JPS6381088A - Transfer-type thermal recording medium - Google Patents

Abstract

PURPOSE:To enable clear printing even on a transfer recording paper poor in smoothness, to obtain an excellent property for release from the transfer recording paper and prevent an ink from being left on the base side, by using a low melting point polyamide resin and a higher fatty acid amide and/or 12- hydroxystearic acid as constituents of a first layer. CONSTITUTION:A transfer-type thermal recording medium comprises a thermally transferrable ink layer comprising at least two layers, namely, a first layer nearest to a base and an uppermost layer nearest to transfer recording layer, the first layer comprising a low melting point polyamide resin and, further, a higher fatty acid amide and/or 12-hydroxystearic acid. The low melting point polyamide modified with the higher fatty acid amide and/or 12-hydroxystearic acid, which is tough and highly adhesive at normal temperature, becomes a low-viscosity liquid at high temperatures and has excellent solvent resistance, is thus used as a constituent of the first layer, whereby clear printing can be performed even on a transfer recording paper poor in surface smoothness.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a transfer type thermosensitive ink layer having a two-layer laminated structure and capable of making clear recordings even on transfer paper with poor surface smoothness. Regarding recording media.

[Prior art]

The transfer type thermal recording method is popular as a plain paper recording method with a simple device, but the print quality is easily affected by the smoothness of the surface of the transfer paper, and it is difficult to use for transfer paper with a poor surface smoothness. It is difficult to print clearly.

In order to improve such defects, conventional methods include heat treatment after printing (Japanese Patent Laid-Open No. 58-76276), magnetic force (Japanese Patent Laid-Open No. 52-96549) or electrostatic force (Japanese Patent Laid-Open No. 55-65) during transfer.
No. 590) etc. are used. Alternatively, add a large amount of oily substance to reduce the melt viscosity during transfer (
JP-A-60-25762), thermally decomposable (JP-A-60-25762)
82389) and heat sensitization by adding a thermally expandable substance (Japanese Patent Application Laid-Open No. 60-25762).

In addition, a technique has been proposed to improve print quality by layering multiple layers of heat-melt ink, in which heat-melt inks with slightly different melting points are layered, and pigments are added to one or both of them. Add (Japanese Patent Application Laid-Open No. 59-224392
Techniques have been proposed, such as providing a layer made of a heat-fusible substance containing no coloring material on a heat-fusible ink layer (Japanese Patent Laid-Open No. 60-97888).

However, in this method of recording by transferring melted ink that has become a liquid, if the surface of the transfer paper has low smoothness, the print quality will be lower than that of paper with a highly smooth surface. After all, only inferior print quality was obtained, and the fundamental problem of transfer type thermal recording, in which print quality was dependent on the smoothness of the surface of the transfer paper, could not be fundamentally solved.

On the other hand, when thermal energy is applied, the ink, which is mainly composed of a resin that exhibits tackiness but does not melt into a low-viscosity liquid and has a certain degree of mechanical strength, can be applied to transfer paper, which has a poor surface smoothness. By using an ink that adheres to the convex portions of the surface and covers the concave portions, high-quality printing can be performed on transfer paper with poor surface smoothness.

However, such resin inks require more energy to print than conventional wax inks, so it is necessary to use a support film with particularly high heat resistance, and it also reduces the lifespan of the thermal head and heat storage. This is not desirable as it causes problems.

As a method for sensitizing such a resin ink, it is known that it is effective to provide a release layer containing an easily meltable substance such as wax under the resin ink recording layer.

However, the easily meltable release layer, which is composed of wax alone or a composition of ordinary wax and a heat-melting resin, has poor storage stability before being used for recording, and is difficult to record at high temperatures or when the thermal head accumulates heat during continuous recording. In this case, the release layer may be absorbed by the ink layer or disintegrate before recording, mainly due to the wax's easy-to-dissolve properties, low melt viscosity, and compatibility between the release layer material and the ink layer material. In addition to having the drawback that even non-printed areas are melted, resulting in stains and blurred characters, there are also relatively large restrictions on manufacturing.

〔the purpose〕

The present invention enables clear printing even on transfer paper with poor surface smoothness, and has excellent releasability from the transfer paper.
Moreover, it is an object of the present invention to provide a transfer type thermosensitive recording medium that does not leave ink residue on the support side.

〔composition〕

According to the present invention, two or more heat-transferable ink layers are provided on a heat-resistant support, and the ink layers are at least close to the heat-resistant support and are easily melted by heat to become a low-viscosity liquid. a first layer adjusted to be viscous, and one layer closest to the receiving paper that is adjusted so that it becomes sticky when heated but does not melt into a low viscosity liquid. In the recording medium, a low melting point polyamide resin is used as a component of the first layer, and a higher fatty acid amide resin is further used as a component of the first layer.
The thermal transfer ink layer consists of at least two layers: the first layer) and the layer closest to the transfer paper (hereinafter referred to as the top layer), and the first layer contains a low melting point polyamide resin and further contains higher fatty acids. It is characterized by containing amide or/and 12-hydroxystearic acid.

The polyamide resin used in the present invention means a low molecular weight polyamide resin with a melting point of 120° C. or lower, which has been conventionally used in printing inks, hot melt adhesives, and the like.

Although these polyamide resins are easily soluble in ordinary organic solvents, they are incompatible with other synthetic resins and ordinary waxes, so it is extremely difficult to lower their melt viscosity while imparting solvent resistance. It's a pity.

As a result of intensive studies on this point, the inventor of the present invention found that when higher fatty acid amide and/or 12-hydroxystearic acid is mixed with a low-melting polyamide resin, the properties of the low-melting polyamide resin are unexpectedly modified, resulting in improved solvent resistance. The present inventors have discovered that a low melting point polyamide resin with excellent properties and low viscosity can be obtained, leading to the completion of the present invention.

In the present invention, the higher fatty acid amide used as a modifier for the low melting point polyamide resin is a higher fatty acid amide having 16 to 24 carbon atoms, preferably 16 to 18 carbon atoms. Such amides of higher fatty acids include, for example, palmitic acid amide (melting point 97-102°C), oleic acid amide (melting point 70-75°C), or stearic acid amide (melting point 9
7 to 102° C.), but it is desirable to use stearic acid amide in terms of the ability to develop a modifying effect, usability, and the like.

In general, the first layer of this type of two-layer laminated transfer type thermal recording medium has the function of easily melting by heat and turning into a low-viscosity liquid to facilitate the transfer of the top layer, as well as the function of the non-printing area (non-heating area). ), the top layer is firmly adhered, so-called "r tailing".
It is necessary to have a function to suppress the phenomenon and the "tomoochi" phenomenon.

In the present invention, as a component of the first layer, higher fatty acid amide or/and 12- Since it uses a low melting point polyamide resin modified with hydroxystearic acid, it can fully demonstrate each of the above functions and can print clearly even on paper with poor surface smoothness. It is possible to obtain a transfer-type thermosensitive recording medium which has excellent releasability from the transfer paper and does not cause the "one tail" phenomenon or the "tomochi" phenomenon.

Moreover, the first layer of the present invention may further contain a pigment. The term "pigment" as used herein refers to a component that is uniformly dispersed in the heat-melting component but not dissolved, and is not melted by thermal energy during recording, and also includes colored pigments as coloring materials. Containing pigment has the effect of increasing stability during storage and high-temperature recording.

Furthermore, if the pigment is a colored pigment, it also has the effect of increasing the clarity of print during recording.

The top layer, unlike the first layer, does not have a clear melting point and becomes sticky to the transfer paper due to thermal energy during recording, but its main component is a resin that does not melt into a low viscosity liquid. layer, and furthermore, due to the function of the top layer, each of these resins has a tensile strength at 20°C (JIS K 6760
-1.966) and elongation rate (JIS K 6766-
1966) has a tensile strength of 20 kg/y or more and an elongation rate of 150
It is desirable that it is z or more.

Examples of such resins include polyester, polyamide, ethylene vinyl acetate copolymer, styrene butadiene copolymer, ethylene-ethyl acrylate copolymer, and the like. It is also possible to add tackifiers and waxes such as terpene resins, coumaron resins, rosins and their derivatives as auxiliary materials to these resins, but the total amount thereof is 20% by weight of the total resin components of the top layer. % or less.

Since the top layer is the main component transferred during recording,
It is advantageous to contain color pigments, and the amount can be determined at an appropriate level based on sensitivity during recording, storage performance, print quality, etc., but excessive amounts are undesirable, and the total dry weight of the top layer It is desirable that the economy is in the 50's or below.

In addition, in the present invention, the first layer and the last layer may contain a dispersant, a penetrant, an adhesion modifier, and
Additives such as fluidity control agents and plasticizers may also be added.

In order to produce a transfer type heat-sensitive recording medium in which the first layer and the top layer are laminated as described below, the first layer is coated on the support film by a hot melt method, a solvent dispersion coating method, an aqueous emulsion coating method, etc. After that, the top layer formed separately using a casting method is laminated, or the first layer is coated, and then the top layer is coated using the same coating method as the first layer. Just pick it up.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example].

[First layer forming component]

A first layer forming liquid was obtained by the above mixing and stirring.

[Components forming the top layer]

Carbon black 2 parts by weight Toluene 38〃The above mixture 40
The mixture was dispersed and kneaded for 20 hours in a ball mill kept at a temperature of 0.degree. C. to obtain a top layer forming liquid.

Next, the first layer forming liquid was applied to a 6 μm thick polyester film by a hot melt method to form a 2 μm thick first layer. Next, the uppermost layer forming liquid was applied onto this first layer using a wire bar so that the thickness after drying would be 4 μm, and then dried at 100° C. for 2 minutes to form a transfer type thermosensitive recording medium of the present invention. Obtained.

Example 2 A transfer type thermosensitive recording medium of the present invention was obtained in the same manner as in Example 1, except that the components forming the first layer in Example 2 were replaced with the following components.

[First layer forming component]

Comparative Example 1 A comparative example was prepared in the same manner as in Example 1, except that 12-hydroxystearic acid was removed from the components forming the first layer in Example 1, and the amount of polyamide resin (Versamide 940) was changed to 10 parts by weight. A transfer type thermosensitive recording medium was obtained.

Comparative Example 2 A comparative example was prepared in the same manner as in Example 2, except that stearamide, which is a component forming the first layer of Example 2, was removed and the amount of polyamide resin (Polyamide S-52) used was 10 parts by weight. A transfer type thermosensitive recording medium was obtained.

Next, a commercially available thermal printer (TP2220;
Printing was performed on bond paper (smoothness: 12 seconds (Ouken type surface smoothness meter)) using a paper (manufactured by Ricoh Co., Ltd.). The results are shown in Table-1.

From Table 1, polyamide resin and 12
- The transfer type thermal recording recording a of the present invention using hydroxystearic acid or stearic acid amide enables clear printing even on transfer paper with poor surface smoothness, has excellent removability, and has excellent support. It can be seen that there is no ink residue on the body side.

Since the function of the first layer of the can is not fully demonstrated, the printed characters may be chipped or faded, making it impossible to print detailed explanations of the invention, and in some cases making it impossible to transfer ink. Become. Furthermore, since the ink is not easily releasable from the support, ink remains on the support side, and in extreme cases, the phenomenon of paper smearing also occurs.

This is due to the high melt viscosity of unmodified low melting point polyamide, but other factors include:
This is believed to be due to its poor solvent resistance, which during coating of the top layer is attacked by the coating solvent, such as toluene, and most of the first layer is incorporated into the top layer.

〔effect〕

The transfer type thermal recording medium of the present invention enables clear printing even on transfer paper with poor surface smoothness, has excellent peelability from the transfer paper, and does not leave ink residue on the support side. It has extremely high practical value.

Claims (1)

[Claims] (1) Two or more heat-transferable ink layers are provided on a heat-resistant support, and the ink layers are adjusted to be at least close to the heat-resistant support and easily melt by heat to become a low-viscosity liquid. In a transfer type heat-sensitive recording medium that includes a first layer that exhibits tackiness when heated, but one layer that is closest to the transfer paper and that is adjusted so that it does not melt into a low viscosity liquid. A transfer type thermosensitive recording medium, characterized in that a low melting point polyamide resin is used as a component of the first layer, and a higher fatty acid amide and/or 12-hydroxystearic acid is further used.