CN108725061B

CN108725061B - Base paper for thermal transfer paper and thermal transfer paper

Info

Publication number: CN108725061B
Application number: CN201810349456.7A
Authority: CN
Inventors: 槌本真和; 远藤智裕; 清水陵
Original assignee: Oji Holdings Corp
Current assignee: Oji Holdings Corp
Priority date: 2017-04-18
Filing date: 2018-04-18
Publication date: 2020-08-28
Anticipated expiration: 2038-04-18
Also published as: CN108725061A; CN111907248A; CN111907247A

Abstract

The invention provides a base paper for thermal transfer paper with excellent tensile strength, tensile strength after heat treatment, printing performance and operation performance, and thermal transfer paper using the base paper. The base paper for thermal transfer paper is characterized by comprising cellulose pulp as a main component; the density is 0.75 to 0.85g/cm³(ii) a The basis weight is 20 to 50g/m²(ii) a The single surface is a smooth surface, and the Wang grinding type smoothness of the smooth surface is more than 500 seconds; and the content of sulfate ion is 0.6mg/l or less. Further, the thermal transfer paper is characterized by comprising: the base paper for thermal transfer paper; and an ink layer formed on the smooth surface side of the base paper for thermal transfer paper, wherein the ink layer contains ink and a binder resin.

Description

Base paper for thermal transfer paper and thermal transfer paper

Technical Field

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

Background

A paper produced by drying a wet paper made from pulp as a raw material by a paper machine with only one side of the wet paper pressed against a mirror-like cylindrical dryer (hereinafter referred to as a yankee dryer) is called a simplex paper because of its extremely high smoothness.

Matte paper is used for packaging, bag making, processing, and the like, and printing is often performed on the smooth surface side that is dried by contacting with a yankee dryer. Therefore, many inventions for improving the printing suitability or the processing suitability on the smooth surface side are known (for example, patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4841515.

Patent document 2: japanese patent No. 4350145.

Disclosure of Invention

As another use using the simplex paper, development toward thermal transfer paper can be considered. This application is to provide an article having excellent design properties by printing various patterns on a smooth surface of a plain paper sheet using a gravure printer or an ink jet printer and thermally transferring the patterns onto a metal substrate such as aluminum or stainless steel. The order of manufacture is as follows. First, sublimation ink is used on a smooth surface of a plain paper, for example, a wood-grain-style pattern is printed, thereby manufacturing a thermal transfer paper. Next, an aqueous paste is applied to the obtained thermal transfer paper, or the paper is closely adhered under vacuum, thereby closely adhering the base material. The portion of the thermal transfer paper exposed to the outside from the base material is cut and removed by a cutter, and then the pattern is transferred onto the base material by heating. After that, when the thermal transfer paper is peeled from the substrate, a substrate having a surface on which a woodgrain-like pattern is applied can be obtained. The application is mainly used for building materials.

Alternatively, the pattern may be transferred to the base material by closely adhering the base material to the printed thermal transfer paper and then heating and pressing the base material with a hot press.

As described above, when the thermal transfer paper is used as a thermal transfer paper for building materials, the above-described steps are required. Therefore, the base paper for thermal transfer paper is required to have excellent properties such as tensile strength and tensile strength after heat treatment. In addition, in order to improve the finishing effect of the pattern, it is required to have excellent printing applicability. Further, it is preferably lightweight from the viewpoint of workability in transfer to and peeling from a substrate.

In the conventional art, no consideration has been made on the above-described application and the required characteristics have been imparted to the plain paper. The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a base paper for thermal transfer paper excellent in tensile strength, tensile strength after heat treatment, printability and workability, and thermal transfer paper using the same.

The present inventors have studied to reduce the amount of aluminum sulfate added in order to improve the tensile strength after heat treatment while keeping the properties as a plain paper. The present invention has been completed based on the above-mentioned studies. That is, the present invention has the following configuration.

(1) A base paper for thermal transfer paper, characterized in that cellulose pulp is used as a main component; the density is 0.75 to 0.85g/cm³(ii) a The basis weight is 20 to 50g/m²(ii) a The single surface is a smooth surface, and the Wang grinding type smoothness of the smooth surface is more than 500 seconds; the content of sulfate ion is less than 0.6 mg/l.

(2) The base paper for thermal transfer paper described in the above (1), wherein 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.

(3) The base paper for thermal transfer paper according to the above (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.

(4) The base paper for thermal transfer paper according to any one of the above (1) to (3), which contains at least one 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.

(5) The base paper for thermal transfer paper according to any one of the above (1) to (4), wherein the cellulose pulp contains hardwood sulfate pulp or softwood sulfate pulp.

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

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

(8) The base paper for thermal transfer paper according to any one of the preceding (1) to (7), wherein the paper is produced by a method according to the Japan pulp and paper industry Association No. 67: an oil absorption of 400 seconds or more as measured by the method of 2000(JAPAN TAPPI No. 67: 2000).

(9) The base paper for thermal transfer paper according to any one of the above (1) to (8), wherein the material to be transferred is made of metal, ceramic, or resin.

(10) A thermal transfer paper comprising the base paper for thermal transfer paper according to any one of the above (1) to (9), and an ink layer formed on the smooth surface side of the base paper for thermal transfer paper, wherein the ink layer contains ink and a binder resin.

The base paper for thermal transfer paper of the present invention has excellent tensile strength, tensile strength after heat treatment, printability and workability. The thermal transfer paper of the present invention uses the base paper for thermal transfer paper, and is therefore suitable for use in applications where a pattern is thermally transferred to a substrate.

Detailed Description

The embodiments of the present invention will be specifically described below. The following description of the constituent elements is based on the representative embodiments and specific examples, but the present invention is not limited to the above-described embodiments. In the present specification, the numerical range expressed by the term "to" means a range including the numerical values described before and after the term "to" as the lower limit value and the upper limit value.

The base paper for thermal transfer paper of the present embodiment is composed of a plain paper. The thermal transfer paper of the present embodiment has 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 a gravure printer, an inkjet printer, or the like, and has various patterns.

The substrate (transfer target material) to be transferred is preferably a member having various shapes made of metal, ceramic, or resin. The thermal transfer paper of the present embodiment is used for imparting design properties 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 not particularly limited, and is a synthetic resin, a natural resin, or the like.

The sequence of operations for transferring the ink layer to the substrate is as follows.

(1) After the aqueous paste is applied to the thermal transfer paper, the thermal transfer paper is brought into close contact with the base material. Alternatively, the thermal transfer paper and the base material are aligned and then brought into close contact with each other by vacuum treatment.

(2) The thermal transfer paper at the portion exposed to the outside from the base material is cut and removed by a cutter.

(3) The ink layer (pattern on the thermal transfer paper) is transferred to the base material by applying heat of about 170 ℃ to 220 ℃.

(4) The thermal transfer paper with the transferred pattern is peeled from the base material. In this case, a cover base material such as a plastic film (vinyl) or the like and a thermal transfer paper may be additionally used, and the cover base material and the thermal transfer paper may be cooled by watering.

In the case of using a hot press, the ink layer is transferred onto the base material by closely contacting the base material with the printed thermal transfer paper and then heating and pressing the base material with the hot press.

Hereinafter, each element constituting the base paper for thermal transfer paper of the present embodiment will be described.

(pulp)

The base paper for thermal transfer paper contains cellulose pulp as a main component. The 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. Preferably, both LKP and NKP are contained.

In general, LKP fibers are shorter and inferior in strength to NKP, but the printed paper is superior in texture and smoothness, and therefore, the printing applicability can be improved. Therefore, the content of LKP in the base paper for thermal transfer paper is preferably 40 mass% or more, more preferably 60 mass%, and still more preferably 80 mass% or more, based on the total mass of the pulp components.

The degree of kogation (freeness) of LKP is preferably 250-400 mlcsf, more preferably 280-380 mlcsf. When the beating degree is within the above range, a base paper having more excellent strength and smoothness can be produced. In addition, since the fixing position of the paper-making chemical described later is increased, a desired paper quality can be easily achieved. Note that the beating of the pulp is performed according to JIS P8121: 2012 to the measured value.

Further, NKP is preferably blended in the base paper for thermal transfer paper. Since the fibers of NKP are long, the tensile strength of the product obtained by sheet-forming can be improved. 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 degree of knocking of NKP is preferably 500mlcsf or less, more preferably 400mlcsf or less. If the degree of percussion of NKP is within the above range, a sufficient strength can be secured as a base paper for thermal transfer paper.

The pulp component may contain pulp other than the NKP and LKP (hereinafter referred to as "other pulp"). Examples of the other pulps include mechanical pulps such as ground wood pulp (SGP), pressure ground wood Pulp (PGW), refining ground wood pulp (RGP), Thermo Ground Pulp (TGP), chemical ground wood pulp (CGP), ground wood pulp (GP) and Thermo Mechanical Pulp (TMP), deinked pulp (DIP) made of tea waste paper, kraft envelope waste paper, old magazine paper, old newspaper, leaflet waste paper, office waste paper, old corrugated paper, high white waste paper, kent waste paper, old model paper, old soil and ground license paper, and pulps chemically or mechanically made of 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 still more preferably less than 1% by mass, relative to the total mass of the pulp components.

Conventionally, aluminum sulfate has been widely used as a fixing agent such as a yield improving agent and a sizing agent. However, when used as base paper for thermal transfer paper, since the base paper is heated to about 200 ℃ during transfer, the cellulose is hydrolyzed by sulfuric acid ions generated from aluminum sulfate during heating, and the tensile strength of the heated paper is greatly reduced. In view of this, the amount of aluminum sulfate added to suppress the decrease in tensile strength due to heat treatment during transfer was investigated. As a result, it was confirmed that the content of sulfate ions in the base paper for thermal transfer paper had to be controlled to 0.6mg/l or less. The content of the sulfuric acid ion is preferably in the range of 0.1 to 0.6mg/l, more preferably in the range of 0.2 to 0.6 mg/l. By controlling the content of the sulfate ion within the above range, the decrease in tensile strength after the heat treatment can be suppressed. Wherein the content of sulfate ions in the paper can be measured using an ion chromatograph.

The content of aluminum sulfate can be measured as the content of sulfate ions and also as the content of aluminum. In this case, the aluminum content in the base paper for thermal transfer paper is preferably 0.09 mass% or less, and more preferably 0.03 to 0.09 mass%.

The base paper for thermal transfer paper of the present embodiment is preferably excellent in wet tensile strength because it is applied with an aqueous paste when it is in close contact with a base material. In addition, it is preferable to have excellent wet tensile strength after heat treatment in view of workability in peeling the thermal transfer paper from the base material. The present inventors have studied a formulation for improving the tensile strength in wet condition. Cationic starches, which have been widely used as paper strength enhancers in the past, have insufficient effect of increasing tensile strength in wet state. Therefore, wet paper strength enhancers capable of substituting cationized starch have been studied. As a result, it was found that the wet paper strength enhancer is preferably at least one selected from the group consisting of polyamide polyamine epichlorohydrin-based resins (PAE), urea-formaldehyde-based resins, and melamine formaldehyde-based resins.

That is, the content of the cationized starch is controlled to 0.01 mass% or less, and the content of the wet paper strength agent is controlled to 0.10 to 0.35 mass%. The content of the wet paper strength agent is preferably 0.10% by mass or more, and more preferably 0.20% by mass or more. When the amount is within the above range, wet tensile strength usable as base paper for thermal transfer paper can be imparted. The content of the wet paper strength agent is preferably 0.35% by mass or less. This is because, if the content of the wet paper strength agent is too large, the wet paper strength agent cannot be completely fixed to the pulp, and an excessive amount of chemicals may be used, which may adversely affect the inside of the paper machine system. The content of the cationized starch and the wet paper strength agent is a ratio to the total mass of the pulp components.

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

As the sizing agent, known products can be used. The sizing agent preferably contains at least one selected from a rosin-based sizing agent, an Alkenyl Succinic Anhydride (ASA) -based sizing agent, a cationic polymer-based sizing agent, and an Alkyl Ketene Dimer (AKD) -based sizing agent. In particular, since the amount of acidic aluminum sulfate to be added is reduced, a neutral rosin-based sizing agent is preferable to an acidic rosin-based sizing agent in view of sizing performance. The content of the sizing agent is not particularly limited, but is preferably 0.05 to 1.0 mass%, more preferably 0.05 to 0.8 mass%, even more preferably 0.10 to 0.8 mass%, and particularly preferably 0.10 to 0.5 mass% in the base paper for thermal transfer paper, from the viewpoint of improving water resistance and workability.

As an additive for papermaking for achieving a desired function, a known chemical agent such as a filler such as calcium carbonate, talc, clay, or kaolin, a yield improver, or a drainage improver may be appropriately mixed with the stock.

The paper stock adjusted in the above manner can be made into a single-gloss paper by a known method. In this case, the type of paper machine is not particularly limited. Generally, paper making is performed by a paper machine having a yankee dryer in order to improve the smoothness of one surface. Therefore, one side of the base paper for thermal transfer paper is smooth. Further, the surface may be subjected to post-treatment such as coating layer providing printability or calendering, as required.

The joker's smoothness of the smooth surface of the base paper for thermal transfer paper is preferably 500 seconds or more, more preferably 600 seconds or more, and further preferably 700 seconds or more. When the amount is within the above range, the printability of the smooth surface of the base paper for thermal transfer paper is improved. That is, when gravure printing or the like is performed, the adhesion to the roller is increased, and high-quality printing can be achieved without providing a coating layer such as an ink-absorbing coating layer. Further, the joker smoothness is preferably 1200 seconds or less. If the smoothness is too high, the difficulty of controlling water content during paper making and the need for a reduction in paper making speed may arise, which may lead to a reduction in workability and productivity. The smoothness of the royal jelly formula is determined according to JIS P8155: 2010 by the royal jelly method.

The base paper for thermal transfer paper preferably has a tackiness of 20g/m and a moisture absorption of bobby (Cobb water absorption)²Hereinafter, more preferably 15g/m²The following. If the wet strength exceeds 20g/m²When the thermal transfer paper is adhered to the base material using the aqueous paste, the strength of the paper is reduced, and the workability in the cutting operation is reduced. In order to control the water absorption of the fiber to 20g/m²The object can be achieved by adding an appropriate amount of the above-mentioned sizing agent to the stock. The brix water absorption was measured according to JIS P8140: 1998 specified 30g/m²Measured by the method.

The base paper for thermal transfer paper preferably has appropriate oil resistance in order to prevent excessive absorption of ink during printing, from the viewpoint of economy in use. That is, the oil absorption of the base paper for thermal transfer paper is preferably 400 seconds or more, and more preferably 450 seconds or more. The oil absorption is according to the number of the Japan Association for the pulp and paper industry 67: 2000(JAPAN TAPPI No. 67: 2000). If the oil absorption is long, it means that oil absorption is difficult, i.e., oil resistance is excellent. If the amount of ink used is less than 400 seconds, the base paper for thermal transfer paper tends to absorb ink excessively, and therefore the amount of ink used increases when printing an image, which is not preferable from the viewpoint of economy. By changing the formula, density and the like of the sizing agent, the oil absorption of the base paper for the thermal transfer paper can be controlled.

The base paper for thermal transfer paper has a basis weight of 20 to 50g/m²Preferably 25 to 35g/m²More preferably 27 to 32g/m². When the basis weight is more than 50g/m²In the case of using the sheet as a thermal transfer paper, the sheet is too heavy, and thus workability in pressing the sheet onto a substrate and peeling the sheet from the substrate is deteriorated. In addition, when the basis weight is less than 20g/m²When it is used, it is difficult to ensure the strength required as the thermal transfer paper.

The density of the base paper for the thermal transfer paper is 0.75 to 0.85g/cm³Preferably 0.78～0.82g/cm³. When the density is more than 0.85g/cm³In this case, the thickness of the paper needs to be extremely thin, thereby reducing productivity. In addition, when the density is less than 0.75g/cm³When it is used, it is difficult to ensure the strength required as the thermal transfer paper. Further, as the gaps between fibers become larger, the oil absorption is also increased, and therefore it is difficult to achieve a preferable oil absorption.

The tensile strength of the base paper for thermal transfer paper at the time of humidity conditioning is preferably 2.0kN/m or more, more preferably 2.4kN/m or more.

The tensile strength of the base paper for thermal transfer paper after heat treatment at 220 ℃ for 25 minutes is preferably 2.0kN/m or more, and more preferably 2.3kN/m or more. The conditions for heat treatment at 220 ℃ for 25 minutes were selected as typical heat treatment conditions for thermal transfer.

The tensile strength reduction (%) of the base paper for thermal transfer paper after heat treatment at 220 ℃ for 25 minutes can be determined by 100 × [ (tensile strength at humidity control) - (tensile strength after heat treatment at 220 ℃ for 25 minutes) ]/(tensile strength at humidity control). The tensile strength reduction rate after the heat treatment is preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less. If the rate of decrease in tensile strength after heat treatment exceeds 20%, the thermal transfer paper is broken when the thermal transfer paper is peeled from the base material after thermal transfer, and the workability is reduced.

The tensile strength after the heat treatment can be suppressed from decreasing by controlling the sulfate ion content in the paper to 0.6mg/l or less, more preferably 0.1 to 0.6 mg/l. In order to secure the tensile strength after the heat treatment, a method of previously increasing the tensile strength before the heat treatment may be employed. However, in this case, it is necessary to take measures such as increasing the amount of the paper strength increasing agent and the like or increasing the basis weight, and therefore, this is not preferable from the viewpoint of cost and workability.

The wet tensile strength of the base paper for thermal transfer paper after heat treatment at 220 ℃ for 25 minutes is preferably 0.80kN/m or more, more preferably 0.83kN/m or more. The above wet paper strength agent may be added to the stock in an appropriate amount so as to control the wet tensile strength after the heat treatment to 0.80kN/m or more. If the wet tensile strength is lower than the above, the workability of cutting off the excess thermal transfer paper in the transfer using the aqueous paste may be lowered. In addition, the work of peeling the thermal transfer paper from the base material after transfer is performed in a high-temperature and high-humidity environment, but in this case, the thermal transfer paper is likely to be broken, and thus the workability may be deteriorated.

The tensile strength is measured in accordance with JIS P8113: 2006. The tensile strength at the time of humidity control was measured in accordance with JIS P8111: 1998 tensile strength measured after leaving in a conditioned environment (temperature 23 ℃ C., humidity 50% RH) for 1 day or more. The tensile strength after the heat treatment was measured after leaving the sheet in an atmosphere of 220 ℃ for 25 minutes and further in a humidity-controlled atmosphere for 15 minutes using a constant temperature dryer.

The wet tensile strength after the heat treatment was set to a value corresponding to a value obtained by leaving the sheet in a constant temperature drier at 220 ℃ for 25 minutes and then leaving the sheet in a humidity-controlled environment for 15 minutes in accordance with JIS P8135: 1998 as specified in the general method.

The tensile strength, the tensile strength after heat treatment, and the wet tensile strength after heat treatment were in any case measured in the MD direction (flow direction of the paper machine) in principle. When the MD direction is not clear, the tensile strength is measured at an angle of 22.5 degrees, and the direction indicating the strongest tensile strength is defined as the MD direction.

The ink and the binder resin constituting the ink layer of the thermal transfer paper are not particularly limited as long as they have the property of being transferable to the substrate (transfer target material) as described above. Known inks and binder resins can be used by being appropriately selected. As the pigment and dye used for the ink, a sublimable or non-sublimable pigment and dye may 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 required.

Examples

Examples and comparative examples are shown below. The materials, the amounts used, the ratios, the contents of the treatments, the procedures of the treatments, and the like shown in the following examples can be appropriately modified without departing from the scope of the present invention. The scope of the invention should therefore not be construed in a limiting sense with reference to the particular examples shown below.

(example 1)

Bleached softwood kraft pulp (NKP) and bleached hardwood kraft pulp (LKP) were each beaten using a double disc refiner (hereinafter referred to as DDR) until the degree of beating became 360 ml. The knocked-down NKP15 mass% and the knocked-down LKP85 mass% were mixed in a slurry tank, respectively. Next, aluminum sulfate and a polyamide polyamine epichlorohydrin resin (PAE wet paper strength enhancer) were added so that the contents of the aluminum sulfate and the polyamide polyamine epichlorohydrin resin were 0.6 mass% and 0.16 mass%, respectively, with respect to the pulp component. Next, a polyacrylamide-based paper strength agent (PAM-based paper strength agent) was added so that the content of the polyacrylamide-based paper strength agent was 0.27 mass% with respect to the pulp component, and a neutral rosin-based sizing agent was further added so that the content of the neutral rosin-based sizing agent was 0.35 mass% with respect to the pulp component, to prepare a paper stock. Using the prepared stock, papermaking was carried out using a papermaking machine equipped with a Yankee dryer to obtain a basis weight of 30g/m²The base paper for thermal transfer paper of (1).

(example 2)

After mixing the pulp in the same manner as in example 1, aluminum sulfate and the PAE-based wet paper strength enhancer were added so that the content of the aluminum sulfate and the content of the PAE-based wet paper strength enhancer were 0.6 mass% and 0.25 mass%, respectively, with respect to the pulp components. Next, a PAM-based paper strength enhancer was added so that the content of the PAM-based paper strength enhancer was 0.27 mass% with respect to the pulp component, and a neutral rosin-based sizing agent was further added so that the content of the neutral rosin-based sizing agent was 0.5 mass% with respect to the pulp component, to prepare a paper stock. Using the prepared stock, papermaking was carried out using a papermaking machine equipped with a Yankee dryer to obtain a basis weight of 31g/m²The base paper for thermal transfer paper of (1).

Comparative example 1

After mixing the pulp in the same manner as in example 1, aluminum sulfate was added so that the content of aluminum sulfate was 1.2 mass% with respect to the pulp components. Next, cationized starch was added so that the content of cationized starch was 0.4 mass% with respect to the pulp component, then, PAM-based paper strength enhancer was added so that the content of PAM-based paper strength enhancer was 0.27 mass% with respect to the pulp component, and further, an acid rosin-based sizing agent was added so that the content of acid rosin-based sizing agent was 0.27 mass% with respect to the pulp component, thereby preparing a paper stock. Using the prepared stock, papermaking was carried out using a papermaking machine equipped with a Yankee dryer to obtain a basis weight of 31g/m²The base paper for thermal transfer paper of (1).

(example 3)

After mixing the pulp in the same manner as in example 1, aluminum sulfate and the PAE-based wet paper strength enhancer were added so that the content of the aluminum sulfate and the content of the PAE-based wet paper strength enhancer were 0.6 mass% and 0.25 mass%, respectively, with respect to the pulp components. Next, a PAM-based paper strength enhancer was added so that the content of the PAM-based paper strength enhancer was 0.27 mass% with respect to the pulp component, and a neutral rosin-based sizing agent was further added so that the content of the neutral rosin-based sizing agent was 0.05 mass% with respect to the pulp component, to prepare a paper stock. Using the prepared stock, papermaking was carried out using a papermaking machine equipped with a Yankee dryer to obtain a basis weight of 31g/m²The base paper for thermal transfer paper of (1).

(example 4)

Pulp and chemicals were added in the same manner as in example 1 to prepare a paper stock. Using the prepared stock, papermaking was carried out using a papermaking machine equipped with a Yankee dryer to obtain a basis weight of 41g/m²The base paper for thermal transfer paper of (1).

(example 5)

NKP and LKP were knocked down separately using DDR until the degree of knocking down became 400 ml. The knocked-down NKP20 mass% and the knocked-down LKP80 mass% were mixed in a slurry tank, respectively. Next, an additive agent was added and a paper stock was adjusted in the same manner as in example 1. Using the conditioned stock to obtainThe basis weight is 30g/m²The base paper for thermal transfer paper of (1).

Comparative example 2

NKP and LKP were knocked down using DDR until the degree of knocking down became 450ml and 430ml, respectively. The knocked-down NKP and LKP were mixed at the same ratio as in example 1. Next, an additive agent was added and a paper stock was adjusted in the same manner as in example 1. Using the conditioned stock, a basis weight of 30g/m was obtained²The base paper for thermal transfer paper of (1).

Comparative example 3

Commercially available products of other companies in japan that are actually used.

Comparative example 4

Commercially available products of other companies in japan and abroad that are actually used.

The base papers for thermal transfer papers obtained in examples and comparative examples were measured for basis weight, density, content of sulfate ion, royal smoothness of smooth surface, tensile strength after heat treatment, rate of decrease in tensile strength due to heat treatment, wet tensile strength after heat treatment, wet absorbency, and oil absorbency. In order to find the suitability as a base paper for thermal transfer paper, printability, thermal transfer properties, ink absorption amount, water resistance, and workability were evaluated.

The evaluation methods of the respective items are as follows.

Basis weight

According to JIS P8124: 2011 measurements were made. The weight was measured using an electronic scale which measures up to 4 decimal places and the basis weight was calculated.

< Density >

According to JIS P8118: 1998 measured the density.

< content of sulfate ion >

2g of the sample was cut into an appropriate size, boiled in 100cc of ion-exchanged water for one hour, and then subjected to filtration treatment using a filter having a pore size of 0.45 μm (manufactured by Mowa Co., Ltd., syringe filter 25HP045 AN). Thereafter, the amount of sulfate ion was measured using an ion chromatograph (manufactured by dean corporation, ダイオネクス, ICS 2000).

< Wang Jiang type smoothness >

In accordance with JIS P8155: 2010, the smoothness of the smooth surface was measured. The measuring machine used was a smoothness and air permeability tester of the Wangyan type (manufactured by Asahi Seiki Seikagaku Co., Ltd.).

< tensile Strength >

According to JIS P8113: 2006, in JIS P8111: 1998 was measured for the tensile strength in the MD direction after the humidity control in the humidity-controlled environment. A horizontal tensile tester (CODE SE-064, manufactured by Louis, Inc. (L & W)) was used as the measuring machine.

< tensile Strength after Heat treatment >

After being left at 220 ℃ for 25 minutes using a constant temperature dryer, the resultant was dried in a vacuum oven under the conditions of JIS P8111: 1998 was left for a further 15 minutes in a humidity-controlled environment, and the humidity was measured according to JIS P8113: the tensile strength in the MD direction was measured by the method specified in 2006. A horizontal tensile tester (CODE SE-064, manufactured by Louis, Inc. (L & W)) was used as the measuring machine.

< wet tensile Strength after Heat treatment >

After being left at 220 ℃ for 25 minutes using a constant temperature dryer, the resultant was dried in a vacuum oven under the conditions of JIS P8111: after further leaving for 15 minutes in a humidity-controlled environment as defined in 1998, the resultant was measured according to JIS P8135: 1998, the wet tensile strength in the MD direction was measured. As the measuring machine, a vertical tensile testing machine (universal materials testing machine (Tensilon), manufactured by eaander corporation (a & D)) was used.

(Brilliant Water absorption degree) >

According to JIS P8140: the 30-second method specified in 1998 was carried out using an electronic scale capable of measuring up to 4 digits after a decimal point.

< oil absorption >

According to the Japan Association for the pulp and paper industry, 67: 2000(JAPAN TAPPI No. 67: 2000). An oil absorption tester (manufactured by Toyo Seiki Seiko Co., Ltd.) of No. 114 was used as a measuring device.

< printability >

On the smooth surface of the base paper for thermal transfer paper obtained in the above examples and comparative examples, a wood grain pattern was printed using an ink jet printer (JV 5-320 DS, manufactured by japan yu shi engineering corporation (ミマキエンジニアリング)), using sublimation ink (Sb 52, 5% ink concentration, manufactured by japan yu shi engineering corporation (ミマキエンジニアリング)), and the printed surface was relatively evaluated.

Good: a clear print was made.

And (delta): there is a portion where the hue is slightly deteriorated.

X: the color loss and the blurring are obvious.

< Heat transferability >

The thermal transfer paper obtained in the experiment for confirming the printability was cut into a size of 10cm × 10cm, the printing surface was pressed in contact with an aluminum plate, and after hot pressing was performed at 220 ℃ for 30 seconds using a small hot press (manufactured by toyo seiko corporation, MINI PRESS-10 MP-SNH) with a load of 5kN, the sharpness of the transferred image was relatively evaluated.

Good: a clear transfer is performed.

And (delta): there is a portion where the hue is slightly deteriorated.

X: light color and unclear.

< ink absorption amount >

A4 size was cut from the base paper for thermal transfer paper obtained by the above examples and comparative examples, and bar coating was performed on the smooth face thereof using the ink used in the printability evaluation (using a wire bar wound at 0.3 mm) until the moisture content became 30g/m². At this time, the ink bleeding amount when viewed from the back surface was relatively compared.

Good: ink fading was not evident.

And (delta): a slight ink fading was confirmed, but within a practical level.

X: the ink fading is obvious.

< Water resistance >

A base paper for thermal transfer paper of 10cm × 10cm was allowed to stand at 105 ℃ for 15 minutes in a constant temperature dryer, and then was immersed in water for 30 seconds. Thereafter, the soaked paper was cut off using a cutter, and a relative evaluation of water resistance was made from the cut thereof.

Good: can be cut off without problems.

And (delta): the cuts are slightly rough but can be cut off.

X: the sheet was broken in the middle of the cutting and was not cut.

< workability >

A 120cm × 70cm thermal transfer paper obtained in the test for confirming printability was attached to a 100cm × 50cm aluminum base material using an aqueous paste, and after thermal transfer using a hot press, workability at the time of peeling was evaluated.

Good: can operate with high efficiency.

And (delta): workability is slightly lowered, but the work is possible.

X: the operation cannot be performed efficiently.

Table 1 shows the results of measurement and evaluation of examples 1 to 5 and comparative examples 1 to 4. In the characteristic evaluation, it was judged to be good when the results were good and Δ.

TABLE 1

As is apparent from Table 1, the base papers for thermal transfer papers of examples 1 to 5 can be suitably used as thermal transfer papers. In addition, the base papers for thermal transfer papers of comparative examples 1 and 3 have a high content of sulfate ions and a large reduction rate of tensile strength by heat treatment, and thus are inferior in water resistance and workability. The base paper for thermal transfer paper of comparative example 4 had poor printability because of low smooth surface smoothness of the royal jelly type. The base paper for thermal transfer of comparative example 2 had a low density and was liable to absorb ink, so that the amount of ink used during printing might increase.

Claims

1. A base paper for thermal transfer paper, characterized in that,

cellulose pulp is used as a main component;

the density is 0.75 to 0.85g/cm³；

The basis weight is 20 to 50g/m²；

The single surface is a smooth surface, and the Wang grinding type smoothness of the smooth surface is more than 500 seconds;

the content of sulfate ions is below 0.6 mg/l;

the content of cationized starch is 0.01 mass% or less;

the content of the wet paper strength enhancer is 0.10 to 0.35 mass%.

2. The base paper for thermal transfer paper according to claim 1, wherein,

the wet paper strength enhancer is one or more selected from polyamide polyamine epichlorohydrin resin, urea resin and melamine formaldehyde resin.

3. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

contains at least one selected from rosin sizing agents, alkenyl succinic anhydride sizing agents, cationic polymer sizing agents and alkyl ketene dimer sizing agents.

4. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

the cellulose pulp contains hardwood sulphate pulp or softwood sulphate pulp.

5. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

the rate of decrease in tensile strength after heat treatment at 220 ℃ for 25 minutes is 20% or less.

6. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

the wet tensile strength after heat treatment at 220 ℃ for 25 minutes is 0.80kN/m or more.

7. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

by following the japan pulp and paper industry association number 67: the oil absorption measured by the method of 2000 is 400 seconds or more.

8. The base paper for thermal transfer paper according to claim 1 or 2, wherein,

the material to be transferred is made of metal, ceramic, or resin.

9. A thermal transfer paper characterized in that,

comprising the base paper for thermal transfer paper according to claim 1 or 2 and an ink layer formed on the smooth surface side of the base paper for thermal transfer paper,

and, the ink layer contains an ink and a binder resin.