Sheet and method for producing sheet

Abstract

To provide a sheet that includes an adhesive layer containing a self-adhesive adhesive and a thermosensitive layer, wherein the sheet can be used even when moisture is attached to the adhesive layer.SOLUTION: A sheet includes a sheet-shaped base material provided with a first surface and a second surface, a thermosensitive layer arranged on the first surface, and an adhesive layer arranged on the second surface, the adhesive layer comprising a hot-melt type self-adhesive adhesive.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sheet and a method for manufacturing the sheet. [Background technology]

[0002] A sheet is known that includes a substrate and an adhesive layer disposed on a first surface of the substrate, the adhesive layer including a self-adhesive adhesive. A self-adhesive adhesive is an adhesive that adheres strongly to other self-adhesive adhesives but hardly adheres to other materials. Examples of self-adhesive adhesives include water-soluble self-adhesives and solvent-based self-adhesives. A water-soluble self-adhesive adhesive is a self-adhesive adhesive in which an emulsified resin or rubber is dispersed in water. A solvent-based self-adhesive adhesive is a self-adhesive adhesive in which a resin is dissolved in an organic solvent.

[0003] As one type of the above-mentioned sheet, for example, Patent Documents 1 and 2 disclose a label in which an adhesive layer containing a self-adhesive adhesive is formed on a long, thin substrate. The label is used for bundling products, etc. Furthermore, Patent Document 3 discloses a packaging material in which an adhesive layer containing a self-adhesive adhesive is formed on a sheet-like substrate, as one type of the above-mentioned sheet. The packaging material is used for storing products, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-27071 [Patent Document 2] Japanese Patent Publication No. 2022-98943 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-231849 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a sheet with a heat-sensitive layer on the side of the substrate opposite the adhesive layer. The heat-sensitive layer contains chemical substances that change color when heated. By pressing a thermal head against the heat-sensitive layer, information can be added to the heat-sensitive layer of the sheet. For example, the information can be the date of manufacture.

[0006] In sheets with a heat-sensitive layer, the adhesive layer made of a water-soluble self-adhesive adhesive loses its adhesive strength when moisture adheres to it, so such sheets cannot be used for bundling or packaging products that are prone to moisture adhering to the adhesive layer (e.g., seafood or leafy vegetables).

[0007] An adhesive layer made of a solvent-based self-adhesive adhesive can maintain its adhesive strength even when moisture is present. However, when forming an adhesive layer using a solvent-based self-adhesive adhesive, after applying the adhesive, it is necessary to volatilize the organic solvent by heat treatment. This heat treatment causes the thermosensitive layer to develop color and lose its functionality. If the heat treatment temperature is low, the color development of the thermosensitive layer can be suppressed, but in that case, a large amount of organic solvent remains in the adhesive layer. For environmental and health reasons, it is desirable to limit the use of organic solvents.

[0008] An object of the present invention is to provide a sheet that includes an adhesive layer containing a self-adhesive adhesive and a heat-sensitive layer, and that can be used even if moisture adheres to the adhesive layer. [Means for solving the problem]

[0009] The present inventors conducted extensive research into the construction of a sheet having an adhesive layer that can maintain its adhesive strength even in environments prone to moisture. As a result, the inventors came up with the idea of ​​using a hot-melt self-adhesive adhesive as the constituent material of the adhesive layer. A hot-melt self-adhesive adhesive is a self-adhesive adhesive that is melted by heating when applied to an object and solidifies after application to form an adhesive layer. Given the characteristics of such hot-melt self-adhesive adhesives, it is thought that applying a hot-melt self-adhesive adhesive to a substrate having a heat-sensitive layer would cause the heat-sensitive layer to develop color. However, as a result of tests conducted by the present inventors, it was found that applying a hot-melt self-adhesive adhesive to a substrate while conveying the substrate, as specified in the sheet manufacturing method described below, suppresses color development of the heat-sensitive layer. Based on this finding, the sheet of the present invention and its manufacturing method are specified below.

[0010] In the following explanation, hot melt type self-adhesive adhesives may be referred to as "HM adhesives."

[0011] (1) A sheet according to one embodiment of the present invention comprises a sheet-like substrate having a first surface and a second surface, a heat-sensitive layer disposed on the first surface, and an adhesive layer disposed on the second surface, the adhesive layer including a hot-melt type self-adhesive adhesive.

[0012] The sheet, which includes adhesive layers containing HM adhesive, can be folded or otherwise brought into contact with each other, thereby firmly bonding the adhesive layers together. The sheet can be used, for example, as a tag attached to a product or as packaging for storing the product. Because the heat-sensitive layer on the sheet is not colored, information can be added to the heat-sensitive layer later using a thermal printer or the like.

[0013] Because HM adhesives are water-insoluble, the adhesive layers remain firmly bonded together even when moisture adheres to the adhesive layers. Therefore, the sheet can be used for bundling or packaging seafood or leafy vegetables, for example. Of course, the sheet can also be used in environments where moisture is difficult to adhere to.

[0014] HM adhesives can be applied to substrates even if they do not contain organic solvents. If an adhesive layer is formed using an HM adhesive that does not contain organic solvents, organic solvents will not adhere to the food even if the sheet is used to bundle or wrap food.

[0015] (2) In the sheet described in (1) above, the adhesive layer may have an average thickness of 20 μm or more and 200 μm or less.

[0016] If the adhesive layer is 20 μm or thicker, the adhesive layer will have sufficient adhesive properties. If the adhesive layer is 200 μm or thinner, the amount of HM adhesive applied to the second surface during the formation of the adhesive layer will not be too large. Therefore, the total heat generated by the melted HM adhesive will not be too large, and the heat-sensitive layer will not easily develop color.

[0017] (3) In the sheet described in (1) or (2) above, the average thickness of the substrate may be 10 μm or more and 200 μm or less.

[0018] If the average thickness of the substrate is 10 μm or more, the heat of the HM adhesive melted during the formation of the adhesive layer is less likely to be transferred to the heat-sensitive layer, and the heat-sensitive layer is less likely to develop color.If the average thickness of the substrate is 200 μm or less, the sheet including the substrate is easier to bend.

[0019] (4) In the sheet according to any one of (1) to (3) above, the self-adhesive adhesive may be made of a polyolefin resin.

[0020] Since the melting point of polyolefin resin is not too high, even if the molten HM adhesive is applied to the second surface of the substrate when forming the adhesive layer, the heat-sensitive layer is less likely to develop color.

[0021] (5) In the sheet according to any one of (1) to (4) above, the adhesive layer may not contain an organic solvent.

[0022] If the adhesive layer does not contain an organic solvent, there is no problem in terms of the working environment or worker health during the production of the sheet, and if the adhesive layer does not contain an organic solvent, it is possible to prevent the organic solvent from adhering to products bound or packaged with the sheet.

[0023] (6) In the sheet according to any one of (1) to (5) above, the melting temperature of the self-adhesive adhesive may be higher than the color-developing temperature of the heat-sensitive layer.

[0024] The HM adhesive has a softening point. The softening point is the temperature at which the HM adhesive begins to soften. When the temperature of the HM adhesive rises above the softening point, the HM adhesive becomes viscous and molten. As specified in the manufacturing method for the sheet material described below, by applying molten HM adhesive to a substrate having a heat-sensitive layer while conveying the substrate, the adhesive layer is formed. This prevents the heat-sensitive layer from developing color even if the melting temperature of the HM adhesive is higher than the color-developing temperature of the heat-sensitive layer.

[0025] (7) In the sheet according to any one of (1) to (6) above, the substrate may be made of polyethylene terephthalate resin or polyolefin resin.

[0026] Polyethylene terephthalate resin and polyolefin resin have excellent heat resistance and strength, so when an adhesive layer is formed on a substrate having a heat-sensitive layer while the substrate is being transported, the substrate is less likely to soften or stretch.

[0027] (8) The sheet described in any one of (1) to (7) above may have an intermediate layer disposed between the substrate and the heat-sensitive layer and / or between the substrate and the adhesive layer.

[0028] The intermediate layer disposed between the substrate and the thermosensitive layer improves the adhesion between the substrate and the thermosensitive layer. The intermediate layer disposed between the substrate and the adhesive layer improves the adhesion between the substrate and the adhesive layer. In addition, the intermediate layer makes it difficult for the heat of the HM adhesive to be transferred to the thermosensitive layer during the formation of the adhesive layer, preventing the thermosensitive layer from developing color.

[0029] (9) A method for manufacturing a sheet according to one embodiment of the present invention includes the steps of: preparing a pre-sheet including a substrate having a first surface and a second surface and a heat-sensitive layer disposed on the first surface; and conveying the pre-sheet by a conveying mechanism while applying a molten raw material to the second surface, thereby producing a sheet including an adhesive layer formed by solidifying the molten raw material. The molten raw material includes a hot-melt type self-adhesive adhesive.

[0030] By coating the molten raw material onto the pre-sheet, which is a substrate having a heat-sensitive layer, while the pre-sheet is being transported, the heat of the molten raw material is easily released to the outside of the pre-sheet. Furthermore, because the molten raw material is coated on the opposite side of the substrate from the heat-sensitive layer, the heat of the molten raw material is not easily transferred to the heat-sensitive layer. Therefore, even if the molten raw material is coated onto the pre-sheet, the heat-sensitive layer is unlikely to develop color.

[0031] (10) In the sheet manufacturing method described in (9) above, the conveying mechanism may include a feed roll that feeds out the pre-sheet, a take-up roll that takes up the sheet, and a backup roll that is disposed between the feed roll and the take-up roll and applies tension to the pre-sheet, and the molten raw material may be applied while the pre-sheet is in contact with the backup roll.

[0032] The heat capacity of the backup roll is greater than that of the pre-sheet, so when the molten material is applied to the pre-sheet, the temperature of the molten material drops quickly, making it difficult for the heat-sensitive layer to develop color.

[0033] (11) In the sheet manufacturing method described in (10) above, the molten raw material may be applied to the pre-sheet while the backup roll is being cooled.

[0034] Cooling is performed, for example, by a cooling mechanism that circulates a refrigerant along the axis of the backup roll. By cooling the backup roll, the pre-sheet in contact with the backup roll is also cooled, so the temperature of the molten material drops rapidly and the heat-sensitive layer is less likely to develop color.

[0035] (12) In the sheet manufacturing method described in (10) or (11) above, the molten raw material may be discharged onto the pre-sheet from a coating head having a slot-shaped discharge opening along the width of the pre-sheet.

[0036] The coating head makes it easy to form an adhesive layer with a uniform thickness.

[0037] (13) In the sheet manufacturing method described in any one of (10) to (12) above, the contact angle between the backup roll and the pre-sheet around the rotation axis of the backup roll may be 60° or more.

[0038] The contact angle is the angle between a first line connecting the contact start point of the pre-sheet with the backup roll and the rotation axis, and a second line connecting the contact end point where the pre-sheet separates from the backup roll and the rotation axis, when viewed along the rotation axis of the backup roll. If this contact angle is 60° or more, the contact area between the pre-sheet and the backup roll is large, so that the heat of the molten raw material is dispersed into the backup roll, and the heat-sensitive layer is less likely to develop color. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram of a sheet according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram of the cross section taken along the line AA in FIG. [Figure 3] FIG. 3 is a schematic diagram of a coater for producing the sheet according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram of a sheet according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] Specific examples of the sheet of the present invention and the method for manufacturing the sheet will be described below with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. The dimensions of the components shown in each drawing are expressed for the purpose of clarity and do not necessarily represent the actual dimensions. The present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0041] <Embodiment 1> <Overall structure> The sheet 1 in this example shown on the left side of Fig. 1 is a long, narrow label. The sheet 1 comprises a long, thin substrate 2, a heat-sensitive layer 3 disposed on a first surface 21 of the substrate 2, and an adhesive layer 4 disposed on a second surface 22 of the substrate 2. As shown in the AA cross-sectional view of Fig. 2, the second surface 22 on which the adhesive layer 4 is disposed is the surface opposite to the first surface 21.

[0042] The sheet 1 in this example is used by wrapping it around an attachment object 8, as shown to the right of the white arrow in FIG. 1. The attachment object 8 is not particularly limited. In this example, the attachment object 8 is the handle of a basket for storing products. When attaching the sheet 1 to the attachment object 8, the sheet 1 is folded so that different portions of the adhesive layer 4 face each other. The adhesive layer 4 contains a self-adhesive adhesive, and adhesive layers 4 arranged to face each other are very firmly bonded to each other.

[0043] The adhesive layer 4 is formed by applying a raw material containing a hot-melt type self-adhesive adhesive (hereinafter referred to as HM adhesive) to the second surface 22. The applied raw material is molten. In other words, when the adhesive layer 4 is formed, the heat of the molten raw material is transferred to the substrate 2. However, the thermosensitive layer 3 in the sheet 1 of this example does not develop color. The mechanism by which the thermosensitive layer 3 does not develop color will be explained in the sheet manufacturing method described below. First, each component of the sheet 1 of this example will be explained in detail.

[0044] ≪Base material≫ The substrate 2 shown in FIG. 2 is the base of the sheet 1. The material of the substrate 2 is not particularly limited. For example, the material of the substrate 2 is polyethylene terephthalate (PET) or a polyolefin resin. For example, the polyolefin resin is polyethylene or biaxially oriented polypropylene (OPP). The material of the substrate 2 may also be synthetic paper whose main raw material is synthetic resin.

[0045] The average thickness t2 of the substrate 2 is, for example, 10 μm or more and 200 μm or less. If the average thickness t2 of the substrate 2 is 10 μm or more, the heat of the HM adhesive melted during the formation of the adhesive layer 4 is less likely to be transmitted to the thermosensitive layer 3, as specified in the manufacturing method of the sheet 1 described below. Therefore, the thermosensitive layer 3 is less likely to develop color during the formation of the adhesive layer 4. If the average thickness t2 of the substrate 2 is 200 μm or less, the sheet 1 including the substrate 2 is easier to bend. The average thickness t2 of the substrate 2 may be 20 μm or more and 150 μm or less.

[0046] The average thickness t2 of the substrate 2 can be measured, for example, using a TH-104 paper / film thickness measuring instrument manufactured by Tester Sangyo Co., Ltd. In this example, the average thickness t2 of the substrate 2 is determined by measuring the thickness at multiple different locations on the substrate 2 and averaging the measured values. The number of measurement locations is, for example, five or more.

[0047] ≪Heat-sensitive layer≫ The thermosensitive layer 3 may be formed on the entire surface of the first surface 21 of the substrate 2, or may be formed on only a part of the surface. In this example, the thermosensitive layer 3 is formed on only a part of the first surface 21, as shown in FIG. 1. The first surface 21 may be pretreated to improve adhesion to the thermosensitive layer 3. The pretreatment may be, for example, a corona treatment, a plasma treatment, or an ozone treatment.

[0048] The thermosensitive layer 3 is a layer that changes color when heated. The color that changes is, for example, black. When the thermosensitive layer 3 is heated by the thermal head of a thermal printer or the like, a part of the thermosensitive layer 3 changes color, and information is printed on the thermosensitive layer 3. The information printed on the thermosensitive layer 3 is, for example, the manufacturing date, best-before date, expiry date, or information that the item has been paid for.

[0049] The materials of the thermosensitive layer 3 are known. The thermosensitive layer 3 contains, for example, a color former that changes color when heated and a color developer. The color former is, for example, a leuco dye. An example of the leuco dye is 2-aniline-3-methyl-6-(N-methyl-p-toluidino)fluoran. An example of the color developer is [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate. The thermosensitive layer 3 may further contain one or more materials selected from the group consisting of fillers, binders, lubricants, wetting agents, and antifoaming agents, as necessary.

[0050] The color-developing temperature of the thermosensitive layer 3 is, for example, 95°C or higher and 130°C or lower. The color-developing temperature of the thermosensitive layer 3 is a temperature that is predetermined when the thermosensitive layer 3 is formed. The color-developing temperature varies depending on the type and amount of color former and the type and amount of color developer contained in the thermosensitive layer 3. The color-developing temperature of the thermosensitive layer 3 is lower than the heating temperature of the thermal head. The thermosensitive layer 3 can be determined to be colored if the black density measured with a densitometer is equal to or higher than a predetermined value. For example, the eXact densitometer manufactured by X-rite TM If the black density of the thermosensitive layer 3 measured by the method is 0.25 or more, it can be determined that the thermosensitive layer 3 is colored.

[0051] The heat-sensitive layer 3 is printed on the first surface 21 by, for example, intaglio printing or letterpress printing. For example, the heat-sensitive layer 3 is formed by a gravure printing machine or the like.

[0052] ≪Adhesive layer≫ The adhesive layer 4 may be formed on the entire surface of the second surface 22 of the substrate 2, or may be formed on only a portion of the surface. In this example, the adhesive layer 4 is formed on the entire surface of the second surface 22. The second surface 22 may be pretreated to improve adhesion to the adhesive layer 4. The pretreatment may be, for example, a corona treatment, a plasma treatment, or an ozone treatment.

[0053] As already mentioned, the adhesive layer 4 contains an HM adhesive. An adhesive layer 4 containing an HM adhesive will adhere strongly to the same HM adhesive, but will barely adhere to other substances. Therefore, when attaching the sheet 1 of this example to an attachment object 8, the sheet 1 is formed into a loop as shown on the right side of Figure 1, and the adhesive layers 4 are brought into contact with each other. The adhesive layers 4 are firmly bonded to each other, making it difficult for the sheet 1 to come off the attachment object 8. On the other hand, the adhesive layer 4 at the looped portion, i.e., the adhesive layer 4 other than the portion where the adhesive layers 4 are bonded to each other, will not adhere to the attachment object 8.

[0054] The content of the HM adhesive in the adhesive layer 4 is, for example, 90% by mass or more when the mass per unit area of ​​the adhesive layer 4 is 100% by mass. The content of the HM adhesive can be determined, for example, by analysis using X-rays. The content may be 95% by mass or more, or 99% by mass or more.

[0055] When melted, the HM adhesive becomes a fluid with a viscosity that allows it to be applied to the second surface 22 of the substrate 2. Therefore, when applying a raw material containing the HM adhesive to the substrate 2, there is no need to add an organic solvent to the raw material to reduce the viscosity of the raw material. The adhesive layer 4 formed from such a raw material does not contain an organic solvent. If the adhesive layer 4 does not contain an organic solvent, there is no problem in terms of the working environment or the health of workers during the production of the sheet 1. If the adhesive layer 4 does not contain an organic solvent, it is possible to prevent the organic solvent from adhering to products bound or packaged with the sheet 1.

[0056] The adhesive layer 4 is made of, for example, a polyolefin resin. Since the melting point of the polyolefin resin is not too high, even if the molten HM adhesive is applied to the second surface 22 of the substrate 2 when the adhesive layer 4 is formed, the thermosensitive layer 3 disposed on the first surface 21 is unlikely to develop color.

[0057] The average thickness t4 of the adhesive layer 4 is, for example, 20 μm or more and 200 μm or less. If the adhesive layer 4 is 20 μm or more, the adhesive layer 4 exhibits sufficient adhesiveness. If the adhesive layer 4 is 200 μm or less, the amount of HM adhesive applied to the second surface 22 when forming the adhesive layer 4 is not too large. Therefore, the total heat amount of the melted HM adhesive does not become too large, making it difficult for the heat-sensitive layer 3 to develop color. The average thickness t4 of the adhesive layer 4 can be measured, for example, using a TH-104 paper / film thickness measuring instrument manufactured by Tester Sangyo Co., Ltd. It is preferable to measure at five or more points.

[0058] <Middle class> The sheet 1 may include an intermediate layer 5 disposed at least one between the substrate 2 and the thermosensitive layer 3 and between the substrate 2 and the adhesive layer 4. In FIG. 3, the intermediate layer 5 disposed between the second surface 22 of the substrate 2 and the adhesive layer 4 is illustrated by a two-dot chain line. This intermediate layer 5 is formed of a material that can improve the adhesion between the substrate 2 and the adhesive layer 4. The material of the intermediate layer 5 is determined appropriately depending on the material of the substrate 2 and the material of the adhesive layer 4. For example, the material of the intermediate layer 5 may be a styrene-acrylic acid copolymer. The intermediate layer 5 is not essential. If the second surface 22 is pretreated, the adhesion between the second surface 22 and the adhesive layer 4 can be improved even without the intermediate layer 5.

[0059] The intermediate layer 5 also exerts the effect of suppressing the heat of the HM adhesive melted during the formation of the adhesive layer 4 from being transferred to the heat-sensitive layer 3 .

[0060] <Other> As shown in FIG. 1 , the sheet 1 may have a printing layer 6 on the first surface 21 of the substrate 2. The printing layer 6 is a layer on which a product name, logo, or the like is printed. The printing layer 6 is printed, for example, by a gravure printing machine. The thermosensitive layer 3 may be disposed on the printing layer 6. In this case, the portion of the printing layer 6 disposed between the substrate 2 and the thermosensitive layer 3 functions as an intermediate layer 5 that prevents heat from the HM adhesive from being transmitted to the thermosensitive layer 3.

[0061] <Sheet manufacturing method> The manufacturing method for manufacturing the sheet 1 includes a step of preparing a pre-sheet, and a step of forming the adhesive layer 4 while transporting the pre-sheet.

[0062] The pre-sheet includes the substrate 2 and the thermosensitive layer 3 shown in FIG. 2. In other words, the pre-sheet is the sheet 1 before the adhesive layer 4 is formed on the second surface 22 of the substrate 2. The pre-sheet may be a commercially available product, or may be prepared by printing the thermosensitive layer 3 on the first surface 21 of the substrate 2. The printing of the thermosensitive layer 3 can be performed, for example, by a gravure printing machine.

[0063] In the step of forming the adhesive layer 4 while conveying the pre-sheet, more precisely, the molten raw material is applied to the second surface 22 while the pre-sheet is conveyed by a conveying mechanism. The raw material applied to the second surface 22 is solidified to form the adhesive layer 4. The molten raw material contains an HM adhesive.

[0064] The step of forming the adhesive layer 4 while conveying the pre-sheet can be performed, for example, by a coating device 9 illustrated in Fig. 3. The coating device 9 includes a conveying mechanism 9A that conveys the pre-sheet 7, and a coating mechanism 9B that applies the raw material of the adhesive layer 4 to the pre-sheet 7 in the conveyed state.

[0065] The conveying mechanism 9A includes a feed roll 91, a backup roll 93, and a take-up roll 95. The feed roll 91 is a roll around which the pre-sheet 7 is wound. The pre-sheet 7 is wound around the feed roll 91 so that the thermosensitive layer 3 faces outward. When the adhesive layer 4 is formed, the pre-sheet 7 is fed from the feed roll 91.

[0066] The backup roll 93 is disposed midway along the conveyance path of the pre-sheet 7 from the delivery roll 91 to the take-up roll 95. The backup roll 93 is a roll that applies tension to the pre-sheet 7 delivered from the delivery roll 91. More specifically, the backup roll 93 contacts the thermosensitive layer 3 of the pre-sheet 7 and presses the pre-sheet 7 against the side opposite the thermosensitive layer 3. The second surface 22 of the pre-sheet 7 faces away from the backup roll 93. The molten raw material is coated onto the second surface 22 of the pre-sheet 7 while the pre-sheet 7 is in contact with the backup roll 93, i.e., while the pre-sheet 7 is being tensioned.

[0067] The molten raw material is applied to the second surface 22 while tension is applied to the pre-sheet 7, which facilitates application of the molten raw material to the second surface 22 with a uniform thickness. Furthermore, the molten raw material is applied to the second surface 22 while the pre-sheet 7 is in contact with the backup roll 93, which facilitates dissipation of heat from the molten raw material to the outside of the pre-sheet 7. Because the heat capacity of the backup roll 93 is significantly greater than that of the pre-sheet 7, the temperature of the molten raw material drops rapidly. As a result, the molten raw material solidifies quickly, forming an adhesive layer 4 containing an HM adhesive.

[0068] The larger the contact area of ​​the pre-sheet 7 with the backup roll 93, the more likely the temperature of the raw material coated on the pre-sheet 7 is to decrease. In relation to the contact area, the contact angle θ between the backup roll 93 and the pre-sheet 7, centered on the rotation axis 93s of the backup roll 93, may be 60° or greater. When the backup roll 93 is viewed along its rotation axis 93s, the contact angle θ is the angle between a first line L1 connecting the contact start point 7S of the pre-sheet 7 with the backup roll 93 and the rotation axis 93s, and a second line L2 connecting the contact end point 7E where the pre-sheet 7 separates from the backup roll 93 and the rotation axis 93s. If the contact angle θ is 60° or greater, the contact area between the pre-sheet 7 and the backup roll 93 is large, which facilitates heat dissipation of the molten raw material to the backup roll 93, thereby preventing color development of the thermosensitive layer 3. If the thermal conductivity of the backup roll 93 is high, the heat of the molten raw material is easily dispersed to the backup roll 93, thereby preventing color development of the thermosensitive layer 3.

[0069] The take-up roll 95 takes up the sheet 1 having the adhesive layer 4 formed on the second surface 22 of the pre-sheet 7. In the sheet 1 taken up on the take-up roll 95, the adhesive layer 4 of the nth layer of the sheet 1 comes into contact with the thermosensitive layer 3 of the n+1th layer of the sheet 1 (n is a natural number greater than or equal to 1). Because the raw material containing the HM adhesive applied to the pre-sheet 7 has already solidified, blocking does not occur between the adhesive layer 4 of the nth layer and the thermosensitive layer 3 of the n+1th layer even when the sheet 1 is taken up on the take-up roll 95. Blocking refers to a state in which the surfaces of stacked films adhere to each other and are difficult to peel off.

[0070] The conveying mechanism 9A of this example further includes guide rolls 92 and 94. The guide roll 92 guides the pre-sheet 7 from the delivery roll 91 toward the backup roll 93, stabilizing the supply of the pre-sheet 7 to the backup roll 93. The guide roll 94 guides the sheet 1 from the backup roll 93 toward the take-up roll 95, stabilizing the winding state of the sheet 1 on the take-up roll 95. The contact angle θ can be adjusted by the positions of the guide rolls 92 and 94. The guide roll 92 and the guide roll 94 do not apply as much tension to the pre-sheet 7 and the sheet 1 as the backup roll 93 does.

[0071] The conveying speed of the pre-sheet 7 by the conveying mechanism 9A is, for example, 5 m / min (meters per minute) or more. At this conveying speed, the raw material coated on the pre-sheet 7 moves quickly to a position away from the coating head 90, making it easier for the temperature of the raw material to drop. The lower the viscosity of the molten raw material, the higher the conveying speed of the pre-sheet 7 can be. Depending on the viscosity of the molten raw material, the conveying speed may be 10 m / min or more, 50 m / min or more, or 100 m / min or more. The upper limit of the conveying speed is regulated by the viscosity of the molten raw material.

[0072] The coating mechanism 9B of this example includes a coating head 90 with a slot-shaped outlet that runs along the width of the pre-sheet 7. The width of the pre-sheet 7 is the length of the pre-sheet 7 perpendicular to the conveying direction of the pre-sheet 7. The raw material discharged onto the pre-sheet 7 from such an outlet is likely to be coated with a uniform thickness on the second surface 22 of the pre-sheet 7. Therefore, the thickness of the adhesive layer 4 formed by solidifying the raw material is likely to be uniform.

[0073] The coating mechanism 9B further includes a tank and piping (not shown). The tank stores the molten raw material. The tank applies heat to the raw material to maintain the raw material in a molten state. The piping is a conduit that supplies the molten raw material from the tank to the coating head 90.

[0074] The coating device 9 described above can form the adhesive layer 4 without causing the thermosensitive layer 3 to develop color. Furthermore, the sheet 1 can be produced continuously, allowing for efficient production of the sheet 1. When shipping the sheet 1, the sheet 1 may be cut to an appropriate length.

[0075] In this example, the thermosensitive layer 3 is formed before the adhesive layer 4. Unlike this example, forming the adhesive layer 4 before the thermosensitive layer 3 is not practical. If the thermosensitive layer 3 were formed on the substrate 2 while the substrate 2, which includes the adhesive layer 4, was being transported by the coating device 9 of this example, the adhesive layer 4 would come into direct contact with the backup roll 93. This would apply strong pressure to the adhesive layer 4, which could significantly change the thickness of the adhesive layer 4 or reduce the surface smoothness of the adhesive layer 4. If the surface smoothness of the adhesive layer 4 decreases, i.e., if the surface roughness of the adhesive layer 4 increases, the adhesive performance of the adhesive layer 4 would decrease. Furthermore, a portion of the adhesive layer 4 pressed against the backup roll 93 could peel off from the substrate 2 and adhere to the backup roll 93. In this case, when the adhesive layer 4 of the substrate 2 newly fed from the feed roll 91 toward the backup roll 93 comes into contact with the adhesive layer 4 adhered to the backup roll 93, the two adhesive layers 4 could be bonded together. Therefore, forming the thermosensitive layer 3 on the substrate 2, which includes the adhesive layer 4, is not practical.

[0076] The coating device 9 may be equipped with a cooling mechanism 9C that cools the backup roll 93. The cooling mechanism 9C, indicated by a two-dot chain line in FIG. 3, is a refrigerant pipe 97 formed on a shaft portion including a rotation shaft 93s of the backup roll 93. A liquid refrigerant such as water flows through the refrigerant pipe 97, and the heat of the backup roll 93 is dissipated by the liquid refrigerant. By providing the coating device 9 with the cooling mechanism 9C, heat from the molten raw material does not accumulate in the backup roll 93. Therefore, color development of the thermosensitive layer 3 is continuously suppressed even when the sheet 1 is continuously produced.

[0077] The cooling mechanism 9C is not limited to a configuration in which a refrigerant is circulated through the backup roll 93. For example, the cooling mechanism 9C may be configured to blow air onto the backup roll 93. In this case, the cooling mechanism 9C includes a blower that blows air onto a portion of the backup roll 93 that is not in contact with the base material 2.

[0078] <Embodiment 2> The sheet 10 of the second embodiment will be described with reference to Fig. 4. The width of the substrate 20 of the sheet 10 is wider than the width of the substrate 2 of the sheet 1 of the first embodiment. This sheet 10 is used as a packaging material.

[0079] In the sheet 10 of the second embodiment, adhesive layers 4, 4 are formed on the second surface 22 of the substrate 20, respectively, along the first side edge and along the second side edge. The two adhesive layers 4 are independent of each other. A heat-sensitive layer is formed on the first surface (not shown) of the substrate 20. When using this sheet 10, as shown by the arc arrows, the sheet 10 is folded in half with the second surface 22 facing inward, and the adhesive layers 4 along the facing first side edges are overlapped, and the adhesive layers 4 along the facing second side edges are overlapped. As a result, the sheet 10 is formed into a bag shape.

[0080] <Test example> The sheet 1 was actually produced using the coating device 9 shown in FIG. 3, and it was confirmed whether or not the adhesive layer 4 could be formed without causing the thermosensitive layer 3 to develop color.

[0081] First, a pre-sheet 7 consisting of a substrate 2 with a thermosensitive layer 3 was prepared and wound around a delivery roll 91 with the thermosensitive layer 3 facing outward. The substrate 2 of the pre-sheet 7 was made of transparent PET resin. The average thickness of the substrate 2 was 50 μm. The color-developing temperature of the thermosensitive layer 3 was 95°C. The ink density of this pre-sheet 7 was measured. Specifically, a mount was prepared by stacking 10 sheets of neutral paper with a whiteness of 85.0±0.5%, and the pre-sheet 7 was placed on the mount with the thermosensitive layer 3 facing up. Then, a densitometer, eXact, manufactured by X-rite, was used to measure the ink density from above the thermosensitive layer 3. TMThe ink density of the thermosensitive layer 3 of the pre-sheet 7 was measured by the following method. The ink density of the thermosensitive layer 3 of the pre-sheet 7 was 0.10.

[0082] Next, the pre-sheet 7 was conveyed from the delivery roll 91 to the take-up roll 95 by the conveying mechanism 9A of the coating device 9, while the molten raw material was coated onto the second surface 22 of the pre-sheet 7. The conveying speed was 5 meters / min.

[0083] The molten raw material was HM adhesive manufactured by Yasuhara Chemical Co., Ltd. This HM adhesive was a polyolefin resin. The softening point of the HM adhesive was 95°C. The viscosity of this HM adhesive at 180°C was 5000 mPa·s (millipascal·second). The coating amount of the molten raw material was 30 g / m 2 (grams per square meter). The thickness of the raw material on the second surface 22 coated by the coating head 90 is considered to be uniform. The average thickness of the raw material on the second surface 22 calculated from the coating amount of the raw material was 30 μm.

[0084] In the test example, temperatures were measured at various locations in the coating device 9 indicated by solid arrows in Figure 3. The temperature of the molten raw material at the discharge port of the coating head 90 indicated by the solid arrow pointing left was 170°C, the temperature of the outer circumferential surface of the coating head 90 indicated by the solid arrow pointing downward was 150°C, and the surface temperature of the adhesive layer 4 at a position 7 cm away from the coating head 90 in the conveyance direction of the pre-sheet 7 indicated by the solid arrow pointing downward to the right was 40°C. In addition, the temperature of the backup roll 93 before coating began was 26.4°C.

[0085] The black density of the thermosensitive layer 3 of the sheet 1 prepared under the above conditions was measured. The method for measuring the black density was the same as that for the thermosensitive layer 3 of the pre-sheet 7. The black density of the thermosensitive layer 3 of the sheet 1 was 0.11.

[0086] The difference in ink density between the thermosensitive layer 3 of the sheet 1 and the thermosensitive layer 3 of the pre-sheet 7 was 0.01, and the ink density of the thermosensitive layer 3 hardly changed before and after the formation of the adhesive layer 4. Therefore, it can be determined that the thermosensitive layer 3 did not develop color. In other words, it was found that the sheet manufacturing method of the embodiment using the coating device 9 in Figure 3 can form the adhesive layer 4 containing the HM adhesive without causing the thermosensitive layer 3 to develop color. [Explanation of symbols]

[0087] 1,10 sheets 2,20 Base material 21 first page, 22 second page 3 Heat sensitive layer 4,40 Adhesive layer 5. Middle class 6 printing layer 7 Pre-sheet 7E contact end point, 7S contact start point 8. Mounting target 9 Coating equipment 9A Conveying mechanism, 9B Coating mechanism, 9C Cooling mechanism 90 Coating head 91 Delivery roll, 92, 94 Guide rolls 93 backup roll, 93s rotating shaft, 95 winding roll, 97 refrigerant pipe θ contact angle L1 first straight line, L2 second straight line t1, t2 average thickness

Claims

1. a sheet-like substrate having a first surface and a second surface; a heat-sensitive layer disposed on the first surface; an adhesive layer disposed on the second surface; The adhesive layer includes a hot melt type self-adhesive adhesive. Sheet.

2. The sheet according to claim 1 , wherein the adhesive layer has an average thickness of 20 μm or more and 200 μm or less.

3. 3. The sheet according to claim 1, wherein the average thickness of the substrate is 10 μm or more and 200 μm or less.

4. 3. The sheet according to claim 1, wherein the self-adhesive adhesive is made of a polyolefin resin.

5. The sheet according to claim 1 or claim 2, wherein the adhesive layer does not contain an organic solvent.

6. 3. The sheet according to claim 1, wherein the melting temperature of the self-adhesive adhesive is higher than the color-developing temperature of the thermosensitive layer.

7. 3. The sheet according to claim 1, wherein the substrate is made of a polyethylene terephthalate resin or a polyolefin resin.

8. 3. The sheet according to claim 1, further comprising an intermediate layer disposed between the substrate and the heat-sensitive layer and / or between the substrate and the adhesive layer.

9. providing a pre-sheet comprising a substrate having a first side and a second side and a heat-sensitive layer disposed on the first side; and coating the molten raw material on the second surface of the pre-sheet while conveying the pre-sheet using a conveying mechanism, thereby producing a sheet having an adhesive layer formed by solidifying the molten raw material. The molten material includes a hot melt type self-adhesive adhesive. Sheet manufacturing method.

10. The transport mechanism includes: a delivery roll for delivering the pre-sheet; a winding roll that winds up the sheet; a backup roll disposed between the delivery roll and the take-up roll and applying tension to the pre-sheet; The sheet manufacturing method according to claim 9 , wherein the molten raw material is applied to the pre-sheet in a state where the pre-sheet is in contact with the backup roll.

11. The method for producing a sheet according to claim 10, wherein the molten raw material is applied to the pre-sheet while the backup roll is being cooled.

12. The method for producing a sheet according to claim 10 or 11, wherein the molten raw material is discharged onto the pre-sheet from a coating head having a slot-shaped discharge opening extending along the width of the pre-sheet.

13. The method for producing a sheet according to claim 10 or 11, wherein a contact angle between the backup roll and the pre-sheet about a rotation axis of the backup roll is 60° or more.

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