JP2023178811A - thermal transfer sheet - Google Patents

Abstract

To provide a thermal transfer sheet having a protective layer excellent in scratch resistance and foil cutting characteristic.SOLUTION: There is provided a thermal transfer sheet obtained by sequentially laminating a first adhesion layer, a protective layer, an adhesion enhancing layer, and a second adhesion layer on a base material, the base material being separable from the first adhesion layer. The base material is a film made of a crystalline resin. The first adhesion layer is formed of an amorphous resin having a glass transition point of less than or equal to 50°C. The protective layer contains a crosslinked product generated from an acrylic polyol and an isocyanate-based compound. The adhesion enhancing layer contains a heat-denatured product of a vinyl-based compound.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thermal transfer sheet that transfers and forms a protective layer on the surface of a recorded matter.

In recent years, thermal transfer sheets have been developed that impart scratch resistance to the recorded surface by transferring a transparent protective layer onto the surface of the recorded matter.

For example, Patent Document 1 discloses a thermal transfer sheet in which a protective layer and a surface layer are laminated on a base material. The surface layer functions as an adhesive layer, and by adhering it to the surface of the recorded object (also called the transfer target) and peeling off the protective layer and surface layer from the base material, it is possible to create a recorded object whose surface is covered with the protective layer. can be manufactured. In addition, the protective layer is formed of a polymer containing polymeric components such as (meth)acrylic acid and carboxyalkyl (meth)acrylate, and by making the thickness 10 μm or less, it is possible to remove the protective layer from the base material. Ensures excellent foil cutting properties.

Japanese Patent Application Publication No. 2018-167567

However, the protective layer of Patent Document 1 was thin and had insufficient scratch resistance. Scratch resistance can be improved by making the protective layer thicker, but if the protective layer is thick, when separating the recorded matter covered with the protective layer from the adhesive between the transfer sheet and the transferred object, the protective layer will be damaged. In some cases, the foil could not be cut neatly along the edges of the body, resulting in poor foil cutting performance.

In order to solve the above problem, a thermal transfer sheet having the following configuration is used.

In a thermal transfer sheet in which a first adhesive layer, a protective layer, an adhesion reinforcing layer, and a second adhesive layer are sequentially laminated on a base material, and the base material is separable from the first adhesive layer, the base material is crystalline. The film is made of resin, the first adhesive layer is made of an acrylic resin having a glass transition point (Tg) of 50°C or less, and the protective layer is made of a crosslinked resin made of an acrylic polyol and an isocyanate compound. The adhesive reinforcing layer contains a thermally modified vinyl compound.

According to the present invention, a thermal transfer sheet having a protective layer with excellent scratch resistance and foil tearability can be provided.

FIG. 1 is a cross-sectional view of a thermal transfer sheet of the present invention. FIG. 3 is an explanatory diagram for explaining the function of the first adhesive layer. FIG. 3 is a top view of a recorded matter in which trailing occurs, viewed from the transfer target side. FIG. 3 is a comparison diagram showing changes in the adhesion-strengthening layer before and after heating. FIG. 2 is an explanatory diagram for explaining a method for manufacturing a recorded matter. It is an explanatory view for explaining volume change of resin with respect to temperature.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[Thermal transfer sheet]
As shown in FIG. 1, the thermal transfer sheet 10 of the present invention has a first adhesive layer 50, a protective layer 40, an adhesive reinforcement layer 30, and a second adhesive layer 20 laminated on a base material 60. As shown in FIG. 2, the thermal transfer sheet 10 is made by bringing the second adhesive layer 20 into contact with the transfer target 80, and covering the first adhesive layer 50, the protective layer 40, the adhesive reinforcing layer 30, and the second adhesive layer 20. By laminating (hereinafter also referred to as transfer) onto the transfer body 80 and then peeling off the base material 60, a recorded material 100 with good foil tearability can be manufactured. Here, foil tearability refers to the ability to strengthen the adhesion between the first adhesive layer 50, the protective layer 40, and This refers to the ease with which the layer 30 and the second adhesive layer 20 are separated when they are peeled off along the edge of the transfer target 80. If the foil cuttability is poor, burrs 70 and trailing 71 occur on the cut surface from the first adhesive layer 50 to the second adhesive layer 20, as shown in FIG. Trailing is a phenomenon that occurs on the downstream side when the recorded material 100 is cut off from one end, and the laminate from the first adhesive layer 50 to the second adhesive layer 20 is greatly separated from the edge of the transfer object 80. It means to cut protrudingly.

[Base material]
The base material 60 used in the present invention plays a role of suppressing curling of the thermal transfer sheet 10 and improving transportability, and at the same time functions as a separator that can be peeled off after transfer.

The material constituting the base material 60 may be appropriately selected depending on the use of the thermal transfer sheet 10. However, since it is heated during transfer, it is preferable to use a resin film in consideration of heat resistance, dimensional stability, ease of processing, etc. The thickness of the base material is preferably 12 μm or more and 50 μm or less, considering that the first adhesive layer and the protective layer are coated and laminated, and that it is heated during transfer. By setting the thickness to 12 μm or more, the effect of curling during coating can be reduced, and by setting the thickness to 50 μm or less, it is possible to increase the thermal conductivity to the second adhesive layer during transfer.

Examples of resin films include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyvinyl fluoride, polyvinylidene fluoride, and polyvinyl fluoride. Polyfluorinated ethylene resins such as tetrafluoroethylene and ethylene-tetrafluoroethylene copolymers; polyamide resins such as nylon 6 and nylon 6,6; vinyl chloride/vinyl acetate copolymers, ethylene/vinyl acetate copolymers Vinyl polymer resins such as coalescence, ethylene/vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; Cellulose resins such as cellulose triacetate and cellophane; Acrylics such as polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate Examples include films made of other synthetic resins such as polyimide and the like. Among them, films made of crystalline resins with melting points (Tm) of 100°C or higher, such as polyester resins, polyolefin resins, and polyamide resins, are relatively inexpensive and easily available, and have excellent heat resistance and dimensional stability. It is preferable because These may be used alone, or two or more types may be used in combination or in a layered manner.

In addition, fillers such as silica, alumina, and graphite are added to the resin film in order to increase thermal conductivity during transfer, and a slip layer is added to the back surface of the film to improve transportability. An ameliorating auxiliary layer may also be provided.

[First adhesive layer]
The thermal transfer sheet 10 of the present invention includes a first adhesive layer 50 between a protective layer 40 and a base material 60, which will be described later.

The first adhesive layer 50 is adhered to both the protective layer 40 and the base material 60, and as shown in FIG. When the recorded matter 100 is cut off, it is peeled off from the base material 60 and remains on the outermost surface of the recorded matter 100. That is, the first adhesive layer 50 has a different function from a general release layer that is provided on a base material and remains on the base material after peeling.

The material constituting the first adhesive layer 50 must be amorphous because it can be adhered to both the base material 60 and the protective layer 40, and it must also have high transparency in order to remain on the outermost surface of the recorded material 100. It is preferable to use a polyacrylic resin. For example, polymethacrylate, styrene-acrylic copolymer, polyethylene acrylic resin, acrylic ester resin, copolymer of acrylic ester and vinyl compound, etc. can be used. Among these, a copolymer of an acrylic acid ester and a vinyl compound is preferred, and in particular, an acrylic polyol having a hydroxyl group in the molecule is the same kind of material as the protective layer 40 described later, and is preferred because it has good adhesion with the protective layer. It can be used preferably.

Moreover, it is preferable that the acrylic resin used for the first adhesive layer 50 has a Tg of 30° C. or more and 50° C. or less. If Tg is 30° C. or higher, even if the first adhesive layer 50 is present on the outermost surface of the recorded material 100, it will not become sticky. Further, by setting Tg to 50° C. or less, adhesiveness with the base material 60 can be ensured. Note that as long as the Tg is within the above range, two or more types of acrylic resins having different Tg may be used in combination.

The average thickness of the first adhesive layer 50 is preferably 0.3 μm or more and less than 1 μm. If the average thickness of the first adhesive layer 50 is 0.3 μm or more, the adhesion with the base material 60 and the protective layer 40 will be good, and the foil tearability will be improved. Furthermore, by making the average thickness of the first adhesive layer 50 less than 1 μm, scratches become less noticeable and scratch resistance becomes better.

The adhesive strength between the first adhesive layer 50 and the base material 60 is preferably 10 N/25 mm or more and 15 N/25 mm or less at 30° C. (ordinary temperature) or less. By making it larger than 10 N/25 mm, it is possible to suppress burrs and trailing that occur when cutting off the recorded material 100, and by making it smaller than 15 N/25 mm, it is possible to easily separate the recorded material 100.

[Protective layer]
The thermal transfer sheet 10 of the present invention includes a protective layer 40 that can protect recorded matter 100 manufactured using the thermal transfer sheet 10 from various environmental changes, chemicals, friction, and the like. Further, since the recorded matter 100 manufactured using the thermal transfer sheet 10 of the present invention is observed through the protective layer 40, the protective layer 40 is transparent, and its transparency is 50% in total light transmittance based on JIS K7375. More preferably, it is 90% or more.

The material for the protective layer 40 is preferably a thermoplastic acrylic resin; for example, polymethacrylate, styrene-acrylic copolymer, polyethylene acrylic resin, acrylic ester resin, copolymer of acrylic ester and vinyl compound, etc. can be used. . Among these, copolymers of acrylic acid esters and vinyl compounds are preferred, and acrylic polyols having a hydroxyl group in the molecule are particularly preferred because they can be crosslinked under mild conditions using an isocyanate-based crosslinking agent.

Note that it is preferable to select a hydrophobic acrylic polyol to be used for the protective layer 40 so that it can be mixed with a hydrophobic crosslinking agent (isocyanate compound) described below.

Further, the Tg (glass transition temperature) of the acrylic polyol used for the protective layer 40 is preferably 40 to 80°C. As long as the Tg is within this range, two or more types of acrylic polyols having different Tg may be used in combination. By using an acrylic polyol with a Tg of 40°C or higher, the scratch resistance is good, and by using an acrylic polyol with a Tg of 80°C or lower, when the thermal transfer sheet 10 is wound into a roll, the protective layer 40 is Peeling from the base material 60 can be suppressed.

Further, the acrylic polyol used in the protective layer 40 preferably has a ratio of weight average molecular weight (Mw) to hydroxyl value (mgKOH/g) in the range of 1,000:1 to 2,500:1. By setting the ratio to 1,000 or more, the distance between the crosslinks between molecules becomes appropriate, and the scratch resistance necessary for the protective layer can be obtained. Further, by setting the ratio to 2,500 or less, it is possible to prevent cracks from occurring in the protective layer when the thermal transfer sheet 10 is wound up into a roll.

Furthermore, nano-sized inorganic particles such as silica or alumina may be added to the protective layer 40 as long as the transparency is not impaired. Thereby, the foil tearability of the protective layer 40 can be further improved.

Although the thickness of the protective layer 40 is not particularly limited, it is preferably 8 μm or more and 30 μm or less. Scratch resistance can be ensured by making the thickness of the protective layer 40 8 μm or more, and foil tearability can be ensured by making the thickness of the protective layer 40 30 μm or less.

[Crosslinking agent]
The protective layer 40 in the present invention contains a crosslinked product in which the main component, acrylic resin (acrylic polyol), is crosslinked with a crosslinking agent. This improves the scratch resistance of the protective layer 40.

As the crosslinking agent, known isocyanate compounds having a functional group (-NCO) that reacts with the hydroxyl group of the acrylic polyol can be used. Isocyanate compounds include bifunctional polyisocyanates such as diisocyanates and trifunctional polyisocyanates as described below, but trifunctional polyisocyanates can achieve a higher degree of crosslinking with a smaller amount. preferable.

In addition, trifunctional polyisocyanates include biuret type and adduct type polyisocyanates in which a functional group (-NCO) is bonded to the end of a three-branched alkyl chain, and three alkyl chains attached to an isocyanurate ring. Although there are isocyanurate-type polyisocyanates to which a functional group (-NCO) is bonded, isocyanurate-type polyisocyanates are preferable because they are structurally more stable. Further, as isocyanurate-type isocyanates, aromatic TDI (toluene diisocyanate) and aliphatic HDI (hexamethylene diisocyanate) exist, but HDI is preferable because it has excellent weather resistance (does not discolor or deteriorate). Can be used.

The amount of the crosslinking agent added can be adjusted so that the molar ratio of the hydroxyl group (-OH) of the acrylic polyol to the functional group (-NCO) of the crosslinking agent is 1:0.75 to 1.0. preferable. By controlling it within this range, a protective layer 40 with excellent scratch resistance can be formed. Note that the content of hydroxyl groups (-OH) and functional groups (-NCO) can be calculated using the following formula.
Amount of hydroxyl groups (mmol) = Amount of acrylic polyol used (g) x Hydroxyl value of acrylic polyol (mgKOH/g) / Formula weight of KOH (56.1 g/mol)...Formula 1
Amount of NCO (mmol) = Amount of crosslinking agent used (g) x NCO content (%) / Formula amount of NCO (42.0 g/mol) x 1000...Formula 2

[Adhesion reinforcement layer]
The thermal transfer sheet 10 of the present invention includes an adhesive reinforcement layer 30 between the protective layer 40 and the second adhesive layer 20 in order to improve the adhesive strength between the protective layer 40 and the second adhesive layer 20. There is no limit to the thickness of the adhesion reinforcing layer 30, but if it is too thin, the adhesive strength cannot be ensured, and if it is too thick, the foil tearability will deteriorate, so it is preferably adjusted within the range of 0.01 μm to 1 μm.

The material used for the adhesion reinforcing layer 30 is not particularly limited and any known material can be used, but since the adhesion reinforcing layer 30 will be placed on the image after transfer, it is preferable to select a transparent material. Specific examples include vinyl compounds such as vinyl acetate, polyvinyl acetal, vinyl chloride-vinyl acetate copolymer, ethylene vinyl acetate, and vinyl chloride. Among these, vinyl chloride-vinyl acetate copolymer is preferred because it has excellent adhesive strength with the protective layer 40.

The thermal transfer sheet 10 of the present invention is produced by forming a first adhesive layer 50, a protective layer 40, and an adhesion reinforcing layer 30 in this order on a base material 60 to produce a laminate, and then subjecting the obtained laminate to a heat treatment. Then, the second adhesive layer 20 is formed on the adhesive reinforcing layer 30 of the laminate. The heat treatment itself is carried out for the purpose of causing the acrylic polyol in the protective layer 40 to react with the crosslinking agent. At this time, by heating the adhesion strengthening layer 30, the crosslinked protective layer 40 (that is, the acrylic polyol and The adhesion between the adhesive reinforcing layer 30 and the protective layer containing a crosslinked product formed with a crosslinking agent (isocyanate compound) can be improved. The temperature and time in the heat treatment are not particularly limited, and there is no problem as long as the acrylic polyol and the crosslinking agent can be crosslinked by 50% or more. Moreover, the apparatus for forming the first adhesive layer 50, the protective layer 40, the adhesive reinforcement layer 30, and the second adhesive layer 20 is not particularly limited, and a known coater can be used.

The detailed reason why heating the adhesion-strengthening layer 30 can improve the adhesiveness between the cross-linked protective layer 40 and the adhesion-strengthening layer 30 is unknown. However, when the adhesion-strengthening layer 30 is formed on the protective layer 40 that has been cross-linked in advance (a protective layer containing a cross-linked product produced from an acrylic polyol and an isocyanate-based compound), the adhesion between the protective layer 40 and the adhesion-strengthening layer 30 is reduced. Significantly decreased. Furthermore, as will be described later, when a heated vinyl compound is analyzed, heat-denatured substances can be confirmed, so it is highly likely that these heat-denatured substances are involved in the adhesion between the protective layer 40 and the adhesion-strengthening layer 30. It is inferred.

The fact that the adhesion-strengthening layer 30 contains a thermally modified vinyl compound can be confirmed by measuring the adhesion-strengthening layer 30 before and after heating using infrared spectroscopy (IR). For example, when the vinyl chloride-vinyl acetate copolymer used for the adhesion-strengthening layer 30 is heat-treated alone, the results shown in FIG. 4 are obtained. The dotted line is the absorption curve of the adhesion-strengthening layer 30 before heating, and the solid line is the absorption curve of the adhesion-strengthening layer 30 after heating.If the reference is set to the peak based on C-O expansion and contraction at 1230 cm ^-1 , the waveform will change before and after heating. It's changing. Specifically, when based on the peak at 1230 cm ^-1 , the relative intensity of the peak at 1700 cm ^-1 after heating (Y) with respect to the peak at 1700 cm ^-1 before heating (X, C=O expansion and contraction) changes. From this change, it can be confirmed that the adhesion reinforcing layer 30 after heating contains a thermally modified substance. When a vinyl chloride-vinyl acetate copolymer is used for the adhesion reinforcing layer 30, if the relative strength of the peak (Y) to the peak (X) is 110% or more, the protective layer 40 containing the crosslinked material and the second adhesive layer 20, which is preferable because the adhesive strength between the two is good.

Furthermore, when observing the infrared spectroscopy data (Figure 4), the change in the peak intensity at 1700 cm ^-1 before and after heating is due to the shift of the peak based on C=O stretching vibration from 1710 cm ^-1 to 1700 cm ^-1 . It looks like it's happening. In other words, the heat-denatured vinyl compound is a product in which a portion of the carbonyl group in the vinyl compound has mutated, and its generation within the adhesive strengthening layer 30 changes the properties of the adhesive strengthening layer 30 itself. It is considered that as a result, the adhesiveness between the crosslinked protective layer 40 and the adhesion reinforcing layer 30 was improved. Note that the heat-denatured vinyl compound in the adhesion-strengthening layer 30 can also be directly confirmed by cutting the cross section of the thermal transfer sheet 10 diagonally and measuring the cut surface using a microinfrared spectrometer. It is possible.

[Second adhesive layer]
The thermal transfer sheet 10 of the present invention has a second adhesive layer 20 on the adhesion reinforcing layer 30 in order to adhere to the transfer target 80 by transfer. The thickness of the second adhesive layer 20 is preferably adjusted within the range of 0.01 μm to 1 μm, because if it is too thin, adhesiveness cannot be ensured, and if it is too thick, it will affect the foil cutting properties.

The material used for the second adhesive layer 20 is not particularly limited and any known material can be used, but since the second adhesive layer 20 will be placed on the image after transfer, it is recommended to select a transparent material. preferable. In addition, in order to prevent the second adhesive layer 20 from sticking to the base material 60 when the manufactured thermal transfer sheet 10 is wound up into a roll, the second adhesive layer 20 has a Tg that is higher than room temperature and lower than the thermal transfer temperature. It is preferable to use a material that is .

Specifically, vinyl acetate, polyol, polyvinyl acetal, vinyl chloride-vinyl acetate copolymer, ethylene vinyl acetate, vinyl chloride, acrylic, polyester, polyamide, cellulose, olefin, styrene, urea, melamine, phenol, resorcinol, epoxy. , polyurethane, silicone, polyamide, polybenzimidazole, polyimide, isocyanate, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, polysulfide, butyl rubber, silicone rubber, acrylic rubber, modified silicone rubber, urethane rubber, silylated urethane, and other resin adhesives. Agent: Examples include water glass-based adhesives such as sodium silicate, and inorganic adhesives such as ceramic-based adhesives. Although one or more of these materials can be used in combination, it is more preferable to use the same material as the adhesive reinforcing layer 30 in consideration of adhesion to the adhesion reinforcing layer 30.

Among them, a material containing a vinyl chloride-vinyl acetate copolymer is preferable because it has excellent adhesive strength with the adhesion reinforcing layer 30 containing a thermally modified material and the transfer target 80 described later.

[Recorded material]
The recorded material 100 of the present invention has a second adhesive layer 20, an adhesive reinforcement layer 30, a protective layer 40, and a first adhesive layer 50 laminated in this order on a transfer target 80.

[Transferred object]
The material of the transfer target 80 is not particularly limited, and known materials can be used. For example, paper made of pulp or cotton, coated paper such as coated paper or art paper, polyester resins such as vinyl chloride (PVC), polyethylene terephthalate (PET), and PET-G, polycarbonate, acrylic resins, and olefin resins. , acrylonitrile-butadiene-styrene copolymer resin, polyester resin, and other films or cards. Further, the transfer target 80 may be a composite of these materials alone or laminated.

[Method for producing recorded matter]
The recorded material 100 of the present invention can be manufactured through the steps shown in FIG.

Specifically, the second adhesive layer 20 is brought into contact with the transfer target 80, and the thermal transfer sheet 10 and the transfer target 80 are overlapped and heated and pressed using a heat roller 90 and a pressure roller 91 to bond them. (See FIGS. 5(a) and (b)). Thereafter, the recording material 100 is obtained by peeling off the base material 60 using a peeling roller 92 (see FIGS. 5(c) and 5(d)). The temperature of the heat roller 90 is such that the temperature of the first adhesive layer 50 and the base material 60 ranges from the glass transition point (Tga) of the amorphous resin constituting the first adhesive layer 50 to the crystalline resin constituting the base material 60. It is preferable to set it within the range of the melting point (Tmc) of the resin. As a result, partial peeling occurs easily at the interface between the first adhesive layer 50 and the base material 60, and the recorded matter 100 can be easily separated from the adhesive between the thermal transfer sheet 10 and the transfer target 80. The device for heating and pressurizing is not particularly limited, and a known laminator can be used.

[Foil breakability during production of recorded matter]
In the production of the recorded material 100, the first adhesive layer 50 has an adhesive force (A) between the first adhesive layer 50 and the base material 60 in the area (a) where the thermal transfer sheet 10 and the transfer target 80 are not adhered; The adhesive force (B) between the first adhesive layer 50 and the base material 60 in the area (b) where the transfer target 80 is adhered to the thermal transfer sheet 10, and the laminate from the second adhesive layer 20 to the first adhesive layer 50 It functions so that the force (C) required to cut is in the relationship A>B and A>C. Thereby, the recorded material 100 can be easily separated, and good foil cutting properties can be obtained.

Although not limited to these, the adhesive force (A) between the first adhesive layer 50 and the base material 60 in the region (a), and the adhesive force (B) between the first adhesive layer 50 and the base material 60 in the region (b) The reason why the relationship between and is A>B is inferred as follows.

In the region (b), as shown in FIGS. 5A and 5B, the thermal transfer sheet 10 and the transfer target 80 are overlapped and heated and pressed by the heat roller 90 and the pressure roller 91. Ru. At this time, each layer of the thermal transfer sheet 10 changes in volume depending on its linear thermal expansion coefficient, but the amount of change is largely different between the first adhesive layer 50 and the base material 60. For example, when the first adhesive layer 50 is formed of acrylic polyol (amorphous resin, glass transition point (Tga): 35°C), which will be described later, the linear thermal expansion coefficient changes from αg to αl as shown in FIG. However, the volume of the first adhesive layer 50 changes significantly in a region exceeding Tga. On the other hand, when a resin film made of polyethylene terephthalate (crystalline resin, melting point (Tmc): 260°C) is used as the base material 60, the linear thermal expansion coefficient αc is constant, so the volume of the base material 60 is does not change as much as the first adhesive layer even when heated above Tga. In this way, when bonding the thermal transfer sheet 10 and the transfer target 80, the first adhesive layer 50 and the base material 60 are bonded at a temperature between the glass transition point (Tga) of the amorphous resin and the melting point (Tmc) of the crystalline resin. When heated at a high temperature, the difference in volume change (ΔV) between the first adhesive layer 50 and the base material 60 becomes large, and partial peeling occurs at the interface between the two, resulting in a decrease in adhesive strength.

On the other hand, in region (a), since there is no transfer target 80, the degree of pressure is low, and heat is difficult to transfer from heat roller 90 to thermal transfer sheet 10, so the temperature of first adhesive layer 50 is lower than region (b). ) will be lower than Therefore, in the region (a), peeling does not occur at the interface between the first adhesive layer 50 and the base material 60, and the adhesive strength remains almost unchanged. It is considered that the relationship A>B occurred because only the adhesive force in region (b) decreased in this way.

Further, the force (C) required to cut the laminate from the second adhesive layer 20 to the first adhesive layer 50 is weakened at the boundary between region (a) and region (b), and this also applies to the It is thought that this contributed to the improvement of cutting performance. Although not limited to these, we speculate as follows.

That is, in the protective layer 40, when the acrylic polyol is crosslinked with the crosslinking agent to form a three-dimensional network structure, the resin itself becomes rigid and the scratch resistance is improved. On the other hand, as the three-dimensional network structure increases, it becomes brittle and cracks are more likely to occur. Therefore, when the thermal transfer sheet 10 of the present invention is bonded by heating and pressurizing, the thermal transfer sheet 10 and the transfer target 80 have a region (a) where they are not adhered to each other (a region which is not heated and pressurized) (a), and a thermal transfer Small cracks are likely to occur in the protective layer 40 at the boundary with the region (b) where the transfer target 80 is adhered to the sheet 10 (the region heated and pressurized), and cuts are likely to occur from this point. This is thought to have improved foil cutting performance.

Further, as described above, the adhesion reinforcing layer 30 containing a thermally modified vinyl compound improves the adhesion between the protective layer 40 and the second adhesive layer 20, and improves the adhesiveness when separating the recorded matter adhered to the transfer sheet. Prevents peeling and improves foil cutting properties.

As described above, in the thermal transfer sheet 10 according to an embodiment of the present invention, the first adhesive layer 50 is easily peeled off from the base material 60 when it is adhered to the transfer target 80 by heating and pressing, and the second adhesive layer 50 is easily peeled off from the base material 60. The laminate from 20 to the first adhesive layer 50 can be easily cut, and the recorded material 100 having high scratch resistance can be separated with good foil cutting properties.

Hereinafter, specific examples of the present invention will be described. However, the present invention is not limited in any way by the following examples. Note that "parts" and "%" in the following description are mass standards unless otherwise specified.

[Preparation of coating liquid a for forming the first adhesive layer]
2.5 parts of acrylic polyol (trade name: Acrydic WAU-137-BA, Tg: 35°C, solid content concentration: 55.0%, manufactured by DIC) and 97.5 parts of MEK were added to form the first adhesive layer. Coating liquid a was prepared.

[Preparation of coating liquid b for forming the first adhesive layer]
2.5 parts of acrylic polyol (trade name: Acrydic TU-979, Tg: 50°C, solid content concentration: 65%, manufactured by DIC) and 97.5 parts of MEK were added to form a coating liquid for forming the first adhesive layer. b was prepared.

[Preparation of coating liquid c for forming the first adhesive layer]
Add 2.5 parts of acrylic polyol (trade name: Acrydic AU-7003, design Tg: 20°C, solid content concentration: 60%, manufactured by DIC) and 97.5 parts of MEK to form a coating for forming the first adhesive layer. Solution c was prepared.

[Preparation of coating liquid d for forming the first adhesive layer]
2.5 parts of acrylic polyol (trade name: Acridic BL-616-BA, Tg: 60°C, solid content concentration: 45%, manufactured by DIC) and 97.5 parts of MEK were added to form a coating for forming the first adhesive layer. A working solution d was prepared.

[Preparation of coating liquid for forming protective layer]
Acrylic polyol (trade name: Acridic BL-616-BA, Tg: 60°C, hydroxyl value: 18mgKOH/g, solid content concentration: 45.0%, manufactured by DIC) 51.9 parts (hydroxyl group amount: 7.49 mmol) ), 1.36 parts of isocyanate compound (trade name: Duranate TPA-100, NCO amount: 23.1%, solid content concentration 100%, manufactured by Asahi Kasei Corporation) (NCO amount: 7.48 mmol), and MEK46.7 A coating solution for forming a protective layer was prepared.

[Preparation of coating liquid for forming adhesion reinforcing layer]
A coating solution for forming an adhesion-strengthening layer was prepared by adding 1 part of MEK to 1 part of vinyl chloride-vinyl acetate copolymer (trade name: Solvine C, solid content: 30%, manufactured by Showa Ink Co., Ltd.).

[Preparation of coating liquid for forming second adhesive layer]
A coating solution for forming a second adhesive layer was prepared by adding 1 part of MEK to 1 part of vinyl chloride-vinyl acetate copolymer (trade name: Solvine C, solid content: 30%, manufactured by Showa Ink Co., Ltd.).

[Manufacture of thermal transfer sheet A]
A PET film (trade name: Tetron G2, melting point: 260°C, thickness: 25 μm, manufactured by Teijin DuPont Films) was prepared as a base material, and coating liquid a for forming the first adhesive layer was applied on it after drying. Coating was performed using a gravure coater (coating speed: 10 m/min, drying temperature: 100° C.) so that the thickness of the first adhesive layer was 0.6 μm. Next, apply the coating solution for forming a protective layer on the first adhesive layer using a gravure coater (coating speed: 10 m/min, drying temperature: 120°C) so that the thickness of the protective layer after drying is 12.5 μm. It was coated using. Next, a coating solution for forming an adhesion reinforcing layer is applied onto the protective layer using a gravure coater (coating speed: 10 m/min, drying temperature: 80°C) so that the thickness of the layer after drying is 1 μm. I worked on it. Thereafter, heat treatment was performed at 60° C. for 5 days. Next, apply the coating liquid for forming the second adhesive layer on the adhesion reinforcing layer using a gravure coater (coating speed: 10 m/min, drying temperature: 80°C) so that the thickness of the second adhesive layer after drying is 1 μm. ) to produce a thermal transfer sheet A.

(Confirmation of thermally modified substances in the adhesion-strengthening layer)
The coating solution for forming an adhesion-strengthening layer was placed in a petri dish and dried at 80° C. to produce two pseudo-adhesion-strengthening layers each having a thickness of 1 μm after drying. After that, one was heated at 60°C for 5 days, and this and the unheated one were each measured 200 x 3 times using IR (product name: IR Prestige-21, manufactured by Shimadzu Corporation), and the average spectrum was determined from the The peak intensity at 1710 cm ⁻¹ of each was determined. Furthermore, the presence or absence of heat-modified substances in the adhesion-strengthening layer was confirmed by determining the relative strength of the heated layer with respect to the unheated layer. The relative strength obtained was 120%.

[Manufacture of thermal transfer sheet B]
Transfer sheet B was produced in the same manner as thermal transfer sheet A except that the first adhesive layer forming coating liquid a was changed to the first adhesive layer forming coating liquid b.

[Manufacture of thermal transfer sheet C]
Thermal transfer sheet C was produced in the same manner as transfer sheet A except that the thickness of the first adhesive layer was changed to 0.3 μm.

[Manufacture of thermal transfer sheet D]
Thermal transfer sheet D was produced in the same manner as transfer sheet A except that the thickness of the first adhesive layer was changed to 1.0 μm.

[Manufacture of thermal transfer sheet E]
Thermal transfer sheet E was produced in the same manner as transfer sheet A except that the thickness of the protective layer was changed to 8.0 μm.

[Manufacture of thermal transfer sheet F]
Thermal transfer sheet F was produced in the same manner as transfer sheet A except that the thickness of the protective layer was changed to 20.0 μm.

[Manufacture of thermal transfer sheet G]
A transfer sheet G was produced in the same manner as the thermal transfer sheet A except that the first adhesive layer forming coating liquid A was changed to the first adhesive layer forming coating liquid C.

[Manufacture of thermal transfer sheet H]
A thermal transfer sheet H was produced in the same manner as the transfer sheet A except that the thickness of the first adhesive layer was changed to 0.2 μm.

[Manufacture of thermal transfer sheet I]
Thermal transfer sheet I was produced in the same manner as transfer sheet A except that the thickness of the first adhesive layer was changed to 1.5 μm.

[Manufacture of thermal transfer sheet J]
Transfer sheet J was produced in the same manner as thermal transfer sheet A except that coating liquid A for forming the first adhesive layer was changed to coating liquid d for forming the first adhesive layer.

[Manufacture of thermal transfer sheet K]
Thermal transfer sheet K was produced in the same manner as transfer sheet A except that the first adhesive layer was not formed.

(Example 1)
The second adhesive layer 20 of the thermal transfer sheet A is brought into contact with the PVC card that is the transfer target 80, and the thermal transfer sheet A and the transfer target 80 are overlapped and bonded by heating and pressing using a heat roller. Recorded material A was manufactured by peeling off the material 60. The set temperature of the heat roller was 180° C., and the conveyance speed was 30 mm/s. Note that when only a PVC card was passed under these conditions, the surface temperature of the upper surface of the card rose to 100°C.

(Evaluation 1: Scratch resistance of protective layer)
Using a Taber abrasion test (product name: Rotary ablation tester TS-2, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the protective layer of recorded material A was tested under the following test conditions: rotation speed: 60 rpm, load: 500 g, and wear wheel: CS-10F. Abrasion resistance was evaluated. The results obtained are shown in Table 1. In the table, "○" in "Scratch resistance" indicates that the printed surface was not scraped even after the wear wheel was rotated more than 2,000 times, and "△" means that the number of rotations of the wear wheel was 1,000 times. The above indicates that the printed surface was scraped less than 2,000 times, and "x" indicates that the printed surface was scraped while the number of rotations of the abrasion wheel was less than 1,000 times.

(Evaluation 2: Foil cutting ability)
After heat-pressing the thermal transfer sheet to the object to be transferred, when peeling off the base material, the non-adhesive part was pulled at an angle of 90°, and the length of the protective layer protruding from the edge of the card remaining on the object to be transferred was evaluated. . The results obtained are shown in Table 1. "〇" in "Foil breakability" in the table indicates that the length of the protective layer protruding from the card edge is less than 0.1 mm, and "△" indicates that the length of the protective layer protruding from the card edge is less than 0.1 mm. It shows that the length is 0.1 mm or more and less than 0.2 mm, and "x" shows that the length of the protective layer protruding from the card edge is 0.2 mm or more.

(Evaluation 3: Tackiness)
In an environment of 25° C. and 55% RH, a PVC film was layered on the first adhesive layer of Recorded Material A, and pressure was applied from above the PVC film at a load of 0.1 kgf/cm ² for 1 hour. Thereafter, the tackiness of the first adhesive layer was evaluated by pulling the end of the PVC film in a direction perpendicular to the film surface and peeling off the PVC film from Recorded Material A. The results obtained are shown in Table 1. "〇" in "Tackiness" in the table indicates that the force when peeling the PVC film from recorded material A was less than 0.1 kgf, and "△" indicates that the force when peeling the PVC film from recorded material A was less than 0.1 kgf. It shows that the force was 0.1 kgf or more and less than 0.2 kgf, and "x" shows that the force when peeling the PVC film from recorded material A was 0.2 kgf or more.

(Evaluation 4: Scratch resistance)
The scratch resistance of the first adhesive layer of Recorded Material A was evaluated using a pencil hardness tester (product name: 501 Pencil Scratch Tester, manufactured by Elcometer). The results obtained are shown in Table 1. "〇" in "Scratch Resistance" in the table indicates that it was not scratched by pencil B, "△" indicates that it was not scratched by pencil 2B, and "x" indicates that it was scratched by pencil 2B. show.

(Examples 2 to 9)
Recorded matter B to recorded matter I were produced in the same manner as in Example 1, except that thermal transfer sheet A was replaced with thermal transfer sheet B to thermal transfer sheet I, and the scratch resistance, foil tearability, tackiness, and scratch resistance were evaluated. did. The results obtained are shown in Table 1 or Table 2.

(Comparative Examples 1-2)
Recorded material J or recorded material K was prepared in the same manner as in Example 1, except that thermal transfer sheet A was replaced with thermal transfer sheet J or thermal transfer sheet K, and the scratch resistance, foil tearability, tackiness, and scratch resistance were evaluated. did. The results obtained are shown in Table 2.

The disclosure of this embodiment includes the following configuration and method.

(Configuration 1)
A thermal transfer sheet in which a first adhesive layer, a protective layer, an adhesion reinforcing layer, and a second adhesive layer are sequentially laminated on a base material, and the base material is separable from the first adhesive layer,
The base material is a film made of crystalline resin,
The first adhesive layer is formed of an amorphous resin having a glass transition point of 50° C. or lower,
The protective layer contains a crosslinked product produced from an acrylic polyol and an isocyanate compound,
The adhesion reinforcing layer contains a heat-modified vinyl compound.
A thermal transfer sheet characterized by:

(Configuration 2)
The thermal transfer sheet according to configuration 1, wherein the crystalline resin has a melting point of 100° C. or higher.

(Configuration 3)
The thermal transfer sheet according to configuration 1 or 2, wherein the amorphous resin has a glass transition point of 30°C or more and 50°C or less.

(Configuration 4)
The thermal transfer sheet according to any one of configurations 1 to 3, wherein the first adhesive layer has an average thickness of 0.3 μm or more and less than 1 μm.

(Configuration 5)
5. The thermal transfer sheet according to any one of configurations 1 to 4, wherein the second adhesive layer is made of a material containing a vinyl compound.

(Configuration 6)
6. The thermal transfer sheet according to any one of configurations 1 to 5, wherein the vinyl compound contains a carbonyl group.

(Configuration 7)
7. The thermal transfer sheet according to any one of configurations 1 to 6, wherein the vinyl compound is a vinyl chloride-vinyl acetate copolymer.

10: Thermal transfer sheet 20: Second adhesive layer 30: Adhesive reinforcing layer 40: Protective layer 50: First adhesive layer 60: Base material 70: Burr 71: Trailing 72: Recorded matter from the adhesive between the thermal transfer sheet and the transferred object Separating direction 80: Transferred object 90: Heat roller 91: Pressure roller 92: Peeling roller 100: Recorded material

Claims (7)

A thermal transfer sheet in which a first adhesive layer, a protective layer, an adhesion reinforcing layer, and a second adhesive layer are sequentially laminated on a base material, and the base material is separable from the first adhesive layer,
The base material is a film made of crystalline resin,
The first adhesive layer is formed of an amorphous resin having a glass transition point of 50° C. or lower,
The protective layer contains a crosslinked product produced from an acrylic polyol and an isocyanate compound,
The adhesion reinforcing layer contains a heat-modified vinyl compound.
A thermal transfer sheet characterized by: The thermal transfer sheet according to claim 1, wherein the crystalline resin has a melting point of 100°C or higher. The thermal transfer sheet according to claim 1, wherein the amorphous resin has a glass transition point of 30°C or more and 50°C or less. The thermal transfer sheet according to any one of claims 1 to 3, wherein the first adhesive layer has an average thickness of 0.3 μm or more and less than 1 μm. The thermal transfer sheet according to any one of claims 1 to 3, wherein the second adhesive layer is made of a material containing a vinyl compound. The thermal transfer sheet according to any one of claims 1 to 3, wherein the vinyl compound contains a carbonyl group. The thermal transfer sheet according to any one of claims 1 to 3, wherein the vinyl compound is a vinyl chloride-vinyl acetate copolymer.

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