JPS6382784A - Transfer-type thermal recording medium - Google Patents

Abstract

PURPOSE:To enable clear printing free of ground contamination even on a transfer recording paper poor in surface smoothness, by providing an intermediate layer between a heat-fusible layer and a heat-softening colored layer and incorporating a coloring agent only in the heat-softening colored layer. CONSTITUTION:A transfer-type thermal recording medium comprises a thermally transferable ink layer comprising a heat-fusible layer so prepared as to be melted to become a low-viscosity liquid when being heated, and a heat-softening colored layer so prepared as to be tacky but not to become a low-viscosity liquid when being heated, while these layers are provided in that order on a heat-resistant base. In the recording medium, an intermediate layer is provided between the heat-fusible layer and a heat-softening layer, and a coloring agent is incorporated only in the heat-softening colored layer. With this arrangement, clear printing free of ground contamination can be performed even on a transfer recording paper poor in smoothness, and ground contamination due to rubbing will not occur in non-image areas.

Description

[Detailed Description of the Invention] [Technical Field] The present invention has a thermally transferable ink layer with a three-layer laminated structure, and enables clear recording without scumming even on transfer paper with poor surface smoothness. The present invention also relates to a transfer type heat-sensitive recording medium which can prevent scumming due to rubbing in non-printed areas.

[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 is low in smoothness, the print quality will still be poor compared to the print quality on transfer paper with a high surface smoothness. It has not been possible to fundamentally solve the drawbacks of transfer-type thermal recording, in which only inferior print quality is obtained and print quality depends on the smoothness of the surface of the transfer paper.

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, it is possible to print with high quality on a transfer paper whose surface has poor 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.

In addition, high boiling point solvents such as phosphoric acid esters, phthalic esters, animal and vegetable oils, mineral oils, higher fatty acids, and higher alcohols are used in the coloring material layer in contact with the heat-resistant support, so that there is no background smearing or deterioration of resolution. Thermal transfer media have also been proposed (Japanese Patent Laid-Open No. 60-239284, Japanese Patent Laid-open No. 60-239285).
This product has low sensitivity and is difficult to print at high speed or with low energy, and in order to prevent the resolution from decreasing, it is necessary to add a large amount of the high boiling point solvent. This causes difficulties in the storage stability and coating properties of the thermal transfer medium.

Furthermore, in a thermal transfer material in which a first ink layer and a second ink layer are provided on a support, a method is also known in which mineral oil or vegetable oil such as machine oil, castor oil, olive oil, or rapeseed oil is contained in the first ink layer. (Unexamined Japanese Patent Publication No. 187593/1983)
Although this product has the advantage of being able to print well even in solid black without line breaks in the so-called first ink layer, it has the drawbacks of being prone to scumming and having poor storage stability.

Furthermore, a thermal transfer material has been proposed in which first to third ink layers are provided on a support, and the melt viscosity and cohesive force of the second ink layer are made larger than those of the first and third ink layers. (Japanese Unexamined Patent Publication No. 60-183192), although the transferred image obtained from this method has excellent print density, there is a problem that scumming occurs in non-printed areas when rubbed with an eraser or the like.

〔the purpose〕

An object of the present invention is to provide a transfer type thermosensitive recording medium that enables clear printing without background smearing even on transfer paper with poor surface smoothness, and can prevent background smudges due to rubbing of non-printing areas. With the goal.

〔composition〕

According to the present invention, on a heat-resistant support, there is provided a heat-fusible layer that is prepared to melt at least into a low-viscosity liquid when heated, and a heat-meltable layer that exhibits adhesiveness when heated but melts to become a low-viscosity liquid. In a transfer type heat-sensitive recording medium in which heat-transferable ink layers consisting of heat-softening colored layers prepared so as to be laminated in that order,
Furthermore, there is provided a transfer type thermosensitive recording medium characterized in that an intermediate layer is provided between the heat-melting layer and the heat-softening colored layer, and a coloring agent is contained only in the heat-softening colored layer.

The transfer type heat-sensitive recording medium of the present invention comprises a heat-resistant support, a heat-meltable layer prepared to at least melt into a low-viscosity liquid, and a heat-meltable layer that exhibits tackiness when heated, but melts into a low-viscosity liquid. In a transfer type heat-sensitive recording medium in which heat-transferable ink layers consisting of heat-softening colored layers prepared so as not to become In addition, since the colorant is contained only in the heat-softening colored layer, it is possible to perform clear printing without background smudges even on transfer paper with poor smoothness. Since it does not cause stains, it has extremely high practical value.

Next, one aspect of the present invention will be explained in more detail.

The heat-fusible layer in the present invention needs to be easily peelable from the support during printing.

For this purpose, it is sufficient that the material is configured such that after being heated, it is thermally melted to become a low-viscosity liquid, and the layer is easily broken near the interface between the heated portion and the non-heated portion.

Therefore, as the main component of the heat-fusible layer, a wax-like substance that is hard at room temperature and melts when heated is preferably used.

Such wax-like substances include, for example, beeswax,
Natural waxes such as carnauba wax, whale wax, wood wax, candelilla wax, Nuka wax, and montan wax,
paraffin wax, microcrystalline wax,
Synthetic waxes such as oxidized wax, osikerite, ceresin, ester wax, and polyethylene wax are preferably used, as well as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and fromenic acid.

Examples include higher fatty acids such as behenic acid, higher alcohols such as stearyl alcohol and behenyl alcohol, esters such as fatty acid ester of sorbitan, and amides such as stearinamide and oleinamide.

In addition, in the present invention, when an oil containing methane group hydrocarbons and naphthenes as main components and having a viscosity of 100 cst or less at 40°C and a viscosity of 20 cst or less at 100°C is added to the heat-fusible layer, the printing effect can be improved. A further improved transfer type thermosensitive recording medium can be obtained. In this case, it is preferable that the heat-fusible layer contains 10 to 50 parts by weight of oil, and it is appropriate that the content of methane group hydrocarbons in the oil be 50% or more.

Specific examples of such oils used in the present invention include, for example, Krystoll 52, Krystolua 2, Krystolua 172. Examples include Crystor 352.

The heat-fusible layer of the present invention further includes polyamide resins, polyester resins, epoxy resins, polyurethane resins,
Elastomers such as acrylic resin, vinyl chloride resin, cellulose resin, polyvinyl alcohol resin, petroleum resin, phenolic resin, styrene resin, natural rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber are also used. However, the amount added is preferably 0 to 20% by weight of the heat-fusible layer.

Moreover, if this heat-fusible layer contains a coloring agent.

Addition of such colorants should be avoided since the peelability of the layer from the support will be impaired.

The intermediate layer does not mix with the heat-softening colored layer during printing,
If it is transferred in a layered manner onto the colored layer, the intended purpose can be achieved. Therefore, as the main component, a material with a high melt viscosity at 150°C is preferable.

In general, heat-softening resins are good. Examples of these resins include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyamide resin, polyester resin, epoxy resin, polyurethane resin, and acrylic resin. Use of elastomers such as vinyl chloride resin, cellulose resin, polyvinyl alcohol resin, oil-based resin, phenolic resin, styrene resin, natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, etc. You can also do it.

In addition, tackifiers such as terpene resins, coumaron resins, rosins and their derivatives, and waxes used in the heat-melting layer may be added to the intermediate layer as melt viscosity or hardness adjusters. The total amount thereof is desirably 60% by weight or less of all resin components of the intermediate layer.

Unlike the heat-melting layer, the heat-softening colored layer does not have a clear melting point and becomes sticky to the transfer paper due to the thermal energy during recording, but it is made of a resin that does not melt into a low-viscosity liquid. This layer is the main component, and due to the function of this layer, each of these resins alone has a tensile strength (JIS
K 6760-1966) is preferably 20 kg/rri or more.

As such resin, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and polyester resin are preferably used. In addition, polyamide resins, epoxy resins, polyurethane resins, acrylic resins, vinyl chloride resins, cellulose resins, polyvinyl alcohol resins, petroleum resins, phenolic resins, styrene resins, natural rubber, styrene-butadiene rubber Elastomers such as , isoprene rubber, and chloroprene rubber can also be used. In addition, tackifiers such as terpene resins, coumaron resins, rosin and their derivatives, and waxes used in the heat-melting layer can be added as auxiliary materials to these resins, but the total amount of them is It is desirable that the weight of all the resin components of the colored layer is 60% by weight or less.

Since the heat-softening colored layer is the main component transferred during recording, it must contain a colorant, but the amount should be adjusted to an appropriate level from the viewpoint of sensitivity during recording, storage performance, print quality, etc. However, an excessive amount is not desirable, and it is desirable that the amount is 70 weight or less of the total dry weight of the heat-softening colored layer.

The coloring agent used in the present invention is appropriately selected from conventionally known dyes and pigments. As the dye, basic dyes, oil-soluble dyes, acid dyes, direct dyes, disperse dyes, etc. are preferably used. Also as a pigment.

Carbon black, phthalocyanine pigments, etc. are preferably used.

Further, the thickness of the heat-melting layer is preferably 2 to 10 μm, the thickness of the intermediate layer and the heat-softening colored layer is preferably in the range of 0.2 to 5 μm, and the total thickness of the heat transferable ink layer is 4 to 20 μm.
It is preferable that

Additionally, additives such as a dispersant, a penetrant, an adhesion modifier, and a fluidity control agent may be added to the heat-fusible layer, intermediate layer, and heat-softening colored layer, respectively, if necessary.

Furthermore, in the present invention, in order to improve the printing effect and the effect of preventing scumming in non-printing areas, the melt viscosity at 150° C. is set to 600 cps or less for the heat-melting layer, 1000 cps or more for the intermediate layer, and a heat-softening layer. Colored layer is 1000-20
It is preferable that the penetration rate of the heat-fusible layer is smaller than that of the intermediate layer, and the hardness of the intermediate layer is higher than that of the heat-fusible layer.

Supports include polyester, polycarbonate, triacetyl cellulose, and nylon.

Relatively heat-resistant plastic films such as polyimide, cellophane, parchment paper, condenser paper, etc. can be used.
If necessary, a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. or a stick prevention layer such as wax may be provided on the surface of the support that comes into contact with the thermal head.

The thickness of the support is preferably 2 to 6 μm, but it may be 2 to 6 μm if used or treated to improve heat transfer efficiency.
Thicknesses up to 20 μm can be used.

The three-layer laminated transfer type thermosensitive recording medium of the present invention as described above can be prepared by coating the support film with a hot melt method, a solvent dispersion coating method,
It is obtained by applying the components forming each layer using a water-based emulsion coating method or the like.

〔Example〕

The present invention will be explained below using Examples.

Example 1 [Thermofusible layer forming components] Paraffin wax (m, p, 65° C.) 80 parts by weight The above mixture was heated and then dispersed in a ball mill for 3 hours to obtain a thermofusible layer forming liquid.

[Ingredients forming the intermediate layer]

Vinyl chloride-vinyl acetate copolymer 42-layer polyethylene wax (mρ, 100”C) 18 I
I The above mixture was diluted with 30% toluene using an attritor.
0 parts by weight to obtain an intermediate layer forming liquid.

[Thermosoftening colored layer]

Polyethylene wax 20 II carbon black 20 The above mixture,
The mixture was dispersed in 300 parts by weight of toluene using an attritor to obtain a heat-softening colored layer forming liquid.

Next, a 3.5 μm thick polyester film.

The thermofusible layer forming liquid was applied by a hot melt coating method to form a thermofusible layer with a thickness of 6 μm.Next, the intermediate layer forming liquid was applied onto the hotfusible layer using a wire bar and dried. Then, an intermediate layer with a thickness of 1.0 μm was formed, and then the heat-softening colored layer forming liquid was applied using a wire bar and dried to form a heat-softening colored layer with a thickness of 3 μm. A transfer type thermosensitive recording medium of the invention was obtained.

Comparative Example 1 A comparative transfer type thermosensitive recording medium was obtained in the same manner as in Example 1 except that the intermediate layer of Example 1 was removed.

Next, we have a thermal transfer printer (JP-
300), printing was carried out on bond paper (Beck smoothness: 5 to 6 seconds) using the transfer-type heat-sensitive recording media of the above-mentioned Examples and Comparative Examples, and it was found that the transfer-type heat-sensitive recording material of Example 1 had no white spots. Good printing with no background smearing was obtained.

Furthermore, even if the printed area was rubbed five times with a plastic eraser, the printing did not disappear, and there was no scumming in the non-printed area. On the other hand, in the comparative example, the print was easily erased, and the background smudge due to rubbing in the non-print area was noticeable.

〔effect〕

According to the present invention, it is possible to obtain a clear transferred recorded image without white spots and background smear even on transfer paper with poor smoothness, and to prevent background smear due to rubbing of non-printed areas.

Claims (6)

[Claims] (1) On a heat-resistant support, there is a heat-fusible layer prepared to at least melt under heat to become a low-viscosity liquid, and a heat-fusible layer that exhibits stickiness when heated but does not melt to become a low-viscosity liquid. In the transfer-type thermosensitive recording medium in which heat-transferable ink layers consisting of the prepared heat-softening colored layers are laminated in that order, an intermediate layer is further provided between the heat-meltable layer and the heat-softening colored layer, and a heat-softening colored layer is further provided. A transfer type heat-sensitive recording medium characterized in that only a colored layer contains a coloring agent. (2) The heat-fusible layer has a viscosity of 100 cst at 40°C.
2. The transfer type heat-sensitive recording medium according to claim 1, further comprising an oil containing methane group hydrocarbon and naphthene as main components and having a viscosity of 20 cst or less at 100°C. (3) The melt viscosity of each layer at 150°C is 600 cps or less for the heat-melting layer, 1000 cps or more for the intermediate layer, and 1000 to 200,000 cps for the heat-softening colored layer. transfer type thermal recording medium. (4) The transfer type thermosensitive recording medium according to any one of claims 1 to 3, wherein the heat-fusible layer contains 10 to 50% by weight of oil. (5) The transfer type thermosensitive recording medium according to any one of claims 1 to 4, wherein the content of methane group hydrocarbons in the oil is 50% by weight or more. (6) The transfer type thermosensitive recording medium according to any one of claims 1 to 5, wherein the penetration degree of the heat-fusible layer is smaller than the penetration degree of the intermediate layer.