JP2019043053A - Base paper for thermal transfer paper and thermal transfer paper - Google Patents

Abstract

To provide base paper for thermal transfer paper and thermal transfer paper using the same, where tear is hard to occur during a gluing process where the thermal transfer paper and the base material are glued using aqueous glue, and also tear during a peeling process is hard to occur.SOLUTION: The main component of the base paper for thermal transfer paper is cellulose pulp, the content of sulfate ion being 0.6 mg/l or less, the content of the wet paper strength additive being 0.1 to 0.35 mass%, the Cobb water absorbency being 10 to 13 g/mor less, the tear strength being 2.0 kN/m or over, the tear strength after a heating process at 220°C for 25 minutes being 50 mN or over both in the MD direction and the CD direction, the ratio between the post-heating process tear strengths in the MD direction and the CD direction being characteristically 0.8 to 1.2.SELECTED DRAWING: None

Description

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

  A paper produced by pressing and drying only one side of a wet paper made from pulp as raw material by a paper machine in a mirror-like cylindrical cylinder drier (hereinafter referred to as a Yankee drier) has extremely high smoothness and It is called glossy paper.

  The single-glossy paper is used as a packaging application, a bag-making application, a processing application, etc., and printing is often performed on the smooth surface side dried in contact with the Yankee dryer. For this reason, many inventions are known in which the printability and the processability on the smooth surface side are improved (for example, Patent Document 1 and Patent Document 2).

Patent No. 4841515 gazette Patent No. 4350145

  As another application using a single-glossy paper, development to a thermal transfer paper can be considered. In this application, various patterns are printed on a smooth surface of a single-glossy paper using a gravure printer or an ink jet printer, and the patterns are thermally transferred onto a metal substrate such as aluminum or stainless steel for design. It provides excellent articles. The procedure of its manufacture is as follows. First, for example, a woodgrain pattern is printed on a smooth surface of a single-glossy paper using a sublimation ink to produce a thermal transfer paper. Next, an aqueous paste is applied to the obtained thermal transfer paper, or the substrate is brought into close contact with the substrate under vacuum. After the portion of the thermal transfer paper which has been pulled out of the substrate is cut off with a cutter and removed, heat is applied to transfer the design to the substrate. Thereafter, when the thermal transfer paper is peeled off from the substrate, a substrate having a wood grain pattern on the surface can be obtained. This application is mainly useful for building materials.

  As another method, there is also a method of transferring a design onto a substrate by bringing a substrate and a thermal transfer paper after printing into close contact and then heating and pressing with a hot press.

  When an aqueous paste is used to bring the thermal transfer paper into close contact with the substrate, it is necessary to cut the portion of the thermal transfer paper which has become wet with the glue, which has come out of the substrate with a cutter. At this time, if the strength of the thermal transfer paper is small, the closely adhered paper is broken at a position not intended for cutting, and the thermal transfer paper which has been closely adhered must be discarded and the operation must be repeated from the step of adhering the new thermal transfer paper. Etc, there is a problem of causing a decrease in workability.

In addition, the thermal transfer paper needs to be peeled off from the substrate after the transfer of the design by heat treatment. At this time, if the strength of the thermal transfer paper after heating is not sufficiently large, the thermal transfer paper is broken at the time of the peeling operation, and the thermal transfer paper can not be peeled in one operation, causing a problem of deterioration in workability.
In addition, even if the strength in one of the longitudinal direction and the lateral direction is sufficiently high, if the strength in the other direction is insufficient, a tear occurs in the direction in which the strength is low, which also causes a decrease in workability. There is.
The term "longitudinal direction" as used herein refers to the direction in which the slurry (pulp fiber) flows out in the process of forming the paper layer in papermaking of the heat transfer paper base paper. The transverse direction refers to a direction perpendicular to the paper in the longitudinal direction. Hereinafter, the vertical direction is also referred to as the MD direction, and the horizontal direction is also referred to as the CD direction.

  The object of the present invention is to prevent breakage at the time of gluing with a thermal transfer paper and a substrate using an aqueous paste and to hardly cause breakage at the time of peeling off. Providing a thermal transfer sheet.

The present inventors contain a predetermined amount of a wet strength agent, and when the cobb water absorption degree and the tensile strength of the thermal transfer paper are within a predetermined value range, breakage or the like at the time of cutting operation by a cutter at the time of pasting It was found to be reduced.
In addition, the inventors of the present invention have found that the content of sulfate ion of the thermal transfer paper is less than a predetermined amount, and the tear strengths of the thermal transfer paper in the MD direction and the CD direction are both predetermined values or more after heat treatment It has been found that when the ratio of the tear strength in the CD direction is at the predetermined ratio, the breakage during the peeling operation is reduced.
The present inventors were able to arrive at the present invention from the above-mentioned multiple findings. That is, the present invention has the following configuration.

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

(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), wherein the fiber orientation ratio is 1.25 to 1.50.

(4) The base paper for thermal transfer paper according to any one of the above (1) to (3), 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 the above (1) to (4), wherein the tensile strength reduction rate by 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 the above (1) to (5), which has a wet tensile strength of 0.80 kN / m or more after heat treatment at 220 ° C. for 25 minutes. .

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

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

(9) The thermal transfer paper according to the above (8), which is used in a method of using a water-based paste when in close contact with a material to be transferred.

  The base paper for thermal transfer paper of the present invention is less likely to break during the gluing operation and less likely to break during the peeling operation, and is suitable for use in heat-transferring a pattern by gluing to a substrate . In addition, since the thermal transfer paper of the present invention uses the base paper for thermal transfer paper, it is suitable for use for thermally transferring a pattern by gluing to a substrate.

  Hereinafter, embodiments of the present invention will be specifically described. The description of the configuration requirements described below may be made based on typical embodiments and specific examples, but the present invention is not limited to such embodiments. In addition, the numerical range represented using "-" in this specification means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

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

  The substrate (transferred material), which is the target of transfer, is preferably a member of various shapes made of metal, ceramic or resin. The thermal transfer paper of the present embodiment is used to impart design to furniture, building materials and the like, but is not limited to these substrates. 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 operating procedure for transferring the ink layer to the substrate is as follows.
(1) After applying an aqueous paste to the thermal transfer paper, the thermal transfer paper is adhered to the substrate. Alternatively, the thermal transfer paper and the substrate are combined and then vacuumed to bring them into close contact.
(2) A portion of the thermal transfer paper which has run out of the substrate is cut off with a cutter and removed.
(3) Heat at about 170 ° C. to 220 ° C. is applied to transfer the ink layer (pattern on the thermal transfer paper) to the substrate.
(4) Peel off the thermal transfer paper to which the design has been transferred from the substrate. At that time, the base material and the thermal transfer paper may be covered with a vinyl or the like, and may be cooled by adding water to the operation.

  When a hot press is used, the substrate and the thermal transfer paper after printing are brought into close contact with each other and then heated and pressed by the hot press to transfer the ink layer to the substrate.

Hereinafter, each element which comprises the heat transfer paper base paper of this embodiment is demonstrated.
(pulp)
The base paper for thermal transfer paper is mainly composed of cellulose pulp. The cellulose pulp is not particularly limited, but it is preferable to contain a chemical pulp from the viewpoint of strength. The chemical pulp is not particularly limited, but it is preferable to contain hardwood kraft pulp (LKP) or softwood kraft pulp (NKP). The pulp may be bleached pulp or unbleached pulp. Furthermore, it is preferable to contain both LKP and NKP.

  In general, LKP has short fibers and inferior strength as compared to NKP, but it is excellent in formation and smoothness of paper made of paper and can be made to have good 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 more preferably 80% by mass or more based on the total mass of the pulp components. Is more preferred.

  The freeness of LKP is preferably 250 to 400 mlcsf, more preferably 280 to 380 mlcsf. When the freeness is in the above range, it is possible to form a base paper having excellent strength and smoothness. In addition, the desired paper quality can be easily achieved by increasing the fixation site of the papermaking agent described later. In addition, the freeness of pulp is a numerical value measured in accordance with JIS P 8121: 2012.

  In addition, in the base paper for thermal transfer paper, it is preferable to blend NKP. Because of the long fibers, NKP can increase the tensile strength and tear strength of the machined product. Therefore, the content of NKP is preferably 5% by mass or more, and more preferably 10% by mass or more based on the total mass of the pulp components.

  The freeness of NKP is preferably 500 mlcsf or less, more preferably 400 mlcsf or less. If the degree of beating of NKP is in 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 NKP and LKP (hereinafter referred to as other pulp). Other pulps include stone ground pulp (SGP), pressed stone ground pulp (PGW), refiner ground pulp (RGP), thermoground pulp (TGP), chemiground pulp (CGP), ground pulp (GP), thermo Manufactured from mechanical pulp (TMP) and other mechanical pulp, waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, white waste paper, white waste paper, Kent waste paper, imitation waste paper, ground paper waste paper, etc. Examples thereof include disintegrated paper pulp (DIP), and pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp, straw and the like. The content of the other pulp is preferably less than 3% by mass, more preferably less than 2% by mass, and still more preferably less than 1% by mass, based on the total mass of the pulp components.

(Sulfate band)
Sulfate bands (aluminum sulfate) have been widely used as fixing agents such as retention aids and sizing agents. However, when used as a base paper for thermal transfer paper, since it is heated to around 200 ° C. during transfer, the sulfate ion generated from the sulfate band at the time of heating hydrolyzes cellulose, and the tensile strength and tear strength of the paper after heat treatment Greatly reduce Therefore, the content of the sulfate ion in the base paper for thermal transfer paper which can suppress the decrease in tensile strength due to the heat treatment at the time of transfer was examined. As a result, it was found that the content of sulfate ion in the base paper for thermal transfer paper needs to be 0.6 mg / l or less. The content of the sulfate ion 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 the sulfate ion in the above range, it is possible to suppress the decrease in tensile strength after the heat treatment. Here, the content of the sulfate ion 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, from the viewpoint of reducing breakage at the time of peeling work, and 0.7 mass It is more preferable that the content is less than%. The content of the sulfuric acid band can be measured as the content of sulfate ion, but 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 mentioned above, by adjusting the blend of the pulp, the tensile strength can be improved. Then, the present inventors repeated examination about the tensile strength which can reduce the fracture at the time of the cutting operation by the cutter at the time of pasting.
Further, as described above, by adjusting the content of the sulfuric acid band, it is possible to suppress the decrease in tensile strength due to the heat treatment. However, even if it is possible to suppress the strength reduction 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 repeatedly studied about the minimum tensile strength which can reduce the breakage at the time of the peeling operation even if the tensile strength is lowered by the heat treatment.
The inventors of the present invention have found that the tensile strength at the time of humidity control needs to be 2.0 kN / m or more from the above-described multiple findings on the tensile strength. Furthermore, it has been found that it is more preferable if the tensile strength is 2.4 kN / m or more.
In addition, although tensile strength also has MD direction and CD direction similarly to tear strength, it shall be made to represent in MD direction in this embodiment.

(Tear strength)
Moreover, the present inventors repeated examination about the tear strength required in order to reduce the fracture | rupture at the time of the peeling operation after heat processing. 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 be 50 mN or more in both the MD and CD directions, and at this time, either the MD direction or the CD direction It was found that it is more preferable if one of them is 63 mN or more.

(Tear strength ratio)
In order to reduce the fracture at the time of peeling from the substrate after heat treatment, it is necessary not only to have a sufficiently high tensile strength and tear strength, but also to have a balance of tear strength in the MD direction and the CD direction. It is. The present inventors paid attention to this point and repeated studies on the ratio of tear strength in the MD direction and the CD direction that can reduce breakage. As a result, it is necessary that the ratio of tear strength in the MD direction and the CD direction in the case of heat treatment at 220 ° C. for 25 minutes be in the range of 0.8 to 1.2, and 0.88 to 1. It was found that the range of 12 was more preferable.
Here, the ratio of the tear strength in the MD direction to the CD direction is the value of LMD / LCD when the tear strength in the MD direction is LMD and the tear strength in the CD direction is LCD. The conditions of heat treatment at 220 ° C. for 25 minutes are selected as typical heat treatment conditions for thermal transfer.

(Fiber orientation ratio)
In order to realize the above-mentioned ratio of tear strength in the MD direction and the CD direction, the present inventors paid attention to the bond between 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 wave 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 of pulp fibers to flow out on a wire of a paper machine, to be dewatered, and to be aligned 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 velocity ratio).
The jet wire ratio is the ratio of the flow rate of the pulp fibers to the running speed of the wire, and is expressed by the flow rate of the slurry flowing / the running speed of the wire.

  Generally, as a method of measuring fiber orientation of paper etc., for example, thermal expansion method, mechanical breaking strength method, X-ray diffraction method, ultrasonic method, microwave method, NMR method, polarization fluorescence method, dielectric measurement method etc. are mentioned. Be In the present invention, the ultrasonic method is employed to measure the longitudinal ultrasonic wave propagation velocity (Vmd) and the transverse ultrasonic wave propagation velocity (Vcd), and the ratio (Vmd / Vcd) is taken as the fiber orientation ratio to determine 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, the adjustment of the sulfuric acid band can suppress the deterioration of the thermal transfer paper due to the heat treatment, and can improve the tear strength and the tensile strength. In addition, by appropriately mixing NKPs having long fibers, it is possible to strengthen the bond between the fibers and to improve the tear strength and the tensile strength. In addition to these, it is possible to adjust the ratio of tear strength in the MD direction and the CD direction by adjusting the fiber orientation.
By these formulations, the tear strength after heat treatment is 50 mN or more in both the MD direction and the CD direction, and the ratio of the MD direction to the CD direction of the tear strength after heat treatment is 0.8 to 1.2. A base paper for thermal transfer paper can be realized.

(Paper strength agent)
The base paper for thermal transfer paper of this embodiment is required to be excellent in wet tensile strength because a water-based paste is applied when the base paper is brought into close contact with the substrate. Furthermore, it is necessary that the wet tensile strength after the heat treatment be excellent from the workability when the thermal transfer paper is peeled off from the substrate. The present inventors examined a formulation for improving the tensile strength in the wet state. In the case of cationized starch which has been widely used as a paper strengthening agent conventionally, the effect of improving the tensile strength when wet is not sufficient. Therefore, a wet strength agent to replace cationized starch was examined. As a result, as a wet paper strengthening agent, one or more selected from polyamidepolyamine 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 strength agent is 0.10 to 0.35% by mass. The content of the wet strength agent is 0.10% by mass or more, and preferably 0.20% by mass or more. If it is said range, it will become possible to provide the wet tensile strength which can be used as heat transfer paper base paper. On the other hand, the content of the wet strength agent is 0.35% by mass or less. This is because if the wet strength agent content is too high, it can not be fixed in the pulp, and excessive chemicals will be used, which may cause adverse effects such as staining the inside of the paper machine system. . Here, the content of the cationized starch and the wet strength agent is a ratio to the total mass of the pulp component.

  As a dry paper strengthening agent, although a well-known thing can be used, for example, a polyacrylamide based paper strengthening agent (PAM) and starch can be used. There is no particular limitation on PAM and starch, and any of cationic, anionic and amphoteric can be used. However, in consideration of the fixability of the wet strength agent, an anionic or amphoteric dry strength agent is preferred.

(Size agent)
A well-known thing can be used as a sizing agent. Among sizing agents, one or more selected from a rosin sizing agent, an alkenyl succinic anhydride (ASA) sizing agent, a cationic polymer sizing agent, and an alkyl ketene dimer (AKD) sizing agent may be selected from 0.30 to 1.5. The content is preferably 20% by mass, more preferably 0.40 to 0.80% by mass, and still more preferably 0.50 to 0.80% by mass. In particular, since the addition amount of the acidic sulfate band is reduced, the neutral rosin sizing agent is preferable to the acidic rosin sizing agent from the viewpoint of size development.

  In addition, known additives such as calcium carbonate, talc, clay, fillers such as kaolin, retention improvers, drainage improvers, etc. are appropriately blended in the stock as papermaking additives for achieving the desired function. can do.

  The stock prepared as described above can be made as a single-gloss paper by a known method. The type of paper machine in that case is not particularly limited. Generally, in order to improve the smoothness on one side, it is made by a paper machine having a Yankee dryer. Therefore, one side of the heat transfer paper base paper is smooth. Moreover, you may add post-processes, such as providing the coating layer which gives printability to the surface, and calendering, as needed.

(Cobb water absorption)
The Cob absorbency of the base paper for thermal transfer paper can be adjusted by the sizing agent. Cobb's water absorbency is a performance that greatly affects the cuttability of the wet thermal transfer paper. If the cobb's water absorption is too high, the thermal transfer paper absorbs a large amount of water, which makes it very difficult to cut.
Therefore, the present inventors have examined Cobb's water absorbency of the heat transfer paper base paper in order to realize a heat transfer paper which can be easily cut even when it is 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 Cobb's water absorption exceeds 13 g / m ² , when the thermal transfer paper is made to adhere to the substrate using aqueous paste, the strength of the paper is reduced and the workability in the cutting operation is significantly reduced. . In order to set the Cobb water absorption to 13 g / m ² or less, it can be achieved by adding an appropriate amount of the sizing agent described above to the stock. Cobb water absorption is measured by the 30 g / m ² method defined in JIS P 8140: 1998.

  Furthermore, when the thermal transfer paper after the heat treatment is peeled off from the substrate, the tensile strength after the heat treatment becomes important. The tensile strength of the heat transfer paper base 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 tensile strength reduction rate (%) of the heat transfer paper base paper by heat treatment at 220 ° C for 25 minutes is
100 * [(tensile strength at the time of humidity control)-(tensile strength after heat treatment at 220 ° C. for 25 minutes)] / (tensile strength at the time of humidity control). The tensile strength reduction rate after heat treatment is preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less. If the tensile strength reduction rate after the heat treatment exceeds 20%, the thermal transfer paper tears when the thermal transfer paper is peeled off from the substrate after thermal transfer, and the workability is lowered.

  The tensile strength after heat treatment can be controlled by setting the content of sulfate ion 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 decline. Moreover, in order to ensure the tensile strength after heat processing, the method of making high the tensile strength before heat processing is also employable. However, in that case, it is necessary to take measures such as increasing the paper strength enhancing agent etc. or raising the basis weight, which is not necessarily desirable from the aspect of cost and workability.

  The wet tensile strength of the heat transfer paper base 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 heat treatment 0.80 kN / m or more, an appropriate amount of the wet paper strength agent described above may be added to the stock. If the wet tensile strength is lower than the above, there is a concern that the workability of the work of cutting the excess heat transfer paper when transferred using an aqueous paste is reduced. In addition, although the work of peeling the thermal transfer paper from the substrate after transfer is performed under a high temperature and high humidity environment, the thermal transfer paper is easily torn at that time, and the workability may be deteriorated.

  The tensile strength is measured in accordance with JIS P 8113: 2006. Moreover, the tensile strength at the time of humidity control is a tensile strength measured after leaving it to stand in a humidity controlled environment (temperature 23 ° C., humidity 50% RH) according to JIS P 8111: 1998 for one day or more. Further, the tensile strength after the heat treatment is measured after leaving for 25 minutes in an environment of 220 ° C. with a constant temperature drier and further leaving for 15 minutes in a humidity controlled environment.

  The wet tensile strength after heat treatment is defined as a general method according to JIS P 8135: 1998 after leaving for 25 minutes in an environment of 220 ° C. with a constant temperature drier and further standing for 15 minutes in a humidity controlled environment. It measures according to the following method.

  Here, the above-mentioned tensile strength, tensile strength after heat treatment, and wet tensile strength after heat treatment are measured in principle in the MD direction (flow direction of the paper machine) in any case. However, when it is unclear whether it is in the MD direction, the tensile strength is measured at every angle of 22.5 degrees, and the direction showing the strongest tensile strength is taken as the MD direction.

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

  Examples and comparative examples are shown below. The materials, amounts used, proportions, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below.

Example 1
The bleached softwood kraft pulp (NKP) and the bleached hardwood kraft pulp (LKP) were each beaten to a freeness of 360 ml using a double disc refiner (hereinafter referred to as "DDR"). 15% by mass of beaten NKP and 85% by weight of beaten LKP were respectively mixed in a mixing chest. Next, a sulfuric acid band and a polyamidepolyamine epichlorohydrin resin (PAE wet paper strengthening agent) were added so as to be 0.6% by mass and 0.25% by mass, respectively, with respect to the pulp component. Then, a polyacrylamide-based paper strength agent (PAM-based paper strength agent) is added to 0.5% by mass with respect to the pulp component, and a neutral rosin-based sizing agent is further added with respect to the pulp component. The paper stock was prepared by adding .60 mass%. The prepared stock was used for paper making with a paper machine having a Yankee drier to obtain a heat transfer paper base paper having a fiber orientation ratio of 1.37.

(Example 2)
After mixing the pulp in the same manner as in Example 1, a sulfuric acid band and a PAE-based wet strength agent were added so as to be 0.8% by mass and 0.35% by mass, respectively, with respect to the pulp component. Then, a PAM-based paper strengthening agent is added to 0.35% by mass with respect to the pulp component, and a neutral rosin sizing agent is further added to 0.60% by mass with respect to the pulp component The stock was prepared. The prepared stock was used for paper making with a paper machine having 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 sulfuric acid band and a PAE-based wet strength agent were added so as to be 0.6% by mass and 0.35% by mass, respectively, with respect to the pulp component. Then, a PAM-based paper strengthening agent is added to 0.35% by mass with respect to the pulp component, and a neutral rosin sizing agent is further added to 0.60% by mass with respect to the pulp component The stock was prepared. The prepared stock was used for paper making with a paper machine having a Yankee drier to obtain a base paper for thermal transfer paper with a fiber orientation ratio of 1.52.

(Example 4)
After the pulp was mixed in the same manner as in Example 1, a sulfuric acid band and a PAE-based wet strength agent were added so as to be 0.6% by mass and 0.25% by mass, respectively, with respect to the pulp component. Then, a PAM-based paper strengthening agent is added to 0.27% by mass with respect to the pulp component, and a neutral rosin sizing agent is further added to 0.40% by mass with respect to the pulp component The stock was prepared. The prepared stock was used for paper making with a paper machine having a Yankee drier to obtain a base paper for thermal transfer paper with a fiber orientation ratio of 1.4.

(Comparative example 1)
After mixing the pulp in the same manner as in Example 1, a sulfuric acid band was added so as to be 1.2% by mass with respect to the pulp component. Then, cationized starch is added to 0.4% by mass with respect to the pulp component, and then a PAM-based paper strengthening agent is added to 0.27% by mass with respect to the pulp component, and further A stock was prepared by adding an acid rosin sizing agent at 0.27% by mass with respect to the pulp component and a neutral rosin sizing agent at 0.20% by mass with respect to the pulp component. The prepared stock was used for paper making with a paper machine having a Yankee drier to obtain a base paper for thermal transfer paper with a fiber orientation ratio of 1.49.

(Comparative example 2)
It is another domestic product that is actually used and obtained in the city.

(Comparative example 3)
It is another company's product that is actually used and obtained outside the city.

Regarding the base paper for thermal transfer paper of the obtained examples and comparative examples, the content of sulfate ion, 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 tensile strength reduction rate by heat treatment, the wet tensile strength after heat treatment, and the Cobb water absorption were measured. In addition, in order to examine the suitability as a heat transfer paper base paper, the peelability and the cutter knife suitability were evaluated.
The evaluation method of each item is as shown below.

<Content of sulfate ion>
A 2 g sample was cut into a suitable size and boiled in 100 cc of ion-exchanged water for 1 hour, followed by filtration with a filter with a pore size of 0.45 μm (Advantec's syringe filter 25HP045AN). Thereafter, the amount of sulfate ion was measured using an ion chromatograph (manufactured by Dionex, ICS 2000).

<Fiber orientation ratio>
It measured using the apparatus (SST-2500, Nomura Corporation make) which measures the fiber orientation of a sheet | seat from the angular distribution of the propagation speed of an ultrasonic wave.

<Tear strength>
According to the method defined in JIS-P8116, the tear strength in the MD direction and the CD direction after humidity control was measured in a humidity controlled environment defined in JIS P 8111: 1998. An Elmendorf tear tester (manufactured by Toyo Seiki, model SA-W) was used as a measuring instrument.

<Tear strength after heat treatment>
After leaving for 25 minutes in an environment of 220 ° C. in a constant temperature drier, MD after humidity adjustment in a humidity controlled environment defined in JIS P 8111: 1998 in accordance with the method defined in JIS-P 8116 Measurements of tear strength in the direction and in the CD direction were made. An Elmendorf tear tester (manufactured by Toyo Seiki, SA-W type) was used as a measuring instrument.

<Tensile strength>
According to the method defined in JIS P 8113: 2006, the tensile strength in the MD direction after humidity control was measured in a humidity controlled environment defined in JIS P 8111: 1998. As a measuring machine, a horizontal tensile tester (manufactured by L & W, CODE SE-064) was used.

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

<Wet tensile strength after heat treatment>
After standing for 25 minutes in an environment of 220 ° C. in a constant temperature dryer, and for a further 15 minutes in a humidity controlled environment defined in JIS P 8111: 1998, it was defined as a general method of JIS P 8135: 1998. Measurement of wet tensile strength in the MD direction was performed according to the method. As a measuring machine, a vertical tensile tester (manufactured by A & D, Tensilon) was used.

<Cobb water absorption>
The measurement was performed using an electronic balance that can measure up to the last four digits in accordance with the 30-second method defined in JIS P 8140: 1998.

<Heat transferability>
A size of 10 cm × 10 cm is cut out from the thermal transfer paper obtained in the confirmation of the printability, and the aluminum plate is pressed against the printing surface so that the compact hot press (Mini PRESS-10 MP-SNH manufactured by Toyo Seiki Co., Ltd.) ) Using a 5 kN load for 30 seconds at 220 ° C., and a relative evaluation of the sharpness of the transferred image was made.
:: sharp transfer is made △: some color is slightly inferior ×: color is thin and unclear

<Cut knife suitability>
After leaving it to stand in an environment of 105 ° C. for 15 minutes in a thermostatic dryer using a 10 cm × 10 cm base paper for thermal transfer paper, it was impregnated with water for 30 seconds. Thereafter, the paper impregnated with water was cut with a cutter, and relative evaluation of water resistance was performed from the cut end.
○: can be cut without any problem Δ: some cuts are rough but cut is possible ×: tears occur on the way and can not be cut

<Peeling aptitude>
The thermal transfer paper obtained by the confirmation of the printability of 120 cm × 70 cm is pasted on a 100 cm × 50 cm aluminum substrate using an aqueous paste, thermally transferred using a hot press machine, and workability at the time of peeling off evaluated.
○: Workable efficiently △: Workability is slightly deteriorated, but workable ×: Worklessly performed

  The measurement and 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 pass when と and の.

As is apparent from Table 1, the base paper for thermal transfer paper of Examples 1 to 4 can be used as a thermal transfer paper, and among them, Example 1 was extremely excellent in workability.
Comparative Example 1 had a high content of sulfate ion and no wet paper strengthening agent was used, so the tear strength after wet heat treatment and the wet tensile strength were both small, and the workability at the time of peeling was inferior. Moreover, since the content of the neutral rosin type sizing agent having high size development was small, Comparative Example 1 had a high degree of Cobb water absorption, and was inferior also in the workability at the time of the cutting operation by the cutter at the time of pasting.
In Comparative Example 2, although the tensile strength of the thermal transfer paper before heat treatment is a little small, the content of the sulfate ion is small, so the rate of decrease in tensile strength due to heat treatment is low, which is sufficient to enable the peeling operation. . In addition, the tear strength after heat treatment and the aspect ratio of the tear strength are also good. From the above, although it is somewhat inferior in workability, it is possible to perform the peeling operation sufficiently. However, since the tensile strength before the heat treatment is a little small and the cobb's water absorption is high, the workability at the time of the cutting operation by the cutter at the time of pasting is inferior.
In Comparative Example 3, the tensile strength of the thermal transfer paper before heat treatment is large, and the cobb's water absorption is low, so that the workability at the time of the cutting operation by the cutter at the time of pasting is excellent. However, Comparative Example 3 has a high content of sulfate ion and a high tensile strength reduction rate due to the heat treatment, so the tensile strength after the heat treatment is small. Moreover, the tear strength is also greatly reduced by the heat treatment. From the above, the workability at the time of the peeling work was inferior.

Claims (9)

Mainly composed of cellulose pulp,
The content of sulfate ion is 0.6 mg / l or less,
The content of the wet strength agent is 0.1 to 0.35% by mass,
Cobb water absorption is 10-13 g / m ² ,
Tensile strength is more than 2.0 kN / m,
The tear strength after heat treatment at 220 ° C for 25 minutes is 50 mN or more in both the MD and CD directions,
The base paper for thermal transfer paper, wherein the ratio of the MD direction to the CD direction of the tear strength after the heat treatment is 0.8 to 1.2.   0.30 to 1.20% by mass of one or more selected from rosin type sizing agents, alkenyl succinic anhydride type sizing agents, cationic polymer type sizing agents, and alkyl ketene dimer type sizing agents The heat transfer paper base paper according to Item 1.   The base paper for thermal transfer paper according to claim 1 or 2, wherein the fiber orientation ratio is 1.25 to 1.50.   The heat transfer paper base paper according to any one of claims 1 to 3, wherein the content of the cationized starch is 0.01 mass% or less.   The base paper for thermal transfer paper according to any one of claims 1 to 4, wherein a tensile strength reduction rate by 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, which has a wet tensile strength of 0.80 kN / m or more after heat treatment at 220 ° C for 25 minutes.   The base material for thermal transfer paper according to any one of claims 1 to 6, wherein the material to be transferred is made of metal, ceramic or resin.   The heat transfer paper base paper according to any one of claims 1 to 7 and an ink layer formed on the smooth surface side of the heat transfer paper base paper, wherein the ink layer contains an ink and a binder resin. Thermal transfer paper characterized by   9. The thermal transfer paper according to claim 8, which is used in a method of using a water-based glue when in close contact with a transfer material.