Adhesive sheet, method for producing the same, and article with adhesive sheet

Abstract

To provide an adhesive sheet capable of changing the direction in which adhesive strength increases or decreases, according to the needs of the consumer.SOLUTION: An adhesive sheet 10 sequentially comprises a sheet-like substrate, an adhesive layer 3, and a printed portion 5. After 24 hours have elapsed since adhesion of the adhesive sheet to an adherend, the maximum adhesive strength A1 max (N / 50 mm) when peeled 180° in a first direction is smaller than the maximum adhesive strength A2 max (N / 50 mm) when peeled 180° in a second direction, which is at a 90° angle to the first direction in a plan view. The printed portion 5 is formed by cured ink and is provided on one or more printing areas 12 set on the adhesive layer 3 as a printing range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a pressure-sensitive adhesive sheet that can be used as a label, a graphic sheet, or a pressure-sensitive adhesive sheet for temporary fixing. [Background technology]

[0002] Adhesive sheets comprising a substrate and an adhesive layer are used in many applications, such as labels, graphic sheets, wallpaper, and temporary fixing sheets. The adhesive properties of the adhesive sheet are set according to the respective applications. For example, in the case of a graphic sheet that is frequently replaced, the adhesive strength is designed to be balanced so that it does not peel off during use but can be easily peeled off after use.

[0003] Patent Document 1 describes an adhesive sheet that exhibits different adhesive strength depending on the peeling direction by forming a predetermined pattern of irregularities on the surface of a resin substrate facing the adhesive layer. Patent Document 2 also describes a method for using an adhesive sheet that includes a substrate with an embossed surface and an adhesive layer laminated on the embossed surface. In this adhesive sheet, a predetermined embossed pattern is formed on the substrate, which creates irregularities on the attachment surface of the adhesive layer, resulting in a configuration in which different adhesive strengths are produced depending on the peeling direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-79263 [Patent Document 2] Japanese Patent Application Publication No. 2018-172615 Summary of the Invention [Problem to be solved by the invention]

[0005] The pressure-sensitive adhesive sheets described in Patent Documents 1 and 2 are designed to be easily peeled off by peeling them off in the direction of weak adhesive strength after being attached to an adherend. However, the appropriate adhesive strength and difference in adhesive strength between the strong and weak adhesive strength directions vary depending on the application. For example, an adhesive sheet used to temporarily fasten components together may be able to have extremely weak adhesive strength in one direction, but wallpaper and other materials used for long periods of time may peel off during use in the direction of weak adhesive strength. In this regard, the pressure-sensitive adhesive sheets described in Patent Documents 1 and 2 have preset peeling directions for strong and weak adhesive strength, and cannot be changed according to the needs of consumers.

[0006] In view of the above problems, an object of the present invention is to provide an adhesive sheet that can change the direction in which adhesive strength is increased or decreased according to the needs of the consumer. [Means for solving the problem]

[0007] An example of a pressure-sensitive adhesive sheet disclosed in this specification includes, in this order, a sheet-like substrate, a pressure-sensitive adhesive layer, and a printed portion provided directly on the pressure-sensitive adhesive layer. The maximum adhesive strength A1 of the pressure-sensitive adhesive sheet when peeled from the adherend at a 180° angle along a first direction 24 hours after being attached to the adherend is 0.05%. max (N / 50mm) is the maximum adhesive strength A2 when peeled 180° from the adherend along a second direction that is at an angle of 90° to the first direction in a plan view. max (N / 50 mm) or less. The printed portion is formed from a cured ink product, and is provided on one or more print areas set as print ranges on the pressure-sensitive adhesive layer.

[0008] One example of an article disclosed herein includes a first member having a side surface, a second member having a contact surface with the first member and a side surface, a pressure-sensitive adhesive layer, and a sheet-like substrate formed on one surface of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet has a maximum adhesive strength A1max (N / 50 mm) when peeled along a first direction that is smaller than a maximum adhesive strength A2max (N / 50 mm) when peeled along a second direction that is at an angle of 90° to the first direction in a plan view, and is attached from at least a portion of the side surface of the first member to at least a portion of the side surface of the second member. The first member and the second member are fixed by the pressure-sensitive adhesive sheet so as not to move along at least one of the first direction and the second direction.

[0009] The method for producing a pressure-sensitive adhesive sheet disclosed in this specification includes the steps of: preparing a pressure-sensitive adhesive sheet including a sheet-like substrate and a pressure-sensitive adhesive layer; and providing a printed portion formed by an ink cured product by an inkjet method on a printing region on the exposed surface of the pressure-sensitive adhesive layer of the prepared pressure-sensitive adhesive sheet. In the pressure-sensitive adhesive sheet provided with the printed portion, 24 hours after being attached to an adherend, the maximum adhesive strength A1max (N / 50 mm) when peeled 180° from the adherend along a first direction is smaller than the maximum adhesive strength A2max (N / 50 mm) when peeled 180° from the adherend along a second direction that forms an angle of 90° with respect to the first direction in a plan view. [Effects of the Invention]

[0010] According to the adhesive sheet disclosed in this specification, by providing a printed portion having a pattern that is appropriately modified according to the needs of the consumer, the direction in which the adhesive strength increases and decreases, and the ratio between the maximum adhesive strength and the minimum adhesive strength, can be set as desired. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view of a pressure-sensitive adhesive sheet according to a first embodiment of the present disclosure with the release liner removed, viewed from the pressure-sensitive adhesive layer side. [Figure 2] FIG. 2 is a cross-sectional view of the pressure-sensitive adhesive sheet according to the first embodiment taken along line II-II shown in FIG. [Figure 3] 3 is a cross-sectional view of the pressure-sensitive adhesive sheet according to the first embodiment taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a plan view of the pressure-sensitive adhesive sheet according to the second embodiment with the release liner removed, viewed from the pressure-sensitive adhesive layer side. [Figure 5] FIG. 5 is a plan view of the pressure-sensitive adhesive sheet according to the third embodiment as viewed from the substrate side. [Figure 6] FIG. 6 is a perspective view schematically showing an article according to a fourth embodiment provided with a pressure-sensitive adhesive sheet. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment) [Adhesive sheet composition] Fig. 1 is a plan view of a pressure-sensitive adhesive sheet according to a first embodiment of the present disclosure with the release liner removed, viewed from the pressure-sensitive adhesive layer side. Fig. 2 is a cross-sectional view of the pressure-sensitive adhesive sheet according to the first embodiment, taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view of the pressure-sensitive adhesive sheet according to the first embodiment, taken along line III-III in Fig. 1. Note that in these figures, the thickness ratios of each layer and the length-width ratios of the sheet, etc., do not necessarily correspond to the actual products.

[0013] As shown in Figures 1 to 3, the pressure-sensitive adhesive sheet 10 of this embodiment comprises, in this order, a sheet-like substrate 1, a pressure-sensitive adhesive layer 3, and a printed area 5 provided directly on the pressure-sensitive adhesive layer 3. A release liner 7 may be provided on the surface of the pressure-sensitive adhesive layer 3 on which the printed area 5 is formed, with the printed area 5 sandwiched therebetween. The release liner 7 protects the adhesive surface of the pressure-sensitive adhesive layer 3 on which the printed area 5 is provided, allowing storage not only in roll form but also in the form of a flat plate. The release liner 7 may be a known one primarily made of paper or resin, and a release agent layer containing a silicone-based release agent or a fluorine-based release agent may be provided on the side facing the pressure-sensitive adhesive layer 3.

[0014] The printing portion 5 is formed from a cured ink, and is provided on one or more printing areas 12 set as printing ranges on the pressure-sensitive adhesive layer 3. The planar shape of the printing portion 5 is the same as the planar shape of the printing area 12.

[0015] In the adhesive sheet 10 of this embodiment, as an example, a plurality of printing areas 12 extending in a strip shape from one end to the other end in the flow direction (MD direction) of the substrate 1 are set at regular intervals, and a printing section 5 is formed on this printing area 12 with a predetermined thickness.

[0016] The printed portion 5 can be formed by a printing method using a plate such as gravure printing, offset printing, flexographic printing, or letterpress printing (relief printing), but can also be formed by an inkjet method, as will be described later.

[0017] When the printed portion 5 is formed by a printing method using a plate, the adhesive force theoretically disappears in the printing area 12 covered by the printed portion 5. However, by pressing the printed portion 5 strongly, the printed portion 5 may partially sink into the adhesive layer 3, and a slight adhesive force may be generated even on the printed portion 5.

[0018] When the printed portion 5 is formed by the inkjet method, the printed portion 5 is composed of a large number of dots. Therefore, if the average thickness of the printed portion 5 is equal to or less than a predetermined value, the adhesive component of the adhesive layer 3 will seep out from between the dots due to pressure bonding. The amount of adhesive component seeping out increases as the thickness of the printed portion 5 becomes thinner (i.e., the dot density becomes lower). By using the inkjet method, the printed portion 5 can be formed without using expensive plates. In this case, the printed portion 5 contains an average of five or more dots per 0.5 mm square, and the diameter of the dots is, for example, 0.1 μm to 50 μm.

[0019] The ink used to form the printed portion 5 is not limited, and one or more inks selected from photocurable inks, electron beam curable inks, and solvent-based inks can be used. Among these, photocurable inks and electron beam curable inks that are cured by ultraviolet (UV) or visible light are preferred because they make it difficult for the ink to diffuse into the adhesive layer 3 when forming the printed portion 5, making it easier to ensure the required thickness of the printed portion 5. Furthermore, because UV curable inks and electron beam curable inks can be cured instantly after printing, using these inks can shorten the production time of the adhesive sheet 10 compared to using solvent-based inks.

[0020] The color of the ink used to form the printed portion 5 is not particularly limited, and may be only black (K), or may be at least one or a combination of multiple colors selected from, for example, cyan (C), magenta (M), yellow (Y), black (K), white (W), gray, light cyan, light magenta, red, and transparent.

[0021] The average thickness of the printed portion 5 may be, for example, about 0.1 μm or more and about 30 μm or less, or about 1 μm or more and about 20 μm or less. If the average thickness of the printed portion 5 is less than 0.1 μm, the printed portion 5 will easily sink into the adhesive layer 3 upon compression, making it difficult to produce differences in adhesive strength depending on the peel direction, as described below. If the average thickness of the printed portion 5 is 1 μm or more, the printed portion 5 will also be less likely to sink upon compression. If the average thickness of the printed portion 5 exceeds 30 μm, the portions of the adhesive layer 3 not covered by the printed portion 5 will be less likely to come into contact with the adherend even upon compression, which may result in excessively weak adhesive strength of the entire adhesive sheet 10.

[0022] Furthermore, when the printed portions 5 are formed by an inkjet method, if the average thickness of the printed portions 5 exceeds 30 μm, the printing time becomes longer and the cost becomes less efficient. If the average thickness of the printed portions 5 is in the range of 0.1 μm or more and 20 μm or less, the adhesive component of the adhesive layer 3 can be generated from the printed portions 5 during compression bonding, so the adhesive strength of the adhesive sheet 10 can be controlled not only by the pattern of the printed regions 12 but also by the thickness of the printed portions 5. The ease with which the adhesive component seeps out varies depending on the hardness of the adhesive layer 3, so if the average thickness of the printed portions 5 is in the range of 1 μm or more and 6 μm or less, the types of adhesives that can be used as the main agent of the adhesive layer 3 can be further expanded, which is preferable.

[0023] On the other hand, when the printed portion 5 is formed from cured white, black, and color inks and the substrate 1 is transparent or translucent, making the average thickness greater than 6 μm makes it easier for the user to see the pattern of the printed region 12 through the substrate 1. This makes it possible for the user of the adhesive sheet 10 to recognize any pattern, letter, symbol, etc.

[0024] With the above-described configuration, the pressure-sensitive adhesive sheet 10 of this embodiment has a maximum adhesive strength A1 when peeled from the adherend at 180° along the first direction after 24 hours have passed since it was attached to the adherend at 23°C. max (N / 50mm) is the maximum adhesive strength A2 when peeled 180° from the adherend along a second direction that is at an angle of 90° to the first direction in a plan view. max (N / 50mm). In the example shown in Fig. 1, the first direction is the MD direction, and the second direction is the perpendicular direction (TD direction). For this reason, the adhesive sheet 10 of this embodiment is easier to peel along the MD direction than along the TD direction.

[0025] The adhesive strength of adhesive sheet 10 varies depending on the width ratio of printed area 12 (the area covered with printed section 5) to non-printed area (the area not covered with printed section 5) in the cross section perpendicular to the peeling direction. If the width ratio of printed area 12 is large, the adhesive strength in that area will be weaker, and if the width ratio of the non-printed area is large, the adhesive strength in that area will be stronger.

[0026] When the adhesive sheet 10 of this embodiment is peeled along the MD direction, the ratio of the printed area 12 to the non-printed area in the TD cross section is constant regardless of the position, so the maximum adhesive strength A1 max and minimum value A1 min The value is almost the same as A1 max is smaller than the maximum adhesive strength of the adhesive sheet when the printed region 12 is not provided. In contrast, when the adhesive sheet 10 is peeled along the TD direction, the MD cross section passes alternately through the printed region 12 and the non-printed region, so the adhesive strength is small (minimum value A2 min ) and the larger value (maximum value A2 max ) are observed alternately. This maximum value A2 max is close to the maximum adhesive strength of the adhesive sheet when the printing area 12 is not provided. max is A1 max It's getting bigger.

[0027] In the adhesive sheet 10, A1 max / A2 max The value of A1 may be a value smaller than 1.0, but is preferably 0.10 or more and 0.85 or less, since this maintains an adhesive strength sufficient to prevent the entire sheet from falling off the adherend, and allows the user to clearly feel the difference in adhesive strength depending on the peeling direction, even taking into account error. max / A2 max It is more preferable in practical use if the value is 0.20 or more and 0.70 or less.

[0028] In the adhesive sheet 10 of this embodiment, for example, by changing the width of each print area 12 or by changing the interval between the strip-shaped print areas 12, A1 maxcan be changed accordingly, resulting in A1 max / A2 max The value of A1 can also be changed. In addition, the amount of adhesive component seeping out can be changed by changing the thickness of the printed portion 5. max can be changed.

[0029] In the adhesive sheet 10, in the second direction in which the maximum value of the adhesive strength increases, the maximum value A2 of the adhesive strength max and minimum value A2 min Ratio in percentage (100 x A2 min / A2 max ) is preferably 70.0% or less. In this case, A1 min / A1 max The value of A2 min / A2 max is larger than the value of

[0030] In the adhesive sheet 10 of this embodiment, an adhesive sheet comprising a substrate 1 and an adhesive layer 3 can be manufactured without forming a printed portion 5, and then the printed portion 5 can be provided on a printing area 12 of an appropriately set pattern, so that the adhesive strength can be adjusted in either a stronger or weaker direction according to the needs of the consumer.

[0031] According to the pressure-sensitive adhesive sheet 10, the maximum adhesive strength in the MD direction is smaller than the maximum adhesive strength in the TD direction, but the holding strength in the MD direction can be made to be approximately the same as the holding strength in the TD direction. In contrast, in a pressure-sensitive adhesive sheet having unevenness on the adhesive surface of the pressure-sensitive adhesive layer as described in Patent Document 2, if the proportion of recesses in the pressure-sensitive adhesive layer is increased to create anisotropy in the adhesive strength, the sheet will be more likely to fall off from the adherend in a holding strength test.

[0032] According to the adhesive sheet 10 of this embodiment, in a holding power test at 40°C and a load of 1 kg, it is possible to reduce the difference between the amount of displacement measured in the first direction after 50,000 seconds and the amount of displacement measured in the second direction after 50,000 seconds to 1 mm or less.

[0033] Therefore, when the pressure-sensitive adhesive sheet 10 of this embodiment is used as a graphic sheet or wallpaper, it can be easily peeled off in the first direction, and even if it is applied regardless of the length and width of the sheet, it is less likely to fall off. Also, when it is used as a fixing sheet for fixing two members together, it can be easily peeled off in the first direction, while effectively preventing the two members from shifting not only in the second direction but also in the first direction.

[0034] The adhesive used to form the adhesive layer 3 is not particularly limited, and may be, for example, one or a mixture of two or more selected from acrylic adhesives, acrylic-urethane adhesives, urethane adhesives, silicone adhesives, and rubber adhesives. The adhesive used may be a water-based adhesive, a solvent-based adhesive, a solventless adhesive, or the like.

[0035] The thickness of the adhesive layer 3 is not particularly limited, but may be approximately 10.0 times or less the average thickness of the printed 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. When the thickness of the adhesive layer 3 is 100 μm or less, excessive sinking of the printed portion 5 during pressure bonding can be prevented.

[0036] The adhesive layer 3 may contain an appropriate curing agent during production, and may also contain additives such as a tackifier, antistatic agent, colorant, filler, etc. as needed. At least one of the adhesive and additives used to form the adhesive layer 3 may contain a biologically derived component. For example, the adhesive layer 3 may contain approximately 10% by mass or more and 50% by mass or less of a terpene-based or rosin-based tackifier. The biomass content of the adhesive layer 3 may be, for example, approximately 10% by mass or more and 50% or less.

[0037] The storage modulus G' of the pressure-sensitive adhesive layer 3 at 23°C and a frequency of 1 Hz is not particularly limited, but is preferably 1.0 × 10 4 Pa or more 5.0×10 6 Pa or less, and 4 Pa or more 2.0×10 6The storage modulus may be less than 100 Pa. When the printed portion 5 is formed by an inkjet method, a storage modulus within the above range allows the adhesive component to easily exude from the printed portion 5 during pressure bonding. As a result, the adhesive strength in each of the MD and TD directions can be adjusted not only by the pattern of the printed region 12 but also by the thickness of the printed portion 5.

[0038] Known materials such as resin sheets, synthetic paper, paper, nonwoven fabrics, woven fabrics, and laminates thereof can be used for the substrate 1. Materials that can be used to form the resin sheets include, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyimide (PI), and polyamide.

[0039] The substrate 1 may be formed from an unstretched resin sheet, or may be formed from a uniaxially stretched film or a biaxially stretched film. In this case, if the stretch rate in the first direction (here, the MD direction) is smaller than the stretch rate in the second direction (here, the TD direction), the elongation of the substrate 1 when peeled in the MD direction can be made larger than the elongation of the substrate 1 when peeled in the TD direction. This can further increase the difference between the adhesive strength of the pressure-sensitive adhesive sheet 10 when peeled in the MD direction and the adhesive strength of the pressure-sensitive adhesive sheet 10 when peeled in the TD direction. When a substrate 1 having different stretch rates depending on the direction is used, the breaking elongation in the MD direction is larger than the breaking elongation in the TD direction, and the value of (breaking elongation in the MD direction) / (breaking elongation in the TD direction) may be, for example, 1.1 or more and 3.0 or less.

[0040] The thickness of the substrate 1 is not particularly limited, but may be, for example, about 2 μm to 300 μm, 5 μm to 250 μm, or 10 μm to 100 μm. If necessary, a known easy-adhesion layer or antistatic layer may be provided on at least one surface of the substrate 1, and the substrate may be subjected to a surface treatment such as corona treatment. The easy-adhesion layer improves adhesion not only to the pressure-sensitive adhesive layer 3 but also to ink.

[0041] A printed layer may be formed on at least one of the surface of the substrate 1 facing the pressure-sensitive adhesive layer 3 and the opposite surface. When the pressure-sensitive adhesive sheet 10 is used as a label, graphic sheet, or the like, it is preferable that a printed layer with an appropriate design be formed.

[0042] To reduce the environmental impact, biomass materials or recycled materials may be used in part or in whole for the substrate 1. It is also preferable to produce the pressure-sensitive adhesive sheet 10 using materials, including the substrate 1, that emit as little CO2 equivalent emissions as possible during production.

[0043] The shape of each printed area 12 is not limited to a strip, and the spacing and width between the printed areas 12 are not particularly limited as long as they can ensure sufficient adhesive strength to maintain adhesion to the substrate and the adhesive strength in the first direction and the adhesive strength in the second direction are clearly different.

[0044] The thickness of the printed portion 5 may be constant or may differ from one another on each printed region 12. When the pressure-sensitive adhesive sheet 10 is viewed as a whole, the thickness of the printed portion 5 may be set to change stepwise along at least one of the first direction and the second direction.

[0045] [Manufacturing method of adhesive sheet] When producing the pressure-sensitive adhesive sheet 10 of this embodiment, first, a coating liquid prepared by mixing a pressure-sensitive adhesive and a curing agent is applied to the release surface of a known release liner using a known comma-type coater or the like to a predetermined thickness, and then dried to form the pressure-sensitive adhesive layer 3. Next, the pressure-sensitive adhesive sheet is produced by laminating one side of the sheet-like substrate 1 to the pressure-sensitive adhesive layer 3 on the release liner. Next, the release liner is peeled off to expose the pressure-sensitive adhesive layer 3, and a printed portion 5 made of a cured ink is formed in the printing area 12 set in the pressure-sensitive adhesive layer 3 using, for example, an inkjet printer. Next, the pressure-sensitive adhesive sheet 10 can be produced by laminating a known release liner 7 to the pressure-sensitive adhesive layer 3 on which the printed portion 5 has been formed.

[0046] The printing section 5 may be formed by an inkjet printer on a sheet-type (planographic) adhesive sheet, or may be formed continuously on a roll-type adhesive sheet.

[0047] As mentioned above, the printed portion 5 may be produced by a printing method other than the inkjet method.

[0048] (Second embodiment) Fig. 4 is a plan view of a pressure-sensitive adhesive sheet according to the second embodiment with the release liner removed, viewed from the pressure-sensitive adhesive layer side. As shown in the figure, the pressure-sensitive adhesive sheet 10a of this embodiment differs from the pressure-sensitive adhesive sheet 10 of the first embodiment in that multiple elliptical printed regions 12 are arranged at predetermined intervals in both the MD and TD directions. Fig. 4 shows an example in which the major axis of each printed region 12 is inclined at 45° with respect to the MD direction. A printed section 5 is formed on the printed region 12 of the pressure-sensitive adhesive layer 3. The pressure-sensitive adhesive sheet 10a of this embodiment has the same configuration as the pressure-sensitive adhesive sheet 10 of the first embodiment, except for the shape of the printed region 12.

[0049] In the adhesive sheet 10a of this embodiment, the first direction in which the maximum adhesive strength is weak is a direction inclined at 45° to the MD direction and parallel to the long axis of the printing area 12 (hereinafter referred to as the "long axis direction"), and the second direction in which the maximum adhesive strength is strong is a direction parallel to the short axis of the printing area 12 (hereinafter referred to as the "short axis direction").

[0050] This is thought to be because when the adhesive sheet 10a is peeled along the long axis direction, the cross section in the short axis direction, which is perpendicular to the long axis direction, always crosses the printed area 12, whereas when peeling along the short axis direction, there are cross sections in the long axis direction that do not cross the printed area 12.

[0051] Therefore, the maximum adhesive strength A2 when peeled off in the minor axis direction of the adhesive sheet 10a max and minimum value A2 min The ratio of the adhesive strength when the adhesive sheet 10a is peeled in the longitudinal direction can be set to 70.0% or less.max , the minimum value is A1 min Then, A1 min / A1 max The value of A2 min / A2 max is larger than the value of

[0052] According to the adhesive sheet 10a of this embodiment, even if a resin sheet having different elongation rates in the MD and TD directions is used as the substrate 1, it is possible to set directions that are easy to peel and directions that are difficult to peel, regardless of the ease with which the substrate 1 stretches depending on the peeling direction.

[0053] The print area 12 can be selected from a variety of patterns, not limited to the adhesive sheet 10a of this embodiment.

[0054] (Third embodiment) 5 is a plan view of a pressure-sensitive adhesive sheet according to a third embodiment, as viewed from the substrate side. As shown in the figure, in the pressure-sensitive adhesive sheet 10b of this embodiment, the printed region 12 provided with the printed portion 5 includes shapes such as letters, symbols, and figures indicating the direction in which peeling is easy, such as arrow shapes and the words "peel direction." The substrate 1 is transparent or translucent and is made of, for example, resin. Therefore, the shape of the printed region 12, including the letters, symbols, and figures, can be seen through the substrate 1 by a user of the pressure-sensitive adhesive sheet 10b.

[0055] According to this configuration, when the adhesive sheet 10b is used as a sheet for fixing a member or a laminate film for a graphic sheet, the user can be informed of the direction in which it is easy to peel off.

[0056] The printed area 12 is not limited to the example shown in FIG. 5 as long as it includes at least one of the letters, symbols, and figures described above, and indicates the peeling direction to the user.

[0057] (Fourth embodiment) Fig. 6 is a perspective view schematically showing an article according to a fourth embodiment having an adhesive sheet. The figure shows an example of an article in which the adhesive sheet according to the first to third embodiments disclosed herein is used as a fixing adhesive sheet for fixing two members together. In Fig. 6, the printed part 5 (printed area 12) is shown by a solid line for ease of understanding.

[0058] As shown in Figure 6, the article 20 of this embodiment comprises a first member 11 having a side surface, a second member 13 having a contact surface with the first member 11 and a side surface, an adhesive layer 3 (not shown), and an adhesive sheet 10 having a sheet-like substrate 1 formed on one surface of the adhesive layer 3.

[0059] The adhesive sheet 10 has a maximum adhesive strength A1 when peeled along a first direction. max (N / 50mm) is the maximum adhesive strength A2 when peeled along a second direction that is at an angle of 90° to the first direction in a plan view. max (N / 50mm). In addition, in a holding power test of the adhesive sheet 10 at 40°C and a load of 1 kg, the difference between the amount of displacement measured in the first direction after 50,000 seconds and the amount of displacement measured in the second direction after 50,000 seconds was 1 mm or less, and no falling off occurred.

[0060] This adhesive sheet 10 is attached from at least a portion of the side surface of the first member 11 to at least a portion of the side surface of the second member 13, and fixes the first member 11 and the second member 13 so that they do not move along at least one of the first direction and the second direction.

[0061] 6 shows an example of a pressure-sensitive adhesive sheet 10 according to the first embodiment, in which a transparent resin sheet is used as the substrate 1 and the printed region 12 has a shape including an arrow indicating a first direction that facilitates peeling. The shapes of the first member 11 and the second member 13 and the planar shape of the pressure-sensitive adhesive sheet 10 are not particularly limited, but for example, the first member 11 and the second member 13 are both cylindrical, and the lower surface of the first member 11 and the upper surface of the second member 13 are in contact with each other, with their side surfaces in contact and flush with each other. In this article 20, the first direction of the pressure-sensitive adhesive sheet 10 is the circumferential direction from left to right of the article 20 shown in FIG. 6, and the second direction is the thickness direction of the article 20, which forms an angle of 90° with the circumferential direction.

[0062] In this way, the adhesive sheet 10 maintains adhesive strength sufficient to prevent it from peeling off from the first member 11 and the second member 13 during use, and can be easily peeled off along the first direction when it is peeled off from the first member 11 and the second member 13 during alignment during application or after use. On the other hand, with the adhesive sheet 10, the difference in holding strength depending on the direction is smaller than when unevenness is formed on the surface of the adhesive layer, so the first member 11 and the second member 13 are less likely to shift in the direction parallel to the first direction and the direction parallel to the second direction.

[0063] 6 shows an example in which the planar shape of the adhesive sheet 10 is quadrilateral, but any shape is acceptable as long as it can fix the first member 11 and the second member 13. In addition, a printed layer of any design, including a symbol indicating the direction in which peeling is easy, may be formed separately on the surface of the substrate 1.

[0064] The adhesive sheets 10, 10a, 10b and the article 20 including them according to the embodiments described above are examples of the present invention, and the constituent materials, thickness, shape, formation position, color, etc. of the substrate 1, adhesive layer 3, printed portion 5, etc. can be changed as appropriate within the scope that does not deviate from the spirit of the present invention. [Example]

[0065] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0066] [Preparation of adhesive sheet] Example 1 An appropriate amount of an isocyanate-based curing agent was added to each of commercially available acrylic adhesives and mixed to obtain PSA composition A. PSA composition A contained a rosin-based tackifier equivalent to approximately 14 mass% of the weight of the PSA layer after drying, so the biomass degree of the PSA layer formed was approximately 14%.

[0067] Next, PSA composition A was applied to the release surface of a commercially available release liner made of PET film, which had a 50 μm-thick release agent layer containing a silicone-based release agent formed on its release surface, using a known comma-type coater, and then dried to form a PSA layer. The PSA layer thickness was 20 μm. The coated side of the release liner was then attached to one side of a substrate to transfer the PSA layer to the substrate, and the resulting substrate was aged at 40°C for approximately 3 days to form a PSA sheet. The substrate used was a 50 μm-thick PET film A (manufactured by Toyobo Co., Ltd., product name: COSMOSHINE (registered trademark) A4360) with easy-adhesion layers formed on both sides. The PET film was a biaxially stretched film, with the stretch ratio in the MD direction being smaller than that in the TD direction. The breaking elongation of this PET film, measured according to a method in accordance with JIS C-2318, was 155% in the MD direction and 103% in the TD direction.

[0068] Next, a UV-curable ink was ejected and cured using a UV inkjet printer (UJF-6042MkII, manufactured by Mimaki Engineering Co., Ltd.) onto the area designated as the printing area on the exposed surface of the adhesive layer of the prepared adhesive sheet. The UV-curable ink used was black ink, LH-100, manufactured by Mimaki Engineering Co., Ltd. The ink volume was set to K30%. Each printing area was elliptical with a major axis of 1.00 cm and a minor axis of 0.63 cm. Multiple printing areas were spaced approximately 0.42 cm apart in both the MD and TD directions, forming a pattern tilted at 45° relative to the MD (the pattern shown in Figure 4).

[0069] (Comparative Example 1) The adhesive composition A was applied to the release surface of a release liner using a comma-type coater and dried to form an adhesive layer with a thickness of 28 μm. The release liner used was release paper "MX3" manufactured by Nichiei Shinka Co., Ltd. This release liner had lattice-shaped convex shapes with a width of 110 μm formed on the release surface, and the top of the opening of the depression formed by the convex shapes was a square with sides of 330 μm, and the bottom of the opening was a square with sides of 230 μm. The depth of the opening was 25 μm.

[0070] Next, the coated side of the release liner was attached to one side of the substrate to transfer the adhesive layer onto the substrate, and then aging was performed for about 3 days at 40°C to form an adhesive sheet. The substrate used was a 25µm thick PET film B (manufactured by Toray Advanced Film Co., Ltd., product name: Lumirror (registered trademark)). The PET film was a biaxially stretched film, and the breaking elongation measured by a method in accordance with JIS C-2318-72 was 160% in the MD direction and 130% in the TD direction.

[0071] (Comparative Example 2) A pressure-sensitive adhesive sheet comprising a substrate, a pressure-sensitive adhesive layer, and a release liner in this order was produced by the method described above in Example 1, but without performing the step of forming printed portion 5. The thickness of the pressure-sensitive adhesive layer was 20 μm, the same as the pressure-sensitive adhesive sheet produced in Example 1.

[0072] (Comparative Example 3) Using the method described in Example 1 above, the printing area was changed to cover the entire adhesive surface of the adhesive layer, thereby producing an adhesive sheet comprising, from top to bottom, substrate / adhesive layer / printed area / release liner. The printed area was formed to cover the entire adhesive surface of the adhesive layer. However, the ink volume setting of the UV inkjet printer was set to 20%.

[0073] Comparative Example 4 An adhesive film was produced in the same manner as in Comparative Example 3. However, the ink volume of the UV inkjet printer was set to 30%.

[0074] [Measurement method] <Measurement of storage modulus G', loss modulus G'', loss tangent (tanδ) and glass transition temperature Tg of adhesive layer> The storage modulus G', loss modulus G'', and loss tangent of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet were measured by the following method. First, a substrate-less tape having a 50 μm-thick pressure-sensitive adhesive layer was produced using the prepared pressure-sensitive adhesive composition A. This substrate-less tape was then aged at 40°C for 72 hours. Next, the pressure-sensitive adhesive layer alone was laminated until the total thickness reached 1 mm, and then punched out to a diameter of 8 mm to produce a tablet. This tablet was sandwiched between the plates of a rheometer (product name: AR2000ex), and the storage modulus G' and loss modulus G'' were measured under conditions of a frequency of 1 Hz, a strain of 0.05%, and a measurement temperature of -40 to 100°C. The value of loss modulus G'' / storage modulus G' was calculated as the loss tangent. The temperature at which the loss tangent was maximized was read as the glass transition temperature of the pressure-sensitive adhesive layer.

[0075] <Measurement of the thickness of the printed area> A print was created on a 50 μm thick PET film using a UV inkjet printer (UJF-6042MkII manufactured by Mimaki Engineering Co., Ltd.) with the ink volume set to K20% and K30%. The total thickness of each sheet sample was measured using a constant pressure thickness gauge, and the thickness of the PET film (50 μm) was subtracted from the measured value to calculate the thickness of each print.

[0076] As a result of the measurements, the thickness of the printed area (ink thickness) was approximately 3 to 4 μm for K20%, and approximately 5 μm for K30%.

[0077] <Measurement of adhesive strength to SUS> The release liner was peeled off to expose the adhesive surface of the pressure-sensitive adhesive sheet prepared in Example 1, which was then attached to a SUS steel plate that had been polished with 360-grit waterproof paper using a method in accordance with JIS Z 0237, and adhesive strength was measured. Specifically, rectangular test pieces of the pressure-sensitive adhesive sheet, cut into pieces 50 mm wide and 150 mm long, were attached to the SUS steel plate as the adherend, pressed against the plate using a 2 kg roller with one reciprocating motion, and then allowed to stand at 23°C and 50% relative humidity for 20 minutes or 24 hours. The force required to peel these test pieces from the SUS steel plate was measured as adhesive strength (N / 50 mm) using a universal testing machine (TENSILON RTI-1225, manufactured by A&D Co., Ltd.) at a peel angle of 180° and a peel rate of 300 mm / min. Adhesive strength measurements were performed in the MD, a first direction tilted 45° counterclockwise from the MD (see Table 1), and a second direction tilted 45° clockwise from the MD. The maximum and minimum adhesive strength values were recorded within a range of 15 mm or more in the movement distance (equal to twice the peeling length) of the gripping tool gripping and peeling the adhesive sheet.

[0078] For the pressure-sensitive adhesive sheets produced in Comparative Examples 1 to 4, the test pieces were rectangular, 25 mm wide and 150 mm long, and the adhesive strength was measured when peeled along the MD direction in the same manner as for the pressure-sensitive adhesive sheet of Example 1. For Comparative Example 1 only, the adhesive strength was also measured when peeled along the TD direction, and the maximum and minimum values of the adhesive strength were also recorded.

[0079] <Measurement of holding power and holding power duration> Test pieces measuring 25 mm wide and 100 mm long were cut out from the pressure-sensitive adhesive sheets produced in Example 1 and Comparative Examples 1 to 4, and a 25 mm × 25 mm portion of the pressure-sensitive adhesive layer at one end of the test piece was exposed and attached to a SUS steel plate. The square portion attached to the SUS steel plate was strongly and uniformly pressed using a squeegee.

[0080] Next, under a condition of 40°C, the SUS steel plate was positioned vertically so that the square part of the test piece was facing upward, and a 1 kg weight was hung from the other end of the test piece positioned downward. In this state, the time until the pressure-sensitive adhesive sheet was completely peeled off was measured as the holding power duration. If the test piece had not fallen off within 50,000 seconds from the start of measurement, the amount of displacement of the test piece (unit: mm) was measured as a value representing the holding power. For the pressure-sensitive adhesive sheet produced in Example 1, the holding power was measured in the MD direction and the first and second directions described above, and for the pressure-sensitive adhesive sheet produced in Comparative Example 1, the holding power was measured in the MD and TD directions. For the pressure-sensitive adhesive sheets produced in Comparative Examples 2 to 4, the holding power was measured only in the MD direction.

[0081] [Measurement results] The storage modulus G' of the adhesive layer of the adhesive sheet at 23°C is 9.87 x 10 4 Pa, and the loss modulus G'' is 6.31 x 10 4 The loss tangent tanδ was 0.64. The glass transition temperature was -8°C.

[0082] The measurement results of the adhesive strength and holding power of the pressure-sensitive adhesive sheets produced in Example 1 and Comparative Example 1 are shown in Table 1. The measurement results of the adhesive strength and holding power of the pressure-sensitive adhesive sheets produced in Comparative Examples 1 to 4 are shown in Table 2 (the results of Comparative Example 1 are shown in both tables). In Table 2, to match the notation with Table 1, the adhesive strengths are converted to (N / 50 mm).

[0083] [Table 1]

[0084] [Table 2] From the results shown in Table 1, the adhesive sheet produced in Example 1 had a maximum adhesive strength A1 after 24 hours when peeled along the long axis direction (first direction) of the printed area. max is 31.6 (N / 50 mm), and the maximum adhesive strength A2 when peeled along the minor axis direction (second direction) of the printed area max It was confirmed that the maximum adhesive strength in the MD direction was smaller than A1 (42.1 (N / 50 mm)). max and A2 max The value was between .

[0085] In addition, in the adhesive sheet produced in Example 1, the maximum value A2 of the adhesive strength in the second direction max and minimum value A2 min A2 as a percentage of min / A2 max The ratio of maximum adhesive strength to minimum adhesive strength (100 × MIN / MAX) when peeled along the MD, first and second directions was 63.6%, 89.6% and 60.7%, respectively.

[0086] In the holding power test of the adhesive sheet produced in Example 1, the deviations in the MD direction, first direction, and second direction were 0.11 mm, 0.07 mm, and 0.07 mm, respectively, and no significant difference was observed in the deviations in the first direction and second direction.

[0087] In contrast, for the PSA sheet produced in Comparative Example 1, the ratios of maximum adhesive strength to minimum adhesive strength (100 × MIN / MAX) when peeled along the MD and TD directions were 82.8% and 80.0%, respectively, exceeding 70% in both directions. Furthermore, because the adhesive surface of the PSA layer had lattice-shaped grooves corresponding to the convex portions of the release liner, the PSA tended to have lower adhesive strength in the same direction compared to the PSA sheet of Comparative Example 2, which did not have grooves in the PSA layer (see Table 2). In the holding power test, it was confirmed that the PSA sheet of Comparative Example 1 was more susceptible to detachment, despite having an adhesive layer with the same composition as that of Comparative Example 2.

[0088] The measurement results of the pressure-sensitive adhesive sheets produced in Comparative Examples 2, 3, and 4 confirmed that, within a range where the thickness of the printed portion is equal to or less than a predetermined value, the adhesive strength decreases as the printed portion becomes thicker. On the other hand, it was also found that the change in holding power is small even when the printed portion is made thicker. [Industrial Applicability]

[0089] The pressure-sensitive adhesive sheets disclosed in this specification can be used in a variety of fields, such as labels, graphic sheets, component fixing sheets, various protective sheets, and temporary fixing sheets for articles. [Explanation of symbols]

[0090] 1 Base material 3. Adhesive layer 5 Printing Department 7 Release Liner 10, 10a, 10b Adhesive sheet 11 First member 12 Print area 13 Second member 20 Goods

Claims

1. A sheet-like substrate, a pressure-sensitive adhesive layer, and a printed portion provided directly on the pressure-sensitive adhesive layer in this order, Maximum adhesive strength A1 when peeled 180° from the adherend along the first direction 24 hours after attachment to the adherend ｍａｘ (N / 50 mm) is the maximum adhesive strength A2 when peeled 180° from the adherend along a second direction that is at an angle of 90° to the first direction in a plan view. ｍａｘ (N / 50mm) or less, The printed portion is formed from a cured ink and is provided on one or more printing areas set as printing ranges in the adhesive layer of the adhesive sheet.

2. A1 ｍａｘ / A2 ｍａｘ The pressure-sensitive adhesive sheet according to claim 1 , wherein the value of is 0.10 or more and 0.85 or less.

3. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein in a holding power test at 40°C and a load of 1 kg, the difference between the amount of displacement measured in the first direction after 50,000 seconds and the amount of displacement measured in the second direction after 50,000 seconds is 1 mm or less.

4. The pressure-sensitive adhesive layer has a storage modulus of 1.0×10 at 23° C. and a frequency of 1 Hz. ４ Pa or more 5.0×10 ６ The pressure-sensitive adhesive sheet according to claim 1 , wherein the surface tension is 0.05 Pa or less.

5. the substrate is formed of a uniaxially stretched resin film or a biaxially stretched resin film, the first direction coincides with the machine direction of the substrate, and the second direction coincides with the transverse direction of the substrate; The pressure-sensitive adhesive sheet according to claim 1 , wherein the stretching ratio of the substrate in the MD direction is smaller than the stretching ratio of the substrate in the TD direction.

6. The minimum adhesive strength when peeled 180° from the adherend along the first direction is defined as A1 ｍｉｎ (N / 50 mm), and the minimum adhesive strength A2 when peeled 180° from the adherend along the second direction ｍｉｎ (N / 50mm), 100 x A2 ｍｉｎ / A2 ｍａｘ The value of is 70.0% or less, A1 ｍｉｎ / A1 ｍａｘ The value of A2 ｍｉｎ / A2 ｍａｘ The pressure-sensitive adhesive sheet according to claim 1 , wherein the value is greater than or equal to the above.

7. the substrate is transparent or translucent; The pressure-sensitive adhesive sheet according to claim 1 , wherein when viewed from above the substrate, the printed area includes at least one shape selected from the group consisting of letters, symbols, and figures that indicate the peeling direction.

8. The pressure-sensitive adhesive sheet according to claim 1 , wherein in the printed region, the thickness of the printed portion varies stepwise along at least one of the first direction and the second direction.

9. a first member having a side surface; a second member having a contact surface with the first member and a side surface; a pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which has a pressure-sensitive adhesive layer and a sheet-like substrate formed on one surface of the pressure-sensitive adhesive layer; The pressure-sensitive adhesive sheet has a maximum adhesive strength A1 when peeled along a first direction. ｍａｘ (N / 50 mm) is the maximum adhesive strength A2 when peeled along a second direction that is at an angle of 90° to the first direction in a plan view. ｍａｘ (N / 50 mm) or less, and is attached from at least a portion of a side surface of the first member to at least a portion of a side surface of the second member, An article, wherein the first member and the second member are fixed by the adhesive sheet so as not to move along at least one of the first direction and the second direction.

10. A step of preparing a pressure-sensitive adhesive sheet including a sheet-like substrate and a pressure-sensitive adhesive layer; providing a printing portion formed of an ink cured product by an inkjet method on a printing area on an exposed surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet produced; a maximum adhesive strength A1max (N / 50 mm) of the pressure-sensitive adhesive sheet provided with the printed portion when peeled 180° from the adherend along a first direction 24 hours after being attached to the adherend is smaller than a maximum adhesive strength A2max (N / 50 mm) of the pressure-sensitive adhesive sheet when peeled 180° from the adherend along a second direction that forms an angle of 90° with respect to the first direction in a plan view.

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