Adhesive sheet, method for manufacturing the same, and bonding method.

Abstract

To provide an adhesive sheet with high bonding strength. [Solution] The material comprises a base layer 20, a printing layer 40 containing an acrylic resin, and an adhesive layer 50 containing an ultraviolet-curable acrylic resin, in this order. The printing layer 40 is adjacent to a portion of the surface of the adhesive layer 50 and may have a thickness of 8 μm to 20 μm. The acrylic resin in the printing layer 40 may be an ultraviolet-curable acrylic resin. The base layer 20 may be made of resin, and the printing layer 40 may be formed by UV inkjet printing. Furthermore, a release layer 10 may be provided on the side of the base layer 20 facing the printing layer, and the adhesive layer 50 may be wound so as to touch the release layer 10.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet, a method for manufacturing the same, and an adhesion method.

Background Art

[0002] Conventionally, the following methods have been proposed as methods for increasing the adhesive strength of an adhesive sheet. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2018-123250) proposes a laminated sheet that is difficult to peel off from an end face after being bonded to a decorated body, and a decorative article using the same.

[0003] The laminated sheet described in Patent Document 1 is configured such that a rigid layer that is thinner than the base sheet and has a higher Young's modulus than the base sheet and an adhesive layer are sequentially laminated on one surface of the base sheet. Further, the laminated sheet of the present invention is configured such that a rigid layer that is thinner than the base sheet and has a higher Young's modulus than the base sheet is laminated on one surface of the base sheet, and an adhesive layer is laminated on the other surface. The decorative article of the present invention is configured such that the laminated sheet is bonded to the surface of a resin molded product or a glass processed product via an adhesive layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the laminated sheet described in Patent Document 1, a rigid layer that is thinner than the base sheet and has a higher Young's modulus than the base sheet is laminated on one surface of the base sheet. As a result, the base sheet is difficult to bend, and the rigidity of the entire laminated sheet is increased, thereby increasing the peel strength. However, the adhesive strength is not sufficient, and it is not possible to increase the adhesive strength only at an arbitrary portion.

[0006] In view of the above-mentioned problems, the main object of the present invention is to provide an adhesive sheet with high adhesive strength. Another object of the present invention is to provide an adhesive sheet with high adhesive strength only in any part. Furthermore, the present invention aims to provide a method for manufacturing an adhesive sheet and a method for bonding. [Means for solving the problem]

[0007] (1) The adhesive sheet conforming to a single curve comprises, in this order, a base layer, a printed layer containing an acrylic resin, and an adhesive layer containing an ultraviolet-curable acrylic resin, with the printed layer positioned so as to be in contact with a portion of one side of the adhesive layer, and having a thickness of 8 μm to 20 μm.

[0008] A single-curve adhesive sheet can be made by having the printed layer and the adhesive layer both contain acrylic resin, and by having the printed layer have a predetermined thickness, allowing the components of the printed layer and the adhesive layer to interact and create an adhesive sheet with high adhesive strength. Furthermore, since the adhesive strength is improved only in the areas of the substrate layer where the printed layer is provided (i.e., only in the printed areas), it is possible to create a difference in adhesive strength between the areas with and without the printed layer. In other words, when the sheet is placed on a substrate, it is possible to have areas that are difficult to peel off (areas with the printed layer) and areas that are easy to peel off (areas without the printed layer) on the same sheet. Furthermore, when creating differences in adhesive strength, adhesives or bonding agents with different adhesive strengths are usually used. In this respect, the sheet of the present invention does not require the use of two or more types of adhesives or bonding agents. Therefore, the process for manufacturing the sheet is reduced.

[0009] (2) In the adhesive sheet described in (1) above, the acrylic resin of the printing layer may be an ultraviolet-curing acrylic resin.

[0010] With the above configuration, because the printing layer formed from UV-curable acrylic resin is thick, some of the monomers of the printing ink tend to remain within the printing layer. These remaining monomers then act on the adhesive layer, potentially improving its adhesion. This can lead to an improvement in the adhesive strength of the adhesive layer to the substrate.

[0011] Furthermore, UV-curable acrylic resins form a strong film, which can improve the abrasion resistance and durability of the printed layer. They can also improve adhesion to the substrate layer. Additionally, because UV-curable acrylic resins cure quickly when exposed to light, the time required to form the printed layer can be shortened. This can improve the efficiency of sheet production.

[0012] (3) The adhesive sheet according to the third invention is a single-sided or second-sided adhesive sheet, wherein the base layer is made of resin and the printed layer may be formed by UV inkjet printing.

[0013] This makes it easier to adjust the print layer to a predetermined thickness by controlling the ink discharge rate, which in turn makes it easier for unreacted monomers to remain in the print layer laminated on the substrate layer. Then, the unreacted monomers migrate to the adhesive layer, which can improve the wettability of the adhesive layer and potentially enhance the adhesion strength with the substrate.

[0014] Furthermore, the adhesive strength can be easily improved in the areas where the printed layer is laminated onto the base layer, allowing for variations in adhesive strength between areas with and without the printed layer. This makes it possible to have areas that are difficult to peel off (areas with the printed layer) and areas that are easy to peel off (areas without the printed layer) on the same sheet when the sheet is placed on top of the substrate. Furthermore, when creating differences in adhesive strength, adhesives or bonding agents with different adhesive strengths are usually used. In this respect, the sheet of the present invention does not require the use of two or more types of adhesives or bonding agents. Therefore, the effect of reducing the number of steps required to manufacture the sheet can be achieved. In addition, since there is no need to create a printing plate during printing, the cost can be reduced even for small lots. Also, even in the case of a printing design with different sizes for each character, printing can be easily performed. Also, an ink can be absorbed into the resin base material layer without bleeding, and a printing layer can be formed on the base material layer.

[0015] (4) The adhesive sheet according to the fourth invention is, in one aspect, the adhesive sheet according to any one of the third inventions, and the ultraviolet curable acrylic resin of the adhesive layer may have a benzophenone group.

[0016] Thereby, the cohesive force of the adhesive is reduced, and the wettability with respect to the adherend can be improved.

[0017] (5) The adhesive sheet according to the fifth invention is, in one aspect, the adhesive sheet according to any one of the fourth inventions, and an anchor coat layer may be further provided between the base material layer and the printing layer.

[0018] Thereby, the adhesion between the printing layer and the base material layer can be improved.

[0019] (6) The adhesive sheet according to the sixth invention is, in one aspect, the adhesive sheet according to any one of the fifth inventions, and the adhesive force to SUS may be 4.0 (N / 10 mm) or more.

[0020] Thereby, in the portion provided with the printing layer, an adhesive sheet with higher adhesive force and less likely to peel off can be obtained. Especially when the base material layer is OPP or PET, it can adhere with a strong strength exceeding the strength of the base material.

[0021] (7) The adhesive sheet according to the seventh invention is, in one aspect, the adhesive sheet according to any one of the sixth inventions, and a release layer is further provided on the surface side of the base material layer facing the printing layer, and the adhesive layer may be wound so as to overlap the release layer.

[0022] This allows the sheet with the above configuration to be easily peeled off even if adhesive tape is attached to the release layer side. In particular, when the adhesive sheet is rolled up, overlapping sheets can be easily separated. Therefore, it is possible to create an adhesive sheet that is easy to carry and work with.

[0023] (8) A method for manufacturing an adhesive sheet according to other specifications includes a printing layer formation step of forming a printed layer on a substrate layer by inkjet printing, and an adhesive layer formation step of applying a heated adhesive to the printed layer, wherein the thickness of the printed layer is 8 μm or more and 20 μm or less.

[0024] With the above configuration, the printed layer has a predetermined thickness, and unreacted monomers tend to remain in the printed layer. Then, the remaining unreacted monomers migrate to the adhesive layer, causing the components of the printed layer and the adhesive layer to interact. As a result, an adhesive sheet can be made in which the area where the printed layer is formed (the inkjet printed area) has high adhesive strength.

[0025] (9) The bonding method according to the ninth invention comprises a bonding step of attaching an adhesive sheet according to any of the eighth inventions to a workpiece from one surface.

[0026] As a result, the adhesive sheet, once attached to the substrate, will have particularly high adhesive strength in the areas where the printed layer is formed, making it difficult to peel off the substrate. Therefore, it is possible to create products with varying adhesive strengths in different areas. [Effects of the Invention]

[0027] According to the present invention, it is possible to create an adhesive sheet with high adhesive strength. Furthermore, the adhesive sheet of the present invention can easily have areas with high adhesive strength and areas with low adhesive strength. [Brief explanation of the drawing]

[0028] [Figure 1]This is a schematic cross-sectional view illustrating the adhesive sheet of the first embodiment. [Figure 2] This shows an example of an application of the adhesive sheet of the first embodiment. [Modes for carrying out the invention]

[0029] The manufacturing method of this embodiment will be described in detail below. Preferred embodiments of the present invention are as follows, but the present invention is not limited thereto. Furthermore, at least a part of the configuration of each embodiment can be appropriately combined with a part of other embodiments without departing from the spirit and scope of the present invention.

[0030] Figure 1 shows a schematic cross-sectional view illustrating the adhesive sheet 1 of this embodiment. The adhesive sheet 1 comprises a release layer 10, a base material layer 20, an anchor coat layer 30, a printed layer 40, and an adhesive layer 50 in this order. As described later, an anchor coating agent may be applied to the printing area before printing on the substrate layer 20. Alternatively, instead of an anchor coating, a treatment such as corona treatment may be performed.

[0031] Examples of release agents used in the release layer 10 of this embodiment include silicone-based, fluorine-based, wax-based, polyethylene-based, and ester-based agents. Diluting solvents and additives may also be included as needed. Of these, it is preferable to use a silicone-based mold release agent from the viewpoint of safety, stain resistance, and odor prevention. This makes it possible to wind the film while overlapping the adhesive surface without using release paper, preventing the films from sticking together. Furthermore, when the adhesive sheet 1 is pulled out from the roll, it can be pulled out smoothly without reducing the adhesive strength of the adhesive layer 50.

[0032] The base material layer 20 in this embodiment is not particularly limited and may be made of paper or resin, preferably a thermoplastic resin base material that is excellent in processability and mass productivity. Among thermoplastic resins, for example, polypropylene resin, polyethylene resin, polyethylene terephthalate resin, polyamide resin, polyester resin, vinyl chloride resin, polycarbonate resin, acrylic resin, or mixtures thereof can be used. Of these, polyethylene terephthalate resin and / or polypropylene resin are preferred in terms of excellent processability and mass productivity, and polypropylene resin is preferred in terms of cost advantage.

[0033] Biaxial stretching is preferable to increase the rigidity of the adhesive sheet 1. However, if the adhesive sheet 1 needs to be tearable by hand, uniaxial stretching may be used.

[0034] The base layer 20 may contain additives as appropriate. Examples of additives include oxygen absorbers, plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, friction reducers, slip agents, mold release agents, antioxidants, ion exchange agents, antiblocking agents, and colorants.

[0035] The thickness of the base layer 20 is preferably 20 μm to 70 μm, more preferably 30 μm to 60 μm, and even more preferably 40 μm to 50 μm. This results in an adhesive sheet 1 with high rigidity.

[0036] The adhesive sheet 1 according to this embodiment may include an anchor coat layer 30.

[0037] As shown in Figure 1, the anchor coat layer 30 is a layer provided between the base material layer 20 and the printed layer 40, and is formed by applying an anchoring agent to the base material layer 20. Then, the printed layer 40 is laminated by applying or printing ink resin onto the anchor coat layer 30. This improves the adhesion of the printed layer 40 to the base material layer 20.

[0038] Examples of anchor coating agents include acrylic resin, polypropylene resin, vinyl resin, epoxy resin, polyurethane resin, polyester resin, and silicone resin. Of these, it is preferable that the anchor coating agent be the same type of resin as the printing layer 40, from the viewpoint of adhesion to the printing ink.

[0039] The ink forming the printing layer 40 can be an acrylic resin, urethane resin, polyester resin, vinyl resin, epoxy resin, or a mixture thereof, but from the viewpoint of improving adhesion, it is preferable to select the same type of resin as the adhesive layer 50. Furthermore, from the viewpoint of UV curability, acrylic resins, urethane resins, epoxy resins, and polyester resins are preferred, and it is more preferable to include an acrylic resin.

[0040] Examples of monomers that can be used to constitute the acrylic resin include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate. Of these, from the viewpoint of favorably reducing the cohesive force of the adhesive, it is more preferable that ethyl acrylate and / or methyl acrylate are included.

[0041] The ink forming the printed layer 40 is preferably an ultraviolet-curable acrylic resin containing a photoradical polymerization initiator. The photoradical polymerization initiator used can be any agent that generates radicals when irradiated with ionizing radiation such as ultraviolet light, such as benzophenone, acetophenone, Michler ketone, benzyl ketal, or benzoin derivatives. This allows for a faster curing speed.

[0042] The resin that makes up the ink mainly contains acrylic monomers and may also contain additives such as pigments, dispersants, and surfactants.

[0043] Here, we will explain the relationship between the curability of the printed layer 40 and the adhesive strength of the adhesive layer 50. The curability of the printed layer 40 is affected by its thickness. This is thought to be because unreacted monomers remain when the printed layer 40 is thick. The curability of the printed layer 40 is also affected by the ink color and pigment concentration. When using dark inks or highly concentrated pigments (white, black, gold, silver, etc.), especially when the printed layer 40 is thick, UV light does not easily penetrate the printed layer 40, and areas occur where sufficient UV light does not reach the photoradical polymerization initiator, thus worsening the curability of the printed layer 40. Thus, even if the surface of the printed layer 40 hardens, the internal hardening is insufficient, making it easier for unreacted monomers to remain. As a result, the unreacted residual monomers in the printed layer 40 migrate to the adhesive layer 50 adjacent to the printed layer 40, reducing the cohesive force of the adhesive and improving the wettability to the adherend. It is presumed that this improved the adhesive strength of the adhesive sheet 1.

[0044] The lower limit of the thickness of the printed layer 40 is preferably 8 μm or more, more preferably 9 μm or more, and even more preferably 10 μm or more. The upper limit of the thickness is preferably 20 μm or less, more preferably 17 μm or less, and even more preferably 15 μm or less. When the thickness of the printed layer 40 is above the lower limit, unreacted monomers in the printed layer 40 are preferably retained, and when the adhesive layer 50 is laminated, some of the unreacted ink components are more likely to diffuse and migrate to the adhesive layer 50. This improves the wettability of the adhesive layer 50 and increases the adhesion strength with the substrate.

[0045] Any printing method that can adjust the thickness of the printed layer 40 to a predetermined value or higher is acceptable for forming the printed layer 40, and examples include inkjet printing, gravure printing, letterpress printing, flexographic printing, and offset printing. Among these, inkjet printing can form a thickness to a predetermined value or higher by adjusting the amount of ink ejected. Furthermore, since the adhesive strength is improved only in the portion where the printed layer 40 is laminated on the substrate layer 20, a difference in adhesive strength can be created between the portion with the printed layer 40 and the portion without the printed layer 40.

[0046] The resin used in the adhesive layer 50 can be an acrylic resin, epoxy resin, urethane resin, silicone resin, elastomer, or a mixture thereof, but it is preferable to select the same type of resin as the printed layer 40 from the viewpoint of improving adhesive strength. Furthermore, it is preferable to use an acrylic resin from the viewpoint of transparency and design flexibility of adhesive properties, and it is even more preferable to use an ultraviolet-curable acrylic resin.

[0047] UV-curable acrylic resins can be any resin whose main structure is acrylate, which contains a photoradical polymerization initiator, and which can be cured by UV irradiation. Examples include epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, and melamine acrylate. In addition, additives such as UV absorbers, crosslinking agents, softeners, pigments, and antioxidants can be added as needed.

[0048] The adhesive layer 50 preferably uses an acrylic hot-melt adhesive that becomes highly viscous at room temperature and fluid (35 Pas to 45 Pas) at high temperatures (120°C to 130°C). This results in an adhesive with excellent processability, suitable application even to uneven printed surfaces, and superior transparency and flexibility.

[0049] The base resin of such a hot-melt UV acrylic resin preferably contains a C4-C8 alkyl acrylate in the main chain and a benzophenone group bonded to the side chain, and more preferably uses an acrylic polymer with a 2-ethylhexyl acrylate component as the main chain and a benzophenone group bonded to the side chain. As a result, after being coated on the printed layer 40 or the substrate layer 20, the coating layer can be crosslinked by UV irradiation to produce the desired adhesive properties.

[0050] Because the adhesive layer 50 contains a hot-melt adhesive, when it is laminated onto the printed layer 40, heating and melting it can easily fill in any irregularities in the printed layer 40, thereby improving adhesion to the printed layer 40.

[0051] The thickness of the adhesive layer 50 is preferably 5 μm to 35 μm, more preferably 10 μm to 30 μm, and even more preferably 15 μm to 25 μm. This allows for sufficient adhesive strength to be provided.

[0052] The coating method for forming the adhesive layer 50 is not particularly limited and includes a roll coater method using a direct roll, a gravure roll, an extrusion coater method, and a slit orifice coater method.

[0053] (Flap label) Figure 2 shows an example in which the adhesive sheet 1 of the embodiment is used as the lid 60 (flap label) of a wet wipe container 2. The adhesive sheet 1 can provide strong adhesive force only to the portion where the printed layer 40 is provided. Therefore, the printed layer 40 is provided on the connecting portion 61 between the container 2 and the lid 60, and the lid 60 is fixed in an openable and closable manner. In the portion without the printed layer 40, the adhesive force is weak, so the lid 60 can be easily opened and closed by hand.

[0054] (Method for manufacturing adhesive sheet 1) The adhesive method for the adhesive sheet 1 according to this embodiment will be described in detail below. The adhesive method for the adhesive sheet 1 in this embodiment includes the following five steps. (1) Release layer formation process: A release agent is applied to the base material layer 20. (2) Anchor coat layer formation process: An anchor coat agent is applied to the surface of the base material layer 20 opposite to the release layer 10. (3) Printing layer formation process: Ink is applied to the anchor coat layer 30 of the substrate layer 20 to form the printing layer 40. (4) Adhesive layer formation process: A heated adhesive is applied to the printed layer 40 obtained in the printing process. (5) Winding process: The adhesive sheet 1 obtained in the above process is wound up with the adhesive layer 50 on the inside. The following details each step.

[0055] (Release layer formation process) A release agent is applied to the base layer 20, and the release layer 10 is formed by drying the coated surface.

[0056] (Anchor coat layer formation process) An anchor coat agent is applied to the side of the base layer 20 that is opposite to the release layer 10 laminated on it, and the coated surface is dried to form the anchor coat layer 30. (Print layer formation process) A printed layer 40 is formed by applying ink to the anchor coat layer 30. The resin of the ink used to form the printed layer 40 and the application method can be the printing method described above, such as inkjet spraying. This allows for the ink to be layered to a predetermined thickness, improving the adhesion of the printed layer 40 to the substrate layer 20. Depending on the type of ink, the printed layer 40 may be subjected to appropriate treatments, such as curing the ink by irradiating it with ultraviolet light after printing or coating.

[0057] (Adhesive layer formation process) A hot-melt adhesive heated to 150 degrees Celsius is applied to the printed layer 40 obtained in the printed layer formation process. The heating temperature is preferably between 120 degrees Celsius and 160 degrees Celsius, and more preferably between 140 degrees Celsius and 150 degrees Celsius. This melts the hot-melt adhesive and increases its fluidity, thereby improving its adhesion to the printed layer 40. Next, ultraviolet light is irradiated onto the adhesive laminated to the printed layer 40 in the adhesive layer formation process. This causes the adhesive to harden and form an adhesive layer 50. As a result, an adhesive sheet 1 with high adhesive strength to the substrate can be obtained. (winding process) The adhesive sheet 1 obtained in the above process is wound up so that the adhesive layer 50 is in contact with the release layer 10. This makes it possible to form it into a roll that is convenient for carrying.

[0058] (Example 1) A biaxially oriented polypropylene film (manufactured by Toyobo Co., Ltd.) with a thickness of 40 μm was prepared as the base layer 20. A polyurethane resin anchor coating agent was applied to the base layer 20, and a silicone resin release agent was applied to the entire surface of the side facing the anchor layer 30 laminated on the base layer 20. <Anchor layer formation process, release layer formation process> Next, UV inkjet printing was performed on the anchor coat layer using an acrylic resin ink to form a printed layer 40. The main component of this ink is 2-[2-(vinyloxy)ethoxy]ethyl acrylate, with a specific gravity of 1.04 g / cm³. 2 ~1.08 g / cm³ 2 It is a UV-curable inkjet ink with a viscosity of 9 mPa·s to 12 mPa·s. <Printing layer formation process> Next, an ultraviolet-curable acrylic resin adhesive heated to 150°C was applied to the printed layer 40. This acrylic resin adhesive's main component is 2-ethylhexyl acrylate with a benzophenone side group attached, and its specific gravity is 1.04 g / cm³. 2 ~1.08 g / cm³ 2 This is a hot-melt adhesive with a glass transition temperature of -38°C to -30°C and a viscosity (at 130°C) of 20 Pa·s to 55 Pa·s. <Adhesive layer formation process> Next, the heated adhesive was cured by irradiating it with ultraviolet light to form an adhesive layer 50. Then, an adhesive sheet was fabricated.

[0059] (Example 2) The adhesive sheet 1 was prepared by following the same process as in Example 1, except that the film used for the base layer 20 was changed to a 25 μm thick polyethylene terephthalate film (manufactured by Toray Industries, Inc.).

[0060] (Comparative Example 1) Adhesive sheet 1 was created by following the same process as in Example 1, except that no anchoring agent was applied and the UV inkjet printing process was changed to gravure printing during the printing process.

[0061] (Comparative Example 2) Adhesive sheet 1 was created by following the same process as in Example 1, except that the application of an anchoring agent was omitted and the printing process was changed from UV inkjet printing to letterpress printing.

[0062] (Comparative Example 3) Adhesive sheet 1 was created by following the same process as in Example 1, except that UV inkjet printing was not performed in the printing process.

[0063] (Comparative Example 4) Adhesive sheet 1 was created by following the same process as in Example 1, except that no anchoring agent was applied and UV inkjet printing was not performed in the printing process.

[0064] (Comparative Example 5) Adhesive sheet 1 was created by following the same process as in Example 2, except that UV inkjet printing was not performed in the printing process.

[0065] Table 1 shows the results of the evaluation tests conducted for Examples 1-2 and Comparative Examples 1-5.

[0066] [Table 1]

[0067] (Adhesion strength test) The adhesive sheets 1 from Examples 1-2 and Comparative Examples 1-5 were cut to a width of 25 mm and a length of 100 mm, and peel adhesion tests were performed under conditions compliant with JIS Z 0237 (2009). The peel test was performed using a Tensilon type universal tester (product name "RTC-1210A") manufactured by Orientec Co., Ltd. Cut adhesive sheet 1 was bonded to stainless steel plate (SUS304 manufactured by Nippon Test Panel Co., Ltd.; SUS plate), polypropylene plate (manufactured by Nippon Test Panel Co., Ltd.; PP plate), and polyethylene plate (manufactured by Nippon Test Panel Co., Ltd.; PE plate) in an environment of 23°C and 50% humidity. The other end of adhesive sheet 1 was peeled off at a speed of 300 mm / min in the peeling direction at a 180° angle, and the adhesive strength to the SUS plate, PP plate, and PE plate at that time was measured.

[0068] Table 2 shows the results of the above tests for Examples 1 and 2 and Comparative Examples 1 to 5. The values ​​listed in Table 2 are converted from (N / 25mm) to (N / 10mm).

[0069] [Table 2]

[0070] As a result, Example 1 exhibited strong adhesion to all substrates, and the substrate broke when the values ​​in Table 2 were reached. In Example 2, although peeling occurred at the predetermined values ​​for the PP board and PE board, it was confirmed that the adhesive strength value was higher compared to Comparative Example 5. In particular, when comparing Comparative Examples 1 and 2, which had a thinner printed layer 40, with the Example, it was confirmed that the adhesive strength of the Example was significantly higher. Furthermore, in Comparative Examples 3 and 5, which contained only the anchor coat layer 30 without the printed layer 40, and Comparative Example 4, which contained neither the anchor coat layer 30 nor the printed layer 40, the same level of adhesive strength as the Example could not be obtained. From this, it was confirmed that the adhesive strength of the adhesive sheet 1 is affected by the thickness of the printed layer 40, and that the adhesive strength can be increased by making the thickness of the printed layer 40 greater than a predetermined value. Furthermore, it was confirmed that the adhesive strength to the SUS plate was strong enough to destroy the base material layer 20.

[0071] (Retention strength test) Adhesive sheet 1 from the examples and comparative examples was cut to a width of 25 mm and a length of 70 mm for holding strength tests. The holding strength test was performed using a holding strength measuring device (product name "SS-HT-8") manufactured by ChemInstruments. The cut adhesive sheet 1 was attached to a stainless steel plate (SUS304; SUS plate manufactured by Nippon Test Panel Co., Ltd.) in an environment of 23℃ and 50% humidity, with a density of 0.16 kg / cm² in the longitudinal direction. 2 , 0.44 kg / cm 2 Each load was applied, and the elapsed time (minutes) until adhesive sheet 1 peeled off from the SUS plate, or the distance (mm) after a predetermined time, was measured. The upper limit for measurement time was set at 4320 minutes (3 days).

[0072] Table 3 shows the results of the above tests conducted for Example 1 and Comparative Examples 1-2.

[0073] [Table 3]

[0074] From the results in Table 3, Example 1 had a load of 0.16 kg / cm². 2 In this case, the weight fell after 2629 minutes. It was confirmed that the adhesive layer 50 of adhesive sheet 1 underwent cohesive failure, and the adhesive layer 50 separated from the SUS plate and the adhesive film and peeled off. On the other hand, in comparative examples 1 and 2, cohesive failure did not occur, and it was confirmed that the material did not peel off even after 4320 minutes, which is the upper limit of measurement. From this, it was confirmed that the cohesive force of the adhesive in the adhesive sheet 1 was reduced in Example 1. Therefore, it was confirmed that the cohesive force of the adhesive was reduced because the thickness of the printed layer 40 was greater than a predetermined value, causing some of the monomers contained in the printed layer to migrate to the adhesive layer 50. Therefore, it is believed that by reducing the cohesive force, wettability was improved, resulting in superior adhesion to the substrate and higher adhesive strength.

[0075] In the present invention, the base material layer 20 corresponds to the "base material layer," the printing layer 40 corresponds to the "printing layer," the adhesive layer 50 corresponds to the "adhesive layer," the anchor coat layer 30 corresponds to the "anchor coat layer," and the release layer 10 corresponds to the "release layer."

[0076] While preferred embodiments of the present invention are as described above, the present invention is not limited thereto. It will be understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the operation and effects of the configuration of the present invention are described in this embodiment, these operation and effects are examples and do not limit the present invention. [Explanation of Symbols]

[0077] 1 Adhesive sheet 10 Release layer 20 Base material layer 30 Anchor Coat Layer 40 printing layer 50 Adhesive layer 2 containers 60 Lid 61 Connecting part

Claims

1. The structure comprises, in this order, a base layer, a printing layer containing an acrylic resin, and an adhesive layer containing an ultraviolet-curable acrylic resin. The printed layer is arranged so as to be in contact with a part of one surface of the adhesive layer, and the adhesive sheet has a thickness of 8 μm or more and 20 μm or less.

2. The adhesive sheet according to claim 1, wherein the acrylic resin of the printed layer is an ultraviolet-curable acrylic resin.

3. The aforementioned substrate layer is formed from resin, The adhesive sheet according to claim 1, wherein the printed layer is formed by UV inkjet printing.

4. The adhesive sheet according to claim 1, wherein the ultraviolet-curable acrylic resin of the adhesive layer has a benzophenone group.

5. The adhesive sheet according to claim 1, further comprising an anchor coat layer between the base material layer and the printing layer.

6. The adhesive sheet according to claim 1, wherein the adhesive strength to SUS is 4.0 (N / 10mm) or more.

7. A release layer is further provided on the side of the substrate layer facing the printing layer. The adhesive sheet according to claim 1, wherein the adhesive layer is wound so as to overlap the release layer.

8. A printing layer formation process in which a printed layer is formed on a substrate layer by inkjet printing, The process includes an adhesive layer forming step of applying a heated adhesive to the printed layer, A method for manufacturing an adhesive sheet, wherein the thickness of the printed layer is 8 μm or more and 20 μm or less.

9. A bonding method comprising a bonding step of attaching the adhesive sheet described in claim 1 to an object to be bonded.

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