JPH0229038B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal transfer recording medium used in a thermal recording device, and more particularly to a thermal transfer recording medium that can be suitably used even under high temperature and high humidity conditions. The thermal transfer recording medium referred to in the present invention is one in which an ink layer having the property of being fluidized or sublimated by heating is provided on one side of a base paper. A thermal recording device such as a thermal printer or a thermal facsimile machine is used for recording on the recording medium. Recording is carried out by superimposing plain paper on the ink layer side of the recording medium and heating it from the base paper side with a thermal head to fluidize or sublimate the ink layer and transfer it to the plain paper. Compared to dye-colored thermal recording paper, such a thermal transfer recording material can use 1. plain paper. 2.The ink layer is composed of a mixture of wax, etc., which becomes fluidized by heating, mixed with pigments or dyes, or sublimation dyes, etc., so it has good light resistance.
It has excellent storage stability, such as solvent resistance, and the ability to select the recording hue, making it compatible with color printing. Thin paper with excellent smoothness has conventionally been used as the base paper for such thermal transfer recording media, and is disclosed in JP-A-55-3919 and JP-A-57-146693. In addition to conventionally used thermal printers, thermal facsimile machines, and the like as recording devices, a number of dedicated devices developed for thermal transfer recording have recently been announced. These dedicated devices usually use a system in which a rolled thermal transfer recording medium 1 (hereinafter referred to as a supply roll) is installed in the device in order to continuously supply the thermal transfer recording medium to the recording section, as shown in Figure 1. We are hiring. In these specialized devices, if the thermal transfer recording medium 2 is left in a particularly high temperature and high humidity environment for a long period of time, the portions that are fed out from the supply roll and in contact with the atmosphere, such as portions A and B in FIG. 1, will stretch. It is easy to cause wavy wrinkles. When the wavy and wrinkled portions generated by the elongation of the base paper are heated by the thermal head 3, they tend to become folded. When such creases occur in a thermal transfer recording medium, the ink may not be transferred well to the plain recording paper in the recording section, resulting in omissions or chips in the ink image. When such a phenomenon occurs, there are disadvantages in that not only the quality of the recorded image deteriorates, but also necessary image information may not be reproduced. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal transfer recording medium using a base paper that does not wrinkle under the conditions used in a thermal transfer recording device. That is, in the present invention, an ink layer having a property of being fluidized or sublimated by heating has a thickness of 4 to 25 μm, a density of 0.8 to 1.45 g/cm ³ , and a smoothness (Oken type) of 500 to 500.
50,000 seconds on one side of a base paper, the base paper has a ratio of hardwood pulp of 5% to 80% of the constituent wood pipe fibers, and the size degree according to JISP8122 is 1 to 7 seconds. can be,
The thermal transfer recording medium is characterized in that the water content in the base paper after providing the ink layer is 8 to 11% by weight. The present invention also provides the thermal transfer recording medium, characterized in that the base paper contains 15% by weight or less of a pigment having a particle size of 3 μm or less. When making the base paper in the present invention, wood pulp is beaten, and its specific surface area is 10 to 60 m ² /g.
A range of from 20 to 40 m ² /g is particularly preferred. If it is less than 10m ² /g, beating will not be sufficient and uneven formation and pinholes will easily occur during paper making, and if it exceeds 60m ² /g, dimensional stability will deteriorate and it will not work well in high temperature and high humidity conditions. Waving and wrinkles tend to occur during use, and the pulp becomes too fine, resulting in a low papermaking speed, making it uneconomical. Next, the base JISP
The size degree according to -8122 is 1 to 7 seconds, but is preferably adjusted to a range of 3 to 5 seconds. When the size degree is lower than 1 second, waving and wrinkles occur at high temperatures and high humidity. Furthermore, if the sizing degree exceeds 7 seconds, the content of the sizing agent in the base paper increases and staking with the thermal head tends to occur. Furthermore, the wires, blankets, etc. of the paper machine tend to get dirty during paper making, making it uneconomical. Next, the thickness of the base paper is 4 to 25 μm, especially 6 to 25 μm.
It is preferably in the range of 20 μm. If the thickness is smaller than these ranges, it will be difficult to industrially manufacture the base paper, and if the thickness exceeds 25 μm, the heat applied from the thermal head will be diffused and transferred to the ink layer, resulting in poor resolution. Not only does it become more expensive, but a large amount of thermal energy is required for thermal transfer recording.
As the power supply capacity of the device increases, the lifespan of the thermal head becomes shorter. The density of the base paper is 0.8~1.45g/cm ³ , especially 0.9~
It is preferably in the range of 1.4 g/cm ³ . If the density is smaller than these ranges, there will be many air holes in the base paper, which will impede heat conduction from the thermal head, making it impossible to perform efficient thermal transfer recording. Moreover, when the amount is larger than these ranges, it is difficult to industrially manufacture the base paper. Furthermore, the smoothness of the base paper is determined by the Oken type smoothness (Japan
TAPPI paper pulp test method No. 5 Smoothness and air permeability test method of paper and paperboard using air micrometer type tester B, Oken type smoothness and air permeability tester (pressure type)
method) ranges from 500 to 50000 seconds, among others
It is preferably in the range of 3000 to 30000 seconds. If it is smaller than these ranges, the smoothness will deteriorate and the adhesion between the base paper and the thermal head will deteriorate. This causes unevenness in the transferred density of the ink image. Furthermore, in general, the higher the smoothness of the ink layer, the thinner and more uniformly the ink layer can be applied. Therefore, low smoothness is not preferable for the application of the ink layer. on the other hand,
Even if the smoothness is increased beyond these ranges, the effect of improving thermal transfer recorded images is small, and industrial production is also difficult. In addition, the formation of the base paper has a large relationship with the thermal transfer recording characteristics, and if mottling is observed when visually inspecting the base paper with transmitted light, the thermal conductivity is different between the mottled area and the surrounding area, and thermal conductivity is different. When the amount of heat energy applied from the head is small, spots occur in the thermal transfer recorded image obtained. Furthermore, if the base paper has a penetrating portion such as a pinhole, the ink layer passes through the base paper and adheres to the thermal head, significantly impairing recording workability. Next, the water content in the base paper after providing the ink layer is preferably adjusted to 6 to 13% by weight, particularly 8 to 11% by weight. As already mentioned, adjusting the size of the base paper appropriately to prevent the occurrence of waviness and wrinkles at high temperatures and high humidity has a remarkable effect, but if the moisture content of the base paper is low, In particular, at high temperatures and high humidity, the difference between the equilibrium moisture content and the moisture content in the base paper becomes large, and the base paper rapidly absorbs moisture, resulting in the occurrence of wavy wrinkles. In order to prevent the occurrence of such undulating wrinkles, the effect can be significantly increased by appropriately adjusting the size of the base paper and also adjusting the moisture content in the base paper. If the moisture content after forming the ink layer is less than 6% by weight, rapid absorption of moisture is likely to occur at high temperatures and high humidity, resulting in the occurrence of wavy wrinkles. If it exceeds 13% by weight, coating spots are likely to occur during ink application, and the base paper becomes stiff, resulting in poor workability during ink application and recording. Increasing the proportion of hardwood pulp from 5% to 80% of the constituent wood pulp fibers has a great effect in preventing waviness and wrinkling, especially at high temperatures and high humidity. It is recognized that the effect is significantly increased. The effect of hardwood pulp on preventing waviness and wrinkles is considered to be good for dimensional stability because the fibers of hardwood pulp are thicker and more rigid than those of softwood pulp.
If the proportion of hardwood pulp is less than 5%, the effect of preventing the occurrence of waviness and wrinkles will be small, and if it exceeds 80%, the strength will not be sufficient when producing the ultra-thin paper of the present invention with a thickness of 4 to 25 μm. Paper breaks easily occur in the wet and dry parts. Containing 15% by weight or less of pigments with a particle size of 3 μm or less in the base paper is particularly effective in preventing waviness and wrinkling at high temperatures and high humidity. It is recognized that the effect is significantly increased by combining it with the effect. It is thought that by including pigments in the base paper, the pigments act as a lubricant at the bonding points of pulp fibers, improving dimensional stability and increasing the effect of preventing waviness and wrinkles. If the particle size of the pigment exceeds 3 μm, penetrating portions such as pinholes are likely to occur in the base paper, and it is also thought that surface abrasion of the thermal head will be accelerated. If it is included in the base paper in an amount exceeding 15% by weight, paper breakage is likely to occur during ink application when producing the ultra-thin paper of the present invention with a thickness of 4 to 25 μm. In producing the above-mentioned base paper according to the present invention, ordinary paper making equipment is possible, and in particular, equipment for making paper is preferable for condenser paper and one-time carbon paper. The manufactured paper is adjusted to a predetermined range of thickness, density, and smoothness by supercalendering. In addition, methods for adjusting the moisture content of thermal transfer recording media include (1) increasing the moisture content at the outlet of the paper machine;
For example, one method is to set the moisture content at 25 to 35% during supercalendering and heat the rolls to achieve the desired moisture content, or to lower the moisture content at the outlet of the paper machine, such as 4 to 6%, and maintain the desired moisture content while adding moisture during supercalendering. In this method, the moisture in the base paper is adjusted in advance before ink application, such as the method of adding moisture after supercalender treatment to achieve the desired moisture content, and then adjusting the moisture content to the desired moisture range according to the present invention after applying the ink. (2) Adding moisture during ink application or after application to adjust the moisture content to a desired range. Next, materials used in the present invention will be briefly described, but these materials do not particularly limit the present invention. Sizing agents include various internal sizing agents such as rosin sizing agents, petroleum resin sizing agents, synthetic resin sizing agents, and surface sizing agents. The sizing agent can be applied by a conventional method, an internal addition method, or an external addition method using a size press or the like. In addition, paper strength agents, water resistance agents, dimensional stabilizers, which are commonly used in paper making,
Various fixing agents and the like may be used as necessary. As the wood pulp, chemical pulp such as kraft method, sulfite method, semi-chemical pulp, etc. are used. As pigments for internal addition to the base paper, titanium dioxide, talc, clay, kaolin, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, zinc dioxide, precipitated barium sulfate, etc. are used. Ink that is fluidized by heat can be broadly classified into a colorant and a vehicle that fixes the colorant on the base paper and serves as a carrier for thermally transferring the colorant. Vehicles usually consist of waxes and oils.
Colorants include pigments that are insoluble in oils, basic dyes that are soluble in oil, and oil-soluble dyes. Pigments include carbon black, ultramarine blue, Prussian blue, chrome yellow, cadmium yellow, titanium yellow, red iron, lead vermilion, cadmium red, Rekired C, same D, rhodamine lake B,
There are chromium oxides, etc., and oil-soluble dyes include C.1. Solvent Yellow 2, Solvent Yellow 2, Solvent Yellow 19, Solvent Yellow 21, Solvent Yellow 61, C.1. Solvent Orange 40, C.1. Solvent Red 3,
8, 25, 49, 82, 100, C.1. Solvent Violet 8, 21, C.1. Solvent Blue
25, 73, Diaresin Blue G, Balifurst Blue #2604, C.1.Solvent Green 3,
C.1.Solvent Black 3rd and 7th class will be listed. Examples of waxes include natural waxes such as carnauba wax, auricilla wax, and Montan wax, and synthetic waxes such as paraffin wax, microcrystalline wax, IG-wax, and polyethylene wax. Oils include light mineral oil, heavy mineral oil, castor oil, oleic acid, and peanut oil. Ink that sublimes by heat is composed of a disperse dye as a coloring agent and a vehicle.
As disperse dyes, Kayaset Yellow A-G (Nippon Kayaku, hereinafter the same), Kayaset Yellow A-G, Kayaset Yellow 186, Kayaset Scarlet 926, Kayaset Red 026, Kayaset B, Kayaset Yellow
130, Kayaset Blue A-2R, 906, 136,
Same FR, Kaya Set Black 922, Same 922(D), Same 928
etc. Vehicles include cellulose derivatives such as nitrified cotton, cellulose acetate propionate, and acetyl cellulose. The thermal transfer recording medium of the present invention produced in this way does not cause undulations and wrinkles even under high temperature and high humidity conditions, has a smooth surface, and has good thermal conductivity, so it is suitable for thermal transfer recording. Very good recorded images can be obtained. Furthermore, since the base paper has a uniform texture, there are no problems such as pinholes in the base paper or spots of the ink layer coming out on the opposite side when an ink layer is provided. The present invention will be explained in more detail with reference to Examples below. Example 1 NUKP (softwood unbleached kraft pulp) for insulation paper
70%, LUKP (hardwood unbleached kraft pulp) 30%
The specific surface area is 40 using a refiner (beating device).
m ² /g, an internal sizing agent (RF size 550 manufactured by Hamano Industries) was added, paper was made by a conventional method, dried, and subjected to super calendering to produce paper. The obtained paper had a basis weight of 17 g/m ² , a thickness of 13 μm, a density of 1.3 g/cm ³ , a smoothness of 13000 seconds, a size degree of 3 seconds, and a moisture content of 9%. Using this paper as a base paper, one side is coated with thermofluid ink consisting of the following composition to create a thickness.
A thermal transfer recording medium was obtained by forming an ink layer of 5 μm. The moisture content in the base paper of this medium was 8.5%. (Ingredients) (Parts by weight) Carbon black 20 parts Carnauba wax 20 parts Ester wax 40 parts Oil 20 parts Example 2 In Example 1, the constituent pulp fibers of the base paper
A thermal transfer recording medium was obtained in the same manner as in Example 1, except that light calcium carbonate having a maximum particle size of 2.5 μm and an average particle size of 0.7 μm was added to NUKP+LUKP to give a concentration of 10%. Example 3 In Example 1, NUKP80%, LUKP20%
A thermal transfer recording medium was obtained in exactly the same manner as in Example 1, except that 10% light calcium carbonate was added to the pulp to make paper, and the sizing degree of the obtained base paper was set to 5 seconds. Example 4 In Example 1, NUKP98%, LUKP10%
Example 1 was carried out, except that the paper was made by adding 10% light calcium carbonate to the pulp of Example 1, and the sizing degree of the obtained base paper was 5 seconds, the moisture content was 11.5%, and the moisture content after ink application was 11%. A thermal transfer recording medium was obtained in exactly the same manner. Comparative Example 1 In Example 1, paper was made using 100% NUKP without blending hardwood pulp and without adding any internal sizing agent, and the resulting paper had a size degree of 0 seconds and a moisture content.
A thermal transfer recording medium with a base paper having a moisture content of 5% after ink application was obtained in exactly the same manner as in Example 1, except that the water content was 5.5%. Comparative Example 2 A thermal transfer recording medium was obtained in exactly the same manner as in Example 1, except that paper was made without adding the internal sizing agent and the sizing degree of the obtained base paper was 0 seconds. . Comparative Example 3 A thermal transfer recording medium was obtained in exactly the same manner as in Example 1, except that the water content of the base paper obtained by papermaking was 5.5%, and the water content after ink application was 5%. Comparative Example 4 A thermal transfer recording medium was obtained in exactly the same manner as in Example 1 except that NUKP was 100% blended and hardwood pulp was not used. Comparative Example 5 A thermal transfer recording medium was obtained in exactly the same manner as in Example 2, except that paper was made without adding an internal sizing agent and the sizing degree of the obtained base paper was set to 0 seconds. Comparative Example 6 A thermal transfer recording medium was obtained in exactly the same manner as in Example 2, except that the base paper obtained by papermaking had a moisture content of 5.5%, and the moisture content after ink application was 5%. Comparative Example 7 A thermal transfer recording medium was obtained in exactly the same manner as in Example 2, except that 100% NUKP was blended and no hardwood pulp was blended. Comparative Example 8 Paper was produced in the same manner as in Example 1 by beating the pulp to a specific surface area of 7 m ² /g. The resulting paper had a basis weight of 17 g/m ² , a thickness of 20 μm, a density of 0.85, a smoothness of 600 seconds, a size degree of 5 seconds, and a moisture content of 5%. Using this paper as a base paper, an ink layer was provided on one side in the same manner as in Example 1, but the ink layer came out in spots on the opposite side. Regarding the thermal transfer recording media obtained in Examples 1 to 4 and Comparative Examples 1 to 7, 20°C, 65%RH,
30℃, 80%RH, 30℃, 90%RH, 30℃, 95%
Leave it in an environment of RH, 35℃, 90%RH for 10 minutes,
The first result is the observation of the occurrence of wavy wrinkles.
Shown in the table.

[Table] Next, these obtained thermal transfer recording media were installed in the thermal transfer recording device described above, and heated at 30℃ and 90%RH.
When left for 10 minutes in an environment of There isn't. Next, transfer recording was performed, but the occurrence of creases in the thermal head portion 3 was not the same as in the example, and a good recorded image could be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a thermal transfer recording device, and FIG. 2 is an enlarged principle diagram showing the vicinity of the recording section of this thermal transfer recording device. 1... Supply roll, 2... Thermal transfer recording medium, 3
...Thermal head, 4...Platen roll, 5
... Plain paper for recording, 6 ... Plain paper for recording roll, 2A ... Base paper, 2B ... Ink layer.

Claims (1)

[Claims] 1. An ink layer with a property of fluidizing or sublimating when heated, with a thickness of 4 to 25 μm and a density of 0.8 to 1.45.
g/cm ³ and a smoothness (Oken style) of 500 to 50,000 seconds in a thermal transfer recording medium provided on one side of a base paper.
The base paper has a proportion of hardwood pulp of 5% to 80% of the constituent wood pulp fibers, a sizing degree according to JISP8122 of 1 to 7 seconds, and a moisture content of the base paper after forming the ink layer of 8 to 80%. A thermal transfer recording medium characterized by having a content of 11% by weight. 2 15 pigments with a particle size of 3 μm or less are added to the base paper.
The thermal transfer recording medium according to claim 1, characterized in that it contains not more than % by weight.