young's modulus increase ratio = (Y1 / Y0)

[0145] In preparing the rod-shaped sample, the cut width of the adhesive layer was set to 80 mm because the cross-sectional area of ​​the adhesive layer in the cross section along the width direction was set to 2.0 to 2.5 mm ２ It is desirable to adjust the cutting width depending on the thickness of the adhesive layer so that the cross-sectional area is approximately the same.

[0146] (Gel Fraction) The gel fraction of a pressure-sensitive adhesive (weight ratio of ethyl acetate insoluble matter) is measured by the following method. Approximately 0.1 g of a pressure-sensitive adhesive sample (weight Wg1) is wrapped in a porous polytetrafluoroethylene membrane (weight Wg2) with an average pore size of 0.2 μm in the shape of a purse, and the opening is tied with string (weight Wg3). The porous polytetrafluoroethylene (PTFE) membrane used is available from Nitto Denko Corporation under the trade name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent. The wrapped piece is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer out of the membrane. The wrapped piece is then removed, the ethyl acetate adhering to the outer surface is wiped off, and the wrapped piece is dried at 130° C. for 2 hours, and the weight of the wrapped piece (Wg4) is measured. Then, by substituting each value into the following formula, the gel fraction of the adhesive can be calculated: Gel fraction [%] = [(Wg4 - Wg2 - Wg3) / Wg1] x 100

[0147] Using the above method, the gel fraction (initial gel fraction) G0 [%] of the pressure-sensitive adhesive sample taken from the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) S2 before the treatment according to each example was measured, and the gel fraction (post-treatment gel fraction) G1 [%] of the pressure-sensitive adhesive sample taken from the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) S2 after the treatment according to each example (heating / UV treatment in the Examples, UV irradiation treatment in Comparative Example 1) was measured.

[0148] The initial gel fraction G0 [%] and the post-treatment gel fraction G1 [%] were substituted into the following formula to calculate the increase in gel fraction [%]: Increase in gel fraction [%] = (G1 - G0)

[0149] (Amount of carbon-carbon double bonds (C=C amount)) The pressure-sensitive adhesive sheet (adhesive layer) S2 before treatment according to each example was cut to an appropriate size, one release liner was removed from the pressure-sensitive adhesive layer, and the exposed adhesive surface was bonded to an alkali glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35 mm, blue plate edge polished product) by pressing with a 2 kg roller moving back and forth once, and then left to stand for 2 hours. This was used as an evaluation sample. The other release liner was removed from the pressure-sensitive adhesive layer of the evaluation sample, and microscopic Raman analysis was performed on the exposed adhesive surface (adhesive surface before treatment) under the following conditions. In the obtained Raman spectrum, －１ The intensity of the C═O peak near Ｃ＝Ｏ ) and 1630 cm －１ The intensity of the C═C peak (I Ｃ＝Ｃ ) and the peak intensity ratio (I Ｃ＝Ｃ / I Ｃ＝Ｏ ) was calculated, and the obtained value was defined as the initial carbon-carbon double bond amount D0. [Analysis conditions] Apparatus: Laser Raman microscope "RAMANTouch" manufactured by nanophoton Co., Ltd. Excitation wavelength: 532 nm Measurement wave number range: 200 to 3760 cm －１ Objective lens: 100x Detector: CCD

[0150] Furthermore, evaluation samples prepared in the same manner as above were subjected to the treatments according to each example (heating / UV treatment in the Examples, UV irradiation treatment in Comparative Example 1), and then the other release liner was removed from the pressure-sensitive adhesive layer, and the exposed adhesive surface (adhesive surface after treatment) was subjected to microscopic Raman analysis in the same manner as above. When the treatments according to each example were performed, the evaluation samples were placed on the hot plate with the alkali glass plate side facing downward. In the obtained Raman spectrum, －１ The intensity of the C═O peak near Ｃ＝Ｏ ) and 1630 cm －１ The intensity of the C═C peak (I Ｃ＝Ｃ ) and the peak intensity ratio (I Ｃ＝Ｃ / I Ｃ＝Ｏ) was calculated, and the obtained value was designated as the post-treatment carbon-carbon double bond amount D1. The post-treatment carbon-carbon double bond amount D1 values ​​of Examples 1 and 2 were converted into relative values, with the post-treatment carbon-carbon double bond amount D1 value of Comparative Example 1 being set to 100.

[0151] The outline of each example and the evaluation results are shown in Table 1.

[0152]

[0153] As shown in Table 1, in Examples 1 and 2, in which the adhesive was cured by UV irradiation treatment including heating / UV treatment, the Young's modulus Y1 after treatment was clearly higher than in Comparative Example 1, in which external heating was not performed. Furthermore, in Examples 1 and 2, the carbon-carbon double bond content D1 after treatment was clearly lower than in Comparative Example 1, and the amount of remaining carbon-carbon double bonds was small. These measurement results show that in Examples 1 and 2, the reactivity of the radically polymerizable functional groups contained in the adhesive (object to be treated) was able to be increased more than in Comparative Example 1.

[0154] Before the treatment of each example, the pressure-sensitive adhesive sheet S1 was cut to a size of 20 mm wide and 100 mm long, and then pressed against a circuit board (glass cloth-based epoxy resin copper-clad laminate) having an uneven surface under an environment of 23 ° C. and 50% RH with a 2 kg roller going back and forth once. The evaluation sample was then left to stand for 6 hours under the same environment, and the treatment of each example described above was then performed. The evaluation sample was then heated in an oven at 180 ° C. for 60 minutes, removed from an environment of 23 ° C. and 50% RH, and left to stand for 30 minutes. After that, the pressure-sensitive adhesive sheet was peeled off from the circuit board (adherend) at a peel angle of 180 ° C. and a speed of 300 mm / min. The surface of the adherend after peeling was observed with an optical microscope, and it was confirmed that adhesive residue was suppressed in Examples 1 and 2 compared to Comparative Example 1. A particularly significant adhesive residue suppression effect was observed in Example 2.

[0155] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0156] REFERENCE SIGNS LIST 1 Pressure-sensitive adhesive sheet 1A Adhesive surface 1B Back surface 10 Base material layer 10A One surface 10B Other surface 20 Pressure-sensitive adhesive layer 20A Adhesive surface 30 Release liner 50 Pressure-sensitive adhesive sheet with release liner

Claims

1. A polymerization method applied to the curing or production of an adhesive, comprising subjecting an object to be treated, which includes at least one of a monomer having a radically polymerizable functional group and a polymer having a radically polymerizable functional group, to an active energy ray irradiation treatment including a heating / AEL treatment in which active energy rays (AEL) are irradiated while heat is applied.

2. The polymerization method according to claim 1, wherein the active energy rays are non-thermal energy rays.

3. The polymerization method according to claim 1, wherein the active energy rays are ultraviolet (UV) rays.

4. The polymerization method according to claim 1, wherein the object to be treated is an adhesive forming an adhesive layer of an adhesive sheet.

5. The polymerization method according to claim 4, wherein the adhesive has a Young's modulus [MPa] of 0.005 MPa or more before being subjected to the active energy ray irradiation treatment including the heating / AEL treatment.

6. The polymerization method according to claim 4, wherein the active energy ray irradiation treatment including the heating / AEL treatment is carried out so that the Young's modulus [MPa] of a cured product obtained by subjecting the treatment object to the active energy ray irradiation treatment including the heating / AEL treatment is 1.2 times or more of the Young's modulus [MPa] of a cured product obtained by irradiating the treatment object with active energy rays under the same conditions except that heat is not applied to the treatment object.

7. The polymerization method according to claim 4, wherein the pressure-sensitive adhesive sheet has a peel strength reduction rate higher than 20% as calculated by the following formula: Peel strength reduction rate [%] = (1 - F1 / F0) x ​​100 (wherein F0 is the initial peel strength of the pressure-sensitive adhesive sheet against a glass plate [N / 20 mm], and F1 is the post-treatment peel strength [N / 20 mm] measured after the pressure-sensitive adhesive sheet is attached to a glass plate and subjected to an active energy ray irradiation treatment including the heating / AEL treatment.) 8. The polymerization method according to any one of claims 1 to 7, wherein the object to be treated contains a radically polymerizable functional group containing a carbon-carbon double bond as the radically polymerizable functional group, and the active energy ray irradiation treatment including the heating / AEL treatment is carried out so that, in a carbon-carbon double bond amount measurement based on a peak intensity ratio in a microscopic Raman analysis, the amount of carbon-carbon double bonds remaining in a cured product obtained by subjecting the object to the active energy ray irradiation treatment including the heating / AEL treatment is 5% or more less than the amount of carbon-carbon double bonds remaining in a cured product obtained by irradiating the object to be treated with active energy rays under the same conditions except for not heating the object to be treated.

9. A method for producing an adhesive sheet, comprising subjecting an adhesive containing at least one of a monomer and a polymer having a radically polymerizable functional group to an active energy ray irradiation treatment including a heating / AEL treatment in which the adhesive is irradiated with active energy rays while being heated.

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