Method for producing re-peelable adhesive sheet

Abstract

To provide a method for producing a re-peelable adhesive sheet which can be easily peeled off without an adhesive residue after being securely attached to an object for a certain period of time.SOLUTION: There is provided a method for producing a re-peelable adhesive sheet, which comprises an adhesive part formation step of forming a number of dot-like adhesive parts on at least a part of one surface of a base material sheet, wherein the adhesive part formation step is performed by pattern coating of a hot-melt type adhesive by a letterpress printing method, the viscosity of the hot-melt type adhesive by a type B viscometer at 140°C is 10000 to 50000 mPa s and the sheet surface temperature immediately after the pattern coating is 40 to 90°C.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a re-peelable adhesive sheet.

Background Art

[0002] A re-peelable adhesive sheet is known as an adhesive sheet that can be easily peeled from an object after being attached to the object for a certain period of time. The re-peelable adhesive sheet is used, for example, for attaching on personal information written on a postcard so that the recipient can peel it off to read the personal information. Further, it is used for applications such as printing necessary information as a management label between manufacturing processes of a product or a logistics management label in the distribution process of a product and peeling off the label when the purpose of information transmission becomes unnecessary. The re-peelable adhesive sheet is required to have good re-peelability such that it adheres well to an object during attachment, while on the other hand, there is no adhesive residue or breakage of the base material during re-peeling and it can be easily peeled off.

[0003] As the re-peelable adhesive sheet, an adhesive sheet in which an adhesive layer is formed on a base material using an adhesive coating liquid containing adhesive fine particles is known (see, for example, Patent Document 1). The adhesive layer thus formed has an uneven surface due to the inclusion of adhesive fine particles. Therefore, when the re-peelable adhesive sheet is attached to an object, the contact area between the adhesive layer and the object decreases, and the re-peelability is improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since such a re-peelable adhesive sheet suppresses the adhesive force by blending adhesive fine particles, although it is excellent in re-peelability, its adhesiveness is insufficient. Therefore, although it can be used for applications where it is pasted for a short time, it is not suitable for applications such as logistics management labels that need to be securely pasted to an object for a certain period of time.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a re-peelable adhesive sheet that can be easily re-peeled without adhesive residue after being securely pasted to an object for a certain period of time.

Means for Solving the Problems

[0007] The present invention has the following configuration. [1] A method for manufacturing a re-peelable adhesive sheet having an adhesive portion forming step of forming a large number of dot-shaped adhesive portions on at least a part of one surface of a base sheet, The adhesive portion forming step is performed by pattern coating a hot melt type adhesive by a letterpress printing method, The viscosity of the hot melt type adhesive measured by a B-type viscometer at 140°C is 10,000 to 50,000 mPa·s, A method for manufacturing a re-peelable adhesive sheet in which the sheet surface temperature immediately after the pattern coating is 40 to 90°C. [2] The method for manufacturing a re-peelable adhesive sheet according to [1], wherein the average diameter Da of the adhesive portions is 1.5 to 3 mm and the average shortest distance La between the adhesive portions is 1 to 3 mm. [3] The method for manufacturing a re-peelable adhesive sheet according to [1] or [2], wherein the hot melt type adhesive has a 180-degree peel strength (JIS Z 0237) of 1.6 N / 25 mm or more with respect to the following test plate of the following test piece having an adhesive layer made of the hot melt type adhesive. Test plate: A test plate obtained by mirror finishing a SUS304 steel plate specified in JIS G 4305. Test piece: A test piece in which a 20-μm-thick adhesive layer made of the hot melt type adhesive is formed on the entire surface of a polyethylene terephthalate base material having a thickness of 200 μm and an arithmetic mean roughness Ra of 0.25 μm. [4] The releasable pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the hot-melt pressure-sensitive adhesive is a rubber-based hot-melt pressure-sensitive adhesive. [Advantages of the Invention]

[0008] According to the present invention, it is possible to manufacture a releasable pressure-sensitive adhesive sheet that can be reliably attached to an object for a certain period of time and then easily peeled off without any adhesive residue. [Brief Description of the Drawings]

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0010] Hereinafter, the present invention will be described in detail. [Releasable Pressure-Sensitive Adhesive Sheet] FIG. 1 is a longitudinal sectional view showing a layer structure of an example of a releasable pressure-sensitive adhesive sheet manufactured by the manufacturing method of the present invention, FIG. 2 is a plan view of the releasable pressure-sensitive adhesive sheet of FIG. 1 as viewed from the direction of the arrow indicated by A in FIG. 1, and FIG. 3 is an enlarged plan view showing a part of the plan view of FIG. 2 in an enlarged manner.

[0011] The releasable adhesive sheet 10 of this example has a rectangular base sheet 11, a number of dot-shaped adhesive portions 12,..., 12 regularly arranged on one surface 11a of the base sheet 11, and a release agent layer 13 formed on the other surface 11b of the base sheet 11. In the releasable adhesive sheet 10 of this example, as shown in FIG. 2, a number of adhesive portions 12,..., 12 are dispersedly arranged in a regular pattern over the entire surface of one surface 11a of the base sheet 11, whereby the entire surface of one surface 11a of the base sheet 11 becomes an adhesive area that adheres to an object.

[0012] As shown in FIG. 1, the releasable adhesive sheet 10 of this example has a release agent layer 13 on the surface opposite to the surface on which the adhesive portions 12,..., 12 are formed. Therefore, it can be commercialized in a form that does not require release paper, such as a laminated label in which a plurality of releasable adhesive sheets 10 are stacked so that the adhesive portions 12,..., 12 and the release agent layer 13 are in contact with each other, or a roll-type adhesive tape in which a tape-shaped releasable adhesive sheet 10 is wound.

[0013] In this example, the dot-shaped adhesive portions 12,..., 12 arranged on one surface 11a of the base sheet 11 are all circular in plan view, as shown in FIGS. 2 and 3. Also, the adhesive portions 12,..., 12 are regularly arranged such that, with any one adhesive portion 12 as the center, the six surrounding adhesive portions 12 adjacent to the adhesive portion 12 form a regular hexagon. Hereinafter, such an arrangement pattern of the adhesive portions is also referred to as a "regular hexagon type arrangement". In the case of the regular hexagon type arrangement, the angle α in FIG. 2 is 60°.

[0014] The average diameter Da of the adhesive portions 12, …, 12 is preferably 1.5 to 3 mm, more preferably 1.8 to 2.2 mm. The average shortest interval La between the adhesive portions 12, …, 12 is preferably 1 to 3 mm, more preferably 1.8 to 2.2 mm. When the average diameter Da and the average shortest interval La of the adhesive portions 12, …, 12 are within the above ranges, the balance between the adhesiveness and the re - peelability of the adhesive region formed by these adhesive portions 12, …, 12 is excellent. Therefore, when the re - peelable adhesive sheet 10 is attached to an object, it can adhere to the object reliably for a certain period of time. On the other hand, at the time of re - peeling, it can be easily re - peeled without causing a large peeling resistance, breakage of the base sheet, adhesive residue, etc.

[0015] In this specification, the average diameter Da is the average value of the measured values when arbitrarily selecting 10 adhesive portions from the adhesive region and measuring the diameter D (diameter in the case of a perfect circle) for each adhesive portion. Note that the shape of the adhesive portion may be other than a perfect circle. In that case, as the diameter of each adhesive portion, the maximum length in the radial direction (for example, the major axis in the case of an ellipse and the longest diagonal length in the case of a polygon) is adopted. Also, the average shortest interval La is the average value of the measured values when arbitrarily selecting 10 adhesive portions from the adhesive region and measuring the shortest interval L with the other adhesive portion closest to each adhesive portion.

[0016] From the viewpoint that uniform adhesiveness and re - peelability are easily obtained over the entire surface of the adhesive region, among the values of the diameter D measured for the 10 adhesive portions, the minimum value is preferably 1.5 mm or more, and the maximum value is preferably 3.0 mm or less. Among the values of the shortest interval L measured for the 10 adhesive portions, the minimum value is preferably 1.5 mm or more, and the maximum value is preferably 3.0 mm or less.

[0017] Note that when the re - peelable adhesive sheet is a small label and the number of adhesive portions is less than 10, the above - mentioned respective measurements are performed for all the adhesive portions, and the average value is adopted. In addition, when there is an adhesive portion without a complete shape at the peripheral end of the re-peelable adhesive sheet, that adhesive portion is not selected as the adhesive portion to be measured.

[0018] The thickness of each of the adhesive portions 12,…,12 is preferably 5 to 40 μm, more preferably 10 to 25 μm. If the thickness is within the above range, the balance between adhesiveness and re-peelability is excellent, and since the thickness is not larger than necessary, it is also excellent in terms of cost.

[0019] The re-peelable adhesive sheet 10 of this example is, for example, used for applications such as being pasted on personal information written on a postcard and the recipient peeling it off to read the personal information; a management label between manufacturing processes of a product; a logistics management label in the distribution process of a product; etc. It is preferably used for applications that are required to adhere well to an object for a certain period of time and to be easily peeled off without adhesive residue or breakage of the base sheet when peeled.

[0020] [Method for manufacturing a re-peelable adhesive sheet] The re-peelable adhesive sheet 10 in the illustrated example can be manufactured by a method having the following release agent layer forming step and adhesive portion forming step. Release agent layer forming step: A step of forming a release agent layer 13 on the other surface 11b of the base sheet 11 to obtain a laminated sheet of the base sheet 11 and the release agent layer 13. Adhesive portion forming step: A step of providing a large number of dot-shaped adhesive portions 12,…,12 on one surface 11a of the base sheet 11 by pattern coating of a hot melt type adhesive by a relief printing method. Note that the release agent layer forming step and the adhesive portion forming step may be performed in either order, but it is preferable to perform the release agent layer forming step first because it can maintain the shape of the adhesive portion and suppress the adhesion of foreign substances. Also, when protecting the adhesive portion with a known release sheet, it is not necessary to perform the release agent layer forming step.

[0021] (Release agent layer forming step) The method for forming the release agent layer 13 is not particularly limited. For example, there is a method of applying a release agent using a bar coater, a multi-stage roll coater, an air knife coater, a gravure coater, an offset gravure coater, etc. When the release agent is curable, after application, the release agent layer 13 can be formed by curing using a hot air dryer, an infrared dryer, an ultraviolet irradiation device, an electron beam irradiation device, etc. The coating amount of the release agent is preferably adjusted so that the dry mass of the release agent layer 13 is within the range described below. Before forming the release agent layer 13, if necessary, printing such as patterns and characters may be performed on the other surface 11b of the base sheet 11. The printing method is not particularly limited. For example, it can be performed using a known ink such as an ultraviolet curable ink by a known method such as letterpress printing, offset printing, or flexographic printing.

[0022] (Adhesive portion forming step) In the adhesive portion forming step, a large number of dot-shaped adhesive portions 12,..., 12 are formed on one surface 11a of the base sheet 11 by pattern coating of a hot melt type adhesive by the letterpress printing method. Pattern coating has the advantage that it can handle small lot production, for example, compared to die coating, etc., and it is also easy to form an adhesive portion only on a part of the base sheet. Pattern coating by the letterpress printing method can be continuously performed by a coating device 20 including a plate cylinder 21 having a large number of convex portions 21a provided on the outer peripheral surface corresponding to the arrangement pattern of the adhesive portions 12,..., 12 and a pressure cylinder 22 provided at a position facing the plate cylinder 21, as schematically shown in FIG. 4, for example. The convex portions 21a of the plate cylinder 21 are made of, for example, a silicone resin or the like.

[0023] In the adhesive portion forming step, specifically, the hot-melt type adhesive S is transferred and supplied from the adhesive supply unit 23 onto the convex portion 21a of the plate cylinder 21, and the laminated sheet 30 of the base material sheet 11 and the release agent layer 13 obtained in the release agent layer forming step is supplied between the plate cylinder 21 and the impression cylinder 22. Thereby, while the laminated sheet 30 is sandwiched between the plate cylinder 21 and the impression cylinder 22, it is conveyed in the direction of arrow B in FIG. 4. The laminated sheet 30 is supplied such that one surface 11a of the base material sheet 11 is positioned on the side of the plate cylinder 21. Thereby, the hot-melt type adhesive S transferred from the adhesive supply unit 23 onto the convex portion 21a of the plate cylinder 21 is further transferred onto one surface 11a of the base material sheet 11, and the releasable pressure-sensitive adhesive sheet 10 in the illustrated example in which a large number of dot-shaped adhesive portions 12,..., 12 are formed can be manufactured. The thickness of the adhesive portions 12,..., 12 to be formed can be controlled by adjusting the distance between the plate cylinder 21 and the impression cylinder 22.

[0024] The temperature of the sheet surface during pattern coating in the adhesive portion forming step is 40 to 90°C, preferably 50 to 80°C. When the temperature of the sheet surface is less than the lower limit value of the above range, when transferring the hot-melt type adhesive S, the adhesive cannot maintain a molten state, and transfer is likely to be difficult. On the other hand, when the temperature of the sheet surface exceeds the upper limit value of the above range, when transferring the hot-melt type adhesive S, the viscosity of the adhesive is too low, and transfer is likely to be difficult. In contrast, by performing pattern coating at a relatively low temperature such as the above temperature range, the hot-melt type adhesive S can be transferred from the convex portion 21a of the plate cylinder 21 onto one surface 11a of the base material sheet 11 in a state where the viscosity of the hot-melt type adhesive S is relatively high. Therefore, the surface of the adhesive portions 12,..., 12 formed by transfer becomes appropriately rough, the adhesive force of the adhesive region exhibited by the hot-melt type adhesive is appropriately suppressed, and the balance between adhesiveness and releasability is considered to be excellent. When the hot-melt type adhesive S is transferred in a state where the viscosity is relatively high, the surface of the formed adhesive portion 12 becomes smooth. The releasable pressure-sensitive adhesive sheet 10 thus obtained can surely adhere to an object over a certain period of time. On the other hand, at the time of releasability, it can be easily released without causing a large release resistance, breakage of the base material sheet, adhesive residue, etc.

[0025] Note that the temperature of the sheet surface during pattern coating is the paper surface temperature of the plate cylinder during coating, which can be measured by an infrared surface thermometer.

[0026] As the hot melt adhesive, an adhesive having a viscosity of 10,000 to 50,000 mPa·s at 140°C measured by a B-type viscometer is used. The viscosity is preferably 15,000 to 43,000 mPa·s, and more preferably 18,000 to 38,000 mPa·s. When the viscosity of the hot melt adhesive is equal to or higher than the lower limit value of the above range, the viscosity of the hot melt adhesive is not too low, and it is difficult for adhesive residue to occur during the re-peeling of the re-peelable adhesive sheet 10. On the other hand, when the viscosity of the hot melt adhesive is equal to or lower than the upper limit value of the above range, the viscosity of the hot melt adhesive is not too high, and since it has flexibility, it has excellent adhesive strength to the object. Further, when using a hot melt adhesive having a viscosity within the above range, by performing pattern coating at the above temperature, it is considered that an adhesive portion 12,..., 12 having a moderately rough surface can be formed, and an adhesive region excellent in the balance between adhesiveness and re-peelability can be provided.

[0027] From the viewpoint of the balance between adhesiveness and re-peelability, the hot melt adhesive is preferably one in which the 180-degree peel strength (hereinafter, also referred to as "adhesive strength to SUS plate") of a test piece formed with an adhesive layer made of the hot melt adhesive is 1.3 N / 25 mm or more. When using a hot melt adhesive that can obtain such a relatively large adhesive strength to SUS plate, when pattern coating is performed as described above and an adhesive portion 12,..., 12 having a moderately rough surface is formed, the adhesive strength is moderately suppressed, and it is considered that an adhesive region excellent in the balance between adhesiveness and re-peelability can be formed. The adhesive strength to SUS plate is more preferably 1.6 N / 25 mm or more. The preferable upper limit value of the adhesive strength to SUS plate is about 2.6 N / 25 mm.

[0028] In this specification, the "adhesive strength to SUS plate" is the 180-degree peel strength (JIS Z 0237) of the following test piece having an adhesive layer made of a hot melt adhesive with respect to the following test plate. Test plate: A test plate obtained by mirror-finishing a SUS304 steel plate specified in JIS G 4305. Test piece: A test piece having a thickness of 200 μm and an arithmetic mean roughness Ra of 0.25 μm, with a 20-μm-thick adhesive layer made of the hot-melt adhesive formed on the entire surface of a polyethylene terephthalate base material.

[0029] (Base material sheet) As the base material sheet 11, known base materials used for re-peelable adhesive sheets such as logistics management labels can be used. For example, paper base materials, resin films, metal foils, laminates formed by appropriately combining these, etc. can be mentioned, and they can be appropriately used according to the application. Among them, paper base materials are preferred because when the object to which the label is to be attached is paper, they are likely to be recycled as waste paper. Hereinafter, the paper base material will be described in detail as a representative example.

[0030] Examples of the paper base material include those composed mainly of wood pulp and containing additives such as pigments and various auxiliaries as required. As the wood pulp, either hardwood (L wood) or softwood (N wood) can be used, and various chemical pulps, semi-chemical pulps, mechanical pulps, recycled pulps, etc. may be used. Examples of chemical pulps include kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), etc. Examples of semi-chemical pulps include semi-chemical pulp (SCP), chemigroundwood pulp (CGP), etc. Examples of mechanical pulps include groundwood pulp (GP), thermomechanical pulp (TMP), bleached chemithermomechanical pulp (BCTMP), refiner groundwood pulp (RGP), etc. Examples of recycled pulps include deinked pulp (DIP) made from waste paper. Also, non-wood pulp made from materials such as kozo, mitsumata, hemp, kenaf, etc. may be used.

[0031] When using a paper base material with high whiteness, pulp bleached by combining various bleaching methods using chlorine, chlorine dioxide, oxygen, ozone, hydrogen peroxide, hypochlorous acid, etc. can be used. Among them, pulp obtained by chlorine-free bleaching (ECF) or totally chlorine-free bleaching (TCF) produced in a process that does not use chlorine is preferably used because it is less likely to turn yellow. The pulp forming the paper base material may be one type or two or more types.

[0032] Based on the Canadian Standard Freeness (drainage degree; CSF) defined in JIS P 8121 for the pulp used in the paper base material, the freeness after disintegration is preferably 80 to 650 mL, more preferably 200 to 600 mL. If the freeness is below the upper limit value, the surface of the paper base material is likely to be smooth, and the paper strength of the paper base material can be easily obtained sufficiently. If the freeness is above the lower limit value, good papermaking suitability such as good drainage property and sufficient papermaking speed can be obtained. Also, when printing patterns, characters, etc. on the paper base material, the printing is likely to be clear and excellent in printability. Also, when a layer on which writing, stamping, etc. can be performed is provided as the release agent layer 13, good writing performance and stamping performance can be easily obtained.

[0033] A pigment may be added to the paper base material. By adding a pigment to the paper base material, writing performance, stamping performance, printability, etc. can be imparted to the surface of the paper base material. Also, opacity can be imparted to the paper base material. Examples of the pigment include light calcium carbonate, calcined kaolin, white carbon, talc, titanium oxide, etc. Among them, talc, light calcium carbonate, and white carbon are preferred, and talc and light calcium carbonate are particularly preferred because they are excellent in papermaking suitability (wear suitability of the wire) and tend to stay during papermaking. When a pigment is added to the paper base material, the content rate (ash content) of the pigment in the paper base material is preferably 0.1 to 30% by mass, more preferably 10 to 20% by mass. If the content rate of the pigment is above the lower limit value of the above range, the above-described printability, writing performance, and stamping performance will be good. If the content rate of the pigment is below the upper limit value of the above range, sufficient paper strength can be easily obtained.

[0034] An auxiliary agent may be added to the paper base material. Examples of the auxiliary agents include internal sizing agents (such as higher fatty acids and alkyl ketene dimers), fixing agents (such as aluminum sulfate and cationic polyelectrolytes), paper strength enhancers (such as starch, polyacrylamide, and polyvinyl alcohol), cationizing agents, yield improvers, dyes, fluorescent brighteners, and mildew inhibitors.

[0035] The paper base material can be obtained by papermaking using known papermaking machines such as a Fourdrinier machine, a cylinder machine, a Yankee machine, a twin-wire former, an inclined wire former, and a dryer (such as a Yankee dryer and a multi-cylinder dryer). The paper base material may be subjected to known treatments such as calendering.

[0036] The paper base material may be size-treated with a size press or a gate roll for the purpose of adjusting surface strength, sizing property, etc. Examples of the size treatment liquid used for the size treatment include treatment liquids in which starches, polyvinyl alcohols, polyacrylamides, surface sizing agents, cation resins, etc. are blended in a solvent. Examples of the surface sizing agent include styrene maleic acid copolymers, olefin copolymers, alkyl ketene dimer compounds, alkenyl succinic anhydride compounds, styrene-acrylic copolymers, higher fatty acid compounds, petroleum resin sizing agents, and rosin sizing agents.

[0037] When performing the size treatment, the coating amount of the size treatment liquid is preferably 0.3 to 5.0 g / m 2 in terms of dry mass, and more preferably 0.5 to 3.0 g / m 2 in terms of dry mass. If the coating amount is at least the lower limit value of the above range, the effect of the size treatment can be easily obtained. Also, if the coating amount exceeds the upper limit value, the effect of the size treatment levels off. Therefore, if the coating amount is below the upper limit value, it is advantageous in terms of cost. When performing the size treatment on both sides, it is preferable that the total coating amount of the size treatment liquid on both sides is within the above range.

[0038] The basis weight of the paper base material is 40 to 210 g / m2 is preferable, and 60 to 120 g / m 2 is more preferable. If the basis weight is at least the lower limit of the above range, sufficient paper strength can be easily obtained. If the basis weight is at most the upper limit of the above range, it is easy to reduce the paper thickness. The density of the paper base material is 0.55 to 1.00 g / m 3 is preferable. If the density is at least the lower limit of the above range, sufficient paper strength can be easily obtained. If the density is at most the upper limit of the above range, the above-described printability, writability, and stamping property will be good.

[0039] The paper base material is preferably uncoated paper or single-sided coated paper having a coating layer on one side. The coating layer can be provided, for example, by a blade coater, a knife coater, a bar coater, an air knife coater, a die coater, a slot die coater, a gravure coater, or the like.

[0040] (Release agent layer) As the release agent for forming the release agent layer 13, a silicone-based release agent is preferable. Examples of the silicone-based release agent include thermosetting release agents (addition-curing silicone-based release agents, condensation-curing silicone-based release agents, etc.), electron beam-curing silicone-based release agents, and ultraviolet-curing silicone-based release agents (radical-curing silicone-based release agents, cation-curing silicone-based release agents, mercapto-curing silicone-based release agents, etc.). Among them, from the viewpoints of fast curing speed, difficulty in penetrating into the base sheet 11, and thus light peeling, an electron beam-curing silicone-based release agent or an ultraviolet-curing silicone-based release agent is preferable. Further, from the viewpoint of requiring less equipment investment, an ultraviolet-curing silicone-based release agent is more preferable, and a cation-curing silicone-based release agent using an onium salt-based photoinitiator or the like is particularly preferable. Various auxiliary agents such as other ultraviolet-curing resins, electron beam-curing resins, photoinitiators, crosslinking agents, dyes, pigments, wetting agents, defoaming agents, dispersants, antistatic agents, leveling agents, and lubricants may be blended with the release agent as necessary.

[0041] The dry mass of the release agent layer 13 is preferably 0.2 to 2.0 g / m 2 and more preferably 0.5 to 1.5 g / m2 When the dry mass of the release agent layer 13 is equal to or greater than the lower limit of the above range, peeling becomes easy, and when the dry mass of the release agent layer 13 is equal to or less than the upper limit of the above range, the above-mentioned printability, writability, and stampability become good.

[0042] From the viewpoint of easier peeling, the surface smoothness of the release agent layer 13 is preferably 30 seconds or more, and more preferably 50 seconds or more. From the viewpoint of the above-mentioned printability, writability, and stampability, the surface smoothness of the release agent layer 13 is preferably 200 seconds or less, and more preferably 150 seconds or less. The smoothness is a value specified in the "Oken Smoothness Based on JAPAN TAPPI Paper Pulp Test Method No. 5-2."

[0043] (Adhesive part) Examples of hot melt adhesives that form the dot-shaped adhesive portions 12 include rubber-based hot melt adhesives, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, etc. Among these, rubber-based hot melt adhesives are preferred from the standpoints of adhesive strength stability, bleeding, and cost.

[0044] Examples of rubber-based hot melt pressure-sensitive adhesives include styrene-based copolymers such as styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-ethylene-propylene-styrene block copolymer (SEPS). Hot melt pressure-sensitive adhesives containing a styrene copolymer as an adhesive component are preferred because the adhesive strength of a test piece having an adhesive layer made of the hot melt pressure-sensitive adhesive formed thereon to a SUS plate can be easily adjusted to the above range, and the adhesive area formed has a better balance between the adhesiveness and removability. In particular, SIS is particularly preferred.

[0045] As the styrene copolymer, it is preferably at least composed of a styrene copolymer (I) having a weight average molecular weight (Mw) of 1,000 or more and less than 100,000, and a styrene copolymer (II) having a weight average molecular weight (Mw) of 100,000 or more and 10,000,000 or less. More preferably, it is a pressure-sensitive adhesive containing at least a styrene copolymer (I) having a weight average molecular weight (Mw) of 1,000 or more and less than 100,000 and a dispersity (Mw / Mn) of 1.0 to 1.2, and a styrene copolymer (II) having a weight average molecular weight (Mw) of 100,000 or more and 10,000,000 or less and a dispersity (Mw / Mn) of 1.0 to 1.2. The weight average molecular weight (Mw) and the dispersity (Mw / Mn) are measured by gel chromatography.

[0046] The hot-melt adhesive may contain a tackifier, a softener, a wax, an antioxidant, etc. The tackifier improves the adhesiveness of the adhesive portions 12,..., 12. The softener adjusts the viscosity of the hot-melt adhesive to the above-mentioned appropriate range. The wax reduces the instantaneous adhesiveness of the adhesive portions 12,..., 12 and enhances the peelability when it is necessary to peel off the object immediately after sticking.

[0047] Examples of the tackifier include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, copolymer (C5 / C9) petroleum resins, dicyclopentadiene (DCPD) petroleum resins, coumarone-indene resins, acrylic resins, styrene resins, rosins, rosin ester resins, terpene resins, aromatic-modified terpene resins, terpene phenol resins, and hydrogenated resins thereof. Rosin ester resins are preferred because it is easy to adjust the adhesion of the test piece having an adhesive layer made of the hot-melt adhesive to the SUS plate within the above range, and the balance between the adhesiveness and re-peelability of the formed adhesive region is more excellent.

[0048] Examples of the softening agent include various plasticizers, polybutene, liquid tackifier resins, polyisobutylene low polymers, polyvinyl isobutyl ether low polymers, lanolin, block copolymer rubbers, process oils, naphthenic oils, paraffinic oils, vulcanized oils, and the like. Paraffinic oils are preferred because it is easy to adjust the viscosity of the hot melt adhesive within the above-mentioned range.

[0049] Examples of the wax include plant waxes, animal waxes, mineral waxes, petroleum waxes, synthetic waxes, and processed / modified waxes thereof. As the plant wax, carnauba wax and candelilla wax are more preferred. As the animal wax, beeswax is more preferred. As the mineral wax, montan wax and ozokerite are more preferred. As the petroleum wax, paraffin wax and microcrystalline wax are preferred. As the synthetic wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, oil-based (ester, ketones, amide) synthetic wax, and hydrogenated wax are more preferred. As the processed / modified wax, processed / modified waxes of the above-mentioned more preferred waxes are preferred. From the viewpoint of reducing the instantaneous adhesiveness of the adhesive parts 12,..., 12 and enhancing the peelability when it is necessary to peel off the object immediately after sticking, for example, paraffin wax having a melting point of 42 to 73°C is preferred.

[0050] Polyolefin wax generally has a molecular weight of about 1,000 to 10,000, that is, it is generally known as polyolefin wax. This polyolefin wax is usually obtained by a high-pressure polymerization method, a low-pressure polymerization method, or thermal decomposition of a high-molecular-weight polyolefin. Specific examples of the processed / modified wax include, for example, those obtained by oxidizing the above-mentioned wax and introducing polar groups such as hydroxyl groups, ester groups, carboxyl groups, aldehyde groups, and peroxide groups into the wax.

[0051] When using a tackifier, the content of the tackifier in the hot-melt adhesive is preferably 10 to 70 parts by mass, more preferably 30 to 60 parts by mass, per 100 parts by mass of the adhesive component (styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc.). If the content of the tackifier is within the above range, it is easy to adjust the adhesion of the test piece formed with the adhesive layer composed of the hot-melt adhesive to the SUS plate within the above range, and the balance between the adhesiveness and re-peelability of the formed adhesive area is more excellent.

[0052] When using a softening agent, the content of the softening agent in the hot-melt adhesive is preferably 1 to 50 parts by mass, more preferably 5 to 35 parts by mass, per 100 parts by mass of the adhesive component (styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc.). If the content of the softening agent is within the above range, it is easy to maintain the viscosity of the hot-melt adhesive within the above-mentioned appropriate range, and it is easy to perform pattern coating by the letterpress printing method.

[0053] When using wax, the content of the wax in the hot-melt adhesive is preferably 0.1 to 25 parts by mass, more preferably 0.5 to 15 parts by mass, per 100 parts by mass of the adhesive component (styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc.). If the content of the wax is within the above range, it reduces the instantaneous adhesiveness of the adhesive parts 12,..., 12, enhances the peelability when it is necessary to peel off the object immediately after pasting, etc., and also has excellent persistent adhesiveness.

[0054] In the method for manufacturing the re-peelable pressure-sensitive adhesive sheet described above, when performing the adhesive portion forming step by pattern coating a hot-melt type pressure-sensitive adhesive by a letterpress printing method, as the hot-melt type pressure-sensitive adhesive, an adhesive having a viscosity of 10,000 to 50,000 mPa·s as measured by a B-type viscometer at 140°C is used, and the pattern coating is performed at 40 to 90°C. Therefore, the transfer of the hot-melt type pressure-sensitive adhesive onto one surface of the base sheet can be performed well. Also, it is considered that the surface of the formed adhesive portion becomes moderately rough, and it is considered that the balance between adhesiveness and re-peelability is excellent and residue hardly occurs.

[0055] [Regarding another embodiment of the re-peelable pressure-sensitive adhesive sheet] In the re-peelable pressure-sensitive adhesive sheet 10 of the illustrated example, the arrangement pattern of the plurality of adhesive portions 12,..., 12 was a "regular hexagonal arrangement". That is, with any one of the adhesive portions 12,..., 12 as the center, the six surrounding adhesive portions 12,..., 12 adjacent to the adhesive portion 12,..., 12 were regularly arranged so as to form a regular hexagon. However, the arrangement pattern of the adhesive portions is not limited to the regular hexagonal arrangement. For example, as shown in FIG. 5, with any one of the adhesive portions 12 as the center, the four surrounding adhesive portions 12,..., 12 adjacent to the adhesive portion 12 may be arranged in a regular pattern such that a square is formed, which is a "square arrangement". The "regular hexagonal arrangement" and the "square arrangement" are preferable because uniform adhesiveness and re-peelability can be easily obtained over the entire adhesive area. Also, the plurality of adhesive portions may be arranged in other regular patterns or may be arranged irregularly (randomly).

[0056] In addition, in the releasable adhesive sheet 10 shown in the figure, a large number of adhesive portions 12, …, 12 are regularly and dispersedly arranged over the entire surface 11a of one surface of the base material sheet 11. As a result, the entire surface 11a of one surface of the base material sheet 11 is an adhesive region. However, only a part of one surface of the base material sheet may be an adhesive region. For example, as shown in FIG. 6, in one surface 11a of the base material sheet 11, an adhesive portion is not formed in a region (non-adhesive region) C2 including one of the four corners, and a large number of adhesive portions 12, …, 12 are arranged in a portion excluding this region C2 to form an adhesive region C1. When a part of one surface 11a of the base material sheet 11 is made into the non-adhesive region C2 in this way, since the non-adhesive region C2 does not adhere to the object, it serves as a turning margin during re-peeling. Such a releasable adhesive sheet is easy to re-peel.

[0057] In addition, in the releasable adhesive sheet 10 shown in the figure, each of the adhesive portions 12, …, 12 is a perfect circle. Therefore, it is easier to obtain a uniform adhesive force and peeling force over the entire adhesive region. However, the shape of the adhesive portion is not limited to a perfect circle, and as described above, it may be an ellipse, a polygon, or the like.

[0058] Furthermore, the releasable adhesive sheet 10 shown in the figure has a release agent layer 13 on the other surface 11b side of the base material sheet. Therefore, it can be commercialized in a form that does not require release paper, such as a laminated label in which a plurality of releasable adhesive sheets 10 are stacked so that the adhesive portions 12, …, 12 are in contact with the release agent layer 13, or a roll-type adhesive tape in which a tape-shaped releasable adhesive sheet 10 is wound. However, it may be in a form that does not include a release agent layer and instead has a known release paper that covers the adhesive portions 12, …, 12.

Example

[0059] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In the examples, parts and % indicate “parts by mass” and “mass %” unless otherwise specified.

[0060] [Example 1] (Manufacture of paper base material (base material sheet)) The hardwood kraft pulp (LBKP) was beaten until it reached a freeness of 440 mL (CSF), and a pulp slurry with a concentration of 0.5% was prepared. Into this pulp slurry, 2.0% of cationized starch, 0.4% of alkyl ketene dimer, 0.1% of anionic polyacrylamide resin, 0.7% of polyamide polyamine epichlorohydrin resin, and talc as a pigment were added based on the absolute dry mass of the pulp, and they were thoroughly stirred and dispersed. The addition amount of talc was adjusted to be 2% based on the resulting paper substrate. Next, water was added to oxidized starch (trade name: "Ace A", manufactured by Oji Cornstarch Co., Ltd.) and heated to dissolve it, and the concentration was adjusted to 5% to obtain a size press solution. After the pulp slurry was formed into a base paper using a paper making machine, size treatment was performed on both sides of the base paper with the size press solution using the size press attached to the paper making machine to obtain a paper substrate. The absorption amount of the size press solution into the paper substrate was 50 mL / m in total for both sides. 2 It was. Finally, calendering treatment was performed using the machine calender at the end of the paper making machine to obtain a paper substrate with a basis weight of 100 g / m 2 , a density of 0.85 g / cm 3 , and a Stöckigt sizing degree of 35 seconds.

[0061] (Manufacture of laminated sheet) On one surface of the obtained paper substrate, pictures and letter patterns were printed using an amine-free UV ink (trade name: NVR) manufactured by TOKA. Then, on the entire surface thereof, a release agent paint obtained by mixing 5 parts of an onium salt-based photoinitiator (trade name: "Silicorelease CATA211", manufactured by Rhodia) with 100 parts of polyorganosiloxane (trade name: "Silicorelease POLY201", manufactured by Rhodia) was coated using a flexographic printing machine, and cured under the condition of an ultraviolet irradiation dose of 140 mJ / cm 2 to form a release agent layer. The coating amount of the release agent paint used for the formation of the release agent layer was 1 g / m in terms of the solid content mass (dry mass). 2 It was. Thereby, a laminated sheet having a release agent layer formed on one surface of the printed substrate sheet was obtained.

[0062] (Manufacture of Hot-Melt Adhesive) Next, 20 parts of SIS with 10% styrene component, 90% isoprene component, weight average molecular weight (Mw) = 5×104, and dispersity (Mw / Mn) = 1.02, 20 parts of SIS with 30% styrene component, 70% isoprene component, weight average molecular weight (Mw) = 5×105, and dispersity (Mw / Mn) = 1.05, 40 parts of rosin ester ("Ester Gum 105" manufactured by Arakawa Chemical Industries, Ltd.), 20 parts of paraffinic oil ("Shellflex 371N" manufactured by Shell Chemical Company, USA), 5 parts of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.), and 1 part of antioxidant ("Sumilizer GM" manufactured by Sumitomo Chemical Co., Ltd.) were blended and stirred and mixed under heating at 150°C to obtain a hot-melt adhesive. Incidentally, the viscosity of this hot-melt adhesive measured by a B-type viscometer ("DVD VII" manufactured by Brookfield) at 140°C and the adhesion force to SUS plate measured by the method described above were as shown in Table 1.

[0063] (Pattern Coating) Using the above-described hot-melt adhesive, a large number of dot-shaped adhesive portions each having a thickness of about 20 μm were formed on the entire surface of the side of the base sheet where the release agent layer was not formed. The formation of the adhesive portions was performed by pattern coating by the letterpress printing method using an apparatus (manufactured by Santool Co., Ltd.) equipped with a plate cylinder 21 and a pressure cylinder 22 as shown in FIG. 4. The temperature of the sheet surface immediately after the pattern coating was 50°C. The temperature of the sheet surface was the paper surface temperature of the plate cylinder during coating and was measured by an infrared surface thermometer. The thickness of the adhesive portions was measured using a THIKNESS METER B-1 manufactured by Toyo Seiki Co., Ltd. The arrangement pattern of the large number of dot-shaped adhesive portions was set as the "regular hexagonal arrangement" shown in FIGS. 2 and 3. Also, each adhesive portion was a perfect circle with a diameter of 2 mm, and the shortest distance between any adhesive portion and another adhesive portion closest to the adhesive portion was 2 mm. That is, both the average diameter Da and the average shortest distance La were 2 mm. In this way, the re-peelable adhesive sheet of Example 1 was obtained. The obtained re-peelable adhesive sheet was cut into rectangles measuring 8 cm in length and 12 cm in width, and 50 labels made of the re-peelable adhesive sheet were obtained. Then, these 50 labels were stacked such that the adhesive portion was in contact with the release agent layer to form a laminated label.

[0064] (Evaluation of re-peelability) Ten re-peelable adhesive sheets were peeled off one by one from the laminated label and pasted onto a cardboard made of K-liner (kraft liner). After leaving this in an environment of 23°C and 50% RH for one week, the re-peelability when peeling the ten re-peelable adhesive sheets from the cardboard by hand was evaluated in the following four grades. The results are shown in Table 1. In the cases of "◎", "○", and "× (adhesive residue)" described below, all ten re-peelable adhesive sheets were well adhered to the cardboard even after being left in an environment of 23°C and 50% RH for one week. ◎: Very good. For all ten re-peelable adhesive sheets, re-peeling was possible without feeling a large resistance during peeling. ○: Good. For all ten re-peelable adhesive sheets, a slight resistance was felt during peeling, but re-peeling was possible without problems. × (adhesive residue): Poor. For all ten re-peelable adhesive sheets, adhesive residue occurred during peeling.

[0065] [Examples 2 - 3] In the pattern coating of Example 1, a laminated label was obtained in the same manner as in Example 1, except that the temperature of the sheet surface, the diameter of the adhesive portion, and the shortest interval shown in Table 1 were used. The arrangement pattern of the adhesive portions was "regular hexagonal arrangement". Also, a large number of adhesive portions were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0066] [Example 4] In the production of the hot-melt adhesive of Example 1, a hot-melt adhesive was obtained in the same manner as in Example 1, except that 4.5 parts of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.) was used. Using this adhesive, pattern coating was performed so as to obtain the temperature of the sheet surface, the diameter of the adhesive part, and the shortest interval shown in Table 1, and a laminated label was obtained. The arrangement pattern of the adhesive parts was "regular hexagonal arrangement". Also, a large number of adhesive parts were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0067] [Comparative Example 1] In the production of the hot-melt adhesive of Example 1, a hot-melt adhesive was obtained in the same manner as in Example 1, except that 15 parts of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.) was used. Using this adhesive, pattern coating was performed so as to obtain the temperature of the sheet surface, the diameter of the adhesive part, and the shortest interval shown in Table 1, and a laminated label was obtained. The arrangement pattern of the adhesive parts was "regular hexagonal arrangement". Also, a large number of adhesive parts were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0068] [Comparative Example 2] In the production of the hot-melt adhesive of Example 1, a hot-melt adhesive was obtained in the same manner as in Example 1, except that 1 part of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.) was used. Using this adhesive, pattern coating was performed so as to obtain the temperature of the sheet surface, the diameter of the adhesive part, and the shortest interval shown in Table 1, and a laminated label was obtained. The arrangement pattern of the adhesive parts was "regular hexagonal arrangement". Also, a large number of adhesive parts were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0069] [Comparative Example 3] In the production of the hot-melt type adhesive of Example 1, a hot-melt type adhesive was obtained in the same manner as in Example 1, except that 10 parts of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.) was used. Using this adhesive, pattern coating was performed so as to obtain the temperature of the sheet surface, the diameter of the adhesive portion, and the shortest interval shown in Table 1, and a laminated label was obtained. The arrangement pattern of the adhesive portions was "regular hexagonal arrangement". Also, a large number of adhesive portions were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0070] [Comparative Example 4] In the production of the hot-melt type adhesive of Example 1, a hot-melt type adhesive was obtained in the same manner as in Example 1, except that 4 parts of paraffin wax ("155F" manufactured by Nippon Seiro Co., Ltd.) was used. Using this adhesive, pattern coating was performed so as to obtain the temperature of the sheet surface, the diameter of the adhesive portion, and the shortest interval shown in Table 1, and a laminated label was obtained. The arrangement pattern of the adhesive portions was "regular hexagonal arrangement". Also, a large number of adhesive portions were all perfect circles with the same diameter, and the shortest intervals were also the same (constant).

[0071] (Comparative Example 5) In the same manner as in Example 1, a laminated sheet and a hot-melt type adhesive were produced. Then, with a hot-melt die coater, the hot-melt type adhesive was applied to the entire surface of the side of the laminated sheet where the release agent layer was not formed. The coating temperature was the temperature shown in Table 1, and the thickness of the adhesive layer was 20 μm. The obtained re-peelable adhesive sheet was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0072]

Table 1

[0073] As shown in Table 1, according to each example, an adhesive portion excellent in adhesiveness could be formed without causing transfer defects. Also, the re-peelable adhesive sheets of each example could be peeled without adhesive residue and were excellent in re-peelability. On the other hand, in Comparative Example 1 where the viscosity of the hot-melt type adhesive was low, adhesive residue occurred, and in Comparative Example 2 where the viscosity was high, and in Comparative Examples 3 and 4 where the temperature of the sheet surface during pattern coating was inappropriate, transfer failure occurred. In Comparative Example 5 where the adhesive portion was not dot-shaped, the re-peelability was poor.

Explanation of Signs

[0074] 10 Re-peelable adhesive sheet 11 Base sheet 11a One surface of the base sheet 12 Adhesive portion 13 Release agent layer

Claims

1. A method for manufacturing a re - peelable adhesive sheet having an adhesive portion forming step of forming a large number of dot - shaped adhesive portions on at least a part of one surface of a base sheet, wherein the adhesive portion forming step is performed by pattern coating a hot - melt type adhesive by a letterpress printing method, the viscosity of the hot - melt type adhesive measured by a B - type viscometer at 140°C is 10,000 to 50,000 mPa·s, and the sheet surface temperature immediately after the pattern coating is 40 to 90°C. A method for manufacturing a re - peelable adhesive sheet.

2. The method for manufacturing a re - peelable adhesive sheet according to Claim 1, wherein the average diameter Da of the adhesive portions is 1.5 to 3 mm, and the average shortest interval La between the adhesive portions is 1 to 3 mm.

3. The method for manufacturing a re - peelable adhesive sheet according to Claim 1 or 2, wherein the 180 - degree peel strength (JIS Z 0237) of the following test piece having an adhesive layer made of the hot - melt type adhesive with respect to the following test plate is 1.6 N / 25 mm or more. Test plate: A test plate obtained by mirror - finishing a SUS304 steel plate defined in JIS G 4305. Test piece: A test piece having a thickness of 200 μm and an arithmetic mean roughness Ra of 0.25 μm, and having an adhesive layer with a thickness of 20 μm made of the hot - melt type adhesive formed on the entire surface of a polyethylene terephthalate base material.

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