Adhesive sheet for laser processing

Abstract

Provided is an adhesive sheet for laser processing, said sheet comprising a resin film as a base material and an adhesive layer provided to a first surface of the base material. The main component of the base material is a polyethylene. A resin material constituting the first surface of the base material contains 2 wt% or more of a resin A having a melting point of 120°C or higher.

Description

Laser processing adhesive sheet

[0001] The present invention relates to an adhesive sheet for laser processing. This application claims priority to Japanese Patent Application No. 2024-152737, filed on September 4, 2024, 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 in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Utilizing this property, adhesives are widely used in various fields for purposes such as bonding, fixing, surface protection, masking, and marking, for example, in the form of adhesive sheets having an adhesive layer on a substrate. For example, Patent Document 1 is a technical document relating to an adhesive film that can be used for surface protection during laser processing.

[0003] Japanese Patent Application Publication No. 2014-005372

[0004] In recent years, interest in laser processing techniques has grown. Laser processing techniques are widely used for cutting and drilling various materials. Typical examples of lasers used in such processing include carbon dioxide lasers with a dominant wavelength of approximately 9.3 μm to 10.6 μm and short-wavelength lasers with a dominant wavelength of approximately 0.9 μm to 1.1 μm. One example of laser processing involves attaching an adhesive sheet (laser processing adhesive sheet) as an auxiliary material to an adherend (a workpiece) and then irradiating the workpiece with laser light to cut the adhesive sheet and the workpiece. In particular, using short-wavelength laser light with a dominant wavelength of approximately 0.9 μm to 1.1 μm allows the energy required for processing to be efficiently applied to the workpiece. This can be advantageous for laser processing (e.g., cutting) workpieces made of iron-based materials such as stainless steel (SUS) as well as metal materials with high thermal conductivity (hereinafter also referred to as high-thermal-conductivity materials), such as aluminum and copper.

[0005] On the other hand, when laser processing such as cutting is performed on a workpiece in the above-mentioned manner, the adhesive sheet may float, peel, turn up, etc. near the processed end (typically, a location adjacent to the processed end), and a part of the workpiece surface may become exposed from the adhesive sheet. A workpiece to which an adhesive sheet has been attached and laser processing such as cutting is sometimes subjected to post-processing such as bending or drawing with the adhesive sheet still attached, and suppressing exposure of the workpiece surface after laser processing is beneficial, for example, from the viewpoint of suppressing damage to the workpiece or processing equipment (e.g., a mold) during the post-processing.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide an adhesive sheet for laser processing that can suppress exposure of the workpiece surface at the laser cut edge.

[0007] The present inventors have noticed that after laser cutting a workpiece with an adhesive sheet for laser processing attached together with the adhesive sheet, the exposed surface of the workpiece tends to occur more easily in areas where the laser cutting is nonlinear (e.g., broken lines), and that when laser cutting a workpiece made of a highly thermally conductive material, the exposed width of the workpiece surface from the cut edge tends to be large. Based on these trends, they have conducted various studies and found that using a specific resin material on the first surface side of the substrate (the work side when the adhesive sheet for laser processing is attached to the workpiece and used, and therefore the side that is susceptible to the temperature rise of the workpiece) is effective in suppressing the exposure of the workpiece surface at the laser cut edge, thereby completing the present invention.

[0008] The adhesive sheet for laser processing provided by this specification comprises a resin film as a substrate and an adhesive layer provided on a first surface of the substrate. The substrate is primarily composed of polyethylene. The resin material constituting the first surface of the substrate contains 2 wt. % or more of resin A having a melting point of 120°C or higher. An adhesive sheet for laser processing (hereinafter also referred to simply as "adhesive sheet") having such a configuration has moderate flexibility due to the use of a substrate (polyethylene-based substrate) primarily composed of polyethylene. This is advantageous from the viewpoints of ease of application of the adhesive sheet to a workpiece and conformability (ability to conform to surface shape, ability to conform to workpiece deformation, etc.). A polyethylene-based substrate is also preferable from the viewpoint of cuttability with laser light. Furthermore, at least the first surface of the polyethylene-based substrate (the side closest to the workpiece during use) is composed of a resin material containing 2 wt. % or more of resin A having a melting point of 120°C or higher, thereby effectively suppressing exposure of the workpiece surface at the laser-cut edge.

[0009] In some embodiments, the pressure-sensitive adhesive sheet preferably has a laser light absorption rate of 20% or more in the wavelength range of 900 nm to 1100 nm, thereby efficiently absorbing short-wavelength laser light (hereinafter also referred to as "specific laser light") having a dominant wavelength of 900 nm to 1100 nm, and enabling efficient laser processing using the energy of the absorbed specific laser light.

[0010] In some embodiments, the substrate is primarily made of low-density polyethylene (LDPE). Laser processing adhesive sheets having a substrate primarily made of LDPE are preferred in terms of ease of application to a workpiece, conformability (surface shape conformability, conformability to deformation, etc.), and laser cuttability. In a substrate primarily made of LDPE, the resin material constituting the first surface of the substrate contains 2 wt. % or more of resin A with a melting point of 120°C or higher, thereby achieving both the advantages of ease of application, conformability, and cuttability, as well as the suppression of exposure of the workpiece surface at the laser-cut edge. Generally, the melting point of LDPE is below 120°C.

[0011] In some embodiments, the resin material constituting the first surface of the substrate preferably contains a polyolefin as the resin A. For example, the resin material constituting the first surface of the substrate preferably contains at least one selected from the group consisting of high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP) as the resin A. The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in an embodiment having a substrate with such a configuration.

[0012] In some embodiments of the PSA sheet disclosed herein, the weight ratio of the resin A in the resin material constituting the first surface of the substrate may be higher than the weight ratio of the resin A in the entire weight of the substrate. Such a configuration in which the content of resin A on the first surface side of the substrate is higher than that of the entire substrate is preferable because it is possible to achieve the effect of suppressing exposure of the workpiece surface at the laser-cut edge by the composition of the first surface side of the substrate (the side that is susceptible to the temperature rise of the workpiece), while making it easy to adjust other properties that may be required of the substrate.

[0013] The pressure-sensitive adhesive sheet disclosed herein can contain a laser beam absorbent as needed. By containing a laser beam absorbent in the pressure-sensitive adhesive sheet, the laser beam absorption rate can be increased, and the laser processability of the adherend to which the pressure-sensitive adhesive sheet is attached can be improved. From the viewpoint of easily achieving both good laser beam absorbency and desired adhesive properties, it is preferable that the laser beam absorbent be contained in at least the substrate.

[0014] In some embodiments, the laser beam absorbent may preferably be at least one selected from the group consisting of carbon black, titanium oxide, titanium black, iron-based oxides, and manganese-based oxides. From the viewpoint of stable availability of materials, preferred laser beam absorbents include carbon black and iron-based oxides.

[0015] The adhesive sheet disclosed herein can be used, for example, by being attached to a workpiece and cut together with the workpiece by laser light, thereby exhibiting the effect of suppressing exposure of the workpiece surface at the laser cut edge. Therefore, the adhesive sheet disclosed herein can be preferably used as an adhesive sheet for laser processing that is cut with laser light (e.g., laser light such as a carbon dioxide laser or a short-wavelength laser). The adhesive sheet is particularly suitable as an adhesive sheet for laser processing that is cut with a short-wavelength laser light having a dominant wavelength in the range of 900 nm to 1100 nm (e.g., 1000 nm to 1100 nm). A suitable example of the laser processing application is the application of protecting the surface of a metal plate during laser processing of the metal plate.

[0016] It is a cross-sectional view showing a typical example of a configuration of an adhesive sheet for laser processing.It is a cross-sectional view showing a typical example of another configuration of an adhesive sheet for laser processing.It is a plan view showing a typical shape of a cutting line in a laser cutting test.

[0017] 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. Furthermore, 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 for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0018] In this specification, unless otherwise specified, the term "to" indicating a range of values ​​means that the range includes the values ​​before and after it as the lower and upper limits.

[0019] In addition, 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."

[0020] The concept of adhesive sheet in this specification may include those referred to as adhesive tape, adhesive label, adhesive film, etc. The adhesive layer referred to here is typically formed continuously, but is not limited to such a form and may be an adhesive layer formed in a regular or random pattern such as a dotted or striped pattern. The adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, it may be cut, punched, or otherwise processed into an appropriate shape depending on the application or mode of use.

[0021] As used herein, the term "adhesive" refers to a material that is in a soft solid (viscoelastic) state at temperatures around room temperature and that easily adheres to an adherend by pressure. The adhesive referred to here generally has a complex tensile modulus E ＊ (1Hz) <10 ７ dyne / cm ２ The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0022] <Configuration Example of Pressure-Sensitive Adhesive Sheet> One configuration example of the pressure-sensitive adhesive sheet for laser processing provided by the present specification is schematically shown in Figure 1. This pressure-sensitive adhesive sheet for laser processing 1 comprises a resin film 10 as a substrate and a pressure-sensitive adhesive layer 20 provided on its first surface 10A, and is used by attaching the pressure-sensitive adhesive layer 20 to an adherend (object to be processed, workpiece). In a preferred embodiment, the second surface 10B, which is the back surface of the resin film 10 (the surface opposite to the surface on which the pressure-sensitive adhesive layer 20 is provided), is a surface (release surface) having releasability. Before use (i.e., before being attached to an adherend), the pressure-sensitive adhesive sheet 1 may be wound into a roll so that the surface (adhesive surface) 20A of the pressure-sensitive adhesive layer 20 abuts against the back surface 10B of the resin film 10, thereby protecting the surface 20A. Alternatively, the surface of the pressure-sensitive adhesive layer may be protected by a release liner, at least the pressure-sensitive adhesive layer side of which serves as a release surface.

[0023] The resin film used as a substrate may have at least a two-layer structure. Therefore, the resin film may include at least a first layer and a second layer. In the example shown in FIG. 1 , the resin film 10 has a three-layer structure consisting of a first layer 11, a second layer 12, and an intermediate layer 13. The first layer 11 is disposed on the PSA layer 20 side relative to the second layer 12, and constitutes a first surface 10A, which is the surface of the resin film 10 facing the PSA layer 20 (hereinafter also referred to as the "front surface"). The second layer 12 is disposed on the back surface 10B side relative to the first layer 11, and constitutes a second surface (back surface) 10B of the resin film 10. This back surface 10B may become the outer surface of the PSA sheet 1 when the PSA sheet 1 is bonded to an adherend. Furthermore, the intermediate layer 13 is provided between the first layer 11 and the second layer 12. In an embodiment in which the resin film has at least a two-layer structure, the number of layers in the resin film is preferably about 2 to 7 (e.g., about 2 to 5), from the viewpoint of imparting different properties to each layer and from the viewpoint of manufacturing. In some embodiments using a resin film having a two or more layer structure, the resin film preferably has a three-layer structure, a four-layer structure, or a five-layer structure, with a three-layer structure being particularly preferred.

[0024] Furthermore, the adhesive sheet for laser processing disclosed herein may include a single-layer resin film 10 as a substrate, such as the adhesive sheet for laser processing 2 shown in FIG. 2 . A single-layer substrate can be advantageous, for example, in terms of the productivity and quality stability of the substrate. In this specification, the layer constituting the first surface of the substrate may be referred to as the first layer, regardless of whether the substrate has a single-layer or multilayer structure. Therefore, in the example shown in FIG. 2 , the resin film 10 has a single-layer structure consisting of a first layer 11, and both the first surface 10A and the second surface 10B are composed of the first layer 11.

[0025] In the adhesive sheet for laser processing disclosed herein, regardless of whether the substrate has a single-layer structure or a multilayer structure, the main component of the resin film 10 serving as the substrate is polyethylene. Furthermore, at least the layer (first layer) constituting the first surface 10A of the resin film (substrate) 10 is composed of a resin material containing 2% by weight or more of resin A having a melting point of 120°C or higher. This effectively prevents exposure of the workpiece surface at the laser-cut edge in an adhesive sheet for laser processing using a polyethylene-based substrate. Below, each element that can be included in the adhesive sheet for laser processing will be described in more detail.

[0026] <Substrate> The pressure-sensitive adhesive sheet disclosed herein includes a resin film (PE-based substrate) primarily composed of polyethylene (PE). Here, in this specification, "main component" refers to a component present in an amount of more than 50% by weight, unless otherwise specified. Therefore, when a resin film is primarily composed of PE, it means that the resin film contains more than 50% by weight of PE based on its total weight. The PE-based substrate may contain one type of PE or two or more types of PE. A PE-based substrate can easily provide adequate flexibility and flexibility. This is advantageous from the perspective of ease of application of the pressure-sensitive adhesive sheet to a workpiece and its conformability (such as conformability to the surface shape and conformability to workpiece deformation). Furthermore, a PE-based substrate can easily provide good cutting properties with a laser beam, and can effectively suppress exposure of the workpiece surface at the laser-cut edge. In some embodiments, the PE content in the PE-based substrate (when two or more types of PE are contained, the total content thereof) is preferably 60 wt% or more, more preferably 70 wt% or more, and may be 80 wt% or more, 90 wt% or more, 93 wt% or more, or 95 wt% or more. The PE content in the PE-based substrate may be 100 wt%, and in some embodiments, it is suitably less than 100 wt% (e.g., 99.5 wt% or less), and is preferably 99 wt% or less, and may be 98 wt% or less, or may be 97 wt% or less.

[0027] The PE contained in the PE-based substrate may be various polymers (ethylene-based polymers) containing ethylene as the main constituent monomer unit. The ethylene-based polymer may be a homopolymer of ethylene, or may be a copolymer (random copolymer, block copolymer, etc.) of ethylene as the main monomer with another α-olefin as a secondary monomer. Suitable examples of the α-olefin include α-olefins having 3 to 10 carbon atoms, such as propylene, 1-butene (which may be branched 1-butene), 1-hexene, 4-methyl-1-pentene, and 1-octene. The α-olefin as the secondary monomer may be copolymerized with the ethylene-based polymer at a ratio of, for example, approximately 10% by weight or less (typically approximately 5% by weight or less).

[0028] The PE may also be a PE containing a copolymer of ethylene with a monomer (functional group-containing monomer) having another functional group in addition to the polymerizable functional group, or a PE in which such a functional group-containing monomer is copolymerized with an ethylene-based polymer. Examples of copolymers of ethylene and functional group-containing monomers include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), and ethylene-(meth)acrylic acid (i.e., acrylic acid and / or methacrylic acid) copolymers crosslinked with metal ions.

[0029] The concept of PE here includes high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE). Although not particularly limited, the density of LDPE is generally 0.94 g / cm. ３ Less than (e.g., 0.90 g / cm ３ 0.94g / cm or more ３ The density of the HDPE is 0.94 g / cm ３ or more (for example, 0.94 g / cm ３ 0.97g / cm or more ３(See below).

[0030] The resin film used as the substrate may contain, in addition to PE as the main component, a resin other than PE as another resin component. Examples of resins other than PE (hereinafter also referred to as non-PE resins) include, but are not limited to, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polymers containing propylene as the main constituent monomer unit (homopolypropylene, random copolymers (random polypropylene) and block copolymers (block polypropylene) of propylene and other monomers), polyolefins copolymerized with ethylene as a secondary monomer, copolymers in which ethylene is copolymerized with the above-mentioned functional group-containing monomers as a secondary monomer, vinyl chloride resins (typically soft vinyl chloride resins), vinyl acetate resins, polyamide-based resins, and the like. The non-PE resin may be used, for example, to adjust the physical properties of the substrate. The non-PE resin may be blended with PE or, for example, may be contained in a layer other than PE in a multilayer substrate.

[0031] The PE substrate constituting the adhesive sheet disclosed herein has a resin material constituting its first surface (i.e., a resin composition forming the first layer of the substrate; hereinafter, also referred to as "resin material C1") containing 2 wt. % or more of resin A having a melting point of 120°C or higher. By using resin material C1 of this composition to form at least the first surface of the PE substrate, exposure of the workpiece surface at the laser-cut edge can be effectively suppressed. The reason for this is not particularly limited, but is thought to be as follows: During laser processing of a workpiece (typically a metal material), heat transfer from the area being processed by laser light irradiation (the processed edge) causes the temperature of the workpiece adjacent to the processed edge to rise, and this temperature increase is also transmitted to the adhesive sheet attached to the workpiece. In particular, when laser cutting a workpiece made of a highly thermally conductive material or in a non-linear area where the laser cutting is performed (where the laser irradiation time per unit area is long or where heat is likely to stagnate), the temperature rise of the workpiece adjacent to the processed edge tends to be greater. According to the adhesive sheet disclosed herein, the resin material C1 that constitutes the first surface of the PE-based substrate (i.e., the side that is most susceptible to the temperature rise of the workpiece) contains resin A with a melting point of 120°C or higher, which is thought to impart appropriate heat resistance to the substrate and to be effective in suppressing exposure of the workpiece surface at the laser-cut end (for example, lifting, peeling, rolling up, etc. of the adhesive sheet (this may be a state in which the substrate peels off or rolls up, leaving the adhesive layer or part thereof on the surface of the workpiece)).

[0032] Resin A can be selected from the various resins described above or other known resins that satisfy the requirement of a melting point of 120°C or higher, and can be used alone or in combination of two or more. The melting point can be a value based on differential scanning calorimetry (DSC). More specifically, the melting point of Resin A can be measured according to the melting point measurement method described in the Examples below. The measurement temperature range in DSC can be adjusted appropriately depending on the melting point of Resin A. For example, if the melting point is expected to exceed 190°C, the upper limit of the measurement temperature range can be set to 250°C or 300°C. Furthermore, if the manufacturer provides a nominal melting point value based on DSC, that value can also be used. Note that if the nominal melting point range has a range, for example, if the melting point is expressed as X°C to Y°C, (X+Y) / 2 [°C] should be used as the melting point. Furthermore, if the nominal melting point value is expressed as, for example, P°C ± Q°C, P°C should be used as the melting point. The same applies to other resin components that may be contained in the base material (for example, resin B, which will be described later).

[0033] The melting point of resin A may be, for example, 120°C or higher and 350°C or lower, and from the viewpoint of ease of laser cutting of the substrate, it is suitably 300°C or lower, advantageously 250°C or lower, preferably 200°C or lower, more preferably 180°C or lower, may be 170°C or lower, may be 165°C or lower, may be 160°C or lower, may be 150°C or lower, may be 140°C or lower, or may be 130°C or lower. In some embodiments, the melting point of resin A may be higher than 120°C (e.g., 121°C or higher or 122°C or higher), may be 125°C or higher, may be 130°C or higher, or may be 140°C or higher.

[0034] In some embodiments, a polyolefin satisfying the melting point requirement described above may be preferably used as resin A. Selecting a polyolefin (e.g., polyethylene) as resin A, which is a component of resin material C1 constituting at least the first surface of a PE-based substrate, may be advantageous in terms of the laser cuttability of the substrate. Suitable examples of polyolefins that can be used as resin A include HDPE, LLDPE, and PP (including homo-PP, random PP, and block PP). These may be used alone or in combination of two or more. Among these, HDPE and LLDPE are preferred, with HDPE (e.g., HDPE with a melting point in the range of approximately 125°C to 150°C) being particularly preferred.

[0035] In some embodiments, the content of resin A in the resin material (resin material C1) constituting the first surface of the substrate may be, for example, 2.5% by weight or more or 3% by weight or more. From the viewpoint of better suppressing exposure of the workpiece surface at the laser-cut edge, it is advantageous to have a content of more than 3% by weight (e.g., 3.5% by weight or more), preferably 4% by weight or more, more preferably 5% by weight or more, 7.5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 30% by weight or more, 40% 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, 80% by weight or more, 90% by weight or more, or 95% by weight or more. Resin material C1 having a content of resin A exceeding 50% by weight can be preferably used, for example, as a material for forming the layer (first layer) constituting the first surface of a substrate having a multilayer structure of two or more layers. The content of resin A in resin material C1 may be 100% by weight. In some embodiments, from the viewpoint of the cuttability of the substrate with laser light, the content of resin A in resin material C1 is suitably 99.9% by weight or less, preferably 99.8% by weight or less, or may be 99.5% by weight or less, or may be 99.2% by weight or less. In some embodiments, from the viewpoint of the balance with other properties, the moldability and productivity of the substrate, etc., the content of resin A in resin material C1 may be, for example, 95% by weight or less, 85% by weight or less, 75% by weight or less, 65% by weight or less, 55% by weight or less, 50% by weight or less (e.g., less than 50% by weight), 45% by weight or less, 35% by weight or less, or 25% by weight or less. Resin material C1 having a resin A content of less than 50% by weight can be preferably used, for example, as a material for forming a substrate having a single-layer structure.

[0036] In some embodiments, the weight percentage of resin A in resin material C1 is preferably higher than the weight percentage of resin A in the entire weight of the substrate. This configuration allows the weight percentage of resin A in the entire substrate to be reduced while suppressing exposure of the workpiece surface at the laser-cut edge by the composition of the first surface side of the substrate. This can be advantageous from the perspective of ease of adjusting other properties required of the substrate and the formability of the substrate. In such an embodiment, the difference (S-T) between the weight percentage of resin A in resin material C1 (S wt%) and the weight percentage of resin A in the entire weight of the substrate (T wt%) is greater than 0 wt%, and may be, for example, 1 wt% or more. In some embodiments, it is preferably 2 wt% or more, and may be 5 wt% or more, 10 wt% or more, 15 wt% or more, or 25 wt% or more.

[0037] In some embodiments, the resin material C1 may contain, in addition to the resin A, a resin having a melting point of less than 120°C (hereinafter also referred to as "resin B") as another resin component. Resin B may be selected from the various resins described above or other known resins that satisfy the requirement of a melting point of less than 120°C, and one type may be used alone or two or more types may be used in combination. From the viewpoint of making it easier to optimally exhibit the effects of resin A, the melting point of resin B is suitably 90°C or higher, preferably 100°C or higher, and may be 105°C or higher, or may be 110°C or higher.

[0038] In some embodiments, a polyolefin having a melting point of less than 120°C may be preferably used as resin B. Selecting a polyolefin (e.g., polyethylene) as resin B, which is a component of resin material C1 constituting at least the first surface of a PE-based substrate, can be advantageous in terms of the laser cuttability of the substrate. A particularly preferred example of resin B is LDPE (e.g., LDPE having a melting point in the range of approximately 105°C to 115°C). LDPE may be used in combination with other resins. From the viewpoints of laser cuttability and moldability, it is preferable that both resin A and resin B are polyolefins, and it is more preferable that both resin A and resin B are polyolefins and at least one of them (e.g., at least resin B) is polyethylene. Suitable examples of combinations in which resin A and resin B are both polyolefins include a combination of HDPE and LDPE, a combination of PP and LDPE, and a combination of LLDPE and LDPE.

[0039] In embodiments in which resin material C1 includes resin B (e.g., LDPE) in addition to resin A, the content of resin B in resin material C1 can be selected so that the total content with resin A is 100% by weight or less (preferably 99.9% by weight or less, e.g., 99.8% by weight or less, 99.5% by weight or less, or 99.2% by weight or less). In some embodiments, the content of resin B in resin material C1 may be, for example, less than 98% by weight, preferably 97% by weight or less, more preferably 96% by weight or less, and may be 95% by weight or less, 90% by weight or less, 85% by weight or less, 75% by weight or less, 65% by weight or less, 55% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, or 10% by weight or less. Furthermore, from the viewpoint of making it easier to obtain the effects of using resin B, in some embodiments, the content of resin B in resin material C1 may be, for example, 25% by weight or more, 35% by weight or more, 45% by weight or more, 55% by weight or more, 65% by weight or more, 75% by weight or more, 85% by weight or more, or 90% by weight or more.

[0040] The thickness of the layer (first layer) constituting the first surface of the substrate can be, for example, 1 μm or more from the viewpoint of the moldability of the substrate. In some embodiments, from the viewpoint of making it easier for the first layer to exhibit the effect of containing a predetermined amount of resin A, the thickness of the first layer is advantageously 2 μm or more, preferably 3 μm or more, more preferably 4 μm or more, may be 5 μm or more, may be 7 μm or more, may be 10 μm or more, may be 20 μm or more, may be 30 μm or more, may be 50 μm or more, may be 70 μm or more. In addition, from the viewpoint of avoiding the total thickness of the substrate becoming too large, the thickness of the first layer of the substrate is suitably 150 μm or less, preferably 130 μm or less, more preferably 110 μm or less, may be 90 μm or less, may be 70 μm or less, may be 50 μm or less, may be 40 μm or less, may be 25 μm or less, may be 20 μm or less, may be 15 μm or less, may be 10 μm or less.

[0041] In embodiments in which the substrate is a multilayer resin film having two or more layers, the composition of the resin material constituting the layers other than the first layer is selected so that PE is the main component of the entire substrate. Therefore, in a multilayer substrate, each layer other than the first layer may contain PE as a main or secondary component, or may not contain PE, and may contain resin A or may not contain resin A. In embodiments in which any layer other than the first layer (e.g., a layer adjacent to the back side of the first layer) contains resin A, the content of resin A in that layer is not particularly limited and may be, for example, greater than 0 wt %, 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, or may be selected from the range of values ​​exemplified for the content of resin A in the first layer. The content (weight percentage) of resin A in the first layer and layers other than the first layer may be similar or different. In some embodiments, it is preferable that the weight percentage of resin A in layers other than the first layer is lower than that of the first layer, or that no resin A is contained. This makes it possible to suitably realize a configuration in which the weight ratio of resin A in the first layer of a multilayer substrate is higher than the weight ratio of resin A in the entire substrate.

[0042] In some embodiments, the main component of the substrate is preferably LDPE (e.g., LDPE having a melting point in the range of approximately 105°C to 115°C). Substrates primarily composed of LDPE have moderate softness and flexibility, which is advantageous in terms of ease of application of the PSA sheet to a workpiece and conformability (conformability to the surface shape, conformability to workpiece deformation, etc.). Furthermore, substrates primarily composed of LDPE are more likely to exhibit good cuttability with laser light and are more likely to exhibit the effect of suppressing exposure of the workpiece surface at the laser cut edge. In some embodiments, the LDPE content in the PE-based substrate is preferably 60% by weight or more, more preferably 70% by weight or more, and may be 75% by weight or more, 80% by weight or more, 90% by weight or more, 92% by weight or more, or 93% by weight or more. In some embodiments, the LDPE content in the PE-based substrate may be, for example, 99.5% by weight or less, preferably 99% by weight or less, more preferably 98% by weight or less, or may be 97% by weight or less, or may be 95% by weight or less.

[0043] (Laser beam absorbent) The substrate may contain a laser beam absorbent as needed. A suitable example of a substrate containing a laser beam absorbent is a substrate containing a laser beam absorbing layer. In a substrate having a multilayer structure containing two or more layers, it is preferable that at least one layer is a laser beam absorbing layer containing a laser beam absorbent. For example, it is preferable that the layer (first layer) constituting at least the first surface of the substrate is a laser beam absorbing layer containing a laser beam absorbent. In a substrate having a multilayer structure of three or more layers, it is preferable that at least the first layer (the layer constituting the first surface) and the second layer (the layer constituting the second surface) are laser beam absorbing layers. Each layer constituting a substrate having a multilayer structure of two or more layers may be a laser beam absorbing layer.

[0044] Examples of laser light absorbers include metals such as aluminum, iron, stainless steel, titanium, nickel, zirconium, tungsten, copper, silver, gold, zinc, molybdenum, chromium, manganese, and alloys containing these as main components; metal compounds such as oxides, sulfides, nitrides, carbides, hydroxides, and oxyhydroxides of the above metals; and other inorganic materials (e.g., calcium carbonate, silica, alumina, titanium oxide, talc, clay, aluminum silicate, basic lead carbonate, zinc oxide, strontium titanate, barium sulfate, calcium sulfate, iron oxide (FeO, Fe ３ O ４ , Fe ２ O ３ etc.), manganese dioxide, titanium black, chromium oxide (CrO, Cr ２ O ３ Examples of suitable laser beam absorbents include: ferrite, iron sulfide, molybdenum sulfide, etc.; carbon materials such as carbon black and carbon fiber; and organic compounds such as quaterrylene compounds, perylene compounds, phthalocyanine compounds, cyanine compounds, aminium compounds, naphthalocyanine compounds, naphthoquinone compounds, diimonium compounds, anthraquinone compounds, and aromatic dithiol metal complexes (e.g., nickel complexes). In a laser beam absorbing layer containing a laser beam absorbent in a resin material, it is preferable to use, as the laser beam absorbent, a material having a higher thermal decomposition temperature than the resin component constituting the laser beam absorbing layer.

[0045] When a powdered laser beam absorbent is used, the shape of the particles constituting the powder is not particularly limited and may be, for example, flaky, spherical, needle-like, polyhedral, irregular, etc. Usually, a flaky, spherical, or needle-like laser beam absorbent can be preferably used. The average particle size of the laser beam absorbent is not particularly limited and may be, for example, 0.005 μm or more and 20 μm or less. From the viewpoint of dispersibility, usually, a laser beam absorbent having an average particle size of 10 μm or less or 5 μm or less can be preferably used. From the viewpoint of efficiently increasing the laser beam absorptance with a small amount of laser beam absorbent, in some embodiments, the average particle size of the laser beam absorbent may be, for example, 3 μm or less, 1 μm or less, 0.6 μm or less, 0.4 μm or less, or 0.3 μm or less. Furthermore, from the viewpoint of powder handling ease and ease of uniform dispersion, in some embodiments, the average particle size of the laser beam absorbent may be, for example, 0.008 μm or more, 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, or 0.2 μm or more. In this specification, unless otherwise specified, the term "average particle size" refers to the particle size at 50% of the integrated value in the particle size distribution measured using a particle size distribution measuring device based on a laser scattering / diffraction method (50% volume average particle size).

[0046] In some embodiments, the laser light-absorbing layer may contain carbon black as the laser light-absorbing agent. From the viewpoint of improving the cuttability of the substrate with laser light, for example, it is preferable that at least the layer constituting the first surface of the substrate contains carbon black. In a substrate having a three-layer structure or more, it is preferable that at least one layer among the layer constituting the first surface of the substrate and the layer not constituting the second surface of the substrate contains carbon black. For example, carbon black having an average particle size of 10 nm to 500 nm (more preferably 10 nm to 120 nm) can be used. Carbon black may be used alone or in combination with other laser light-absorbing agents.

[0047] In some embodiments, the laser light absorptivity of the substrate is preferably set so that the laser light absorptivity of the pressure-sensitive adhesive sheet containing the substrate is 20% or more. In some embodiments, the laser light absorptivity of the substrate may be, for example, 15% or more, usually 20% or more is appropriate, and may be 25% or more, 30% or more, 45% or more, 60% or more, or 75% or more. The laser light absorptivity of the substrate may be 100%, but in practice it is preferably 95% or less, may be 90% or less, or may be 85% or less. The transmittance and reflectance of the substrate can be appropriately selected from the same range as the transmittance and reflectance of the pressure-sensitive adhesive sheet described below.

[0048] In this specification, "laser light absorptance" refers to a value calculated from the transmittance T (%) and reflectance R (%) of a sample measured using a spectrophotometer (for example, a spectrophotometer manufactured by Hitachi High-Technologies Corporation, model "U-4100" or an equivalent), using the following formula (I): Absorbance A (%) = 100 (%) - T (%) - R (%) (I)

[0049] In this specification, for example, "laser light absorptance in the wavelength range of 900 nm to 1100 nm" refers to the minimum laser light absorptance in that wavelength range. Furthermore, unless otherwise specified, laser light absorptance in this specification refers to the laser light absorptance on the back surface of the adhesive sheet or substrate (the surface on the side irradiated with laser light, i.e., the surface opposite the surface attached to the workpiece).

[0050] The content of the laser beam absorbent in the laser beam absorbing layer of the substrate can be appropriately set so as to obtain the desired laser beam absorption characteristics. In some embodiments, the content of the laser beam absorbent in the laser beam absorbing layer may be, for example, 0.01 wt % or more, preferably 0.05 wt % or more, more preferably 0.07 wt % or more, and may be 0.1 wt % or more, 0.3 wt % or more, 0.5 wt % or more, 0.8 wt % or more, 1 wt % or more, 3 wt % or more, or 5 wt % or more. In addition, the content of the laser beam absorbent in the laser beam absorbing layer of the substrate (when two or more laser beam absorbents are used, the total content thereof) may be, for example, 20 wt % or less, and from the viewpoint of reducing laser processing residues, it is preferably 15 wt % or less, and more preferably 10 wt % or less. Although not particularly limited, black absorbents (e.g., carbon black, iron oxide (e.g., FeO, Fe ３ O ４ When a black-based absorbent (e.g., titanium black, manganese dioxide, etc.) is used, the content of the black-based absorbent in the laser light absorbing layer is preferably, for example, 3 wt % or less (e.g., less than 3 wt % or 2.5 wt % or less), and more preferably 2 wt % or less (e.g., less than 2 wt % or 1.5 wt % or less), from the viewpoint of improving the appearance of the workpiece after laser processing. Furthermore, when a white-based absorbent (e.g., titanium oxide, calcium carbonate, silica, etc.) is used as the laser light absorbent, the content of the white-based absorbent in the laser light absorbing layer can be, for example, 1 wt % or more, 3 wt % or more, 4 wt % or more, or 5 wt % or more, and can be 20 wt % or less, 15 wt % or less, or 10 wt % or less. A white-based absorbent and a black-based absorbent may be used in combination, and in that case, the total content of the laser light absorbent can be selected from the same range as the content of the white-based absorbent described above. The content of the laser beam absorbent in the entire substrate (i.e., the weight ratio of the laser beam absorbent to the weight of the entire substrate) can be appropriately selected from the same range as the content of the laser beam absorbent in the laser beam absorbing layer.

[0051] In some embodiments, it is preferable that the first and second surfaces of the resin film as a substrate are configured to have different brightnesses. This ensures good cuttability with laser light (e.g., short-wavelength laser light) while imparting properties such as design, surface printability, weather resistance, and identifiability to the second surface (back surface). Such a configuration in which the brightnesses of the first and second surfaces of the substrate are different can be suitably realized, for example, by using a resin film with a multilayer structure of two or more layers as the substrate. The brightness L of the first and second surfaces of the resin film is ＊ The difference is preferably 5 or more, more preferably 10 or more, and particularly preferably 20 or more (e.g., 30 or more, typically 40 or more). The difference may be 65 or less (e.g., 55 or less, typically 45 or less). Here, the term "brightness" or "brightness L" used in this specification refers to the difference between the lightness L and the lightness L. ＊ " means L ＊ a ＊ b ＊ Lightness L defined in the color system ＊ This refers to the standard recommended by the International Commission on Illumination in 1976 or the standard specified in JIS Z 8729.

[0052] The first surface of the resin film is not particularly limited, but may be L ＊ a ＊ b ＊ Lightness L defined in the color system ＊ The lightness L ＊ is preferably 25 or less. ＊ By setting the L of the first surface low, it is easy to achieve a configuration in which the entire adhesive film including the adhesive layer that may be adjacent and the resin film can be suitably cut by laser light (for example, short wavelength laser light). ＊ a ＊ b ＊ Chromaticity a specified in the color system ＊ is not particularly limited, but may be in the range of ±15 (for example, ±10, typically ±5). ＊ is not particularly limited, and may be in the range of ±15 (for example, ±10, typically ±5).

[0053] In some embodiments, the second surface of the resin film is ＊ a ＊ b ＊ Lightness L defined in the color system ＊ The brightness L is suitably 40 or more (for example, 45 or more, typically 55 or more), and preferably 60 or more (for example, 65 or more, typically 70 or more). This increases the whiteness of the outer surface of the PSA film, and provides properties such as designability, surface printability, weather resistance, and distinguishability. ＊ can be 90 or less (for example, 85 or less). ＊ From the same viewpoint, L of the second surface ＊ a ＊ b ＊ Chromaticity a specified in the color system ＊ Although there are no particular limitations, it is preferable that the chromaticity b is in the range of ±15 (for example, ±10, typically -8 to 2). ＊ is not particularly limited, but is preferably in the range of ±15 (for example, ±10, typically ±5).

[0054] The first surface of the substrate (i.e., the surface on which the pressure-sensitive adhesive layer is provided) may be subjected to an appropriate surface treatment, if necessary, to enhance adhesion to the pressure-sensitive adhesive layer. Examples of surface treatments to enhance adhesion include corona discharge treatment, acid treatment, ultraviolet irradiation treatment, and plasma treatment.

[0055] In some preferred embodiments, the second surface of the substrate is a release surface. The phrase "the second surface of the substrate is a release surface" typically means that a PSA sheet, with the surface (adhesive surface) of the PSA layer provided on the first surface of the substrate in contact with the release surface, can be peeled off without leaving any adhesive residue (residual adhesive) on the release surface.

[0056] As a substrate having a second surface as a release surface, a resin film having a release treatment applied to the second surface (typically, a release treatment layer formed by a release treatment agent) can be suitably used. The release treatment layer can be formed using known or conventional release treatment agents. Examples of such release treatment agents include silicone-based release treatment agents and non-silicone-based release treatment agents. Non-silicone-based release treatment agents can include fluorine-based and long-chain alkyl-based release treatment agents. Condensation or addition polymerization release treatment agents of polyamides and the like can also be used. In some embodiments, non-silicone-based release treatment agents (e.g., long-chain alkyl-based release treatment agents) can be preferably used. The release treatment method (typically, the method of applying the release treatment agent) is not particularly limited, and conventional coating means can be appropriately employed. Note that, in this specification, the number of layers constituting the resin film as the substrate does not include the release treatment layer formed by a release treatment agent. For example, a substrate having a three-layer structure in which a release treatment layer formed by a release treatment agent is provided on the second surface of the resin film is counted as having three layers.

[0057] In some embodiments, the resin material constituting the second surface (hereinafter also referred to as "resin material C2") preferably contains a release agent. Resin material C2 is preferably a resin composition containing at least a release agent and a resin component. Examples of the resin component include, but are not limited to, the various materials exemplified as resins constituting the resin film as the substrate. Examples of release agents that can be used as a component of resin material C2 include ethylene-vinyl alcohol copolymers, fatty acid amide-based additives, low-molecular-weight polyolefin waxes, long-chain alkyl-based additives, and silicone-based release agents. The release agents can be used alone or in combination with two or more suitable compounds. Preferred examples of release agents include long-chain alkyl-based additives and silicone-based release agents. Examples of silicone-based release agents include silylated polyolefins, silicone resins, silicone alkoxy oligomers, silicone oligomers, silicone master pellets, silicone rubber powders, and silicone emulsions. Examples of silylated polyolefins that can be used include silylated polyolefins prepared by the method described in the examples of JP 2011-26448 A. Silylated polyolefins are particularly preferred.

[0058] The content of the release agent in resin material C2 is not particularly limited and can be, for example, about 0.01 to 80% by weight. In some embodiments, the content of the release agent may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 0.7% by weight or more, or 1% by weight or more. In some embodiments, the content of the release agent in resin material C2 may be, for example, 70% by weight or less, 50% by weight or less, 30% by weight or less, or 10% by weight or less, from the viewpoint of compatibility with the resin components.

[0059] <Adhesive Layer> The adhesive constituting the adhesive layer in the technology disclosed herein is not particularly limited, and for example, known rubber-based adhesives, acrylic-based adhesives, polyester-based adhesives, polyurethane-based adhesives, silicone-based adhesives, etc. can be used. From the viewpoints of adhesive performance and cost, rubber-based adhesives or acrylic-based adhesives can be preferably used. Here, a rubber-based adhesive refers to an adhesive in which the main component of the polymer component contained in the adhesive (typically a component contained in more than 50 wt%) is a rubber-based polymer, and an acrylic-based adhesive refers to an adhesive in which the main component of the polymer component contained in the adhesive is an acrylic polymer. The same applies to polyester-based adhesives, polyurethane-based adhesives, silicone-based adhesives, etc.

[0060] In this specification, the term "acrylic polymer" refers to a polymer containing more than 50% by weight of monomer units derived from an acrylic monomer as the monomer units constituting the polymer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule.

[0061] In addition, in this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate in a comprehensive sense, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

[0062] The pressure-sensitive adhesive layer may have a single layer structure or a laminate structure having two or more layers with the same or different compositions. From the viewpoint of increasing the uniformity of the pressure-sensitive adhesive layer and reducing the range of variation in the adhesive strength of the back surface, a pressure-sensitive adhesive layer with a single layer structure is preferred.

[0063] As the adhesive constituting the adhesive layer of the adhesive sheet disclosed herein, a rubber-based adhesive is particularly preferably used from the viewpoint of exhibiting better high-speed peel strength. Examples of the rubber-based adhesive include natural rubber-based adhesives and synthetic rubber-based adhesives.

[0064] The concept of the natural rubber-based PSA includes those in which the base polymer is natural rubber and those in which the base polymer is modified natural rubber. The natural rubber is not particularly limited, and examples thereof include standard Malaysian rubber (SMR), standard Vietnamese rubber (SVR), ribbed smoked sheet (RSS), pale crepe, etc. The modified natural rubber preferably has a structural moiety derived from natural rubber of 50% by weight or more (e.g., 60% by weight or more). Specific examples of the modified natural rubber include, but are not limited to, acrylic-modified natural rubber.

[0065] Specific examples of the rubber polymer that serves as the base polymer of the synthetic rubber pressure-sensitive adhesive include polybutadiene, polyisoprene, butyl rubber, polyisobutylene, styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), and the like.

[0066] In a preferred embodiment, the base polymer of the rubber-based pressure-sensitive adhesive layer is natural rubber. For example, natural rubber having a Mooney viscosity of approximately 10 to 60 under measurement conditions of MS(1+4) 100°C (using an L-type rotor, preheating for 1 minute, viscosity measurement time for 4 minutes, and test temperature of 100°C) is preferred. Pressure-sensitive adhesive sheets having a natural rubber-based pressure-sensitive adhesive layer tend to exhibit a more rapid increase in adhesion to an adherend than pressure-sensitive adhesive sheets having a synthetic rubber-based pressure-sensitive adhesive layer. This allows for the pressure-sensitive adhesive sheet to be suitably prevented from lifting or peeling due to assist gas pressure, even if the time between attaching the pressure-sensitive adhesive sheet to a workpiece (adherend) and subjecting the workpiece to laser processing is shortened.

[0067] The rubber-based pressure-sensitive adhesive layer in the technology disclosed herein may have a composition in which a base polymer is blended with another polymer (hereinafter also referred to as a secondary polymer). Such secondary polymers may be, for example, acrylic polymers, polyester polymers, polyurethane polymers, silicone polymers, etc., which can serve as base polymers for acrylic pressure-sensitive adhesives, polyester pressure-sensitive adhesives, polyurethane pressure-sensitive adhesives, silicone pressure-sensitive adhesives, etc. Alternatively, the secondary polymers may be any of the rubber-based polymers described above other than the base polymers. Such secondary polymers may be used alone or in combination of two or more.

[0068] Such a secondary polymer is used in an amount of 100 parts by weight or less (when two or more secondary polymers are used, this refers to the total amount) per 100 parts by weight of the base polymer. Typically, it is appropriate to use 70 parts by weight or less of the secondary polymer per 100 parts by weight of the base polymer, and preferably 50 parts by weight or less. The rubber-based PSA layer may be substantially free of a secondary polymer (i.e., substantially 100% by weight of the polymer component is the base polymer). Alternatively, the rubber-based PSA layer may be substantially free of polymer components other than rubber-based polymers (for example, a rubber-based PSA layer substantially free of polymer components other than natural rubber and modified natural rubber).

[0069] The pressure-sensitive adhesive sheet disclosed herein may have an acrylic pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive. Examples of preferred acrylic pressure-sensitive adhesives include those in which the base polymer (the main component of the polymer components) is an acrylic polymer having a monomer composition in which an alkyl (meth)acrylate such as butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate is the main component, and a modifying monomer copolymerizable with the alkyl (meth)acrylate is added as needed. Examples of the modifying monomer include hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid; styrene-based monomers such as styrene; vinyl esters such as vinyl acetate; and the like. Such acrylic pressure-sensitive adhesives can be obtained by conventional polymerization methods such as solution polymerization, emulsion polymerization, and ultraviolet (UV) polymerization.

[0070] The pressure-sensitive adhesive layer may contain a tackifier as needed. Examples of tackifiers include one or more tackifier resins selected from known rosin-based resins, rosin derivative resins, petroleum-based resins (C5-based, C9-based, etc.), terpene-based resins, and ketone-based resins. Examples of rosin-based resins include gum rosin, wood rosin, and tall oil rosin, as well as stabilized rosin, polymerized rosin, and modified rosin. Examples of rosin derivative resins include esters of the rosin-based resins, phenol-modified resins, and esters thereof. Examples of petroleum-based resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrogenated versions of these. Examples of terpene-based resins include α-pinene resins, β-pinene resins, aromatic-modified terpene resins, and terpene-phenol resins. Examples of ketone-based resins include ketone-based resins obtained by condensation of ketones with formaldehyde. Such tackifiers may be used alone or in appropriate combination of two or more. Among them, preferred tackifiers include rosin resins, rosin derivative resins, aliphatic (C5) petroleum resins, and terpene resins. These tackifier resins can be suitably used in, for example, a rubber-based pressure-sensitive adhesive layer, an acrylic-based pressure-sensitive adhesive layer, and the like.

[0071] The amount of the tackifier used (when two or more types are used, the total amount) is typically approximately 20 to 150 parts by weight (preferably approximately 30 to 100 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of improving high-speed peel strength, in some embodiments, the amount of tackifier used may be, for example, 30 parts by weight or more, 40 parts by weight or more, or even 45 parts by weight or more per 100 parts by weight of the base polymer. Furthermore, from the viewpoint of avoiding the occurrence of adhesive residue due to a decrease in cohesive strength, in some embodiments, the amount of tackifier used per 100 parts by weight of the base polymer may be, for example, 85 parts by weight or less, or even 75 parts by weight or less. In some embodiments, the amount of tackifier used per 100 parts by weight of the base polymer may be, for example, less than 70 parts by weight, 65 parts by weight or less, 55 parts by weight or less, or 50 parts by weight or less. Reducing the amount of tackifier used can be advantageous, for example, from the viewpoint of reducing the workload when peeling the PSA sheet from the adherend and preventing the PSA sheet from tearing.

[0072] In some embodiments in which the PSA layer contains natural rubber as the base polymer, a combination of tackifier A having a Hansen solubility parameter distance Ra (NR-A) with the natural rubber of 1.5 or less and tackifier B having a Hansen solubility parameter distance Ra (NR-B) with the natural rubber of 2.5 or more and 5.0 or less can be used. PSA layers formed from PSA containing natural rubber tend to exhibit excellent high-speed peel strength. Furthermore, the use of natural rubber in combination with a tackifier that exhibits specific compatibility with natural rubber tends to favorably improve the adhesiveness of the PSA layer.

[0073] The Hansen solubility parameter (HSP) is a three-dimensional representation of the Hildebrand solubility parameter δ, which is divided into three components: a dispersion term δd, a polar term δp, and a hydrogen bonding term δh. ２ = δd ２ +δp ２ +δh ２The dispersion term δd indicates the effect of dispersion force, the polar term δp indicates the effect of dipole-dipole force, and the hydrogen bond term δh indicates the effect of hydrogen bond force. The HSP distance Ra of two substances is calculated from the difference Δδd in the dispersion term between the two substances, the difference Δδp in the polar term, and the difference Δδh in the hydrogen bond term, Ra = {4 × Δδd ２ +Δδp ２ +Δδh ２} １／２ The Hansen solubility parameter is expressed as follows: the smaller the Ra, the higher the compatibility, and the larger the Ra, the lower the compatibility. Details of the Hansen solubility parameter are described in Charles M. Hansen, Hansen Solubility Parameters; A User's Handbook (CRC Press, 2007), and for substances for which literature values ​​are unknown, the values ​​can be calculated using known computer software such as Hansen Solubility Parameters in Practice (HSPiP).

[0074] The tackifier A tends to be highly compatible with natural rubber, and by using it in combination with natural rubber, even when a relatively large amount of tackifier is contained, the uniformity of the adhesive layer is maintained at a high level, and adhesive properties (e.g., low-speed peel strength) tend to be improved. From the viewpoint of improving low-speed peel strength, Ra(NR-A), which is the HSP distance between tackifier A and natural rubber, is more preferably 1.2 or less (e.g., 1.0 or less), even more preferably 0.9 or less, may be 0.88 or less, may be 0.87 or less, may be 0.86 or less, or may be 0.85 or less. The lower limit of Ra(NR-A) is not particularly limited, but from the viewpoint of adhesive properties, it is usually appropriate to be 0.3 or more, preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.7 or more, may be 0.75 or more, or may be 0.8 or more. In addition, when the PSA layer disclosed herein contains two or more types of tackifier A, the HSP distance between tackifier A and natural rubber, Ra(NR-A), is the weighted average of the HSP distances between each tackifier A and natural rubber, calculated by the weight-based content of each tackifier A. Examples of tackifiers that can be suitably used as tackifier A include C5 petroleum resins. Examples of the C5 petroleum resins include aliphatic petroleum resins, alicyclic petroleum resins, and hydrogenated versions thereof. As tackifier A, one of these can be used alone, or two or more can be used in combination.

[0075] The amount of tackifier A used (when two or more types of tackifiers A are used, the total amount) is typically approximately 20 to 170 parts by weight (preferably approximately 30 to 150 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of improving high-speed peel strength, in some embodiments, the amount of tackifier A used may be, for example, 35 parts by weight or more, 40 parts by weight or more, or 45 parts by weight or more per 100 parts by weight of the base polymer. Furthermore, in some embodiments, the amount of tackifier A used per 100 parts by weight of the base polymer may be, for example, 120 parts by weight or less, or even less than 100 parts by weight. In some embodiments, the amount of tackifier A used per 100 parts by weight of the base polymer may be, for example, 95 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, 60 parts by weight or less, or 55 parts by weight or less. Reducing the amount of tackifier A used can be advantageous, for example, from the standpoint of reducing the workload when peeling the PSA sheet from the adherend and preventing the PSA sheet from tearing.

[0076] The PSA layer disclosed herein further contains, as a tackifier, a tackifier B having relatively low compatibility with natural rubber. Specifically, the HSP distance between tackifier B and natural rubber (hereinafter also referred to as "Ra(NR-B)") is 2.5 or greater. Such tackifier B tends to have a high affinity for residues (polishing residues) of abrasives, cleaning agents, etc., which can be factors that reduce peel strength. Therefore, a PSA layer containing tackifier B tends to improve both low-speed peel strength and high-speed peel strength, even for workpieces with polishing residues attached to their surfaces. From the viewpoint of maintaining the uniformity of the PSA layer, it is preferable that Ra(NR-B), which is the HSP distance between tackifier B and natural rubber, is not too large. From this viewpoint, Ra(NR-B) is preferably 5.0 or less. For example, when Ra(NR-B) is 2.5 or more and 5.0 or less, the adhesive has a sufficiently high affinity for both natural rubber and polishing residues, and therefore when used together with natural rubber, the adhesive tends to improve the peel strength (low-speed peel strength and high-speed peel strength) even for workpieces having polishing residues present.

[0077] From the viewpoint of improving affinity with residues that may be present on the surface of the object to be processed, Ra(NR-B), which is the HSP distance between tackifier B and natural rubber, is more preferably 2.6 or more (e.g., 2.65 or more), even more preferably 2.7 or more, and particularly preferably 2.8 or more (e.g., 2.85 or more). From the viewpoint of uniformity of the PSA layer, Ra(NR-B) is more preferably 4.5 or less, even more preferably 4.0 or less, and particularly preferably 3.0 or less (e.g., 2.9 or less). In addition, when the PSA layer disclosed herein contains two or more types of tackifier B, the HSP distance between tackifier B and natural rubber, Ra(NR-B), is the weighted average of the HSP distances between each tackifier B and natural rubber, calculated based on the weight content of each tackifier B.

[0078] Examples of tackifiers that can be suitably used as tackifier B include rosin-based resins, rosin derivative resins, C9 petroleum resins, terpene-based resins, ketone-based resins, and xylene-based resins. Examples of the rosin-based resins include gum rosin, wood rosin, tall oil rosin, and other rosins, as well as stabilized rosin, polymerized rosin, and modified rosin. Examples of the rosin derivative resins include esters of the rosin-based resins, phenol-modified resins, and esterified products thereof. Examples of the C9 petroleum resins include aromatic petroleum resins, copolymerized petroleum resins, and hydrogenated versions of these. Examples of the terpene-based resins include α-pinene resins, β-pinene resins, aromatic-modified terpene resins, and terpene phenol-based resins. Examples of the ketone-based resins include ketone-based resins obtained by condensation of ketones with formaldehyde. Examples of the xylene-based resin include xylene resins formed by crosslinking m-xylene with methylene bonds or ether bonds, and resins obtained by modifying these with phenols or polyhydric alcohols. Among these, rosin-based resins, rosin derivative resins, terpene-based resins, and xylene-based resins are preferred, with rosin-based resins, rosin derivative resins, and terpene-based resins being particularly preferred. As the tackifier B, one of these can be used alone, or two or more can be used in combination.

[0079] The amount of tackifier B used (when two or more types of tackifiers B are used, the total amount) is typically approximately 0.5 to 75 parts by weight (preferably approximately 1 to 60 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of improving low-speed peel strength, in some embodiments, the amount of tackifier B used may be, for example, 3 parts by weight or more, 5 parts by weight or more, or 7 parts by weight or more per 100 parts by weight of the base polymer. Furthermore, in some embodiments, the amount of tackifier B used per 100 parts by weight of the base polymer may be, for example, 50 parts by weight or less, 40 parts by weight or less, or less than 35 parts by weight. In some embodiments, the amount of tackifier B used per 100 parts by weight of the base polymer may be, for example, 32 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 15 parts by weight or less. Reducing the amount of tackifier B used can be advantageous, for example, from the standpoint of reducing the workload when peeling the PSA sheet from the adherend and preventing the PSA sheet from tearing.

[0080] The relationship between Ra(NR-A) and Ra(NR-B) is not particularly limited. From the viewpoint of imparting affinity to both natural rubber and polishing residue, it is effective to use a combination of two or more tackifiers that differ in compatibility with natural rubber. From this viewpoint, it is preferable to use a combination of tackifier A and tackifier B, in which the difference between Ra(NR-A) and Ra(NR-B) is 1.2 or more. The difference between Ra(NR-A) and Ra(NR-B) is more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. Furthermore, from the viewpoint of improving compatibility in the pressure-sensitive adhesive layer and improving adhesive properties, the difference between Ra(NR-A) and Ra(NR-B) is preferably 4.5 or less, more preferably 3.5 or less (for example, 3.0 or less), even more preferably 2.5 or less, and may be 2.3 or less.

[0081] The PSA layer disclosed herein may further contain a tackifier other than tackifier A and tackifier B, provided that the effects of the present invention are not significantly impaired. Examples of such other tackifiers include those having an HSP distance from natural rubber of more than 1.5 and less than 2.5, or more than 5.0. From the viewpoint of maintaining the uniformity of the PSA layer, it is preferable to select as the other tackifier a tackifier having an HSP distance from natural rubber of more than 1.5 and less than 2.5.

[0082] The amount of the other tackifier used is not particularly limited. The amount of the other tackifier used is usually 20 parts by weight or less per 100 parts by weight of the base polymer, and may be 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or 1 part by weight or less. From the viewpoint of simplifying the composition, in a preferred embodiment, the PSA layer disclosed herein does not contain any tackifier other than tackifier A and tackifier B.

[0083] The total amount of tackifier used is typically approximately 20 to 200 parts by weight (e.g., approximately 20 to 150 parts by weight, preferably approximately 30 to 100 parts by weight) per 100 parts by weight of base polymer (e.g., a base polymer containing natural rubber). From the viewpoint of improving high-speed peel strength, in some embodiments, the amount of tackifier used may be, for example, 30 parts by weight or more, 40 parts by weight or more, or even 45 parts by weight or more per 100 parts by weight of base polymer. Furthermore, in some embodiments, the amount of tackifier used per 100 parts by weight of base polymer may be, for example, 85 parts by weight or less, or 75 parts by weight or less. In some embodiments, the amount of tackifier used per 100 parts by weight of base polymer may be, for example, less than 70 parts by weight, 65 parts by weight or less, 55 parts by weight or less, or 50 parts by weight or less. Reducing the amount of tackifier used can be advantageous, for example, from the viewpoint of reducing the workload when peeling the PSA sheet from the adherend and preventing the PSA sheet from tearing.

[0084] The pressure-sensitive adhesive layer can contain a crosslinking agent. The use of a crosslinking agent can impart appropriate cohesive strength to the pressure-sensitive adhesive layer. A pressure-sensitive adhesive layer containing a crosslinking agent can be obtained, for example, by forming the pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing the crosslinking agent. The crosslinking agent can be contained in the pressure-sensitive adhesive layer in a form after crosslinking reaction, a form before crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, or the like. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction.

[0085] The amount of crosslinking agent used can be, for example, in the range of 0.005 parts by weight or more and 10 parts by weight or less per 100 parts by weight of the base polymer. The amount of crosslinking agent used per 100 parts by weight of the base polymer may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more. Furthermore, from the viewpoint of improving adhesion to the surface of the adherend (object to be processed), the amount of crosslinking agent used per 100 parts by weight of the base polymer may be, for example, less than 5.0 parts by weight, less than 4.0 parts by weight, 3.5 parts by weight or less, or 2.5 parts by weight or less. The technology disclosed herein can also be suitably implemented in an embodiment in which the amount of crosslinking agent used per 100 parts by weight of the base polymer is less than 2.0 parts by weight or 1.5 parts by weight or less.

[0086] Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, peroxide-based crosslinking agents, and the like. Preferred examples of the crosslinking agents include isocyanate-based crosslinking agents and epoxy-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. In some embodiments, isocyanate-based crosslinking agents can be preferably used. The isocyanate-based crosslinking agents can be used alone or in combination of two or more. The isocyanate-based crosslinking agent may be used in combination with another crosslinking agent, for example, an epoxy-based crosslinking agent.

[0087] The isocyanate crosslinking agent can be a compound having two or more isocyanate groups per molecule (including isocyanate regenerating functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization, etc.) Examples of the isocyanate crosslinking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

[0088] More specifically, examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), polymeric MDI, xylylene diisocyanate and polymethylene polyphenyl isocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name: Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name: Coronate HL), and isocyanates of hexamethylene diisocyanate. Examples of suitable isocyanate adducts include an anurate (manufactured by Tosoh Corporation, trade name: Coronate HX), a trimethylolpropane adduct of xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D110N), a trimethylolpropane adduct of xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D120N), a trimethylolpropane adduct of isophorone diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D140N), a trimethylolpropane adduct of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D160N); polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols; and polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, aromatic isocyanates and alicyclic isocyanates are preferred.

[0089] The amount of the isocyanate crosslinking agent used may be, for example, about 0.1 parts by weight or more, about 0.5 parts by weight or more, about 1.0 parts by weight or more, or more than 1.5 parts by weight, relative to 100 parts by weight of the base polymer. From the viewpoint of obtaining a higher usage effect, in some preferred embodiments of the pressure-sensitive adhesive layer, the amount of the isocyanate crosslinking agent used relative to 100 parts by weight of the base polymer may be, for example, more than 2.0 parts by weight, about 2.5 parts by weight or more, more than 2.5 parts by weight, or about 2.7 parts by weight or more. Furthermore, the amount of the isocyanate crosslinking agent used relative to 100 parts by weight of the base polymer may be, for example, 10 parts by weight or less, 7 parts by weight or less, or 5 parts by weight or less.

[0090] The adhesive layer (e.g., a rubber-based adhesive layer) can contain a laser beam absorbent as needed. That is, the adhesive layer can be a laser beam absorbing layer. In an adhesive layer consisting of multiple layers, a laser beam absorbent can be contained in at least one of the layers. As the laser beam absorbent to be contained in the adhesive layer, one or more types can be appropriately selected from the laser beam absorbents exemplified above. The content of the laser beam absorbent in the adhesive layer is usually 5 wt% or less of the adhesive layer, and from the viewpoint of adhesive performance, it is preferably 3 wt% or less, and may be 1 wt% or less. The technology disclosed herein can also be preferably implemented in an embodiment in which the adhesive layer does not substantially contain a laser beam absorbent.

[0091] In addition, the pressure-sensitive adhesive layer may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesives, such as crosslinking aids, plasticizers, softeners, fillers, antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, light stabilizers, etc. As such additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed explanations thereof will be omitted.

[0092] The method for providing such a pressure-sensitive adhesive layer on the first surface of the substrate is not particularly limited. For example, a pressure-sensitive adhesive composition containing pressure-sensitive adhesive layer-forming components in an appropriate medium (e.g., a solution in which the pressure-sensitive adhesive layer-forming components are dissolved in an organic solvent, or a dispersion in which the components are dispersed in an aqueous solvent) can be applied to the substrate and dried or cured to form a pressure-sensitive adhesive layer directly on the substrate; a pressure-sensitive adhesive layer formed on a surface having releasability is transferred to the substrate; or the pressure-sensitive adhesive layer-forming components are melt-heated together with the substrate-forming components and laminated by co-extrusion molding. To form a pressure-sensitive adhesive layer constituting a pressure-sensitive adhesive sheet with higher high-speed peel strength, a method of applying a pressure-sensitive adhesive composition is preferably adopted from the viewpoint of ease of handling of the pressure-sensitive adhesive layer-forming components. The pressure-sensitive adhesive composition can be prepared, for example, by mixing a polymer component, typically a tackifier, other components used as necessary, and the medium using a conventional method. Various conventionally known methods can be used to apply the pressure-sensitive adhesive composition. Specific examples of the coating method include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater or the like.

[0093] The thickness of the pressure-sensitive adhesive layer can be appropriately set so as to obtain appropriate adhesive performance depending on the application of the pressure-sensitive adhesive sheet. The thickness of the pressure-sensitive adhesive layer is typically 0.5 μm to 50 μm. From the viewpoint of improving adhesion to the adherend, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 1.5 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, or 10 μm or more. Furthermore, the thickness of the pressure-sensitive adhesive layer may be, for example, 30 μm or less, 20 μm or less, 18 μm or less, 16 μm or less, or 15 μm or less. A small thickness of the pressure-sensitive adhesive layer can be advantageous, for example, in a pressure-sensitive adhesive sheet that can be used in an embodiment in which it is laser cut together with the adherend (workpiece), from the viewpoint of the speed and precision of laser processing.

[0094] <Adhesive Sheet> (Laser Light Absorption Characteristics) In some embodiments of the adhesive sheet disclosed herein, the adhesive sheet preferably has a laser light absorptivity of 20% or more in the wavelength range of the laser light used for processing (typically, the laser light absorptivity at the main wavelength of the laser light). This laser light absorptivity refers to the proportion of laser light actually absorbed by the adhesive sheet out of the laser light irradiated onto the adhesive sheet. An adhesive sheet with a laser light absorptivity of 20% or more can efficiently absorb laser light. In some embodiments, the laser light absorptivity of the adhesive sheet may be, for example, 25% or more, 30% or more, 45% or more, 60% or more, or 75% or more. The laser light absorptivity of the adhesive sheet may be 100%, but in practice, 95% or less is preferable, and it may be 90% or less, or 85% or less.

[0095] The transmittance and reflectance of the pressure-sensitive adhesive sheet are not particularly limited. In some embodiments, the pressure-sensitive adhesive sheet may have a laser light transmittance of less than 70% at a wavelength at which the laser light absorption rate is minimum within the wavelength range of the laser light used for processing, for example, less than 50%, less than 20%, less than 10%, less than 5%, less than 3%, less than 1%, or even 0%. In some embodiments, the pressure-sensitive adhesive sheet may have a laser light reflectance of less than 50% at a wavelength at which the laser light absorption rate is minimum, for example, less than 40%, less than 20%, or less than 10%. In some embodiments, the reflectance may be, for example, 3% or more, 5% or more, 10% or more, or 15% or more. A pressure-sensitive adhesive sheet that satisfies at least one of the above transmittance and the above reflectance (preferably both) is likely to have the preferred laser light absorbance disclosed herein.

[0096] In the pressure-sensitive adhesive sheet disclosed herein, the lightness L ＊ , chromaticity a ＊ , chromaticity b ＊ is the lightness L of the first surface of the resin film described above. ＊ , chromaticity a ＊ , chromaticity b ＊The lightness L of the back surface of the pressure-sensitive adhesive sheet can be appropriately selected from the same range. ＊ , chromaticity a ＊ , chromaticity b ＊ is the lightness L of the second surface of the resin film described above. ＊ , chromaticity a ＊ , chromaticity b ＊ It can be appropriately selected from the same range.

[0097] The thickness of the pressure-sensitive adhesive sheet is not particularly limited, but is usually approximately 10 μm to 200 μm. From the viewpoint of the handleability of the pressure-sensitive adhesive sheet, in some embodiments, the thickness of the pressure-sensitive adhesive sheet may be, for example, 20 μm or more, 25 μm or more, 40 μm or more, 55 μm or more, or 80 μm or more. Furthermore, from the viewpoint of, for example, the speed and precision of laser processing, the thickness of the pressure-sensitive adhesive sheet may be, for example, 150 μm or less, 120 μm or less, or 100 μm or less. In some cases, the thickness of the pressure-sensitive adhesive sheet may be 80 μm or less, 60 μm or less, or 50 μm or less.

[0098] (Low-Speed ​​Peel Strength) The pressure-sensitive adhesive sheet disclosed herein preferably has a low-speed peel strength (against SUS plate) of 0.5 N / 10 mm or more, measured 30 minutes after application to a stainless steel (SUS) plate at a tensile speed of 0.3 m / min. Pressure-sensitive adhesive sheets with high low-speed peel strength (against SUS plate) tend to effectively suppress peeling of the pressure-sensitive adhesive sheet in subsequent processes (e.g., bending, drawing, etc.). From the viewpoint of achieving even greater effectiveness, in some embodiments, the low-speed peel strength (against SUS plate) of the pressure-sensitive adhesive sheet may be, for example, 1.0 N / 10 mm or more, 1.5 N / 10 mm or more, or 2.0 N / 10 mm or more. Although there is no particular upper limit to the low-speed peel strength (against SUS plate), from the viewpoint of reducing the effort required to peel off the unnecessary PSA sheet after the processing step of the workpiece (adherend) and improving workability, and from the viewpoint of suppressing adhesive residue on the adherend surface after peeling the PSA sheet, in some embodiments, the low-speed peel strength (against SUS plate) of the PSA sheet may be, for example, 10 N / 10 mm or less, 8.0 N / 10 mm or less, 6.0 N / 10 mm or less, or 5.0 N / 10 mm or less. The low-speed peel strength (against SUS plate) can be adjusted, for example, by selecting the type and thickness of the PSA layer, the type and amount of crosslinking agent used, the type and amount of release agent used, the use of optional components such as a tackifying resin, etc.

[0099] The low-speed peel strength (against SUS plate) can be measured by the following method. Specifically, a test piece is prepared by cutting the pressure-sensitive adhesive sheet into a strip measuring 10 mm wide and 100 mm long. The adhesive surface of this test piece is pressed against a stainless steel plate (SUS304BA plate) as an adherend by rolling it back and forth once using a 2 kg rubber roller as specified in JIS Z0237:2000. This sample is left for 30 minutes under a standard environment of 23°C and 50% RH, and then the peel strength (unit: N / 10 mm) is measured under the standard environment at a tensile speed of 0.3 m / min and a peel angle of 180° using a universal tensile tester. A universal tensile / compression tester (device name "Tension / Compression Tester, TCM-1kNB", manufactured by Minebea Co., Ltd.) can be used as the tensile tester.

[0100] (High-speed peel strength) The pressure-sensitive adhesive sheet disclosed herein preferably has a high-speed peel strength (against SUS plate) of 2.0 N / 10 mm or more, measured 30 minutes after application to a stainless steel (SUS) plate at a tensile speed of 30 m / min. Pressure-sensitive adhesive sheets with high high-speed peel strength (against SUS plate) tend to be able to effectively suppress lifting of the pressure-sensitive adhesive sheet (typically, lifting of the pressure-sensitive adhesive layer from the workpiece) when cut. From the viewpoint of achieving a higher effect, in some embodiments, the high-speed peel strength (against SUS plate) of the pressure-sensitive adhesive sheet may be, for example, 2.5 N / 10 mm or more, 3.0 N / 10 mm or more, or 3.5 N / 10 mm or more. Although there is no particular upper limit to the high-speed peel strength (against SUS plate), from the viewpoint of reducing the workload when peeling the PSA sheet from the workpiece and preventing the PSA sheet from tearing, in some embodiments, the high-speed peel strength (against SUS plate) of the PSA sheet may be, for example, 10 N / 10 mm or less, 9.5 N / 10 mm or less, 9.0 N / 10 mm or less, or 8.5 N / 10 mm or less. The high-speed peel strength (against SUS plate) can be adjusted, for example, by selecting the type and thickness of the PSA layer, selecting the type and amount of crosslinking agent, selecting the type and amount of release agent, using optional components such as a tackifying resin, etc.

[0101] The high-speed peel strength (against SUS plate) can be measured by the following method. Specifically, a test piece is prepared by cutting the pressure-sensitive adhesive sheet into a strip of 10 mm width and 100 mm length. The adhesive surface of this test piece is pressed against a stainless steel plate (SUS304BA plate) as an adherend by rolling it back and forth once with a 2 kg rubber roller as specified in JIS Z0237:2000. This sample is left for 30 minutes under a standard environment of 23°C and 50% RH, and then, under the standard environment, the peel strength (unit: N / 10 mm) is measured using a universal tensile tester at a tensile speed of 30 m / min and a peel angle of 180°. As the tensile tester, a universal tensile / compression tester (device name "Tension / Compression Tester, TCM-1kNB", manufactured by Minebea Co., Ltd.) can be used. The stainless steel plate (SUS304BA plate) used as the adherend was cleaned by the method specified in JIS Z0237: 2000. The same applies to the stainless steel plate (SUS304BA plate) used as the adherend in the measurement of low-speed peel strength (against SUS plate) described below.

[0102] <Applications> The adhesive sheet for laser processing disclosed herein can suppress exposure of the workpiece surface at the laser-processed edge (e.g., laser-cut edge) of the workpiece. Taking advantage of its feature of effectively suppressing exposure of the workpiece surface, for example, in laser processing of workpieces made of highly thermally conductive materials or in non-linear portions of laser processing, it can be preferably used in a state where it is attached to a workpiece to be processed with various lasers and laser-cut during the laser processing of the workpiece. The laser light used for the laser processing is not particularly limited, and various conventionally known lasers can be used. For example, excimer lasers such as ArF excimer laser, KrF excimer laser, and XeCl excimer laser, solid-state lasers such as YAG laser, YLF laser, YVO4 laser, and titanium sapphire laser, semiconductor lasers (sometimes referred to as diode lasers), fiber lasers, and carbon dioxide lasers can be used. The type of laser processing performed on a workpiece with the adhesive sheet disclosed herein attached is not particularly limited, and can include, for example, cutting, drilling, milling, and engraving.

[0103] The material of the workpiece is not particularly limited as long as it can be cut by laser light (e.g., laser light from a carbon dioxide laser or fiber laser). Examples of the material include metal or semimetal materials such as iron, iron alloys (carbon steel, stainless steel, chromium steel, nickel steel, etc.), aluminum, aluminum alloys, nickel, tungsten, copper, copper alloys, titanium, titanium alloys, and silicon; resin materials such as polyolefin resin, polycarbonate resin, and acrylic resin; ceramic materials such as alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide, silicon carbide, gallium nitride, and gypsum; glass materials such as aluminosilicate glass, soda-lime glass, soda-aluminosilicate glass, and quartz glass; cellulose-based materials such as paper, cardboard, wood, and plywood; and laminates and composites thereof. Suitable examples of the workpiece include metal materials such as iron, aluminum, copper, titanium, and alloys containing these metals as the main component (e.g., stainless steel). The shape of the workpiece is not particularly limited and may be plate-shaped, cylindrical, block-shaped, or the like.

[0104] The adhesive sheet disclosed herein can be preferably used in such laser processing by adhering it to the surface of the workpiece on the side irradiated with laser light. Furthermore, for purposes such as protecting the surface of the workpiece before, during, or after laser processing, the adhesive sheet can also be attached to the surface (back surface) opposite the side irradiated with laser light. The adhesive sheet disclosed herein can be preferably used in such laser processing using a short-wavelength laser with a dominant wavelength of approximately 900 to 1100 nm (e.g., 1000 to 1100 nm). Examples of such short-wavelength lasers that can be used include fiber lasers with a dominant wavelength of approximately 1050 nm and diode lasers with a dominant wavelength of approximately 950 nm.

[0105] The matters disclosed by this specification include the following. [1] An adhesive sheet for laser processing, comprising a resin film as a substrate and a pressure-sensitive adhesive layer provided on a first surface of the substrate, wherein the substrate is mainly composed of polyethylene, and the resin material constituting the first surface of the substrate contains 2% by weight or more of resin A having a melting point of 120°C or higher. [2] The adhesive sheet for laser processing according to [1] above, wherein the adhesive sheet has a laser light absorptance of 20% or more in a wavelength range of 900 nm to 1100 nm. [3] The adhesive sheet for laser processing according to [1] or [2] above, wherein the substrate is mainly composed of low-density polyethylene. [4] The adhesive sheet for laser processing according to any of [1] to [3] above, wherein the resin material constituting the first surface of the substrate contains polyolefin as resin A. [5] The pressure-sensitive adhesive sheet for laser processing according to any one of [1] to [4] above, wherein the resin material constituting the first surface of the substrate contains, as the resin A, at least one selected from the group consisting of high-density polyethylene, linear low-density polyethylene, and polypropylene. [6] The pressure-sensitive adhesive sheet for laser processing according to any one of [1] to [5] above, wherein the weight ratio of the resin A in the resin material constituting the first surface of the substrate is higher than the weight ratio of the resin A in the total weight of the substrate. [7] The pressure-sensitive adhesive sheet for laser processing according to any one of [1] to [6] above, wherein the pressure-sensitive adhesive layer is a rubber-based pressure-sensitive adhesive layer. [8] The pressure-sensitive adhesive sheet for laser processing according to any one of [1] to [7] above, wherein the substrate contains a laser beam absorbent. [9] The pressure-sensitive adhesive sheet for laser processing according to [8] above, wherein the laser beam absorbent contains at least one selected from the group consisting of carbon black, titanium oxide, iron-based oxide, titanium black, and manganese-based oxide.

[10] The pressure-sensitive adhesive sheet for laser processing according to any one of [1] to [9] above, which is used by being cut with a laser beam having a dominant wavelength of 900 nm to 1100 nm.

[0106] 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 "%" representing amounts used and contents are by weight unless otherwise specified.

[0107] The raw materials used to prepare the PSA sheets in the following examples are as follows: LDPE: low-density polyethylene (manufactured by Tosoh Corporation, trade name "Petrothene 186R") HDPE: high-density polyethylene (manufactured by Tosoh Corporation, trade name "Nipolon Hard 5700") LLDPE: linear low-density polyethylene (manufactured by Tosoh Corporation, trade name "Nipolon Z ZF220") PP: homopolypropylene (manufactured by Prime Polymer Co., Ltd., trade name "Prime Polypro F-300SP") CB: carbon black powder with an average particle size of 20 nm TiO ２ : Titanium dioxide powder having an average particle size of 0.2 μm Tackifier A1: Aliphatic petroleum resin (manufactured by Nippon Zeon Co., Ltd., trade name "Quintone A100", HSP distance to natural rubber 0.8) Tackifier B1: Polymerized rosin (manufactured by Arakawa Chemical Industries, Ltd., trade name "Aradigm R-95", HSP distance to natural rubber 2.9) Adhesive composition P1: To 100 parts of natural rubber, 50 parts of tackifier A1, 25 parts of tackifier B1, 2 parts of an antioxidant (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac NS-5"), 2.5 parts of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals, Inc., trade name "Takenate D-101A"), and toluene were added and mixed to prepare adhesive composition P1.

[0108] The HSP distance between the tackifier and the natural rubber was calculated using structural formula editor software (Material Studio (ver. 8.0) and Open Babel GUI (ver. 2.4.1)) and HSPiP (5th Edition 5.2.06).

[0109] The melting points (melting temperatures) measured by the following method were 110°C for the LDPE, 130°C for the HDPE, 164°C for the PP, and 122°C for the LLDPE. [Melt Point Measurement] The melting points (melting temperatures) were measured under the following conditions in accordance with heat flow rate differential scanning calorimetry of JIS K7121 (1987). Apparatus: TA Instruments, model "DSC Q2000" Sample mass: 3 to 5 mg Measurement temperature range: 25 to 200°C Heating rate: 10°C / min

[0110] <Preparation of Pressure-Sensitive Adhesive Sheet> (Example 1) A pressure-sensitive adhesive film 1 having the same configuration as that shown in FIG. 1 was prepared as follows. Specifically, the raw materials shown in Table 1 were blended to prepare resin materials for forming the first layer, intermediate layer, and second layer. Films were formed using a three-layer co-extrusion blown film molding machine at a die temperature of 165°C (blowing method) to obtain a three-layer resin film with a total thickness of 90 μm. The second surface (surface on the second layer side) of the obtained resin film was subjected to a release treatment using a long-chain alkyl release agent. Furthermore, the first surface (surface on the first layer side) of the resin film was subjected to a corona discharge treatment, and then the pressure-sensitive adhesive composition P1 was applied to the corona discharge-treated surface and dried to form a 12 μm-thick pressure-sensitive adhesive layer. In this way, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on the first surface of a polyethylene substrate was obtained.

[0111] (Examples 2 to 19) Resin films according to each example were obtained in the same manner as in Example 1, except that the compositions and thicknesses of the first layer, intermediate layer, and second layer were as shown in Table 1. Pressure-sensitive adhesive sheets according to each example were obtained in the same manner as in Example 1, except that each of the obtained resin films was used. In the resin film according to Example 16, the first layer, intermediate layer, and second layer were composed of resin materials with the same composition.

[0112] <Measurement and Evaluation> A sample of an appropriate size was cut out from the pressure-sensitive adhesive sheet prepared above, and the following items were measured or evaluated. The results are shown in Table 1.

[0113] (1) Transmittance measuring device: Hitachi High-Technologies Corporation spectrophotometer, model "U-4100" Measurement conditions: Measurement mode applied measurement, data mode %T, scan speed 750 nm / min, sampling interval 1 nm, automatic slit control, photomultiplier voltage automatic 1, light intensity control mode fixed, high-resolution measurement OFF, light attenuation plate not used, PbS sensitivity 1, cell length 10 mm Measurement method: (i) The measuring device was turned on and allowed to stand for at least two hours to stabilize. After that, a baseline was measured without setting a sample. (ii) Next, the sample was set in the transmittance measuring section of the measuring device so that light was incident from the back side of the pressure-sensitive adhesive sheet, and the transmittance in the wavelength range of 900 nm to 1100 nm was measured under the above measurement conditions.

[0114] (2) Reflectance measuring device: Spectrophotometer, model "U-4100" manufactured by Hitachi High-Technologies Corporation. Measurement conditions: Measurement mode: applied measurement, data mode: %R, scan speed: 750 nm / min, sampling interval: 1 nm, slit automatic control, photomultiplier voltage: automatic 1, light intensity control mode: fixed, high-resolution measurement: OFF, light-attenuating plate: not used, PbS sensitivity: 1, cell length: 10 mm. Measurement method: (i) The measuring device was turned on and allowed to stand for at least 2 hours to stabilize. Thereafter, a white standard plate was set in the reflectance measurement section (no sample was set), and a baseline was measured. (ii) Next, the sample was set in the reflectance measurement section. At this time, to prevent reflection of light transmitted through the sample, a resin plate, trade name "Kurarex (registered trademark)" (black, 1 mm thick) manufactured by Nitto Jushi Kogyo Co., Ltd. was placed on the side opposite the light-entering surface of the sample, and a pressure-sensitive adhesive sheet as a sample was bonded to the resin plate (bonding conditions: one reciprocation with a 2 kg roller). Then, the reflectance in the wavelength range of 900 nm to 1100 nm was measured under the above measurement conditions.

[0115] (3) Absorbance The minimum absorbance in the wavelength range of 900 nm to 1100 nm was calculated from the transmittance T (%) and reflectance R (%) using the following formula: 100 (%) - T (%) - R (%).

[0116] (4) Cut Edge Protection The adhesive sheet according to each example was attached to the top surface of an A5052 aluminum plate (thickness 2.0 mm) as a workpiece. A cutting test was performed by irradiating a laser beam from the top side of this workpiece. Specifically, a fiber laser processing machine (manufactured by Amada Co., Ltd., model number "ENSIS3015AJ", dominant wavelength 1050 nm) was used to cut the workpiece under the following conditions along a cutting line including a straight portion Rs and a non-straight portion (a zigzag portion in the shape of a series of isosceles triangles) Rz, as shown schematically in FIG. 3. [Laser Processing Conditions] Cutting speed: 4.0 m / min Output: 2000 W Supply gas and gas pressure: nitrogen gas, pressure 0.8 MPa Nozzle diameter: 2.0 mm Nozzle height: 0.3 mm Laser beam focus: at the same height as the top surface of the workpiece.

[0117] After cutting, the workpiece was observed for the degree of exposure of the workpiece surface at the zigzag portion (Rz) (exposed distance of the workpiece surface from the cut edge), and based on the results, the cut edge protection was evaluated using the following three levels. Note that the exposed distance was the longest value of the exposed lengths measured perpendicular to the cut edge at the zigzag portion (Rz). A: Exposed distance less than 1.0 mm (excellent cut edge protection) B: Exposed distance 1.0 mm or more but 3.0 mm or less (good cut edge protection) C: Exposed distance greater than 3.0 mm (poor cut edge protection)

[0118]

[0119] As shown in Table 1, in PSA sheets having a PSA layer on the first surface of a polyethylene substrate, Examples 3 to 8, 10 to 12, and 14 to 18, in which the resin material constituting the first surface contained 2% or more of resin A with a melting point of 120°C or higher, all achieved good cut edge protection, ranked B or higher. Particularly good results were obtained in Examples 4 to 8, 11 to 12, and 15 to 18. On the other hand, the PSA sheets of Examples 1, 2, 9, 13, and 19, in which the resin material constituting the first surface did not contain resin A with a melting point of 120°C or higher or contained only 1% resin A, were rated C in cut edge protection, indicating poor cut edge protection. In addition, in the linear portion (Rs) of the laser cut, the exposed distance of the workpiece from the cut edge was less than 1.0 mm in all of Examples 1 to 19.

[0120] 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.

[0121] 1, 2: Adhesive sheet for laser processing 10: Resin film (substrate) 11: First layer 12: Second layer 13: Intermediate layer 20: Adhesive layer

Claims

1. An adhesive sheet for laser processing comprising a resin film as a substrate and an adhesive layer provided on the first surface of the substrate, wherein the main component of the substrate is polyethylene, and the resin material constituting the first surface of the substrate contains 2% by weight or more of resin A having a melting point of 120°C or higher.

2. The adhesive sheet for laser processing according to claim 1, wherein the adhesive sheet has a laser light absorption rate of 20% or more in the wavelength range of 900 nm to 1100 nm.

3. The adhesive sheet for laser processing according to claim 1 or 2, wherein the main component of the substrate is low-density polyethylene.

4. An adhesive sheet for laser processing according to claim 1 or 2, wherein the resin material constituting the first surface of the substrate contains polyolefin as the resin A.

5. An adhesive sheet for laser processing as described in claim 1 or 2, wherein the resin material constituting the first surface of the substrate includes, as resin A, at least one selected from the group consisting of high-density polyethylene, linear low-density polyethylene, and polypropylene.

6. An adhesive sheet for laser processing as described in claim 1 or 2, wherein the weight proportion of resin A in the resin material constituting the first surface of the substrate is higher than the weight proportion of resin A in the entire weight of the substrate.

7. The adhesive sheet for laser processing according to claim 1 or 2, wherein the adhesive layer is a rubber-based adhesive layer.

8. The adhesive sheet for laser processing according to claim 1 or 2, wherein the substrate contains a laser beam absorbent.

9. The adhesive sheet for laser processing according to claim 8, wherein the laser beam absorber comprises at least one selected from the group consisting of carbon black, titanium oxide, iron-based oxides, titanium black and manganese-based oxides.

10. The pressure-sensitive adhesive sheet for laser processing according to claim 1 or 2, which is used by cutting with a laser beam having a dominant wavelength of 900 nm to 1100 nm.

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