Thermosensitive recording body

Abstract

Provided is a thermosensitive recording body that comprises a heat-seal layer on one surface thereof, and a topcoat layer on the other surface thereof, and that exhibits high adhesion when the heat-seal layer and the topcoat layer are heat-sealed, resulting in excellent heat sealability.　A thermosensitive recording body (1) comprises: a heat-seal layer (2) containing an anti-blocking agent; and a topcoat layer (9) containing a lubricant. The thermosensitive recording body (1) comprises the heat seal layer (2) on one surface thereof, and the topcoat layer (9) on the other surface thereof. The anti-blocking agent contains the same component as that of the lubricant, and the ratio [the average particle size of the anti-blocking agent / the thickness of the heat-seal layer (2)] of the average particle size of the anti-blocking agent to the thickness of the heat-seal layer (2) is at least 0.5.

Description

Thermal recording device

[0001] This invention relates to a thermal recording material.

[0002] Thermal recording media produce color through a chemical reaction when heated by a thermal head or similar device, resulting in a recorded image. They are used in a wide range of applications, including as recording media for fax machines, automatic ticket vending machines, and scientific measuring instruments, as well as as thermal recording labels used on various products such as food pouches.

[0003] Some of the above-mentioned thermal recording media have a heat-sensitive adhesive layer (heat-seal layer) on one surface. This heat-sensitive adhesive layer does not exhibit tackiness at room temperature, but becomes tacky when heated, allowing thermal recording media equipped with it to be heat-sealed to an adherend. Here, while various objects can be used as the adherend, a heat-sensitive adhesive material for thermal recording has been proposed that can exhibit strong adhesive force to rough-surfaced adherends such as cardboard (see Patent Document 1).

[0004] Japanese Patent Publication No. 2013-208833

[0005] However, until now, many heat-sealable thermal recording materials, such as the heat-sensitive adhesive material for thermal recording described in Patent Document 1, have assumed that an article other than the thermal recording material itself is to be attached, and a thermal recording material that can be heat-sealed by a banding method has not yet been specifically provided. Here, "banding" is a type of binding method that is widely used when bundling stacks of articles such as books, and in this binding method, for example, the stacks are wrapped with a band-shaped band and the front and back surfaces of the band are heat-sealed to bind them together. In other words, a "thermal recording material that can be heat-sealed by a banding method" means a thermal recording material that can heat-seal a heat-seal layer located on one surface and a layer located on the other surface.

[0006] Incidentally, since thermal recording media use a recording method where they are heated and colored upon contact with a thermal head or the like, they are generally equipped with a topcoat layer with excellent heat resistance on the surface that comes into contact with the thermal head or the like. Normally, due to their excellent heat resistance, the topcoat layer does not easily change or melt even when heated, making it difficult to achieve strong adhesion through heat sealing.

[0007] Furthermore, as disclosed in Patent Document 1, it was known that when a lubricant is incorporated into the heat seal layer for purposes such as preventing blocking, the blocking prevention effect is insufficient, and conversely, it leads to a decrease in tackiness. In this case, the top coat layer is often designed to contain a lubricant in order to ensure suitability for thermal heads, and from this point of view, the top coat layer was considered to have inferior heat sealability.

[0008] The present invention was conceived under these circumstances, and its purpose is to provide a thermal recording body having a heat seal layer on one surface and a top coat layer on the other surface, which exhibits high adhesion and excellent heat sealability when the heat seal layer and the top coat layer are heat-sealed together.

[0009] As a result of diligent research to achieve the above objective, the inventors of this invention have found that certain thermal recording materials exhibit high adhesion and excellent heat sealability when the heat seal layer and top coat layer are heat-sealed. This invention was completed based on these findings.

[0010] In other words, the present invention provides a thermal recording body comprising a heat seal layer containing an antiblocking agent and a top coat layer containing a lubricant, wherein the thermal recording body has the heat seal layer on one surface and the top coat layer on the other surface, the antiblocking agent contains the same components as the lubricant, and the ratio of the average particle diameter of the antiblocking agent to the thickness of the heat seal layer [average particle diameter of the antiblocking agent / thickness of the heat seal layer] is 0.5 or more.

[0011] The above lubricant and the above antiblocking agent preferably both have a melting point of 90 to 150°C.

[0012] It is preferable that the antiblocking agent described above is partially exposed from the heat seal layer.

[0013] The hardness of the above antiblocking agent, measured by the penetration method, is preferably 5 or less.

[0014] The heat-seal layer described above preferably contains an acrylic resin.

[0015] The glass transition temperature of the above-mentioned acrylic resin is preferably 40°C or lower.

[0016] The heat seal layer contains a heat sealant, and the mass ratio of the antiblocking agent to the heat sealant content [antiblocking agent / heat sealant] is preferably 0.01 to 1.

[0017] The heat-seal layer is preferably a coated layer formed by coating.

[0018] Furthermore, the present invention provides a thermal recording body comprising the heat-seal layer, a substrate, a thermal recording layer containing a leuco dye and a color developer, and the top coat layer in this order.

[0019] The thermal recording material of the present invention exhibits high adhesion and excellent heat sealability when the heat seal layer and top coat layer are heat-sealed. Therefore, heat sealing using a strip method is possible at any location, providing a thermal recording material that can accommodate products of various circumferences.

[0020] This is a schematic cross-sectional view showing one embodiment of the thermal recording material of the present invention. This is a schematic cross-sectional view showing another embodiment of the thermal recording material of the present invention. This is a schematic diagram showing an example of a band label, which is one embodiment of the thermal recording material of the present invention. This is an enlarged view of the main part of the A-A' cross-section of the band label shown in Figure 3.

[0021] [Thermal Recording Material] The thermal recording material of the present invention has a structure in which a heat seal layer and a top coat layer are laminated. The heat seal layer is located on one surface of the thermal recording material of the present invention, and the top coat layer is located on the other surface of the thermal recording material of the present invention. The thermal recording material of the present invention may also include other layers besides the heat seal layer and the top coat layer. Examples of these other layers include a substrate, a thermal recording layer, a back coat layer, an anchor coat layer, an anchor layer, an undercoat layer, and an intermediate layer. The substrate is a layer located between the heat seal layer and the top coat layer, and functions as a support for the thermal recording material, improving the strength and handling of the thermal recording material of the present invention. The thermal recording layer is a layer located between the substrate and the top coat layer, and can develop color by heating with a thermal head or the like, forming a recorded image. The back coat layer is a layer located between the heat seal layer and the substrate, and can improve the anchoring ability of the heat seal layer to the substrate and / or suppress curling of the thermal recording material. The anchor coat layer is a layer located between the heat seal layer and the substrate, and can improve the anchoring ability of the heat seal layer to the substrate. When the thermal recording body of the present invention includes both a back coat layer and an anchor coat layer, the substrate, anchor coat layer, back coat layer, and heat seal layer are provided in this order. The anchor layer is a layer provided between the substrate and the thermal recording layer, and can improve the anchoring ability of the thermal recording layer to the substrate. However, an undercoat layer, as described later, may be provided instead of the anchor layer. The undercoat layer is a layer provided between the substrate and the thermal recording layer, and can improve the color development efficiency of the thermal recording body. The intermediate layer is a layer located between the thermal recording layer and the top coat layer, and functions as a protective layer to protect the thermal recording layer.

[0022] The thermal recording medium of the present invention preferably includes at least a base material and a thermal recording layer as the other layers described above. The thermal recording medium of the present invention including the base material and the thermal recording layer preferably has a structure in which a heat-sealing layer, a base material, a thermal recording layer, and a top coat layer are laminated in this order.

[0023] Hereinafter, an embodiment of the thermal recording medium of the present invention will be described in detail based on the drawings, but the present invention is not limited to the following embodiments.

[0024] An embodiment of the thermal recording medium of the present invention is shown in FIG. 1. The thermal recording medium 1 shown in FIG. 1 includes a heat-sealing layer 2, a back coat layer 3, an anchor coat layer 4, a base material 5, an anchor layer 6a, a thermal recording layer 7, an intermediate layer 8, and a top coat layer 9 in this order. The heat-sealing layer 2 is located on one surface of the thermal recording medium 1, and the top coat layer 9 is located on the other surface of the thermal recording medium 1. The long thermal recording medium 1 can be wound into a wound body such that the surface of the heat-sealing layer 2 overlaps the surface of the top coat layer 9. According to the thermal recording medium of the present invention, it is suitable for suppressing unintentional adhesion (blocking) between the heat-sealing layer 2 and the top coat layer 9 even when stored as such a wound body. When the base material is a resin film, this embodiment is a preferred embodiment. In the thermal recording medium 1 shown in FIG. 1, it may not include one or more layers selected from the group consisting of the back coat layer 3, the anchor coat layer 4, the base material 5, the anchor layer 6a, the thermal recording layer 7, and the intermediate layer 8.

[0025] Another embodiment of the thermal recording medium of the present invention is shown in FIG. 2. The thermal recording medium 1 shown in FIG. 2 includes a heat-sealing layer 2, a base material 5, an undercoat layer 6b, a thermal recording layer 7, an intermediate layer 8, and a top coat layer 9 in this order. Also in this embodiment, the long thermal recording medium 1 can be wound into a wound body such that the surface of the heat-sealing layer 2 overlaps the surface of the top coat layer 9. When the base material is a paper base material, this embodiment is a preferred embodiment. In the thermal recording medium 1 shown in FIG. 2, it may not include one or more layers selected from the group consisting of the base material 5, the undercoat layer 6b, the thermal recording layer 7, and the intermediate layer 8.

[0026] (Heat - seal layer) The heat - seal layer 2 can exhibit adhesiveness by heating. Further, by containing an anti - blocking agent described later, the heat - seal layer 2 can exhibit not only heat - sealability but also anti - blocking property.

[0027] The heat - seal layer 2 contains at least an anti - blocking agent. As the material constituting the anti - blocking agent, polyethylene wax is preferable. Also, as the material constituting the anti - blocking agent, for example, polyolefin waxes such as polypropylene wax, Fischer - Tropsch wax, fatty acids such as stearic acid, palmitic acid, arachidic acid, behenic acid, fatty acid metal salts such as zinc stearate, magnesium stearate, and fatty acid amides such as stearic acid amide may be used. The anti - blocking agent can be used alone or in combination of two or more.

[0028] The anti - blocking agent contains components of the same kind as the lubricant in the top - coat layer 9. In this specification, the anti - blocking agent containing components of the same kind may be referred to as an "anti - blocking agent of the same kind". In this specification, "components of the same kind" means having the same kind of structural units. As the combination of components when the components in the anti - blocking agent and the components in the lubricant contain components of the same kind, specifically, the combination where the anti - blocking agent is polyethylene wax and the lubricant is polyethylene wax is preferable. That is, it is particularly preferable that both the anti - blocking agent in the heat - seal layer 2 and the lubricant in the top - coat layer 9 contain polyethylene wax. When containing components of the same kind, the affinity between the heat - seal layer 2 and the top - coat layer 9 is improved. Therefore, when heat - sealed, the vicinity of the boundary between the heat - seal layer 2 and the top - coat layer 9 is compatible through components of the same kind. As a result, it is presumed that the adhesion between the heat - seal layer 2 and the top - coat layer 9 is excellent and the heat - sealability is improved.

[0029] The heat seal layer 2 may contain other antiblocking agents. These other antiblocking agents are those that do not contain the same components as the lubricant in the top coat layer 9. In this specification, antiblocking agents that do not contain the same components as described above may be referred to as "other antiblocking agents." As these other antiblocking agents, known antiblocking agents can be used as appropriate, for example, antiblocking agents composed of polymethyl methacrylate (PMMA), rubber such as polybutadiene elastomers, silicone resins, silica, etc.

[0030] The ratio of the average particle size of the antiblocking agent to the thickness of the heat seal layer 2 [average particle size of the antiblocking agent / thickness of the heat seal layer] is 0.5 or more, preferably 0.5 to 2.5, more preferably 0.8 to 2.3, even more preferably 1.0 to 2.0, and particularly preferably 1.1 to 1.5. Also, the thickness of the heat seal layer 2 (μm) and the coating amount (g / m²) are important. ２ Since this is roughly the same value as the coating amount of heat seal layer 2 (g / m ２ The ratio of the average particle size (μm) of the antiblocking agent to the value of the antiblocking agent [average particle size (μm) of the antiblocking agent / amount of heat seal layer coating (g / m ２ The value of the average particle diameter is preferably within the above range. When the average particle diameter is within the above range, the antiblocking agent is adequately exposed from the heat seal layer 2, resulting in even more sufficient heat sealability and blocking resistance. Therefore, it is preferable that all or part of the total amount of the antiblocking agent is partially exposed from the heat seal layer 2. In other words, it is preferable that the surface of the heat seal layer 2 includes a plurality of protrusions formed by the antiblocking agent.

[0031] The average particle size of the antiblocking agent described above is not particularly limited, but from the viewpoint of excellent heat sealability and blocking resistance, it is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and particularly preferably 5 μm or more. Furthermore, the average particle size may be, for example, 20 μm or less, 15 μm or less, 10 μm or less, or 8 μm or less. In particular, it is preferable that the average particle size of the antiblocking agent described above is within the above range. The average particle size can be measured by known or conventional measurement methods, and the average particle size measured by the Coulter counter method can be used.

[0032] The melting point of the antiblocking agent described above is not particularly limited, but is preferably 90 to 150°C, more preferably 100 to 140°C, and even more preferably 105 to 130°C. When the melting point is within the above range, it melts easily when heat-sealed and solidifies easily as it cools after heat-sealing, resulting in even better heat sealability. Furthermore, unintended melting during storage is easily suppressed, resulting in even better antiblocking properties. The melting point can be measured by known or conventional measurement methods, and the melting point measured by the DSC (Differential Scanning Calorimeter) method can be used. In particular, it is preferable that the melting point of the antiblocking agent of the same type described above is within the above range.

[0033] The softening point of the above antiblocking agent is not particularly limited, but is preferably 100 to 160°C, more preferably 105 to 150°C, and even more preferably 110 to 140°C. When the softening point is within the above range, it melts easily when heat-sealed and solidifies easily as it cools after heat-sealing, resulting in even better heat sealability. Furthermore, unintended melting during storage is easily suppressed, resulting in even better antiblocking properties. The above softening point can be measured by known or conventional measurement methods, and the softening point measured according to the environmental method (JIS K2207) can be used. In particular, it is preferable that the softening point of the above antiblocking agent is within the above range.

[0034] The penetration hardness of the above antiblocking agent is not particularly limited, but is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. Furthermore, the penetration hardness may be 20 or less, 15 or less, or 10 or less. When the penetration hardness is within the above range, it provides appropriate malleability, preventing excessive thinning during heat sealing and thus not hindering the action of the heat sealant, resulting in even greater heat sealability. Additionally, it is less prone to crushing during stacked storage, further enhancing its blocking resistance. The penetration hardness can be measured using known or conventional measurement methods, and the penetration hardness measured according to the environmental method (JIS K2207) can be used. Among these, it is preferable that the penetration hardness of the above-mentioned antiblocking agent is within the above range.

[0035] The shape of the antiblocking agent is not particularly limited, but spherical particles are preferred. With this shape, for example, when the thermal recording body 1 is wound, the antiblocking agent in the heat seal layer 2 comes into contact with the top coat layer 9 over a smaller area, making it easier to prevent blocking.

[0036] The content of the antiblocking agent is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, even more preferably 10 to 30% by mass, and particularly preferably 15 to 25% by mass, based on 100% by mass of the total solid content of the heat seal layer 2. When the content is within the above range, the heat seal layer 2 can be given appropriate heat-sensitive tackiness and lubricity, and has excellent heat sealability and antiblocking properties.

[0037] The content ratio of the above-mentioned antiblocking agent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total amount of antiblocking agent in the heat seal layer 2. It may also be 95% by mass or more, or 99% by mass or more. When the above content ratio is within the above range, the heat seal layer 2 can be given appropriate heat-sensitive adhesiveness and lubricity, and has excellent heat sealability and antiblocking properties.

[0038] The heat seal layer 2 preferably further contains a heat sealant. The heat sealant is not particularly limited and can be a material that becomes tacky when heated (e.g., a resin). The heat seal layer 2 may further contain other materials as needed.

[0039] Examples of the heat sealant mentioned above include acrylic resins; polyolefin resins such as polyethylene and polypropylene. In particular, it is preferable that the heat sealant includes an acrylic resin. Specifically, examples of the acrylic resin include acrylic resin, styrene-acrylic resin, acrylic-urethane resin, acrylamide resin, vinyl acetate-acrylic resin, etc. In this specification, "acrylic resin" means a resin obtained by homopolymerizing acrylic monomers (monomers having a (meth)acryloyl group) (acrylic resin), and / or a resin obtained by copolymerizing an acrylic monomer with other monomers (monomers other than acrylic monomers that can copolymerize with acrylic monomers). Here, the acrylic monomer and the other monomer may each be one type or two or more types. Also, when simply referred to as "acrylic," unless otherwise specified, it means (meth)acrylic acid (salt) and / or (meth)acrylic acid ester. Here, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid. Also, "(meth)acrylic acid (salt)" means (meth)acrylic acid and / or (meth)acrylic acid salt. The above heat sealing agents can be used alone or in combination of two or more types.

[0040] The salts in the above-mentioned (meth)acrylate salts are not particularly limited and include, for example, ammonium salts such as ammonia; alkanolamine salts such as triethanolamine, diethanolamine, and monoethanolamine; alkylamine salts such as methylamine, ethylamine, diethylamine, and triethylamine; polyamine salts such as diethyleneamine and diethylenetriamine; alkali metal salts such as lithium, sodium, and potassium; alkaline earth metal salts such as magnesium and calcium; and polyvalent metal salts such as zinc and iron. These salts can be used individually or in combination of two or more.

[0041] The glass transition temperature of the heat sealant described above is not particularly limited, but is preferably 40°C or lower, more preferably -60 to 40°C, even more preferably -50 to 30°C, even more preferably -40 to 20°C, even more preferably -30 to 10°C, and most preferably -25 to 5°C. When the glass transition temperature is within the above range, the heat sealability and blocking resistance become even more sufficient.

[0042] The content of the heat sealant is preferably 50 to 99% by mass, more preferably 60 to 95% by mass, even more preferably 70 to 90% by mass, and particularly preferably 75 to 85% by mass, based on 100% by mass of the total solid content of the heat seal layer 2. When the content is within the above range, the heat seal layer 2 can be given appropriate heat-sensitive adhesiveness and lubricity, and has excellent heat sealability and blocking resistance.

[0043] When the heat seal layer 2 contains an acrylic resin, the content of the acrylic resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total amount of heat sealant in the heat seal layer 2. It may also be 95% by mass or more, or 99% by mass or more. When the content is within the above range, the heat sealability becomes even more sufficient.

[0044] The mass ratio of the antiblocking agent to the heat sealant [antiblocking agent / heat sealant] is preferably 0.01 to 1, more preferably 0.05 to 0.5, even more preferably 0.1 to 0.45, and particularly preferably 0.15 to 0.35. When the mass ratio is within the above range, the heat seal layer 2 can be given appropriate heat-sensitive tackiness and lubricity, and has excellent heat sealability and blocking resistance.

[0045] The coating amount (dry mass) of the heat seal layer 2 is, for example, 0.5 to 40 g / m². ２ Preferably, and more preferably, 1.0 to 30 g / m ２ More preferably 2.0 to 20 g / m ２ Particularly preferred is 3.0 to 10 g / m ２ Therefore, 3.0 to 8.0 g / m ２ That's fine.

[0046] (Top coat layer) The top coat layer 9 can improve the matching properties with the thermal head, and as a result, the color development and other properties of the thermal recording layer 7 can be further improved.

[0047] The top coat layer 9 contains at least a lubricant. As described above in the section on the heat seal layer, the lubricant contains the same components as the antiblocking agent in the heat seal layer 2. In this specification, a lubricant containing the same components may be referred to as "the same type of lubricant." Polyethylene wax is preferred as the material constituting the lubricant. Alternatively, the material constituting the lubricant may be, for example, polyolefin wax such as polypropylene wax, Fischer-Tropsch wax, fatty acids such as stearic acid, palmitic acid, arachidic acid, and behenic acid, fatty acid metal salts such as zinc stearate and magnesium stearate, and fatty acid amides such as stearate amide. The lubricant can be used alone or in combination of two or more types.

[0048] The top coat layer 9 may contain other lubricants. These other lubricants are lubricants that do not contain the same components as the antiblocking agent in the heat seal layer 2. In this specification, lubricants that do not contain the same components as described above may be referred to as "other lubricants." As these other lubricants, known lubricants can be used as appropriate, for example, hydrocarbon waxes such as paraffin, polyethylene, and polystyrene; ester waxes such as carnauba wax; oils such as silicone oil and whale oil; fatty acids such as oleic acid and stearic acid; fatty acid metal salts such as zinc stearate; fatty acid amides such as stearate amide, etc.

[0049] The average particle size of the above lubricant is not particularly limited, but is preferably 0.05 to 1 μm, more preferably 0.08 to 0.5 μm, and even more preferably 0.1 to 0.3 μm.

[0050] The melting point of the above lubricant is not particularly limited, but is preferably 90 to 150°C, more preferably 100 to 140°C, and even more preferably 105 to 130°C. When the melting point is within the above range, it melts easily when heat-sealed and solidifies easily as it cools after heat-sealing, resulting in even better heat sealability. Furthermore, unintended melting during storage is easily suppressed, resulting in even better anti-blocking properties. The above melting point can be measured by known or conventional measurement methods, and the melting point measured by the DSC (Differential Scanning Calorimeter) method can be used. In particular, it is preferable that the melting point of the above lubricant is within the above range. In addition, it is preferable that both the lubricant in the top coat layer 9 and the anti-blocking agent in the heat seal layer 2 have melting points within the above range (preferably 90 to 150°C, more preferably 100 to 140°C, and even more preferably 105 to 130°C).

[0051] The softening point of the above lubricant is not particularly limited, but is preferably 100 to 160°C, more preferably 105 to 150°C, and even more preferably 110 to 140°C. When the softening point is within the above range, it is easier to melt when heat-sealed and easier to solidify as it cools after heat-sealing, resulting in even better heat sealability. Furthermore, unintended melting during storage is easily suppressed, resulting in even better anti-blocking properties. The above softening point can be measured by known or conventional measurement methods, and the softening point measured by the environmental method (JIS K2207) can be used. In particular, it is preferable that the softening point of the above-mentioned lubricant is within the above range. In addition, it is preferable that both the lubricant in the top coat layer 9 and the anti-blocking agent in the heat seal layer 2 have softening points within the above range (preferably 100 to 160°C, more preferably 105 to 150°C, and even more preferably 110 to 140°C).

[0052] The content of the above lubricant is preferably 1 to 40% by mass, more preferably 3 to 30% by mass, even more preferably 5 to 20% by mass, and particularly preferably 8 to 15% by mass, based on 100% by mass of the total solid content of the top coat layer 9. When the content is within the above range, the top coat layer 9 can be given appropriate lubricity while achieving even more sufficient heat sealability.

[0053] The content ratio of the above-mentioned lubricant is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the total amount of lubricant in the top coat layer 9. When the above content ratio is within the above range, the top coat layer 9 can be given appropriate lubricity while achieving even more sufficient heat sealability.

[0054] The topcoat layer 9 may further contain binders, fillers, crosslinking agents, surface tension modifiers, defoamers, preservatives, etc. These materials can be used individually or in combination of two or more types.

[0055] Examples of the above-mentioned binders include known resins. Specifically, these include acrylic resins such as acrylic resins, styrene-acrylic resins, acrylic-urethane resins, acrylamide resins, and vinyl acetate-acrylic resins; maleic acid resins such as maleic acid resins, styrene-maleic acid resins, and olefin-maleic acid resins; styrene-butadiene rubber (SBR); and polyvinyl alcohol resins (PVA) such as fully saponified polyvinyl alcohol resins and partially saponified polyvinyl alcohol resins. Other examples of the above-mentioned binders include starch, casein, gelatin, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, and hydroxypropylcellulose. It is preferable that the above-mentioned binder contains an acrylic resin. The above-mentioned binder may be modified by known methods.

[0056] The content ratio of the above-mentioned binder is preferably 20 to 60% by mass, and more preferably 30 to 50% by mass, based on 100% by mass of the total solid content of the top coat layer 9.

[0057] When the topcoat layer 9 contains an acrylic resin, the content of the acrylic resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total amount of binder in the topcoat layer 9. It may also be 95% by mass or more, or 99% by mass or more. When the content is within the above range, the thermal head suitability and heat sealability will be even more sufficient.

[0058] Examples of the above-mentioned fillers include inorganic fillers such as aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum silicate, calcium carbonate, magnesium carbonate, barium sulfate, silica gel, activated clay, talc, clay, kaolin, calcined kaolin, diatomaceous earth, white carbon, silicon dioxide, silica, colloidal silica, and titanium dioxide; and organic fillers such as polymethyl methacrylate resin particles and polystyrene resin particles.

[0059] The content ratio of the above-mentioned filler is preferably 20 to 60% by mass, more preferably 30 to 50% by mass, based on 100% by mass of the total solid content of the top coat layer 9.

[0060] Examples of the above-mentioned crosslinking agent include inorganic crosslinking agents such as zirconium compounds; organic crosslinking agents such as epichlorohydrin resins and oxazoline compounds. Examples of the above-mentioned zirconium compounds include zirconium carbonate, ammonium zirconium carbonate, zirconium acetate, etc. Examples of the above-mentioned epichlorohydrin resins include polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, polyamide polyamine epichlorohydrin resin, etc. Among them, from the viewpoint of improving heat resistance by forming a crosslinked structure containing metal ions and enhancing suitability for the thermal head, the above-mentioned crosslinking agent is preferably an inorganic crosslinking agent, and more preferably a zirconium compound.

[0061] The content ratio of the above-mentioned crosslinking agent is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1 to 8% by mass, based on 100% by mass of the total solid content of the top coat layer 9.

[0062] Examples of the above-mentioned surface tension adjuster include surfactants. As the above-mentioned surfactant, known ones can be appropriately used. Examples include anionic surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfate salts; nonionic surfactants such as acetylene glycol-based surfactants and polyoxyalkylene alkyl ethers.

[0063] The coating amount (dry mass) of the top coat layer 9 is, for example, preferably 0.1 to 10 g / m ２ and more preferably 1.0 to 5.0 g / m ２ is.

[0064] (Base material) Examples of base material 5 include high-quality paper, art paper, coated paper, kraft paper, laminated paper made by laminating these paper base materials with a thermoplastic resin such as polyethylene, porous materials such as nonwoven fabrics, resin films, and synthetic paper. Examples of resins that make up the resin film and synthetic paper include polypropylene, polyethylene, polyethylene terephthalate, polystyrene, and polycarbonate. Only one type of resin may be used, or two or more types may be used. The resin film may be stretched or not. Furthermore, base material 5 may be a single layer or a multi-layer structure with the same composition or different thicknesses.

[0065] The thickness of the substrate 5 is not particularly limited, but is preferably 5 to 150 μm, and more preferably 10 to 100 μm. When the thickness is within the above range, the coating properties and support properties can be further improved.

[0066] (Thermal recording layer) The thermal recording layer 7 is a layer that develops color when heated by a thermal head or the like, and forms a recorded image. The thermal recording layer 7 preferably contains, for example, a leuco dye and a color developer. The thermal recording layer 7 may further contain other components as needed. Examples of other components include preservatives, binders, crosslinking agents, fillers, lubricants, sensitizers, surface tension modifiers, defoamers, viscosity modifiers, and preservatives.

[0067] The above leuco dyes include, for example, 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroanilinofluorane, 3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluorane, 3-(N-methyl-N-n-propyl)amino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-di Examples include ethylamino-6-methyl-7-p-toluidinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-8-methylfluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-diethylamino-7-chlorofluorane, 3-dibutylamino-6-methyl-7-bromofluorane, 3-dibutylamino-7-(o-chloroanilino)fluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3-dimethylamino-5-methyl-7-methylfluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, and crystal violet lactone. These leuco dyes can be used individually or in combination of two or more.

[0068] Examples of the above-mentioned color developers include 1,1-bis(p-hydroxyphenyl)cyclohexane, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2'-methylenebis(4-chlorophenol), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, and 4-hydroxy-4'-n -Propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 4-hydroxy-4'-allyloxydiphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, poly(4-hydroxybenzoic acid), benzyl 4-hydroxybenzoate, 2,4-bis(phenylsulfonyl)phenol, α-{4-[(4-hydroxyphenyl)sulfonyl]phenyl}-ω-hydroxypoly( Degree of polymerization n=1-7) (oxyethyleneoxyethyleneoxy-p-phenylenesulfonyl-p-phenylene)2,2-bis[(4-methyl-3-phenoxycarbonylaminophenyl)urea]diphenylsulfone, 3,5-bis(α-methylbenzyl)salicylic acid, bis[4-(n-octyloxycarbonylamino)zinc salicylate], 4,4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4-hydroxybenzenesulfonanilide, 2'-(3-phenylureido)benzenesulfonanilide, N-(2-Hyd Examples include roxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-[4-(4-{4-[4-(1-methylethoxy)phenylsulfonyl]phenoxy}butoxy)phenylsulfonyl]phenol, 4-tert-butylphenol / formaldehyde polycondensate, N-(p-toluenesulfonyl)N'-(3-p-toluenesulfonyloxyphenyl)urea, 1-phenyl-3-(4-methylphenylsulfonyl)urea, etc.These color developers can be used individually or in combination of two or more.

[0069] The melting point of the above-mentioned color developer is not particularly limited, but is preferably 80 to 200°C, more preferably 100 to 195°C, even more preferably 130 to 185°C, and may also be 140 to 180°C or 150 to 175°C.

[0070] Examples of the preservatives mentioned above include urea urethane compounds, sodium-2,2'-methylenebis(4,6-di-t-butylphenyl) phosphite, 4,4,butylidenebis(3-methyl-6-t-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, tris(2,6-dimethyl-4-t-butyl-3-hydroxybenzyl) isocyanurate, 4-(2-methylglycyloxy)-4'-benzyloxydiphenyl sulfone, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), diethylthiourea, zinc dibutyldithiocarbamate, and 4,4'-thiobis(6-t-butyl-m-cresol). The above-mentioned preservatives can be used alone or in combination of two or more.

[0071] Examples of the above-mentioned sensitizers include 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2,6-diisopropylnaphthalene, 1,2-diphenoxyethane, 1,2-diphenoxymethylbenzene, 1,2-bis(3,4-dimethylphenol)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl oxalate, p-benzylbiphenyl, m-terphenyl, diphenylsulfone, p-benzyloxybenzoate benzyl, dibenzyl terephthalate, and p-toluenesulfonamide. These sensitizers can be used individually or in combination of two or more.

[0072] The above-mentioned binder is not particularly limited and includes those similar to those exemplified in the section on topcoat layer 9. The above-mentioned crosslinking agent is not particularly limited and includes those similar to those exemplified in the section on topcoat layer 9. The above-mentioned filler is not particularly limited and includes those similar to those exemplified in the section on topcoat layer 9. The above-mentioned lubricant is not particularly limited and includes those similar to those exemplified in the section on topcoat layer 9. The above-mentioned surface tension modifier is not particularly limited and includes those similar to those exemplified in the section on topcoat layer 9. These materials can all be used individually or in combination of two or more types.

[0073] The coating amount (dry mass) of the thermal recording layer 7 is, for example, 0.3 to 10 g / m². ２ Preferably, and more preferably, 2.0 to 6.0 g / m² ２ That is the case.

[0074] (Back Coat Layer) The back coat layer 3 is provided on the surface between the substrate 5 and the heat seal layer 2. The back coat layer 3 preferably contains a binder such as a resin. The back coat layer 3 may further contain other materials as needed. Examples of other materials include crosslinking agents, surface tension modifiers, and defoaming agents. These materials can be used individually or in combination of two or more. The back coat layer 3 is not necessarily required.

[0075] The above-mentioned binder is not particularly limited and may be the same as those exemplified in the section on topcoat layer 9. From the viewpoint of further suppressing curling of the thermal recording material, the above-mentioned binder preferably contains a core-shell type resin. In this specification, "core-shell type resin" means a resin having a structure in which hydrophobic core particles are coated with a water-soluble shell polymer.

[0076] Among the above-mentioned core-shell type resins, a core-shell type resin having a carboxyl group as the water-soluble portion (core-shell type carboxyl group-containing resin) is preferred. Here, the above-mentioned core-shell type carboxyl group-containing resin is considered to contain a carboxyl group in at least the structure of the water-soluble shell polymer.

[0077] Examples of the above-mentioned core-shell type carboxyl group-containing resins include core-shell type acrylic resins such as core-shell type acrylic resins, core-shell type styrene-acrylic resins, core-shell type acrylic-urethane resins, core-shell type acryl-amide resins, and core-shell type vinyl acetate-acrylic resins; and core-shell type maleic acid resins. Core-shell type acrylic resins are preferred as the above-mentioned core-shell type carboxyl group-containing resin.

[0078] The content of the above-mentioned binder is preferably 70% by mass or more (for example, 70 to 99.9% by mass) relative to 100% by mass of the total solid content of the back coat layer 3, more preferably 80% by mass or more (for example, 80 to 99% by mass), and even more preferably 90% by mass or more (for example, 90 to 98% by mass). Furthermore, the content of the above-mentioned core-shell type resin is preferably within the above range relative to 100% by mass of the total solid content of the back coat layer 3.

[0079] The back coat layer 3 preferably contains a crosslinking agent. The crosslinking agent is not particularly limited and may be the same as those exemplified in the section on the top coat layer 9. The crosslinking agent is preferably an epichlorohydrin resin, and more preferably a polyamide epichlorohydrin resin.

[0080] The content ratio of the above crosslinking agent is preferably 30% by mass or less (for example, 0.1 to 30% by mass), more preferably 20% by mass or less (for example, 1 to 20% by mass), and even more preferably 10% by mass or less (for example, 2 to 10% by mass), based on 100% by mass of the total solid content of the back coat layer 3.

[0081] The surface tension modifier mentioned above is not particularly limited, but examples include those similar to those exemplified in the section on topcoat layer 9.

[0082] The coating amount (dry mass) of the back coat layer 3 is, for example, 0.3 to 10 g / m². ２ Preferably, and more preferably, 0.5 to 5.0 g / m ２ That is the case.

[0083] (Anchor Coat Layer) The anchor coat layer 4 is a layer intended to improve the adhesion between the substrate 5 and the heat seal layer 2 and / or the back coat layer 3. Examples of materials included in the anchor coat layer 4 include binders such as resins and known anchoring agents. The anchor coat layer 4 may further include other materials as needed. Examples of other materials include surface tension modifiers. The binder is not particularly limited and is the same as those exemplified in the section on the top coat layer 9. The surface tension modifier is not particularly limited and is the same as those exemplified in the section on the top coat layer 9. These materials can all be used individually or in combination of two or more. The anchor coat layer 4 is not necessarily required.

[0084] The coating amount (dry mass) of the anchor coat layer 4 is preferably, for example, 0.1 to 10 g / m². ２ More preferably, 0.2 to 5.0 g / m ２ Therefore, if the amount of coating is within the above range, it is easier to achieve better adhesion between the substrate 5 and the heat seal layer 2 and / or back coat layer 3.

[0085] (Anchor layer) The anchor layer 6a is a layer intended to improve the adhesion between the substrate 5 and the thermal recording layer 7. Preferably, the anchor layer 6a contains a binder such as a resin. The anchor layer 6a may further contain other materials as needed. Examples of other materials include surface tension modifiers, defoamers, viscosity modifiers, etc. The binder is not particularly limited and is the same as those exemplified in the section on topcoat layer 9. The surface tension modifier is not particularly limited and is the same as those exemplified in the section on topcoat layer 9. These materials can all be used individually or in combination of two or more. Note that the anchor layer 6a is not necessarily required.

[0086] The coating amount (dry mass) of the anchor layer 6a is preferably, for example, 0.1 to 10 g / m². ２ More preferably, 0.2 to 5.0 g / m ２Therefore, if the amount of coating is within the above range, it is easier to achieve better adhesion between the substrate 5 and the thermal recording layer 7.

[0087] (Undercoat layer) The undercoat layer 6b is a heat insulating layer that can improve the color development efficiency of the thermal recording body 1. The undercoat layer 6b preferably contains, for example, a binder and a filler. The undercoat layer 6b may further contain other components as needed. Examples of other components include lubricants, surface tension modifiers, defoamers, viscosity modifiers, and preservatives. The binder is not particularly limited and is the same as those exemplified in the section on topcoat layer 9. The lubricant is not particularly limited and is the same as those exemplified in the section on topcoat layer 9. The surface tension modifier is not particularly limited and is the same as those exemplified in the section on topcoat layer 9. These materials can all be used individually or in combination of two or more. The undercoat layer 6b is not necessarily required.

[0088] The above-mentioned filler is not particularly limited and may be the same as those exemplified in the section on topcoat layer 9. Furthermore, from the viewpoint of improving heat insulation, it is preferable that the filler contains hollow particles. The above-mentioned filler can be used alone or in combination of two or more types.

[0089] The coating amount (dry mass) of the undercoat layer 6b is preferably, for example, 0.1 to 10 g / m². ２ More preferably, 0.2 to 5.0 g / m ２ Therefore, if the amount of coating is within the above range, the thermal insulation of the undercoat layer 6b becomes more sufficient, and the color development efficiency of the thermal recording element 1 becomes more appropriate.

[0090] (Intermediate layer) The intermediate layer 8 prevents water, oil, etc. from penetrating the thermal recording layer 7 and can improve the print retention (water resistance, oil resistance, etc.) of the thermal recording body 1. The intermediate layer 8 preferably contains a binder such as a resin. The intermediate layer 8 may further contain other components as needed. Examples of other components include crosslinking agents, surface tension modifiers, and defoaming agents. The surface tension modifier is not particularly limited and is the same as those exemplified in the section on the top coat layer 9. These materials can be used individually or in combination of two or more. The intermediate layer 8 is not necessarily required.

[0091] The above-mentioned binder is not particularly limited, and examples include those similar to those exemplified in the sections on the top coat layer 9 and the back coat layer 3. Furthermore, the binder preferably contains a core-shell type resin, and more preferably contains a core-shell type acrylic resin, from the viewpoint of further improving print retention and further suppressing curling of the thermal recording material. The above-mentioned binder can be used alone or in combination of two or more types.

[0092] The content of the above-mentioned binder is preferably 60% by mass or more (for example, 60 to 99.9% by mass) relative to 100% by mass of the total solid content of the intermediate layer 8, more preferably 70% by mass or more (for example, 70 to 99% by mass), and even more preferably 80% by mass or more (for example, 80 to 98% by mass). Furthermore, the content of the above-mentioned core-shell type resin is preferably within the above range relative to 100% by mass of the total solid content of the intermediate layer 8.

[0093] The intermediate layer 8 preferably contains a crosslinking agent. The crosslinking agent is not particularly limited and may be the same as those exemplified in the section on the topcoat layer 9. The crosslinking agent is preferably an epichlorohydrin resin, and more preferably a polyamide epichlorohydrin resin.

[0094] The content ratio of the above crosslinking agent is preferably 30% by mass or less (for example, 0.1 to 30% by mass), more preferably 25% by mass or less (for example, 1 to 25% by mass), and even more preferably 20% by mass or less (for example, 2 to 20% by mass), based on 100% by mass of the total solid content of the intermediate layer 8.

[0095] The coating amount (dry mass) of the intermediate layer 8 is, for example, 0.1 to 10 g / m². ２ Preferably, and more preferably, 1.0 to 5.0 g / m ２ Therefore, if the amount of coating is within the above range, the barrier properties of the resulting thermal recording body 1 can be made more appropriate.

[0096] The thermal recording material of the present invention can be preferably used, for example, as a band label of the type in which the band is wrapped around an article, and then the heat seal layer and the top coat layer are heat-sealed to bundle the article. Hereinafter, a band label using the thermal recording material of the present invention may be referred to as "the band label of the present invention."

[0097] (Band Label) An example of a band label, which is a preferred embodiment of the thermal recording body of the present invention, will be described using Figures 3 and 4. The band label 10 shown in Figure 3 is a cylindrical body in which a sealed portion 11 is formed by overlapping the inner surface of one end of the thermal recording body 1, which is formed in a rectangular shape, with the inner surface of the other end overlapping the outer surface of one end of the thermal recording body 1, and the outer surface of the one end and the inner surface of the other end being joined by heat sealing. With the band label of the present invention, heat sealing can be performed between the top coat layer 9 and the heat seal layer 2, so that it is possible to bind by banding over any circumference. In this case, it is preferable that the top coat layer 9 is located on the outside and the heat seal layer 2 is located on the inside. With this embodiment, thermal recording can be performed more easily at any position on the outer surface after banding. Note that if the thermal color development temperature of the thermal recording body 1 is lower than the heat sealing temperature, the areas heated during heat sealing (e.g., the sealed portion 11) can develop color, but the areas that are not heated (non-sealed areas) will not develop color. Therefore, according to the band label of the present invention, thermal recording can be applied to any position on the non-sealed portion at any stage before or after banding.

[0098] Figure 4 is an enlarged view of the A-A' cross-section in Figure 3, that is, the main part near the seal portion 11 of the band label 10. Specifically, in the band label 10, the top coat layer 9 formed on the outer surface of one end of the thermal recording body 1 and the heat seal layer 2 formed on the inner surface of the other end of the thermal recording body 1 are joined by heat sealing. Note that the layer configuration of the band label in Figures 3 and 4 is not limited to the layer configuration shown in Figures 3 and 4 (i.e., the layer configuration of the thermal recording body of the present invention shown in Figure 2), but may be other layer configurations (for example, the layer configuration of the thermal recording body of the present invention shown in Figure 1).

[0099] The width of the sealing portion is not particularly limited, but for example, it is preferably 0.1 to 50 mm, may be 0.3 to 25 mm, or 0.5 to 10 mm.

[0100] [Method for Manufacturing a Thermal Recording Body] The thermal recording body of the present invention can be manufactured by known or conventional methods. Regarding the method for manufacturing the thermal recording body of the present invention, a method for manufacturing the thermal recording body 1 shown in Figure 1 will be specifically described. Note that the manufacturing method described below is one embodiment, and the method for manufacturing the thermal recording body of the present invention is not limited to the above method.

[0101] (Preparation Step) In the above preparation step, coating solutions for forming each layer are prepared. The method for preparing the above coating solutions is not particularly limited. For example, each layer can be prepared by pre-dispersing all the materials in the same solvent. Alternatively, the coating solution may be prepared by preparing one material that reacts with the other (e.g., a dye) and another material (e.g., a color developer) as separate dispersions and then mixing them. In this case, the other materials may be added to either the dispersion containing the first material or the dispersion containing the other materials, or they may be added to both. Examples of methods for preparing the above coating solutions include stirring, ultrasonic treatment, crushing using a ball mill, bead mill, sand mill, high-pressure homogenizer, etc. These methods can be used individually or in combination of two or more.

[0102] (Coating Process) In the above coating process, the coating liquid is applied to form a layer. The method of applying the coating liquid is not particularly limited, and examples include applying it directly to the surface to be laminated (e.g., the substrate), or applying it to a release liner and then transferring it to the surface. Examples of coating methods include air knife coating, barrier blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, and gravure coating. Hand coating using a wire bar is also acceptable. These methods can be used individually or in combination of two or more.

[0103] (Drying process) In the above drying process, the coated layer is dried to stabilize it. The method for drying the coating liquid is not particularly limited and includes, for example, heat drying, room temperature drying, and vacuum drying. These methods can be used individually or in combination of two or more.

[0104] As described above, an anchor coat layer 4, a back coat layer 3, and a heat seal layer 2 are sequentially formed on one surface of the substrate 5. Then, an anchor layer 6, a thermal recording layer 7, an intermediate layer 8, and a top coat layer 9 are sequentially formed on the other surface of the substrate 5. In this way, a thermal recording body 1 can be manufactured. As described above, the heat seal layer 2 of the present invention may be a coated layer formed by coating, or it may be formed by other known methods. Among these, it is preferable that the heat seal layer 2 of the present invention be a coated layer. When the heat seal layer 2 is a coated layer, it can be formed from paint, the coated area can be patterned, and the coating method (flexographic coating method, bar coating method, gravure coating method, etc.) can be selected, thus greatly improving the design freedom of the heat seal layer 2. In addition, it is easier to make the layer thickness thinner, which makes it easier to make the flexibility, ease of cutting, and printer runability of the thermal recording body 1 even more sufficient. Furthermore, if the heat-seal layer is a laminate layer, a heat lamination process is required, and the thermal recording layer must be designed so that it does not develop color due to heat during the manufacturing process. However, if it is a coated layer, the heat lamination process is not essential, which provides greater design flexibility for the thermal recording layer 7. Also, while forming the heat-seal layer with a heat-sealable film can hinder recycling, using a coated layer for the heat-seal layer 2 improves recyclability.

[0105] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. Unless otherwise specified, the mass values ​​described in the examples refer to the mass of each component in its dry state.

[0106] Example 1 (Preparation of a thermal recording material) <Anchor Coat Layer> An aqueous acrylic emulsion (solid content concentration 16% by mass) was coated onto one surface of a resin film (material OPP, thickness 40 μm) which was the base material, by a conventional method and dried, resulting in a coating amount of 1.0 g / m². ２ An anchor coat layer of (dry mass) was formed. In this specification, aqueous acrylic emulsion refers to a dispersion (emulsion) of an acrylic resin containing water as a solvent.

[0107] <Backcoat Layer> A coating solution for the backcoat layer (solid content concentration 14% by mass) containing 94% by mass of core-shell type acrylic resin, 6% by mass of polyamide epichlorohydrin resin, and water was prepared by conventional means. The above backcoat coating solution was applied to the surface of the anchor coat layer by conventional means and dried, resulting in a coating amount of 2.3 g / m². ２ A backcoat layer of (dry mass) was formed.

[0108] <Heat Seal Layer> A heat seal layer coating solution (solid content concentration 40% by mass) containing 90% by mass of heat sealant A, 10% by mass of antiblocking agent A, and water was prepared by conventional means. The above heat seal layer coating solution was applied to the surface of the back coat layer by conventional means and dried, resulting in a coating amount of 5.0 g / m². ２ A heat-seal layer of (dry mass) was formed. The thickness of this heat-seal layer was approximately 5 μm.

[0109] <Anchor layer> A water-based acrylic emulsion (solid content concentration 16% by mass) is applied to the other surface of the above substrate by a conventional method and dried, resulting in a coating amount of 1.0 g / m². ２ An anchor layer of (dry mass) was formed.

[0110] <Thermal Recording Layer> A thermal recording layer coating solution (solid content concentration 23% by mass) was prepared by conventional means, containing 15% by mass of leuco dye, 40% by mass of a color developer (melting point: 157°C), 11% by mass of acrylic resin, 30% by mass of styrene-butadiene latex, 3% by mass of polyethylene wax, 1% by mass of epichlorohydrin resin, and water. The above thermal recording layer coating solution was applied to the surface of the anchor layer by conventional means and dried, resulting in a coating amount of 4.5 g / m². ２ A thermal recording layer of (dry mass) was formed.

[0111] <Intermediate Layer> An intermediate layer coating solution (solid content concentration 19% by mass) containing 85% by mass of core-shell type acrylic resin, 15% by mass of polyamide epichlorohydrin resin, and water was prepared by conventional means. The above intermediate layer coating solution was applied to the surface of the above thermal recording layer by conventional means and dried to achieve a coating amount of 2.0 g / m². ２An intermediate layer of (dry mass) was formed.

[0112] <Topcoat Layer> A coating solution for the topcoat layer (solid content concentration 15% by mass) containing 40% by mass of acrylic resin, 15% by mass of lubricant A, 40% by mass of colloidal silica, 5% by mass of zirconium carbonate, and water was prepared by conventional means. The above topcoat coating solution was applied to the surface of the above intermediate layer by conventional means and dried, resulting in a coating amount of 1.5 g / m². ２ A topcoat layer of (dry mass) was formed. In this way, a thermal recording body of Example 1 having a laminated structure of [heat seal layer / backcoat layer / anchor coat layer / substrate / anchor layer / thermal recording layer / intermediate layer / topcoat layer] was produced.

[0113] Examples 2-16 and Comparative Examples 1-13: A thermal recording body was prepared in the same manner as in Example 1, except that the composition of the heat-seal layer coating liquid was changed as shown in Tables 1-2. The values ​​for each material in Tables 1-2 represent the mass when dry, excluding water, and the unit is "mass%".

[0114] Example 17 In the above-described examples, a resin film was used as the base material, but in Example 17, a paper base material was used to create a thermal recording body.

[0115] (Preparation of thermal recording material) <Heat seal layer> A coating solution for the heat seal layer (solid content concentration 40% by mass) containing 80% by mass of heat sealant A, 20% by mass of antiblocking agent C, and water was prepared by a conventional method. The above coating solution for the heat seal layer was applied to a base material of fine paper (basis weight 67 g / m²). ２ By applying a coating to one surface of the material using a conventional method and drying it, the coating amount is 5.0 g / m². ２ A heat-seal layer of (dry mass) was formed. The thickness of this heat-seal layer was approximately 5 μm.

[0116] <Undercoat Layer> An undercoat coating solution (solid content concentration 25% by mass) containing 75% by mass of hollow particles, 20% by mass of styrene-butadiene latex, 5% by mass of zinc stearate, and water was prepared by conventional means. The above undercoat coating solution was applied to the other surface of the above substrate by conventional means and dried, resulting in a coating amount of 3.0 g / m². ２ An undercoat layer of (dry mass) was formed.

[0117] <Thermal Recording Layer> A thermal recording layer coating solution (solid content concentration 30% by mass) was prepared by conventional means, containing 23% by mass of leuco dye, 34% by mass of a color developer (melting point: 157°C), 10% by mass of polyvinyl alcohol, 10% by mass of styrene butadiene latex, 3% by mass of zinc stearate, 20% by mass of calcium carbonate, and water. The above thermal recording layer coating solution was applied to the surface of the above undercoat layer by conventional means and dried, resulting in a coating amount of 4.0 g / m². ２ A thermal recording layer of (dry mass) was formed.

[0118] <Intermediate Layer> An intermediate layer coating solution (solid content concentration 20% by mass) containing 94% by mass of acrylic resin, 6% by mass of polyamide epichlorohydrin resin, and water was prepared by conventional means. The above intermediate layer coating solution was applied to the surface of the above thermal recording layer by conventional means and dried to achieve a coating amount of 1.6 g / m². ２ An intermediate layer of (dry mass) was formed.

[0119] <Topcoat Layer> A coating solution for the topcoat layer (solid content concentration 23% by mass) containing 45% by mass of acrylic resin, 12% by mass of lubricant B, 3% by mass of zirconium compound, 40% by mass of calcium carbonate, and water was prepared by conventional means. The above topcoat coating solution was applied to the surface of the above intermediate layer by conventional means and dried, resulting in a coating amount of 1.0 g / m². ２ A topcoat layer of (dry mass) was formed. In this way, a thermal recording body of Example 17 having a laminated structure of [heat seal layer / substrate / undercoat layer / thermal recording layer / intermediate layer / topcoat layer] was produced.

[0120] Comparative Example 14 A thermal recording body was prepared in the same manner as in Example 17, except that the composition of the coating liquid for the heat seal layer was changed as shown in Table 2.

[0121] [Evaluation] The thermal recording materials prepared in the examples and comparative examples were evaluated as follows. The results are shown in Tables 1 to 3.

[0122] (1) Peel strength after heat sealing The heat-sealed layer was placed on top of the topcoat layer and heat-sealed under the following conditions. The peel strength was measured when the heat-sealed layer and the topcoat layer were peeled in a T-shape at a temperature of 23°C, humidity of 50%, and peel speed of 300 mm / min. This peel strength is sometimes referred to as the peel strength after heat sealing. A Tensilon type universal tester (product name "RTC-1210A", manufactured by Orientec Co., Ltd.) was used to measure the above peel strength.

[0123] Heat sealing conditions and equipment used: Thermal gradient testing machine (manufactured by Toyo Seiki Co., Ltd.), pressure: 1 kg / cm² ２ Heat sealing time: 1 second, Heat sealing temperature: 150°C

[0124] Furthermore, to evaluate the effect of adding other materials (antiblocking agents, lubricants) on peel strength, the maintenance rate of peel strength related to heat sealability was determined using the following procedure. First, a heat seal layer formed from only the heat sealant was used as the blank heat seal layer, and the peel strength at this time was X Ｂ (100%) was used (for example, Comparative Example 1). Then, the heat sealant contained in the blank heat seal layer and the heat seal layer formed from the above other materials were used as the sample heat seal layer, and the peel strength at this time was set to X Ｓ This was done (for example, Examples 1-8 and Comparative Examples 2-5). Then, the retention rate of peel strength after heat sealing was calculated using the following formula: Retention rate of peel strength [%] = X Ｓ / X Ｂ ×100

[0125] (2) Peel strength after blocking test: The heat-sealed layer was placed on top of the top coat layer and measured at 2.0 kg / cm². ２The sample was subjected to a load and left undisturbed for 24 hours in an environment of 40°C and 80% humidity. Subsequently, the peel strength was measured when the heat seal layer and top coat layer were peeled in a T-shape under conditions of 23°C, 50% humidity, and a peeling speed of 300 mm / min. This peel strength is sometimes referred to as the peel strength after the blocking test. The same testing machine as in evaluation (1) above was used to measure the peel strength. Furthermore, the retention rate of the peel strength was calculated using the same procedure as in evaluation (1) above, and this was referred to as the retention rate of the peel strength after the blocking test.

[0126] (3) Condition of the delamination interface after the blocking test The condition of the delamination interface after T-shaped delamination as evaluated in (2) above was visually observed. The blocking resistance was then evaluated based on the following evaluation criteria. <Evaluation Criteria> ◎: No interface change was observed. ○: Some interface change was observed. △: Many interface changes were observed. ×: Some interface fracture was observed.

[0127] The various raw materials used in the above examples are as follows: <Heat sealants> Heat sealant A: Acrylic resin, glass transition temperature: -8°C Heat sealant B: Acrylic resin (styrene-free type), glass transition temperature: -17°C Heat sealant C: Acrylic resin (acrylic-urethane resin), glass transition temperature: -20°C Heat sealant D: Acrylic resin (styrene-free type), glass transition temperature: -11°C Heat sealant E: Acrylic resin, glass transition temperature: -27°C Heat sealant F: Acrylic resin, glass transition temperature: -4°C Heat sealant G: Acrylic resin, glass transition temperature: 9°C Heat sealant H: Acrylic resin, glass transition temperature: 21°C <Antiblocking agents> Antiblocking agent A: Low molecular weight polyethylene wax (spherical particles), average particle size 6 μm, softening point 113°C, melting point 108°C, hardness by penetrating method 10 Antiblocking agent B: Low molecular weight polyethylene wax (spherical particles), average particle size 3 μm, softening point 132°C, melting point 127°C, hardness by penetration test <1 Antiblocking agent C: Low molecular weight polyethylene wax (spherical particles), average particle size 6 μm, softening point 132°C, melting point 127°C, hardness by penetration test <1 Antiblocking agent D: Low molecular weight polyethylene wax (spherical particles), average particle size 9.5 μm, softening point 132°C, melting point 127°C, hardness by penetration test <1 Antiblocking agent E: Polymethyl methacrylate (PMMA) (spherical particles), average particle size 5 μm, glass transition temperature 113°C <Lubricants> Lubricant A: Low molecular weight polyethylene wax, average particle size 0.2 μm (microtrac method), softening point 110°C, melting point 109°C Lubricant B: Polyethylene wax, average particle size 1.3 μm (microtrac method), softening point 110°C, melting point 110°C

[0128]

[0129] As shown in Table 1, the thermal recording material of the examples had higher peel strength after heat sealing and better heat seal strength than the case where the heat seal layer was formed using only the heat sealant (Comparative Example 1). Therefore, the thermal recording material of the examples was evaluated as having high adhesion when the top coat layer and the heat seal layer were heat sealed, and excellent heat sealability. On the other hand, when an antiblocking agent that did not contain the same components as the lubricant in the top coat layer was used (Comparative Example 2), or when lubricant A was used which was composed of the same components as the lubricant in the top coat layer but had an average particle size significantly smaller than the thickness of the heat seal layer (Comparative Examples 3-5), the peel strength was about the same as Comparative Example 1 which used only the heat sealant, and was evaluated as having poor heat sealability. Here, the antiblocking agents used in Examples 1-8 and the lubricants used in Comparative Examples 3-5 are both particulate materials composed of polyethylene wax, and have common components. However, the antiblocking agents of the examples had relatively large average particle sizes, and the ratio of the average particle size of the antiblocking agent to the thickness of the heat seal layer was 0.5 or more in all cases. In this case, the antiblocking agent is thought to be partially exposed from the heat seal layer and make point contact with the top coat layer. Furthermore, since the antiblocking agent contains the same type of component as the lubricant in the top coat layer, it has a high affinity, and adhesion is created through the same type of component. Therefore, it is presumed that the adhesion due to the affinity, in addition to the adhesion force provided by the heat seal agent, contributed to the improvement in heat seal strength. On the other hand, the lubricant in the comparative example had a small average particle size, and the above ratio was approximately 0.04. In this case, the lubricant is thought to be almost not exposed from the heat seal layer, and therefore, the effect of improving heat seal strength due to the same type of component as in the example was not obtained.

[0130] Furthermore, a comparison between Example 1 and Example 5 revealed a tendency for antiblocking agents with lower penetration hardness (i.e., harder) to exhibit higher heat seal strength. This is presumed to be because, while an antiblocking agent that is too soft may be compressed during heat sealing and spread thinly across the surface of the heat seal layer, potentially hindering the action of the heat sealant, an antiblocking agent that is moderately hard does not spread too thinly during heat sealing, thus allowing for a more efficient compatibility with the action of the heat sealant.

[0131]

[0132] As shown in Table 2, even when the heat sealant was changed from A to any of B to H, the thermal recording bodies of the examples had higher peel strength after heat sealing and better heat seal strength than the thermal recording bodies of the comparative examples in which the heat seal layer was formed from only the heat sealant, and were evaluated as having excellent heat sealability (Examples 9 to 16). Furthermore, when the substrate was changed from a resin film to a paper substrate (Example 17), the paper substrate tore during the peel strength measurement, making proper measurement difficult, but no breakage of the heat-sealed portion was observed, and it was evaluated as having sufficient heat sealability.

[0133]

[0134] As shown in Table 3, the thermal recording materials of the examples exhibited lower peel strength after the blocking test and better blocking resistance than the thermal recording materials of the comparative examples in which the heat seal layer was formed from only the heat sealant (Examples 1, 6, 8, 13-14, 16). Furthermore, when a paper substrate was used as the base material (Example 17), the top coat layer and heat seal layer peeled off very easily and were unsuitable for measuring peel strength. Therefore, the blocking resistance was improved compared to Comparative Example 14 and was evaluated as having excellent blocking resistance. For this reason, the thermal recording materials of the examples were evaluated as having excellent blocking resistance, as blocking was suppressed even when the top coat layer and heat seal layer were stored in a stacked state.

[0135] In summary, the configuration of the present invention and its variations are described below. [Note 1] A thermal recording body comprising a heat seal layer containing an antiblocking agent and a top coat layer containing a lubricant, wherein the thermal recording body has the heat seal layer on one surface and the top coat layer on the other surface, the antiblocking agent contains the same components as the lubricant, and the ratio of the average particle diameter of the antiblocking agent to the thickness of the heat seal layer [average particle diameter of the antiblocking agent / thickness of the heat seal layer] is 0.5 or more. [Note 2] The thermal recording body according to Note 1, wherein both the lubricant and the antiblocking agent have a melting point of 90 to 150°C. [Note 3] The thermal recording body according to Note 1 or 2, wherein both the lubricant and the antiblocking agent have a softening point of 100 to 160°C. [Note 4] The thermal recording body according to any one of Notes 1 to 3, wherein both the lubricant and the antiblocking agent contain polyethylene wax. [Note 5] The antiblocking agent is partially exposed from the heat seal layer, as described in any one of Notes 1 to 4. [Note 6] The penetrability hardness of the antiblocking agent is 5 or less, as described in any one of Notes 1 to 5. [Note 7] The heat seal layer contains an acrylic resin, as described in any one of Notes 1 to 6. [Note 8] The glass transition temperature of the acrylic resin is 40°C or less, as described in Note 7. [Note 9] The heat seal layer contains a heat sealant, and the mass ratio of the antiblocking agent content to the heat sealant content [antiblocking agent / heat sealant] is 0.01 to 1, as described in any one of Notes 1 to 8. [Note 10] The top coat layer contains an acrylic resin, as described in any one of Notes 1 to 9. [Note 11] The heat-seal layer is a coating layer formed by coating, as described in any one of Notes 1 to 10. [Note 12] The heat-seal layer, a substrate, a heat-seal layer containing a leuco dye and a color developer, and the top coat layer are provided in this order, as described in any one of Notes 1 to 11.

[0136] 1. Thermal recording element 2. Heat seal layer 3. Back coat layer 4. Anchor coat layer 5. Substrate 6a. Anchor layer 6b. Undercoat layer 7. Thermal recording layer 8. Intermediate layer 9. Top coat layer 10. Strip label 11. Seal portion

Claims

1. A thermal recording body comprising a heat seal layer containing an antiblocking agent and a top coat layer containing a lubricant, wherein the thermal recording body has the heat seal layer on one surface and the top coat layer on the other surface, the antiblocking agent contains the same components as the lubricant, and the ratio of the average particle diameter of the antiblocking agent to the thickness of the heat seal layer [average particle diameter of the antiblocking agent / thickness of the heat seal layer] is 0.5 or more.

2. The thermal recording body according to claim 1, wherein both the lubricant and the antiblocking agent have a melting point of 90 to 150°C.

3. The thermal recording body according to claim 1 or 2, wherein the antiblocking agent is partially exposed from the heat seal layer.

4. The thermal recording body according to claim 1 or 2, wherein the penetration hardness of the antiblocking agent is 5 or less.

5. The heat-seal layer comprises an acrylic resin, as described in claim 1 or 2.

6. The thermal recording body according to claim 5, wherein the glass transition temperature of the acrylic resin is 40°C or lower.

7. The heat-seal layer contains a heat-sealing agent, and the mass ratio of the anti-blocking agent content to the heat-sealing agent content [anti-blocking agent / heat-sealing agent] is 0.01 to 1, as described in claim 1 or 2.

8. The heat-seal layer is a coated layer formed by coating, according to claim 1 or 2.

9. The thermal recording body according to claim 1 or 2, comprising the heat seal layer, a substrate, a thermal recording layer containing a leuco dye and a color developer, and the top coat layer in this order.

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