JP6870543B2 - Base paper for thermal transfer paper and thermal transfer paper - Google Patents

Description

The present invention relates to a base paper for heat transfer paper and a base paper for heat transfer paper using the base paper for heat transfer paper.

Paper produced by crimping and drying only one side of wet paper made from pulp with a paper machine to a mirror-shaped cylindrical cylinder dryer (hereinafter referred to as Yankee dryer) has extremely high smoothness and is a piece. It is called glossy paper.

Single glossy paper is used for packaging, bag making, processing, etc., and is often printed on the smooth surface side that has been dried in contact with a Yankee dryer. For this reason, many inventions with improved printability and processability on the smooth surface side are known (for example, Patent Document 1 and Patent Document 2).

Japanese Patent No. 4841515 Japanese Patent No. 4350145

As another application using single-gloss paper, development to thermal transfer paper can be considered. In this application, various patterns are printed on the smooth surface of single-gloss paper using a gravure printing machine or an inkjet printing machine, and the patterns are thermally transferred to a metal base material such as aluminum or stainless steel to improve the design. It provides excellent goods. The manufacturing procedure is as follows. First, a sublimation ink is used to print, for example, a wood grain pattern on the smooth surface of the single-gloss paper to produce a heat transfer paper. Next, a water-based glue is applied to the obtained heat transfer paper or the base material is brought into close contact with the obtained heat transfer paper under vacuum. After removing the portion of the heat transfer paper that protrudes from the base material by cutting with a cutter, heat is applied to transfer the pattern to the base material. Then, when the heat transfer paper is peeled off from the base material, a base material having a wood grain pattern on the surface can be obtained. This application is mainly useful for building materials.

Another method is to transfer the pattern to the base material by bringing the base material into close contact with the heat transfer paper after printing and then heating and pressurizing it with a hot press machine.

When a water-based glue is used to bring the heat transfer paper into close contact with the base material, it is necessary to cut the portion of the heat transfer paper moistened by the glue that protrudes from the base material with a cutter. At this time, if the strength of the heat transfer paper is low, the paper that has been adhered to the paper will be torn at a position not intended for cutting, and the work must be restarted from the process of discarding the adhered heat transfer paper and adhering a new heat transfer paper. There is a problem of causing a decrease in workability.

In addition, the heat transfer paper needs to be peeled off from the base material after the design is transferred by heat treatment. At this time, if the strength of the heat transfer paper after heating is not sufficiently high, the heat transfer paper is torn during the peeling operation, and the heat transfer paper cannot be peeled off in one operation, which causes a problem that workability is deteriorated.
Further, even if the strength in either the vertical direction or the horizontal direction is sufficiently high, if the strength in the other direction is insufficient, tearing occurs in the direction in which the strength is low, which also causes a decrease in workability. There is.
The vertical direction referred to here refers to the direction in which the slurry (pulp fiber) flows out in the process of forming the paper layer in the papermaking of the base paper for thermal transfer paper. The horizontal direction refers to a direction perpendicular to the paper in the vertical direction. Hereinafter, the vertical direction is also referred to as an MD direction, and the horizontal direction is also referred to as a CD direction.

An object of the present invention is to use a base paper for heat transfer paper and a base paper for heat transfer paper, which is less likely to break during gluing work using water-based glue between the heat transfer paper and the base material, and also less likely to break during peeling work. It is to provide the heat transfer paper that was used.

The present inventors contain a predetermined amount of a wet paper strength enhancer, and when the Cobb water absorption and tensile strength of the heat transfer paper are within a predetermined value range, breakage during cutting work by a cutter during gluing or the like occurs. Found to reduce.
Further, the present inventors have a sulfate ion content of the heat transfer paper of a predetermined amount or less, and after the heat treatment, the tear strength of the heat transfer paper in both the MD direction and the CD direction is equal to or more than a predetermined value. It has been found that when the ratio of the tear strength in the CD direction is a predetermined ratio, the breakage during the peeling operation is reduced.
From the above plurality of findings, the present inventors have been able to reach the present invention. That is, the present invention has the following configuration.

(1) Cellulose pulp is the main component, the content of sulfate ion is 0.6 mg / l or less, the content of the wet paper strength enhancer is 0.1 to 0.35% by mass, and the water absorption of Cobb is high. It is 10 to 13 g / m ² or less, the tensile strength is 2.0 kN / m or more, and the ratio of the tear strength after heat treatment at 220 ° C. for 25 minutes between the MD direction and the CD direction is 0.8 to 1. 2. The base paper for thermal transfer paper, which has a tear strength of 50 mN or more in both the MD direction and the CD direction after the heat treatment.

(2) It is characterized by containing 0.30 to 1.20% by mass of one or more selected from a rosin-based sizing agent, an alkenyl succinic anhydride-based sizing agent, a cationic polymer-based sizing agent, and an alkyl ketene dimer-based sizing agent. The base paper for thermal transfer paper according to (1) above.

(3) The base paper for thermal transfer paper according to (1) or (2) above, wherein the fiber orientation ratio is 1.25 to 1.50.

(4) The base paper for heat transfer paper according to the base paper for heat transfer paper according to any one of (1) to (3) above, wherein the content of the cationized starch is 0.01% by mass or less. ..

(5) The base paper for thermal transfer paper according to any one of (1) to (4) above, wherein the rate of decrease in tensile strength due to heat treatment at 220 ° C. for 25 minutes is 20% or less.

(6) The base paper for thermal transfer paper according to any one of (1) to (5) above, wherein the wet tensile strength after heat treatment at 220 ° C. for 25 minutes is 0.80 kN / m or more. ..

(7) The base paper for thermal transfer paper according to any one of (1) to (6) above, wherein the material to be transferred is made of metal, ceramics or resin.

(8) The base paper for thermal transfer paper according to any one of (1) to (7) above and an ink layer formed on the smooth surface side of the base paper for thermal transfer paper, and the ink layer is ink. A thermal transfer paper characterized by containing and a binder resin.

(9) The heat transfer paper according to (8) above, which is used in a method of using a water-based glue when adhering to a transfer material.

The base paper for thermal transfer paper of the present invention is less likely to break during gluing work and is less likely to break during peeling work, and is suitable for applications where the design is thermally transferred by gluing to a base material. .. Further, since the thermal transfer paper of the present invention uses the base paper for thermal transfer paper, it is suitable for use in which a pattern is thermally transferred by gluing to a base material.

Hereinafter, embodiments of the present invention will be specifically described. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

The base paper for thermal transfer paper of the present embodiment is made of single-gloss paper. Further, the thermal transfer paper of the present embodiment includes an ink layer formed on the smooth surface side of the base paper for thermal transfer paper. The ink layer contains ink and a binder resin. The ink layer is formed by using a gravure printing machine, an inkjet printing machine, or the like, and has various patterns.

The base material (transfer material) to be transferred is preferably a member having various shapes composed of metal, ceramics or resin. The heat transfer paper of the present embodiment is used to impart designability to furniture, building materials, and the like, but is not limited to these base materials. The metal is aluminum, stainless steel, or the like, and is not particularly limited. The resin is a synthetic resin, a natural resin, or the like, and is not particularly limited.

The operation procedure for transferring the ink layer to the substrate is as follows.
(1) After applying the water-based glue to the heat transfer paper, the heat transfer paper is brought into close contact with the base material. Alternatively, the heat transfer paper and the base material are combined and then evacuated to bring them into close contact with each other.
(2) The heat transfer paper protruding from the base material is cut with a cutter to remove it.
(3) Heat of about 170 ° C. to 220 ° C. is applied to transfer the ink layer (design on the heat transfer paper) to the substrate.
(4) The thermal transfer paper on which the pattern is transferred is peeled off from the base material. At that time, an operation such as covering the base material and the heat transfer paper with vinyl or the like and sprinkling water on the paper to cool the paper may be added.

Further, when a hot press machine is used, the procedure is such that the base material and the heat transfer paper after printing are brought into close contact with each other, and then the ink layer is transferred to the base material by heating and pressurizing with the hot press machine.

Hereinafter, each element constituting the base paper for thermal transfer paper of the present embodiment will be described.
(pulp)
The base paper for heat transfer paper contains cellulose pulp as a main component. Cellulose pulp is not particularly limited, but preferably contains chemical pulp from the viewpoint of strength. The chemical pulp is not particularly limited, but preferably contains hardwood kraft pulp (LKP) or softwood kraft pulp (NKP). The pulp may be bleached pulp or unbleached pulp. Further, it is preferable to contain both LKP and NKP.

In general, LKP has shorter fibers and is inferior in strength to NKP, but it is excellent in the texture and smoothness of the paper that has been made, and can improve printability. Therefore, in the base paper for thermal transfer paper, the content of LKP is preferably 40% by mass or more, more preferably 60% by mass, and 80% by mass or more with respect to the total mass of the pulp components. Is even more preferable.

The degree of beating (freeness) of LKP is preferably 250 to 400 mlcsf, and more preferably 280 to 380 mlcsf. When the beating degree is within the above range, it is possible to make a base paper having excellent strength and smoothness. In addition, by increasing the number of fixing sites for the paper-making chemicals described later, it becomes easier to achieve the desired paper quality. The beating degree of pulp is a numerical value measured in accordance with JIS P 8121: 2012.

Further, in the base paper for heat transfer paper, it is preferable to add NKP. Since NKP has long fibers, it is possible to increase the tensile strength and tear strength of the paper-made product. Therefore, the content of NKP is preferably 5% by mass or more, more preferably 10% by mass or more, based on the total mass of the pulp components.

The beating degree of NKP is preferably 500 mlcsf or less, and more preferably 400 mlcsf or less. When the beating degree of NKP is within the above range, it is possible to secure sufficient strength as a base paper for thermal transfer paper.

The pulp component may contain pulp other than the above-mentioned NKP and LKP (hereinafter, referred to as other pulp). Other pulps include stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), thermogrand pulp (TGP), chemigrand pulp (CGP), crushed wood pulp (GP), and thermo. Manufactured from mechanical pulp such as mechanical pulp (TMP), tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, cardboard waste paper, upper white waste paper, Kent waste paper, imitation waste paper, ground ticket waste paper, etc. Examples thereof include recycled recycled paper pulp (DIP), and pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and reed. The content of the other pulp is preferably less than 3% by mass, more preferably less than 2% by mass, and even more preferably less than 1% by mass with respect to the total mass of the pulp components.

(Aluminum sulfate band)
Aluminum sulfate band (aluminum sulfate) has been widely used as a fixing agent for yield improvers and sizing agents. However, when used as a base paper for heat transfer paper, it is heated to around 200 ° C. during transfer, so sulfate ions generated from the sulfate band during heating hydrolyze cellulose, and the tensile strength and tear strength of the paper after heat treatment. Is greatly reduced. Therefore, the content of sulfate ions in the base paper for thermal transfer paper, which can suppress the decrease in tensile strength due to heat treatment during transfer, was examined. As a result, it was found that it is necessary to keep the content of sulfate ions in the base paper for thermal transfer paper to 0.6 mg / l or less. The sulfate ion content is preferably in the range of 0.1 to 0.6 mg / l, more preferably in the range of 0.2 to 0.6 mg / l. By setting the content of sulfate ions within the above range, it is possible to suppress a decrease in tensile strength after heat treatment. Here, the content of sulfate ions in the paper can be measured using an ion chromatograph.

The content of the sulfate band (aluminum sulfate) that generates sulfate ions is not particularly limited, but is preferably 0.8% by mass or less, preferably 0.7% by mass, from the viewpoint of reducing breakage during peeling work. More preferably, it is less than%. The content of the sulfate band can be measured as the content of sulfate ions, but it can also be measured as the content of aluminum. In this case, the content of aluminum in the base paper for thermal transfer paper is preferably 0.09% by mass or less, and more preferably 0.03 to 0.09% by mass.

(Tensile strength)
As described above, the tensile strength can be improved by adjusting the composition of the pulp. Therefore, the present inventors have repeatedly studied the tensile strength capable of reducing the breakage during the cutting operation by the cutter during gluing.
Further, as described above, by adjusting the content of the aluminum sulfate band, it is possible to suppress a decrease in tensile strength due to heat treatment. However, even if it is possible to suppress the decrease in strength due to the heat treatment, if the tensile strength is too small before the heat treatment, it is not possible to secure a sufficient tensile strength after the heat treatment. Therefore, the present inventors have repeatedly studied the minimum tensile strength that can reduce the breakage during the peeling operation even if the tensile strength decreases due to the heat treatment.
The present inventors have found that the tensile strength at the time of humidity control needs to be 2.0 kN / m or more from a plurality of findings regarding the above tensile strength. Furthermore, it has been found that it is more preferable that the tensile strength is 2.4 kN / m or more.
The tensile strength also has an MD direction and a CD direction as in the tear strength, but in the present embodiment, the MD direction is represented.

(Tear strength)
In addition, the present inventors have repeatedly studied the tear strength required to reduce the breakage during the peeling operation after the heat treatment. As a result, it is necessary that the tear strength at the time of humidity control after heat treatment at 220 ° C. for 25 minutes is 50 mN or more in both the MD direction and the CD direction, and at this time, either the MD direction or the CD direction. It was found that it is more preferable if one is 63 mN or more.

(Tear strength ratio)
In order to reduce breakage during peeling from the base material after heat treatment, it is necessary not only to have sufficiently large tensile strength and tear strength, but also to have a good balance of tear strength in the MD direction and the CD direction. Is. Focusing on this point, the present inventors have repeatedly studied the ratio of the tear strength in the MD direction and the CD direction, which can reduce the fracture. As a result, the ratio of the tear strength in the MD direction and the CD direction when heat-treated at 220 ° C. for 25 minutes needs to be in the range of 0.8 to 1.2, and 0.88 to 1. It was found that the range of 12 is more preferable.
Here, the ratio of the tear strength in the MD direction and the CD direction is the value of the LMD / LCD when the tear strength in the MD direction is LMD and the tear strength in the CD direction is LCD. Further, the condition of heat treatment at 220 ° C. for 25 minutes was selected as a typical heat treatment condition when performing thermal transfer.

(Fiber orientation ratio)
Furthermore, in order to realize the above-mentioned ratio of tear strength in the MD direction and the CD direction, the present inventors focused on the bond between the fibers in the MD direction and the CD direction, and examined the fiber orientation ratio. As a result, it was found that the fiber orientation ratio measured based on the ultrasonic propagation velocity measuring device is preferably in the range of 1.25 to 1.50, and more preferably in the range of 1.35 to 1.50. did.

Here, the fiber orientation is a tendency for pulp fibers to flow out onto a wire of a paper machine, dehydrate, and line up in a specific direction in the process of forming a paper layer. The fiber orientation ratio can be adjusted by changing the jet wire ratio (raw material ejection rate ratio).
The jet wire ratio is the ratio of the outflow speed of the pulp fiber to the running speed of the wire, and is represented by the outflow speed of the slurry / the running speed of the wire.

In general, as a method for measuring the fiber orientation of paper or the like, for example, a thermal expansion method, a mechanical breaking strength method, an X-ray diffraction method, an ultrasonic method, a microwave method, an NMR method, a polarized fluorescence method, a dielectric measurement method and the like can be mentioned. Be done. In the present invention, the ultrasonic method is adopted, the ultrasonic propagation velocity (Vmd) in the vertical direction and the ultrasonic propagation velocity (Vcd) in the horizontal direction are measured, and the ratio (Vmd / Vcd) is used as the fiber orientation ratio to determine the fiber orientation. It was used as an index to evaluate randomness. When the fiber orientation ratio is 1.0, the fibers are completely randomly oriented.

As described above, by adjusting the aluminum sulfate band, deterioration of the heat transfer paper due to heat treatment can be suppressed, and tear strength and tensile strength can be improved. Further, by appropriately mixing NKP having long fibers, the bond between the fibers can be strengthened, and the tear strength and the tensile strength can be improved. In addition to these, the ratio of the tear strength in the MD direction and the CD direction can be adjusted by adjusting the fiber orientation.
According to these formulations, the tear strength after the heat treatment is 50 mN or more in both the MD direction and the CD direction, and the ratio of the tear strength after the heat treatment between the MD direction and the CD direction is 0.8 to 1.2. It is possible to realize a base paper for thermal transfer paper.

(Paper power enhancer)
The base paper for thermal transfer paper of the present embodiment is required to have excellent wet tensile strength because a water-based glue is applied when it is brought into close contact with the base material. Further, it is necessary to have excellent wet tensile strength after heat treatment from the viewpoint of workability when peeling the heat transfer paper from the base material. The present inventors have investigated a formulation for improving the tensile strength when wet. The cationized starch, which has been widely used as a paper strength enhancer, does not have a sufficient effect of improving the tensile strength when wet. Therefore, we investigated a wet paper strength enhancer to replace the cationized starch. As a result, as the wet paper strength enhancer, one or more selected from polyamide polyamine epichlorohydrin resin (PAE), urea formaldehyde resin and melamine formaldehyde resin was preferable.

That is, the content of the cationized starch is 0.01% by mass or less, and the content of the wet paper strength enhancer is 0.10 to 0.35% by mass. The content of the wet paper strength enhancer is 0.10% by mass or more, and preferably 0.20% by mass or more. Within the above range, it is possible to impart wet tensile strength that can be used as a base paper for heat transfer paper. On the other hand, the content of the wet paper strength enhancer is 0.35% by mass or less. This is because if the content of the wet paper strength enhancer is excessive, it cannot be completely fixed to the pulp and an excessive amount of chemicals are used, which may have an adverse effect such as soiling the inside of the paper machine system. .. Here, the content of the cationized starch and the wet paper strength enhancer is a ratio to the total mass of the pulp components.

As the dry paper strength enhancer, known ones can be used, and for example, a polyacrylamide-based paper strength enhancer (PAM) or starch can be used. The PAM and starch are not particularly limited, and any of cationic, anionic and amphoteric can be used. However, considering the fixability of the wet paper strength enhancer, an anionic or amphoteric dry paper strength enhancer is preferable.

(Size agent)
A known sizing agent can be used. Among the sizing agents, one or more selected from rosin-based sizing agents, alkenyl succinic anhydride (ASA) -based sizing agents, cationic polymer-based sizing agents, and alkyl ketene dimer (AKD) -based sizing agents is 0.30 to 1. It is preferably contained in an amount of 20% by mass, more preferably 0.40 to 0.80% by mass, and even more preferably 0.50 to 0.80% by mass. In particular, since the amount of the acidic aluminum sulfate band added is reduced, a neutral rosin-based sizing agent is preferable to an acidic rosin-based sizing agent for the reason of size development.

In addition, known chemicals such as calcium carbonate, talc, clay, kaolin and other fillers, yield improvers, and drainage improvers are appropriately added to the paper materials as papermaking additives to achieve the desired functions. can do.

The paper material adjusted as described above can be made into a single glossy paper by a known method. The type of paper machine at that time is not particularly limited. Generally, in order to improve the smoothness of one side, the paper is made by a paper machine equipped with a Yankee dryer. Therefore, one side of the base paper for thermal transfer paper is smooth. Further, if necessary, a coating layer that imparts printability to the surface may be provided, or post-treatment such as calendar processing may be added.

(Cobb water absorption)
With the above sizing agent, the water absorption of the hump of the base paper for heat transfer paper can be adjusted. Cobb water absorption is a performance that greatly affects the ease of cutting wet heat transfer paper. If the water absorption of the Cobb is too high, the heat transfer paper absorbs a large amount of water, making it extremely difficult to cut.
Therefore, the present inventors have studied the Cobb water absorption of the base paper for thermal transfer paper in order to realize a thermal transfer paper that is easy to cut even when wet. As a result, the size of the base paper for thermal transfer paper ^{needs to have a Cobb water absorption of 10 to 13 g / m 2} , and more preferably 10 to 11 g / m ^2.
When the water absorption of the hump ^{exceeds 13 g / m 2} , the strength of the paper is lowered when the heat transfer paper is brought into close contact with the base material using a water-based glue, and the workability in the cutting work is remarkably lowered. .. In order to reduce the water absorption of the Cobb to 13 g / m ² or less, it can be achieved by adding an appropriate amount of the above-mentioned sizing agent to the paper material. The water absorption of the Cobb is measured by ^{the 30 g / m 2} method specified in JIS P 8140: 1998.

Further, when the heat transfer paper after the heat treatment is peeled off from the base material, the tensile strength after the heat treatment is important. The tensile strength of the base paper for thermal transfer paper after heat treatment at 220 ° C. for 25 minutes is preferably 2.0 kN / m or more, and more preferably 2.3 kN / m or more.

The rate of decrease in tensile strength (%) of the base paper for thermal transfer paper after heat treatment at 220 ° C for 25 minutes is
It is determined by 100 × [(tensile strength at the time of humidity control) − (tensile strength at 220 ° C. after heat treatment for 25 minutes)] / (tensile strength at the time of humidity control). The rate of decrease in tensile strength after heat treatment is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. If the rate of decrease in tensile strength after the heat treatment exceeds 20%, the thermal transfer paper is torn when the thermal transfer paper is peeled off from the base material after the thermal transfer, and the workability is deteriorated.

The tensile strength after the heat treatment is the tensile strength after the heat treatment by setting the content of sulfate ions in the paper to 0.6 mg / l or less, more preferably 0.1 to 0.6 mg / l. It is possible to suppress the decrease. Further, in order to secure the tensile strength after the heat treatment, it is also possible to adopt a method of increasing the tensile strength before the heat treatment. However, in that case, it is necessary to take measures such as increasing the amount of the paper strength enhancer or the like or increasing the basis weight, which is not always desirable from the viewpoint of cost and workability.

The wet tensile strength of the base paper for thermal transfer paper after heat treatment at 220 ° C. for 25 minutes is preferably 0.80 kN / m or more, and more preferably 0.83 kN / m or more. In order to make the wet tensile strength after the heat treatment 0.80 kN / m or more, an appropriate amount of the above-mentioned wet paper strength agent may be added to the paper material. If it is lower than the above-mentioned wet tensile strength, there is a concern that the workability of the work of cutting the excess thermal transfer paper when transferred using the water-based glue is lowered. Further, the work of peeling the heat transfer paper from the base material after the transfer is performed in a high temperature and high humidity environment, but at that time, the heat transfer paper is easily torn, and there is a concern that the workability is deteriorated.

The tensile strength is measured according to JIS P 8113: 2006. The tensile strength at the time of humidity control is the tensile strength measured after being left in a humidity control environment (temperature 23 ° C., humidity 50% RH) according to JIS P 8111: 1998 for 1 day or more. The tensile strength after the heat treatment was measured after being left in a constant temperature dryer for 25 minutes in an environment of 220 ° C. and further left in a humidity control environment for 15 minutes.

The wet tensile strength after heat treatment is defined as a general method of JIS P 8135: 1998 after being left in a constant temperature dryer for 25 minutes in an environment of 220 ° C. and then in a humidity control environment for 15 minutes. It was measured according to the above method.

Here, in all cases, the above-mentioned tensile strength, the tensile strength after the heat treatment, and the wet tensile strength after the heat treatment are measured in the MD direction (flow direction of the paper machine) in principle. However, when it is unclear whether or not it is in the MD direction, the tensile strength is measured at every 22.5 degrees of the angle, and the direction showing the strongest tensile strength is defined as the MD direction.

The ink and the binder resin constituting the ink layer of the heat transfer paper are not particularly limited as long as they have the ability to transfer to the base material (transfer material) as described above. Known inks and binder resins can be appropriately selected and used. As the pigment / dye used as the ink, a sublimable one or a non-sublimable one can be appropriately selected and used as needed. As the binder resin, a thermoplastic resin such as a hot melt resin, a thermosetting resin, or the like can be selected and used as necessary.

Examples and comparative examples are shown below. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the specific examples shown below.

(Example 1)
The bleached softwood kraft pulp (NKP) and the bleached hardwood kraft pulp (LKP) were beaten to a beating degree of 360 ml using a double disc refiner (hereinafter referred to as DDR). 15% by mass of the beaten NKP and 85% by mass of the beaten LKP were mixed in a mixing chest. Next, a sulfate band and a polyamide polyamine epichlorohydrin-based resin (PAE-based wet paper strength enhancer) were added so as to be 0.6% by mass and 0.25% by mass with respect to the pulp components, respectively. Next, a polyacrylamide-based paper strength enhancer (PAM-based paper strength enhancer) was added so as to be 0.5% by mass with respect to the pulp component, and a neutral rosin-based sizing agent was further added to 0 with respect to the pulp component. A paper material was prepared by adding the mixture in an amount of .60% by mass. Using the prepared paper material, papermaking was carried out with a paper machine equipped with a Yankee dryer to obtain a base paper for thermal transfer paper having a fiber orientation ratio of 1.37.

(Example 2)
After mixing the pulp in the same manner as in Example 1, a sulfate band and a PAE-based wet paper strength enhancer were added so as to be 0.8% by mass and 0.35% by mass, respectively, with respect to the pulp component. Next, a PAM-based paper strength enhancer was added so as to be 0.35% by mass with respect to the pulp component, and a neutral rosin-based sizing agent was further added so as to be 0.60% by mass with respect to the pulp component. Then, the paper material was prepared. Using the prepared paper material, papermaking was carried out with a paper machine equipped with a Yankee dryer to obtain a base paper for thermal transfer paper having a fiber orientation ratio of 1.35.

(Example 3)
After mixing the pulp in the same manner as in Example 1, a sulfate band and a PAE-based wet paper strength enhancer were added so as to be 0.6% by mass and 0.35% by mass with respect to the pulp components, respectively. Next, a PAM-based paper strength enhancer was added so as to be 0.35% by mass with respect to the pulp component, and a neutral rosin-based sizing agent was further added so as to be 0.60% by mass with respect to the pulp component. Then, the paper material was prepared. Using the prepared paper material, papermaking was carried out with a paper machine equipped with a Yankee dryer to obtain a base paper for thermal transfer paper having a fiber orientation ratio of 1.52.

(Example 4)
After mixing the pulp in the same manner as in Example 1, a sulfate band and a PAE-based wet paper strength enhancer were added so as to be 0.6% by mass and 0.25% by mass with respect to the pulp components, respectively. Next, a PAM-based paper strength enhancer was added so as to be 0.27% by mass with respect to the pulp component, and a neutral rosin-based sizing agent was further added so as to be 0.40% by mass with respect to the pulp component. Then, the paper material was prepared. Using the prepared paper material, papermaking was carried out with a paper machine equipped with a Yankee dryer to obtain a base paper for thermal transfer paper having a fiber orientation ratio of 1.4.

(Comparative Example 1)
After mixing the pulp in the same manner as in Example 1, a sulfate band was added so as to be 1.2% by mass with respect to the pulp component. Next, the cationized starch was added so as to be 0.4% by mass with respect to the pulp component, and then the PAM-based paper strength enhancer was added so as to be 0.27% by mass with respect to the pulp component, and further. , An acidic rosin-based sizing agent was added so as to be 0.27% by mass based on the pulp component, and a neutral rosin-based sizing agent was added so as to be 0.20% by mass based on the pulp component to prepare a paper material. Using the prepared paper material, papermaking was carried out with a paper machine equipped with a Yankee dryer to obtain a base paper for thermal transfer paper having a fiber orientation ratio of 1.49.

(Comparative Example 2)
It is a product of another company in Japan that is actually used and obtained in the city.

(Comparative Example 3)
It is a product of another foreign company that is actually used and obtained in the city.

Regarding the obtained base papers for thermal transfer papers of Examples and Comparative Examples, the sulfate ion content, fiber orientation ratio, tear strength, tear strength after heat treatment, aspect ratio of tear strength after heat treatment, tensile strength, heat treatment The subsequent tensile strength, the rate of decrease in tensile strength due to heat treatment, the wet tensile strength after heat treatment, and the water absorption of Cobb were measured. In addition, in order to see the suitability as a base paper for thermal transfer paper, the suitability for peeling and the suitability for a cutter knife were evaluated.
The evaluation method for each item is as shown below.

<Sulfate ion content>
A 2 g sample was cut into an appropriate size, boiled in 100 cc of ion-exchanged water for 1 hour, and then filtered with a filter having a pore size of 0.45 μm (Syringe filter 25HP045AN manufactured by Advantech). Then, the amount of sulfate ions was measured using an ion chromatograph (ICS2000 manufactured by Dionex Co., Ltd.).

<Fiber orientation ratio>
The measurement was performed using a device (SST-2500, manufactured by Nomura Shoji Co., Ltd.) for measuring the fiber orientation of the sheet from the angular distribution of the propagation velocity of ultrasonic waves.

<Tear strength>
The tear strength in the MD direction and the CD direction after humidity control was measured under the humidity control environment specified in JIS P 8111: 1998 in accordance with the method specified in JIS-P8116. As a measuring instrument, an Elmendorf type tear tester (manufactured by Toyo Seiki, SA-W type) was used.

<Tear strength after heat treatment>
After leaving it in a constant temperature dryer in an environment of 220 ° C. for 25 minutes, MD after humidity control in a humidity control environment specified in JIS P 8111: 1998 in accordance with the method specified in JIS-P8116. The tear strength in the direction and the CD direction was measured. An Elmendorf type tear tester (manufactured by Toyo Seiki, SA-W type) was used as a measuring instrument.

<Tensile strength>
The tensile strength in the MD direction after humidity control was measured under the humidity control environment specified in JIS P 8111: 1998 in accordance with the method specified in JIS P 8113: 2006. A horizontal tensile tester (manufactured by L & W, CODE SE-064) was used as the measuring machine.

<Tensile strength after heat treatment>
After leaving it in a constant temperature dryer for 25 minutes in an environment of 220 ° C., and then leaving it in a humidity control environment specified in JIS P 8111: 1998 for another 15 minutes, it conforms to the method specified in JIS P 8113: 2006. Then, the tensile strength in the MD direction was measured. A horizontal tensile tester (manufactured by L & W, CODE SE-064) was used as the measuring machine.

<Wet tensile strength after heat treatment>
After leaving it in a constant temperature dryer for 25 minutes in an environment of 220 ° C., and then leaving it in a humidity control environment specified in JIS P 8111: 1998 for another 15 minutes, it was specified as a general law of JIS P 8135: 1998. Wet tensile strength in the MD direction was measured according to the method. A vertical tensile tester (A & D Co., Ltd., Tencilon) was used as the measuring machine.

<Cobb water absorption>
Measurements were performed using an electronic balance capable of measuring up to the last 4 digits in accordance with the 30-second method specified in JIS P 8140: 1998.

<Thermal transferability>
A size of 10 cm x 10 cm was cut out from the thermal transfer paper obtained by checking the printability, and crimped to an aluminum plate so that the printed surface was in contact with each other, and a small hot press machine (MINI PRESS-10 MP-SNH manufactured by Toyo Seiki Co., Ltd.) ) Was used, heat pressing was performed at 220 ° C. for 30 seconds under a load of 5 kN, and a relative evaluation was performed on the sharpness of the transferred image.
◯: The transfer is clear. Δ: Some parts are slightly inferior in color. ×: The color is light and unclear.

<Cutter knife aptitude>
Using a base paper for heat transfer paper of 10 cm × 10 cm, it was left in an environment of 105 ° C. for 15 minutes in a constant temperature dryer, and then impregnated with water for 30 seconds. Then, the paper impregnated with water was cut with a cutter, and the relative evaluation of water resistance was performed from the cut end.
◯: Can be cut without any problem △: The cut end is slightly rough but can be cut ×: Tear occurs in the middle and cannot be cut

<Peeling suitability>
On a 100 cm x 50 cm aluminum base material, the heat transfer paper obtained by confirming the printability of 120 cm x 70 cm is pasted with water-based glue, and heat transfer is performed using a hot press machine to improve workability when peeling. evaluated.
◯: Efficient work is possible △: Workability is slightly deteriorated, but work is possible ×: Efficient work is not possible

The measurement / evaluation results for Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1. In the evaluation of the characteristics, it was judged as acceptable when it was 〇 and Δ.

As is clear from Table 1, the base papers for thermal transfer paper of Examples 1 to 4 can be used as thermal transfer paper, and among them, Example 1 is extremely excellent in workability.
In Comparative Example 1, since the content of sulfate ions was high and no wet paper strength enhancer was used, both the tear strength and the wet tensile strength after the heat treatment were small, and the workability during the peeling work was inferior. Further, in Comparative Example 1, since the content of the neutral rosin-based sizing agent having high size expression was small, the water absorption of the hump was high, and the workability at the time of cutting with a cutter at the time of gluing was also inferior.
In Comparative Example 2, the tensile strength of the heat transfer paper before the heat treatment is slightly small, but since the content of sulfate ions is low, the rate of decrease in the tensile strength due to the heat treatment is low, which is sufficient to enable peeling work. .. In addition, the tear strength after heat treatment and the aspect ratio of the tear strength are also good. From the above, although the workability is slightly inferior, the peeling work can be sufficiently performed. However, since the tensile strength before the heat treatment is slightly small and the water absorption of the hump is high, the workability at the time of cutting with a cutter at the time of gluing is inferior.
In Comparative Example 3, since the tensile strength of the heat transfer paper before the heat treatment is high and the water absorption of the hump is low, the workability at the time of cutting with a cutter at the time of gluing is excellent. However, in Comparative Example 3, since the content of sulfate ions is high and the rate of decrease in tensile strength due to heat treatment is high, the tensile strength after heat treatment is small. In addition, the tear strength is greatly reduced by the heat treatment. From the above, the workability at the time of peeling work was inferior.

Claims (9)

Mainly composed of cellulose pulp
Sulfate ion content is 0.6 mg / l or less,
The content of the wet paper strength enhancer is 0.1 to 0.35% by mass, and the content is 0.1 to 0.35% by mass.
The content of cationized starch is 0.01% by mass or less,
Cobb water absorption is 10 to 13 g / m ² ,
The tensile strength is 2.0 kN / m or more,
The tear strength after heat treatment at 220 ° C. for 25 minutes is 50 mN or more in both the MD direction and the CD direction.
A base paper for heat transfer paper, wherein the ratio of the tear strength after the heat treatment between the MD direction and the CD direction is 0.8 to 1.2.
Here, the content of the sulfate ion is such that a 2 g sample is cut into an appropriate size, boiled in 100 cc of ion-exchanged water for 1 hour, and then filtered through a filter having a pore size of 0.45 μm to obtain an ion chromatograph. It is measured using. A claim characterized by containing 0.30 to 1.20% by mass of one or more selected from a rosin-based sizing agent, an alkenyl succinic anhydride-based sizing agent, a cationic polymer-based sizing agent, and an alkyl ketene dimer-based sizing agent. Item 2. The base paper for thermal transfer paper according to Item 1. The base paper for thermal transfer paper according to claim 1 or 2, wherein the wet paper strength enhancer is one or more selected from a polyamide polyamine epichlorohydrin-based resin, a urea formaldehyde-based resin, and a melamine formaldehyde-based resin. .. The base paper for thermal transfer paper according to any one of claims 1 to 3, wherein the fiber orientation ratio is 1.25 to 1.50. The base paper for thermal transfer paper according to any one of claims 1 to 4, wherein the rate of decrease in tensile strength due to heat treatment at 220 ° C. for 25 minutes is 20% or less. The base paper for thermal transfer paper according to any one of claims 1 to 5, wherein the wet tensile strength after heat treatment at 220 ° C. for 25 minutes is 0.80 kN / m or more. The base paper for thermal transfer paper according to any one of claims 1 to 6, wherein the material to be transferred is made of metal, ceramics or resin. It has the base paper for thermal transfer paper according to any one of claims 1 to 7 and an ink layer formed on the smooth surface side of the base paper for thermal transfer paper, and the ink layer contains ink and a binder resin. Thermal transfer paper characterized by that. The heat transfer paper according to claim 8, which is used in a method of using a water-based glue when adhering to a transfer material.