Adhesive sheet

Abstract

The adhesive sheet (10) includes an adhesive layer (3) and a printed portion (5) formed on at least one surface of the adhesive layer (3). The printed part (5) is formed from a cured ink material, the printed part (5) is provided on a printing region, one or more printing regions are provided on the adhesive layer (3) as a printing range, the adhesive layer (3) in the printing region has a ring-shaped initial adhesion value of less than 1.0 N / 25 mm with respect to an SUS steel plate, and the adhesive layer (3) has an initial adhesion value of less than 1.0 N / 25 mm under the conditions of 23 DEG C, a load at the time of adhesion of 2 kg, a relative humidity of 50%, and a peeling angle of 180 DEG. The adhesive force of the adhesive layer (3) with respect to the SUS steel sheet in the printing region is 0.05 N / 25 mm or more.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an adhesive sheet having a printed portion provided on at least one surface of an adhesive layer. Background Art

[0002] Adhesive sheets including an adhesive layer are used in various fields as sheets for fixing parts of electronic devices, sheets for protecting screens, building materials such as wallpapers, printed materials or laminated sheets of printed materials, various adhesive tapes, etc. Depending on the use of the adhesive sheet, the adhesive sheet may need to be firmly adhered to the adherend and not be easily peeled off, or may need to be easily reattached when pasting.

[0003] The specification of Japanese Patent Publication No. 2003-531253 (Patent Document 1) etc. discloses that a patterned adhesive sheet that is easy to reattach can be produced by forming a non-adhesive polymer having a predetermined pattern on the adhesive surface of an adhesive layer.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Publication No. 2003-531253 Summary of the invention

[0006] -Technical problem to be solved by the invention-

[0007] Sometimes, the stronger the adhesion of an adhesive sheet to an adherend, the better; sometimes, the weaker the adhesion, the better. There is a great demand for adhesive sheets that are easy to reattach during application and difficult to peel off after application, but sometimes other characteristics are also required.

[0008] Here, a non-adhesive polymer is formed in the adhesive sheet described in Patent Document 1, so as to facilitate re-adhesion and discharge the air remaining between the adhesive layer and the adherend. Therefore, the non-adhesive polymer is evenly provided on the entire adhesive surface of the sheet. As a result, the adhesive sheet described in Patent Document 1 is difficult to flexibly meet the requirements when the sheet is expected to have a variety of different properties.

[0009] The object of the present invention is to provide a patch having the properties of being able to easily control the adhesive force and being easy to stick and peel off.

[0010] -Technical solutions to solve technical problems-

[0011] An example of an adhesive sheet disclosed in this specification includes an adhesive layer and a printing portion formed on at least one surface of the adhesive layer. The printing portion is formed of a cured ink, the printing portion is arranged on a printing area, and one or more printing areas are set as printing ranges on the adhesive layer, the ring initial adhesion value of the adhesive layer in the printing area to the SUS steel plate is less than 1.0N / 25mm, and the adhesion of the adhesive layer in the printing area to the SUS steel plate after 24 hours at 23°C, a load of 2kg during lamination, a relative humidity of 50%, and a peeling angle of 180 degrees is 0.05N / 25mm or more.

[0012] - Effects of the Invention -

[0013] According to the adhesive sheet disclosed in this specification, by appropriately changing the thickness of the adhesive layer, the thickness of the printed portion, etc., it is possible to easily control properties such as adhesive strength and ease of attachment and peeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional view showing an example of an adhesive sheet according to an embodiment of the present disclosure;

[0015] Figure 2 Viewed from the printing side Figure 1 A top view of the adhesive sheet shown;

[0016] Figure 3 It is enlarged to show Figure 2 A photographic view of the printed portion in area A shown;

[0017] Figure 4 is a cross-sectional view showing an adhesive sheet according to a first modification example of the present disclosure;

[0018] Figure 5 is a top view schematically showing a method for printing an adhesive sheet according to a second modification of the present disclosure;

[0019] Figure 6 The diagram shows microscopic photographs of the adhesive sheets of Examples 1 to 3 in which the thickness of the printed portion is 2 μm (ink amount K 10%), and measurement results of the number of dots and dot size in the printed portion. DETAILED DESCRIPTION

[0020] The inventors of the present application, while studying a method that can solve the above technical problems without significantly increasing the manufacturing cost, noticed that sometimes the adhesive component seeps out from the printing part formed on the adhesive layer by inkjet method, and there is a tendency that the amount of adhesive component seeping out increases if a load is applied to the printing part. After that, after further repeated studies, it was found that by changing the thickness of the printing part, the degree of reduction in tack and adhesive force can be adjusted more easily than when no printing part is provided, and thus the present invention was conceived.

[0021] [Structure of adhesive sheet]

[0022] Figure 1 1 is a cross-sectional view showing an adhesive sheet 10 which is one example of the embodiment disclosed in this specification. Figure 2 This is a plan view of the adhesive sheet 10 according to the present embodiment as viewed from the printing unit 5 side. Figure 3 It is enlarged to show Figure 2 A photograph of the printed portion in area A is shown.

[0023] like Figure 1 As shown, the adhesive sheet 10 of this embodiment includes an adhesive layer 3 and a printing portion 5, the printing portion 5 is formed on at least one surface of the adhesive layer 3, and the printing portion 5 is configured to ooze out the adhesive component of the adhesive layer 3 to the outside of the printing portion 5. In the adhesive sheet 10 of this embodiment, a sheet-like substrate 1 is provided on the surface of the adhesive layer 3 on the side opposite to the surface on which the printing portion 5 is provided. A release liner 7 may also be provided on the surface of the adhesive layer 3 on which the printing portion 5 is formed, wherein the printing portion 5 is sandwiched between the adhesive layer 3 and the release liner 7. By protecting the adhesive surface of the adhesive layer 3 on which the printing portion 5 is provided with the release liner 7, it can be stored not only in a roll form but also in a planographic state. As the release liner 7, a known release liner can be used, and a release agent layer containing a silicone release agent or a fluorine release agent may also be provided on the side in contact with the adhesive layer 3.

[0024] However, the adhesive sheet 10 of this embodiment has very low viscosity when no load is applied, so it can be stored in a roll even without the release liner 7. When the release liner 7 is not provided, there are advantages of saving resources and reducing the diameter of the roll.

[0025] In the printing area 12 of the adhesive sheet 10 of the present embodiment, since the printing unit 5 is provided, the loop tack value of the adhesive layer 3 to the stainless steel (SUS) steel plate can be set to less than 1.0N / 25mm. On the other hand, the adhesive strength of the adhesive layer 3 to the SUS steel plate after 24 hours at 23°C, a load of 2kg during lamination, a relative humidity of 50%, and a peeling angle of 180 degrees can be 0.05N / 25mm or more.

[0026] Therefore, it is easy to re-stick the adhesive sheet 10 in the printed area 12, and after the sticking position is determined, the adhesive sheet 10 can be fixed by applying a load to the sheet, and the sticking operation becomes easy. In addition, since there are fine bumps on the adhesive surface before sticking, it is difficult for bubbles to enter during sticking, and the air remaining between the adherend and the adherend after crimping is also easy to be discharged.

[0027] According to the adhesive sheet 10 of this embodiment, the viscosity value and the adhesive force can be adjusted to the desired values ​​even when the same adhesive is used by changing the thickness of the printing part 5. For example, it is also possible to use a cheap strong adhesive to make a slightly adhesive sheet instead of a relatively expensive slightly adhesive adhesive.

[0028] In the adhesive sheet 10 of this embodiment, by applying a load after the adhesive layer 3 is brought into contact with the adherend, the constituent components (adhesive components) of the adhesive layer 3 can be promoted to seep out, and by placing it in a state peeled off from the adherend, the adhesive components that once seeped out can be quickly restored to the state before pressing by their elastic force. Therefore, the adhesive sheet 10 can be reused many times. The adhesive sheet 10 can also be used as a temporary fixing sheet such as a sticky note.

[0029] In the adhesive sheet 10, the pressure may be 300 g / cm2 for 10 seconds just after the pressure is applied by the pressing unit. 2 In the printed area 12 after the load is applied, the adhesive layer 3 has a first viscosity value to the SUS steel plate, and after 2 minutes after being peeled off from the pressing unit after the load is applied, the viscosity to the PET film disappears or a second viscosity value smaller than the first viscosity value remains. Alternatively, it can be: 2000g / cm2 is applied just after 10 seconds using the pressing unit. 2 In the printed area 12 after the load is applied, the adhesive layer 3 produces a third viscosity value to the SUS steel plate, and after 3 minutes after being peeled off from the pressing unit after the load is applied, the viscosity to the PET film disappears or a fourth viscosity value smaller than the third viscosity value remains.

[0030] In the adhesive sheet 10 of the present embodiment, the storage modulus G' of the adhesive layer 3 at 23°C and a frequency of 1 Hz may be 1.0×10 4Pa or more and 5.0×10 6 Pa or less, and can also be 9.0×10 4 Pa or more and 2.0×10 6 The storage modulus indicates the hardness of the adhesive layer 3. According to the research conducted by the inventors of the present application, as the storage modulus decreases, the adhesive layer 3 tends to flow and the adhesive component tends to ooze out of the printing portion 5. 6 Pa or less, the viscosity can be kept at a small value, and the adhesive strength can be exerted to a degree that it is not easy to be peeled off after being attached to the adherend. 4 Pa or more, the printing section 5 can be set to an appropriate thickness to allow the adhesive component to ooze out. 4 Pa or more, after a load is applied and viscosity is generated, it can be easily restored to a low viscosity state, so it is easy to use repeatedly. 5 Pa or more can improve the holding force of the adhesive layer 3 described later.

[0031] When the storage elastic modulus of the adhesive layer 3 is large, the loop tack value is more easily reduced than when the storage elastic modulus of the adhesive layer 3 is small even if the thickness of the printed portion 5 is equal.

[0032] The glass transition temperature (Tg) of the adhesive layer 3 may be −50° C. or higher. In this case, when the adhesive sheet 10 is used at room temperature, the adhesive layer 3 has appropriate fluidity, so that the constituent components of the adhesive layer 3 easily ooze out from the printed portion 5 .

[0033] In the printing area 12 of the adhesive sheet 10 of the present embodiment, the holding force duration at 40°C can be more than 1000 seconds. Preferably, in the holding force measurement test described later, the offset (mm / 50000 seconds) at 40°C after 50000 seconds is less than 1 mm. If the adhesive sheet 10 has excellent holding force, it is not easy to peel off or fall off from the adherend when the adhesive sheet 10 is used as a label, graphic sheet, etc. After the adhesive sheet 10 is attached to the adherend, the holding force of the adhesive sheet 10 can be fully exerted by applying appropriate pressure by hand or roller. This is because: the amount of adhesive components that seep out from the printing part 5 increases by pressurization. In the case where the adhesive component seeps out from the printing part 5, the stronger the cohesive force of the adhesive layer 3, the smaller the offset of the adhesive sheet 10.

[0034] The printing section 5 is formed of a cured ink and is provided on a printing area 12. One or more printing areas 12 are set as a printing range on the adhesive layer 3. Figure 2In the example shown, the entire adhesive surface of the adhesive layer 3 serves as the printed area 12, and the printed portion 5 is also formed on the entire adhesive surface.

[0035] like Figure 3 As shown, the printing section 5 is composed of a plurality of dots 15, and the dots 15 are formed by a solidified ink. The diameter of the dots 15 is not particularly limited, and may be, for example, greater than 0.1 μm and less than 100 μm, greater than 0.1 μm and less than 50 μm, or greater than 1 μm and less than 30 μm. The diameter of the dots 15 depends on the printer used. If the dot diameter is less than 50 μm, it is easy to precisely control the viscosity and adhesion of the adhesive sheet 10. The diameter of the dots 15 may be uniform, but may also have a moderate deviation. The printing section 5 may also include an average of more than five dots 15 per 0.5 mm square. When the dot diameter is large, even if the density (number density) of the dots 15 is small, it is easy to reduce the ring initial adhesion value.

[0036] As the dot diameter increases, the height of the dot 15 also increases. For example, the height of the dot 15 can also be greater than 0.05μm and less than 50μm. When the surface tension of the adhesive surface is low and the difference with the surface tension of the ink is large, the dot 15 is difficult to expand, and the height of the dot 15 relative to the dot diameter tends to become higher. Generally, the adhesive layer 3 formed using a silicone adhesive has a lower polarity than the adhesive layer 3 formed using an acrylic adhesive, so there is a tendency for the surface tension of the adhesive surface to decrease. Therefore, in the dot 15 set on the adhesive layer 3 made using a silicone adhesive, the value of the dot height / dot diameter is mostly about 0.1 or more and about 0.6 or less. In contrast, in the dot 15 set on the adhesive layer 3 made using an acrylic adhesive, the value of the dot height / dot diameter is mostly about 0.01 or more and about 0.3 or less.

[0037] When the density of dots 15 is low to a certain extent, there are gaps between dots 15, so that the constituent components of the adhesive layer 3 can seep out. Due to the seepage of the adhesive components, the adhesive sheet 10 of this embodiment has a certain degree of stickiness under pressure and maintains the state of being adhered to the adherend.

[0038] As the density of the dots 15 increases, the gaps between the dots 15 decrease, and the overlapping parts of the dots 15 also increase, so it is difficult to measure the density of the dots 15, and the amount of adhesive components (adhesive components) that seep out from the adhesive layer 3 decreases. Therefore, although the average thickness of the printing unit 5 varies depending on the type of adhesive used, the average thickness of the printing unit 5 is approximately 0.1 μm or more and 20 μm or less, preferably 1 μm or more and 6 μm or less. If the average thickness of the printing unit 5 is less than 0.1 μm, the gaps between the dots 15 become larger, and a large amount of adhesive components easily seep out of the gaps, so the adhesive strength and adhesive force of the adhesive sheet 10 are almost unchanged compared to the case where the dots 15 are not set. If the thickness of the printing unit 5 exceeds 20 μm, the amount of seepage of the components of the adhesive layer 3 becomes smaller, and it is sometimes difficult to stick to the adherend. By making the average thickness of the printing unit 5 less than 6 μm, the types of adhesives that can be used as the main agent of the adhesive layer 3 can be further increased.

[0039] It should be noted that the average thickness of the printing portion 5 is less than 6 μm. When the thickness is thin, even when black ink or color ink is used to form the printing portion 5, the total light transmittance of the adhesive sheet 10 reaches 50% or more, and it becomes translucent. However, by making the thickness of the printing portion 5 greater than 6 μm and less than 20 μm, the loop initial adhesion value can be made less than 1.0 N / 25 mm, and a desired image can be formed by the printing portion 5.

[0040] In the printing area 12, the dots 15 may be arranged regularly or irregularly. When the printing portion 5 is formed by an inkjet printer described later, the dots 15 may be arranged irregularly. In addition, the sizes of the dots 15 constituting the printing portion 5 may be equal or uneven.

[0041] The ink used when forming the printing part 5 is not limited, and one or more inks selected from photocurable inks, electron beam curable inks, and solvent-based inks can be used. In particular, in the case of photocurable inks and electron beam curable inks that are cured by ultraviolet (UV) or visible light, it is possible to make it difficult for the ink to diffuse into the adhesive layer 3 when forming the printing part 5, and it is easy to ensure the required thickness of the printing part 5, so it is preferred. In addition, since UV curable inks and electron beam curable inks can be cured instantly after printing, by using these inks, the time for manufacturing the adhesive sheet 10 can be shortened compared to the case of using solvent-based inks.

[0042] The color of the ink used to form the printing portion 5 is not particularly limited, and may be black (K) alone, or may be a combination of at least one or more colors selected from, for example, cyan (C), magenta (M), yellow (Y), black (K), white (W), gray, light cyan, light magenta, red, and transparent. When using inks of multiple colors, the thickness of the printing portion 5 may be equal to that when using inks of one color.

[0043] The printing part 5 can be formed by a printing method of jetting ink using a known inkjet printer or the like. In contrast, if the printing part 5 is formed by solid printing such as offset printing, gravure printing or screen printing, the adhesive layer 3 is covered without gaps, and the adhesive component cannot seep out. In the printing area 12, dots having a diameter of 0.1 μm or more and 50 μm or less are formed by offset printing or gravure printing to the same extent as the dots 15, and the components in the adhesive layer 3 can also seep out. However, in offset printing, gravure printing, etc., expensive plates are required, whereas, if an inkjet printer is used, it is not necessary to make a plate, so the density and formation position of the dots 15 can be freely changed in a short time.

[0044] In the adhesive sheet 10, the surface roughness (Ra) of the printing part 5 may be 0.3 μm to 10 μm. Since the printing part 5 is composed of a plurality of dots 15, the surface roughness becomes larger when the printing part 5 is not provided than when the printing part is provided by offset printing or screen printing.

[0045] The adhesive force of the adhesive sheet 10 is smaller than the adhesive force of the adhesive layer 3 when the printing part 5 is not provided. Therefore, if a medium-viscosity or strong-viscosity adhesive is used as an adhesive to form the adhesive layer 3, an adhesive sheet 10 having a wide range of adhesive forces can be manufactured. For example, when a strong-viscosity adhesive is used, by setting the printing part 5 thicker, an adhesive sheet 10 having slight adhesiveness in the printing area 12 can be manufactured, and by reducing the thickness of the printing part 5, an adhesive sheet 10 showing slight adhesiveness can also be manufactured.

[0046] The adhesive used when forming the adhesive layer 3 is not particularly limited, and can be, for example, one or a mixture of two or more selected from acrylic adhesives, acrylic-urethane adhesives, urethane adhesives, silicone adhesives, polyester adhesives, and rubber adhesives. As the adhesive used, water-based adhesives, solvent-based adhesives, solvent-free adhesives, etc. can be used.

[0047] The thickness of the adhesive layer 3 is not particularly limited, and may be about 10.0 times or less of the average thickness of the printing portion 5. The thickness of the adhesive layer 3 may be, for example, 0.5 μm or more and 100 μm or less, or 2 μm or more and 50 μm or less. If the thickness of the adhesive layer 3 is within the above range, the loop initial adhesion value and the adhesive force can be easily set within the desired range in the printing area 12.

[0048] When the average thickness of the printed portion 5 is equal, the loop initial tack value and the adhesive force increase as the thickness of the adhesive layer 3 increases. This is believed to be because the thicker the adhesive layer 3 is, the easier it is for the adhesive component to seep out of the printed portion 5 due to the pressure applied during the lamination process after the printed portion 5 is formed.

[0049] In addition to using a curing agent appropriately when manufacturing the adhesive layer 3, the adhesive layer 3 may contain additives such as a tackifier, an antistatic agent, a colorant, and a filler as needed. At least one of the adhesive and the additive used to form the adhesive layer 3 may contain a biological component. For example, the adhesive layer 3 may contain a terpene or rosin tackifier of about 10% by mass or more and about 50% by mass or less. The biomass degree of the adhesive layer 3 may be, for example, about 10% or more and about 50% or less.

[0050] As the substrate 1, known materials such as resin sheets, synthetic paper, paper, nonwoven fabrics, woven fabrics, or laminates thereof can be used. As the constituent material of the resin sheet, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyimide (PI), etc. can be used.

[0051] The thickness of the substrate 1 is not particularly limited, and may be, for example, about 2 μm to 300 μm, or 5 μm to 250 μm. An adhesive layer or an antistatic layer may be provided on at least one surface of the substrate 1 as required.

[0052] To reduce environmental load, the substrate 1 may be made of biomass or recycled materials in part or in its entirety. The adhesive sheet 10 including the substrate 1 is preferably manufactured using materials that emit as little CO2 equivalent as possible during manufacture.

[0053] [Modification of Adhesive Sheet]

[0054] Figure 4 2 is a cross-sectional view showing an adhesive sheet 20 according to a first modification example of the present disclosure. Figure 4As shown, the adhesive sheet 20 involved in this modification includes an adhesive layer 3 and a printing portion 5, wherein the printing portion 5 is formed on at least one surface of the adhesive layer 3, and the printing portion 5 is configured such that the constituent components of the adhesive layer 3 ooze outward from the printing portion 5. The adhesive sheet 20 involved in this modification is different from the adhesive sheet 20 in that the substrate 1 is not provided. Figure 1 The adhesive sheet 10 shown is different. A release liner 7 is attached to the surface of the adhesive layer 3 provided with the printing portion 5, and a second release liner 17 is attached to the other surface of the adhesive layer 3. The release force required for peeling the release liner 7 and the release force required for peeling the second release liner 17 can be made to be the same, but a gap can also be made between the two so that the release liner on the lightly peeled side can be easily peeled off. The other structures of the adhesive sheet 20 are basically the same as those of the adhesive sheet 10.

[0055] When manufacturing the adhesive sheet 20 according to this modification, Figure 4 As shown, the sheet may be prepared and then attached to the adherend, or only the adhesive layer 3 may be prepared before providing the printing portion 5 and the printing portion 5 may be formed after the adhesive layer 3 is attached to the adherend.

[0056] In the adhesive sheet 20 involved in this modification, the adhesive force of the surface (first surface) of the adhesive layer 3 on the side where the printing portion 5 is provided to the adherend is smaller than the adhesive force of the surface (second surface) on the opposite side to the same adherend. In addition, the ring initial adhesion value of the first surface of the adhesive layer 3 is smaller than the ring initial adhesion value of the second surface. Therefore, a double-sided adhesive sheet having different adhesive forces on one surface and the other surface of the adhesive layer 3 can be realized. The adhesive used in the adhesive sheet 20 involved in this modification is not particularly limited.

[0057] On the surface provided with the printing portion 5, the area of ​​the adherend that is in substantial contact with the adhesive component is smaller than that on the opposite surface, and accordingly, the adherend is not easily contaminated by the adhesive. Like the adhesive sheet 10, the adhesive sheet 20 can also be used in various fields.

[0058] For example, an adhesive sheet 20 using a re-peelable adhesive that has less pollution to the adherend can be used as an adhesive sheet for fixing a graphic sheet or the like. In a general double-sided adhesive sheet, if an adhesive with strong adhesive force is selected, the degree of close contact with the adherend is improved, and there is a tendency that the adhesive layer is easily left on the adherend when the graphic sheet is peeled off. Therefore, as an adhesive sheet for fixing, there are many cases in which a re-peelable adhesive layer is set on one face (adherend side) of the core material and a strong adhesive layer is set on the other face. In contrast, according to the adhesive sheet 20 involved in this modification, the adhesive force and viscosity value of one face can be different from the adhesive force and viscosity value of the other face at a relatively low cost.

[0059] Although not shown in the drawings, it is also possible to produce an adhesive sheet in which adhesive layers are provided on both surfaces of a core material and a printed portion is provided on at least one of the adhesive layers.

[0060] Figure 5 2 is a top view schematically showing a printing method of the adhesive sheet 30 according to the second modification of the present disclosure. Figure 5 As shown, in the adhesive sheet 30 according to this modification, a plurality of printing areas are provided on the adhesive layer 3 in the sheet, which is different from the Figure 1 The adhesive sheet 10 shown is different. Figure 5 In the example shown, a first printing area 12A and a second printing area 12B are formed on the adhesive layer 3 provided on one surface of the substrate 1. A first printing portion 5A formed of a solidified ink is provided on the first printing area 12A, and a second printing portion 5B is provided on the second printing area 12B. The average thickness of the first printing portion 5A and the average thickness of the second printing portion 5B may be equal to or different from each other. Figure 5 As shown, a part of the adhesive layer 3 may be exposed instead of being covered by the printed portion.

[0061] exist Figure 5 In the example shown, two printing areas are formed in the adhesive sheet, but three or more printing areas may be formed. The total area of ​​the printing area may be 1% or more and 100% or less of at least one surface of the adhesive layer 3. If the printing area is less than 1%, the adhesive force and the initial ring adhesion value of the adhesive sheet as a whole become substantially equal to those in the case of not having the printing area, so the effect of forming the printing area is reduced.

[0062] like Figure 5 As shown, the planar shape of the first printing area 12A and the second printing area 12B may be a strip shape whose length in the flow direction (coating direction) is longer than that in the width direction, or may be any other shape. In addition, the size of each printing area is not limited.

[0063] The thickness of the first printing portion 5A on the first printing area 12A and the thickness of the second printing portion 5B on the second printing area 12B may not be uniform, and the thickness may be partially unequal. For example, the thickness of the first printing portion 5A and the second printing portion 5B may decrease in a hierarchical manner as they approach the inner side from the outer side in the width direction. In this way, in the first printing area 12A and the second printing area 12B, the adhesive force may be designed to become stronger as they approach the inner side from the end.

[0064] When a plurality of printing sections are formed on one surface of the adhesive layer 3, for example, a known line inkjet printer can be used. After the adhesive layer 3 is formed on one surface of the substrate 1 using a coater and dried, the print head 23 of the line inkjet printer extending in the width direction ejects, for example, UV curing ink to the exposed surface of the adhesive layer 3, followed by UV irradiation, thereby forming the first printing section 5A and the second printing section 5B. It should be noted that, in the case where the printing time is longer, a serial head inkjet printer can also be used to form the printing section. After the printing section is formed, the adhesive sheet 30 can be aged at 40°C for about three days, or it can be aged in advance before the printing section is formed. In addition, the adhesive sheet before the printing section is formed can be cut into the desired size with a slitter to form the printing section.

[0065] When the first printing area 12A and the second printing area 12B extending parallel to each other are formed on one surface of the adhesive layer 3, the adhesive sheet 30 is cut along the flow direction using a strip cutter to separate into the first printing area 12A, the second printing area 12B and the area without the printing area, thereby making three kinds of adhesive sheets by one coating. Then, the produced adhesive sheet is cut along the width direction, thereby making a planographic adhesive sheet of a desired size.

[0066] Alternatively, when a highly adhesive adhesive layer 3 is formed, by cutting the adhesive sheet 30 made into a predetermined length in the width direction, an adhesive sheet having weaker adhesive force at both ends in the width direction than at the center can be made. When the adhesive sheet needs to be peeled off after being attached to an adherend, the adhesive sheet can be easily peeled off from the adherend by peeling off from the ends with weaker adhesive force. By using an inkjet printer, the thickness and formation position of the printing part can be arbitrarily adjusted without making a plate.

[0067] It should be noted that Figure 1 As for the adhesive sheet 10 of the present embodiment shown and the adhesive sheets 20, 30 involved in its modified examples, the adhesive sheets in a state without a printed portion are stored in advance, and once a customer's order is received, a printed portion with viscosity and adhesive strength that meets the customer's requirements can be formed on demand. Therefore, compared with the case of storing adhesive sheets with different viscosity and adhesive strength, the inventory of products can be greatly reduced.

[0068] The adhesive sheet 10 of the present embodiment and the adhesive sheets 20 and 30 involved in the modified examples described above are examples of the present invention, and the constituent materials, thickness, shape, formation position, etc. of the substrate 1, adhesive layer 3, printing part 5, etc. can be appropriately changed within the scope of the main purpose of the present invention.

[0069] Example

[0070] Hereinafter, the present invention will be described in further detail based on Examples, but the present invention is not limited to these Examples.

[0071] [Preparation of adhesive sheet]

[0072] Acrylic adhesive compositions A and E, acrylic-urethane adhesive composition B, and silicone adhesive compositions C and D were prepared by adding appropriate amounts of curing agents to five commercially available adhesives and mixing them. Here, adhesive composition A contained a rosin-based tackifier equivalent to 15% by mass of the weight of the adhesive layer after drying, so the biomass degree of the formed adhesive layer was 15%. The biomass degree of the adhesive layer formed by adhesive composition E was estimated to be about 10%.

[0073] Next, adhesive compositions A, B, and E were coated on the release agent layer of a commercially available release liner having a PET film using a known notch wheel coater, and dried to form an adhesive layer. The thickness of the PET film was 50 μm, and a release agent layer containing a silicone release agent was formed. The thickness of the adhesive layer formed using adhesive compositions A and B was 10 μm and 20 μm, and the thickness of the adhesive layer formed using adhesive composition E was 10 μm. Next, the coated surface of the release liner was attached to one surface of the substrate and the adhesive layer was transferred to the substrate, and then aged at 40°C for about three days to form an adhesive sheet. As a substrate, a PET film with a thickness of 50 μm and an easy-adhesive layer formed on both sides was used (produced by Toyobo Co., Ltd., trade name: COSMOSHINE (registered trademark) A4360). Here, various adhesive sheets without a printing unit were used as Comparative Examples 1 to 4. In addition, as Comparative Examples 5 to 10, adhesive sheets having adhesive layer thicknesses of 10 μm, 20 μm, and 30 μm were prepared by directly coating adhesive compositions C and D on a substrate using a notch wheel coater.

[0074] Next, a UV inkjet printer ("UJF-6042MkII" manufactured by MIMAKI Engineering Co., Ltd.) was used to eject UV curing ink onto the entire surface of the adhesive layer exposed in the prepared adhesive sheet and cure it to form a printed portion. As the UV curing ink, a black ink "LH-100" manufactured by MIMAKI Engineering Co., Ltd. was used. The ink amount was set to K10%, K20%, K30%, K40% and K50%. The composition of the adhesive sheets prepared as Examples 1 to 21 and Comparative Examples 1 to 14 is recorded in Tables 2 to 8 described later.

[0075] [Measurement method]

[0076] <Measurement of storage modulus G', loss modulus G", loss tangent (tanδ), and glass transition temperature Tg of adhesive layer>

[0077] The storage modulus G', loss modulus G", and loss tangent of the adhesive layer of the adhesive sheet were measured by the following method. First, a substrate-free adhesive tape having an adhesive layer with a thickness of 50 μm was prepared using the prepared adhesive compositions A to E. Next, the substrate-free adhesive tape was aged at 40°C for 72 hours. Next, only the adhesive layer was stacked until the total thickness reached 1 mm, and then it was punched into a size of 8 mm in diameter to prepare a small piece. The small piece was sandwiched between the plates of a rheometer (product name: AR2000ex), and the storage modulus G' and loss modulus G". were measured under the conditions of a frequency of 1 Hz, a deformation of 0.05%, and a measurement temperature of -40 to 100°C. In addition, the value of loss modulus G" / storage modulus G' was calculated as the loss tangent. The temperature at which the loss tangent reaches the maximum value is read and taken as the glass transition temperature of the adhesive layer.

[0078] <Measurement of the thickness of the printed part>

[0079] Using a UV inkjet printer ("UJF-6042MkII" manufactured by MIMAKI Engineering Co., Ltd.), the ink volume was set to K10%, 20%, 30%, K40% and K50%, and a printed portion was formed on a 50 μm thick PET film. The total thickness of each sheet sample was measured using a constant pressure thickness meter, and the thickness of the PET film (50 μm) was subtracted from the measured value to calculate the thickness of each printed portion.

[0080] It should be noted that the measurement results show that the thickness of the printed part (ink thickness) is about 2μm when K10%, about 3-4μm when K20%, about 5μm when K30%, about 7μm when K40%, and about 10μm when K50%.

[0081] <Counting the number of dots and checking dot size>

[0082] The printed side of the adhesive sheet samples prepared in Examples 1 to 3 were photographed at 200 times magnification using a microscope. Three 0.5 mm square areas were randomly selected in the microscope photographs, the number of dots was counted, and the average value was used as the count value of the number of dots. In addition, the range of the dot diameter was measured from the above microscope photographs.

[0083] <Measurement of Adhesion to SUS>

[0084] Adhesion was measured by pasting the adhesive sheet with the adhesive surface exposed by peeling off the release liner to a SUS steel plate polished with 360-degree water-resistant paper according to the method of JIS Z 0237. Specifically, a test piece of adhesive sheet cut into a width of 25 mm was pasted on a SUS steel plate as an adherend, and then crimped back and forth twice with a 2kg roller, and left to stand for 20 minutes or 24 hours at 23°C and a relative humidity of 50%. Under the conditions of a peeling angle of 180° and a peeling speed of 300mm / min, the force required to peel the above-mentioned test piece from the SUS steel plate was measured using a universal material testing machine as adhesion (N / 25mm).

[0085] <Measurement of Ring Initial Adhesion Value>

[0086] After cutting a test piece of 25mm wide and 150mm long from the adhesive sheet, peel off the release liner and divide the release liner into two. The split 25mm wide release liner is pasted on the exposed surface of the adhesive layer in a manner that only the 25mm part from the two ends of the exposed surface of the adhesive layer is covered (a 100mm length part in the adhesive layer of the test piece is exposed). The test piece is set in an annular manner on the upper clamping part of the tensile tester in such a way that its adhesive surface side becomes the outside. After the SUS steel plate is installed in the lower clamping part of the tensile tester, the upper clamping part is lowered to a position of 20mm from the height of the lower clamping part at a speed of 300mm / min, so that the adhesive surface of the test piece is in contact with the SUS steel plate. Immediately after contact, the upper clamping part is raised to the original position at a speed of 300mm / min, and the maximum value of the tensile load required when the test piece is peeled off from the SUS steel plate is measured. Repeat the measurement three times, and the average value of the measured value is recorded as the annular initial adhesion value. The measurement was performed under the conditions of 23°C and 50% relative humidity.

[0087] <Restoration test>

[0088] Place the adhesive sheet with the release liner peeled off on an electronic balance, and press the bottom of a stainless steel cylinder (pressing unit) on the adhesive surface with the printed part. Apply a specified load for 10 seconds, and after checking whether there is stickiness, stick a PET film on the adhesive surface after a certain interval. The load of the cylinder is 300g / cm 2 , 1000g / cm 2 , 2000g / cm 2 In each case, the time from peeling off the cylinder until the PET film no longer adhered to the adhesive surface was measured.

[0089] <Measurement of holding power and holding power duration>

[0090] A test piece of 25 mm wide and 100 mm long was cut from the adhesive sheet, and a 25 mm x 25 mm square portion at one end of the test piece was adhered to a SUS steel plate. The square portion adhered to the SUS steel plate was strongly pressed with a squeegee with uniform force.

[0091] Next, the SUS steel plate was made vertical so that the square part of the adhesive sheet was located at the top. In this state, a weight of 1 kg was hung on the other end side of the adhesive sheet located at the bottom. In this state, the time until the adhesive sheet was completely peeled off was measured as the holding force duration. In addition, the offset (unit: mm) of the adhesive sheet after 50,000 seconds from the start of the measurement was measured as the value representing the holding force. It should be noted that the measurement was performed at 40°C.

[0092] [Measurement results]

[0093] Table 1 shows the storage modulus, loss modulus, loss tangent, and glass transition temperature of the adhesive compositions A to E after curing to form the adhesive layer.

[0094] [Table 1]

[0095]

[0096]

[0097] For storage modulus and loss modulus, the order from small to large is: adhesive composition E, adhesive composition A, adhesive composition B, adhesive composition C, and adhesive composition D. For glass transition temperature, the order from low to high is: adhesive composition E, adhesive composition A, adhesive composition B, adhesive composition C, and adhesive composition D.

[0098] Tables 2 to 8 show the measurement results of the adhesive force, loop tack value, and holding power of the adhesive sheets according to Examples 1 to 21 and Comparative Examples 1 to 14.

[0099] [Table 2]

[0100]

[0101] [Table 3]

[0102]

[0103] [Table 4]

[0104]

[0105] [Table 5]

[0106]

[0107] [Table 6]

[0108]

[0109] [Table 7]

[0110]

[0111] [Table 8]

[0112]

[0113] In Comparative Examples 1 to 10 where the printing unit is not provided, the ring initial adhesion values ​​are all above 1.0 N / 25 mm. In contrast, in Examples 1 to 21 where the printing unit is provided, the ring initial adhesion values ​​are less than 1.0 N / 25 mm. By providing the printing unit, it can be confirmed that the viscosity value is greatly reduced. In the case where the printing unit is provided, it can be seen from the results of Examples 10 to 12 and Examples 13 to 15 that if the thickness of the adhesive layer is equal, as the thickness of the printing unit becomes thicker, the viscosity decreases, and the adhesion also tends to decrease. From the comparison of Examples 1 to 3 and 21 with Comparative Example 14, it can be seen that even in the case of a low storage modulus, by thickening the thickness of the printing unit within an appropriate range, the viscosity can be reduced, and the adhesion can be adjusted to 0.05 N / 25 mm or more.

[0114] By comparing Example 1 with Comparative Example 11, and Example 2 with Comparative Example 12, it can be confirmed that when the thickness of the printed portion is equal and the same adhesive composition is used, when the thickness of the adhesive layer is thinner, both the loop initial adhesion value and the adhesive force can be reduced. In addition, the following tendency can be confirmed: the greater the storage modulus of the adhesive composition, the stronger the holding force.

[0115] Tables 9 to 12 show the results of the viscosity recovery test.

[0116] [Table 9]

[0117]

[0118] [Table 10]

[0119]

[0120] [Table 11]

[0121]

[0122] [Table 12]

[0123]

[0124] The results of the recovery tests shown in Tables 9 to 11 show that even when 300 g / cm 2 Even when the pressure was 2000 g / cm2 and the adhesive sheets produced tackiness for 10 seconds, it was confirmed that the adhesive sheets prepared in Examples 1, 3 to 9, 11 to 15, 17, and 20 recovered to a state of low or no tackiness within 2 minutes. 2 In the case where the adhesive sheet was subjected to a load of 10 seconds and produced tack, it was also confirmed that the adhesive sheet recovered to a state of low or no tack within 3 minutes. There was a tendency that the time until the tack disappeared would become longer as the load increased.

[0125] The measurement results and microscope photographs of the number of dots and dot size (dot diameter) in the printed portion of the adhesive sheet having a printed portion thickness of 2 μm are shown in FIG. Figure 6 .

[0126] like Figure 6 As shown, it was confirmed that: when the amount of ink is K10% (the thickness of the printed part is about 2μm), the printed part is composed of many large and small dots. Here, the K value expressed as a percentage is a value indicating the amount of ink, and is a term used in the dedicated software of the UV inkjet printer used this time. It was confirmed that: the average number of large and small dots contained in an area of ​​0.5mm square is more than five in any test piece. The dot diameter of the large dots is about 23μm to 30μm, and the dot diameter of the small dots is about 14μm to 18μm. It should be noted that it can be considered that the density of the dots increases with the increase in the amount of ink, but if the amount of ink exceeds K30%, the overlap between the dots will increase, and counting the number of dots will become difficult.

[0127] - Industrial Applicability -

[0128] The adhesive sheet disclosed in this specification can be used in various fields as a label, a graphic sheet, a component fixing sheet, various protective sheets, a temporary fixing sheet for articles, and the like.

[0129] - Explanation of symbols -

[0130] 1. Substrate

[0131] 3 adhesive layer

[0132] 5 Printing Department

[0133] 5A First Printing Department

[0134] 5B Second Printing Department

[0135] 7 Release liner

[0136] 10, 20, 30 adhesive sheets

[0137] 12 Printing Area

[0138] 15 o'clock

[0139] 17 Second release liner

[0140] 20 Adhesive sheet

[0141] 23 Print head.

Claims

1. An adhesive sheet, characterized in that: The adhesive sheet includes an adhesive layer and a printing portion, The printing part is formed on at least one surface of the adhesive layer. The printing unit is formed of a cured ink, and the printing unit is provided on a printing area, and one or more printing areas are set as a printing range on the adhesive layer. The initial ring adhesion value of the adhesive layer in the printing area to the SUS steel plate is less than 1.0N / 25mm, The adhesive strength of the adhesive layer in the printed area to a SUS steel plate after 24 hours at 23° C., a load of 2 kg during lamination, a relative humidity of 50%, and a peeling angle of 180 degrees is 0.05 N / 25 mm or more.

2. The adhesive sheet according to claim 1, characterized in that: When the pressure unit is used to apply 300g / cm for 10 seconds, 2 The printing area after the load is generated by the first viscosity value of the adhesive layer to the SUS steel plate, After the load is applied and the film is peeled off from the pressing unit and 2 minutes have passed, the adhesiveness to the PET film disappears, or the adhesiveness having a second adhesiveness value smaller than the first adhesiveness value remains.

3. The adhesive sheet according to claim 1, characterized in that: When the pressure unit is used to apply 2000g / cm for 10 seconds, 2 The printing area after the load of , produces a third viscosity value of the adhesive layer to the SUS steel plate, After the load is applied and the film is peeled off from the pressing unit and 3 minutes have passed, the adhesiveness to the PET film disappears, or the adhesiveness having a fourth adhesiveness value smaller than the third adhesiveness value remains.

4. The adhesive sheet according to claim 1, characterized in that: In the printing section, the constituent components of the adhesive layer ooze out due to application of a load.

5. The adhesive sheet according to claim 1, characterized in that: The storage modulus of the adhesive layer at 23°C and a frequency of 1 Hz is 1.0×10 4 Pa or more and 5.0×10 6 Below Pa.

6. The adhesive sheet according to claim 1, characterized in that: In the printed area, the amount of displacement at 40° C. after 50,000 seconds has passed is 1 mm or less.

7. The adhesive sheet according to claim 1, characterized in that: The average thickness of the printed portion is greater than or equal to 0.1 μm and less than or equal to 20 μm.

8. The adhesive sheet according to claim 1, characterized in that: The total area of ​​the printed region occupies 1% or more and 100% or less of at least one surface of the adhesive layer.

9. The adhesive sheet according to claim 1, characterized in that: The printing portion includes dots which are formed of a cured ink and are arranged irregularly on the printing area.

10. The adhesive sheet according to claim 9, characterized in that: The printing portion includes an average of more than five dots per 0.5 mm square. The diameter of the dots is 0.1 μm or more and 50 μm or less.

11. The adhesive sheet according to any one of claims 1 to 10, characterized in that: The printing portion is formed of a cured product of a photocurable ink or an electron beam curable ink.

12. The adhesive sheet according to claim 1, characterized in that: The glass transition temperature of the adhesive layer is above -50°C.

13. The adhesive sheet according to claim 1, characterized in that: The printing part is formed on one surface of the adhesive layer, The adhesive sheet further includes a sheet-shaped base material, and the base material is provided on a surface of the adhesive layer that is opposite to a surface on which the printing unit is provided.

14. The adhesive sheet according to claim 1, characterized in that: The adhesive sheet does not include a base material, and both surfaces of the adhesive layer serve as adhesive surfaces to be attached to an adherend.

15. The adhesive sheet according to claim 1, characterized in that: The printing portion is formed by curing ink applied by an inkjet method.

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