JPS63141787A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enable clear recording on a transfer recording paper having poor surface smoothness and prevent ground contamination, by providing a heat-softenable particu late colorless layer on a thermally transferable ink layer comprising a heat-fusible layer and a heat-softenable colored layer, and incorporating an oil comprising a paraffinic hydrocarbon and a cycloparaffin as main constituent and having a specified viscosity into the heat-fusible layer. CONSTITUTION:A thermally transferable ink layer comprising a heat-fusible layer which becomes a low-viscosity liquid through melting when being heated and a heat- softenable colored layer which becomes tacky but does not becomes a low viscosity liquid through melting when being heated is provided in a laminate form on a heat- resistant base. A heat-softenable particulate colorless layer which becomes tacky but doest not become a low-viscosity liquid when being heated is provided on the ink layer. The particulate colorless layer has an average particle diameter of 0.1-10mum, and does not contain a coloring agent. An oil comprising a paraffinic hydrocarbon and a cycloparaffin as main constituents and having a viscosity of more than 100cst at 40 deg.C and a viscosity of the more than 20cst at 100 deg.C is incorporated in the heat-fusible layer in an amount of 10-50wt.%. The amount of the paraffinic hydrocarbon in the oil is suitably at least 50%.

Description

Detailed Description of the Invention [Technical Field] The present invention has a thermal transfer ink layer with a three-layer laminated structure, which enables clear recording even on transfer paper with poor surface smoothness, and eliminates background stains. The present invention relates to a thermal transfer recording medium without

[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 transfer paper has poor surface smoothness due to ink 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. 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 a large amount of energy to print compared to conventional wax inks, so it is necessary to use a support film with particularly excellent heat resistance, and it also reduces the lifespan of the thermal head and reduces the print quality. This is not desirable as it causes natural problems.

In order to solve this problem, a heat-melting layer is provided between the support and the resin ink layer, and a large amount of a high boiling point solvent is added to the heat-melting layer, so that the resin ink can be heated with low energy. Various methods have been proposed to improve the cutting ability of layers.

However, like these methods, phosphoric acid esters, phthalic acid esters, animal and vegetable oils, and mineral oils.

Although it is possible to print with low energy using high boiling point solvents such as higher fatty acids and higher alcohols, background smearing occurs.
Further, depending on the type, there are some that are ineffective unless added in large amounts, and there are many problems in terms of storage stability, coatability, etc.

〔the purpose〕

An object of the present invention is to provide a thermal transfer recording medium that allows clear printing even on transfer paper with poor surface smoothness, is free from scumming, and has excellent storage stability.

〔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 a heat-transferable ink layer consisting of a heat-softening colored layer made of WA is laminated in that order, it is further made sticky by heat, but does not melt and become a low-viscosity liquid. A colorless layer in the form of heat-softening fine particles treated with 7ArXI is provided, and the heat-fusible layer has a viscosity of 40°C or lower and a viscosity of 2.0°C at 100°C.
Provided is a thermal transfer recording medium characterized in that it contains an oil whose main components are methane group hydrocarbons and naphthenes having a concentration of 0 cst or less.

The heat-sensitive transfer 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 when heated, and a heat-meltable layer that exhibits tackiness when heated but melts into a low-viscosity liquid. A heat-transferable ink layer consisting of a heat-softening colored layer prepared in such a way that it will not become viscous is laminated in that order, and on top of that is a heat-transferable ink layer that exhibits tackiness when heated but does not melt into a low-viscosity liquid. The prepared heat-softening fine-particle colorless layer is provided, and the heat-fusible layer is provided with 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. Because it contains it, it can print clearly even on paper with poor smoothness, does not cause scumming, and has excellent storage stability, so it has extremely practical value. It's expensive.

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

The first heat-melting layer of the heat-sensitive transfer recording medium of the present invention is made of a so-called wax-like substance that has a peak value of 120"c or less in differential thermal analysis and is easily heat-melted to become a low-viscosity liquid. Examples of wax-like substances preferably contained in the heat-melting substance include natural substances such as beeswax, carnauba wax, spermaceti wax, wood wax, candelilla wax, bran wax, and montan wax. Synthetic waxes such as wax, paraffin wax, microcrystalline wax, oxidized wax, osikelite, ceresin, ester wax, and polyethylene wax are preferably used, as well as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, 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.

Further, in the present invention, as described above, the heat-fusible layer has a viscosity of 100 cst or less at 40°C.
A transfer type heat-sensitive recording medium with improved printing effect is obtained by adding an oil mainly composed of methane group hydrocarbons and naphthenes having a viscosity of 20 cst or less. It is preferable to contain 10 to 50 methane series hydrocarbons in the oil, and it is appropriate that the content of methane group hydrocarbons in the oil is 50% or more.

If the amount of oil added to the layer is less than 10% by weight, there is almost no effect of the addition, and if it is more than 50% by weight, the resolution of recorded characters may decrease or background smear may occur, resulting in poor printing. can't get it.

Specific examples of such oils used in the present invention include, for example, Crystoll 52. Christ-Lua 2, Christ-/L/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, imprene rubber, and chloroprene rubber are also used. However, the amount added is preferably 0 to 20% by weight of the heat-fusible layer.

The first layer 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.

Unlike the thermofusible layer, the second 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 does not melt into a low-viscosity liquid. Furthermore, due to the function of this layer, each such resin has a tensile strength (
JIS K 6760-1966) is preferably 20 kg/- or more.

Preferred examples of such resins include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and polyester resin, as well as polyamide resin, epoxy resin, polyurethane resin, acrylic resin, and vinyl chloride. Examples include elastomers such as resins, cellulose resins, polyvinyl alcohol resins, petroleum resins, phenol resins, styrene resins, natural rubber, styrene-butadiene rubber, imprene rubber, and chloroprene rubber. Tackifiers and waxes such as terpene resins, coumaron resins, rosins and their derivatives can also be added as auxiliary materials to these resins, but the total amount of these agents is based on the total resin components of the heat-softening colored layer. It is desirable that the amount 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 preferably 70% by 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.

This heat-softening colored layer can contain a plasticizer.

As the plasticizer, a plasticizer commonly used in plastics, paints, etc. is used. Examples of such plasticizers include phthalate esters, aliphatic dibasic acid esters such as dioctyl adipate, glycol esters, fatty acid esters such as butyl oleate, phosphate esters, and epoxy plasticizers such as epoxidized linseed oil. agent, chlorinated paraffin, etc.

The plasticizer is contained in the second layer in a proportion of 2-30 parts by weight. If the plasticizer is less than 2% by weight, the addition has almost no effect;
If the weight exceeds 30 weight 2, the resolution of recorded characters may decrease,
Good printing cannot be obtained due to background smearing, etc.

The third layer, a heat-softening, colorless layer in the form of fine particles, is mainly composed of a resin that, like the second layer, becomes sticky to the transfer paper due to thermal energy during recording, but does not melt into a low-viscosity liquid. However, in the third layer, this resin is particularly formed in the form of fine particles on the second M.

The average particle diameter of the fine particles is preferably 0.1 to 10 μm. If the average particle diameter is smaller than 0.1 μm, the boundary between the heated part and the non-heated part will be difficult to cut when printing the layer.
If the average particle diameter exceeds 10 μm, problems such as a decrease in sensitivity due to the thickness of the layer, a decrease in fixability to transfer paper, and a decrease in the mechanical strength of the layer will occur.

As the resin used as the fine particles in the third layer, the same resin as the resin used in the second layer can be used.

Since the third layer is in direct contact with the transfer paper, it is preferable that it does not contain coloring agents such as colored dyes and pigments. can be dispersed and contained.

As the support, relatively heat-resistant plastic films such as polyester, polycarbonate, triacetyl cellulose, nylon, and polyimide, cellophane, parchment paper, condenser paper, etc. can be used, and if necessary, the surface of the support in contact with the thermal head can be used. Silicone resin, fluororesin, polyimide resin, epoxy resin, phenolic resin, melamine resin.

A heat-resistant protective layer such as nitrocellulose or a stick prevention layer such as wax may be provided.

The thickness of the support is preferably 2 to 6 μm, but it may be 2 to 20 μm if it has been treated to improve the usage conditions and heat transfer efficiency.
It can be used up to thicknesses in the μ range.

The thickness of the heat-melting layer is 2 to 10 μm, and the thickness of the heat-softening colored layer and the heat-softening fine particle colorless layer is 0.5 to 5 μm.
A range of μm is preferred. Further, the total thickness of the thermally transferable ink layer is preferably 4 to 15 μm.

Further, a dispersant is added to each of the heat-melting layer, the heat-softening colored layer, and the heat-softening fine particulate colorless layer, if necessary.

Additives such as penetrants, adhesion modifiers, flow control agents, etc. may also be added.

The three-layer laminated thermal transfer recording medium of the present invention as described above is as follows:
It is obtained by coating the components forming each layer on a support film by a hot melt method, a solvent dispersion coating method, an aqueous emulsion coating method, or the like.

〔Example〕

The present invention will be explained below using Examples.

Example 1 [Thermofusible layer forming component] Paraffin wax (m, p, 65° C.) 75 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.

[Formation component of heat-softening colored layer]

Ethylene-vinyl acetate copolymer 7 parts by weight Carbon black 3 Toluene
90! ! The above mixture was dispersed in a ball mill for 15 hours to obtain a heat-softening colored layer forming liquid.

[Component forming heat-softening fine particulate colorless layer] Isooctane
90 The above mixture was dispersed in a ball mill for 15 hours to obtain a colorless layer-forming liquid in the form of heat-softening fine particles.

Next, a 3.5 μm thick polyester film.

Applying the hot melt layer forming liquid with a wire bar,
A thermofusible layer having a thickness of 6 μm was formed. Next, the heat-softening colored layer forming liquid was applied onto this heat-melting layer using a wire bar and dried to form a heat-softening colored layer having a thickness of 2.0 μm. Furthermore, the heat-softening fine-particle forming liquid was applied onto the layer using a wire bar, and dried at 45° C. to form a third layer of heat-softening fine-particle colorless layer having a thickness of 2 μm. When the surface of the heat-sensitive recording medium thus prepared was inspected using a microscope photo, the presence of particulate matter was observed on the uppermost surface, and the surface was uneven.

Example 2 50% by weight of the ethylene-vinyl acetate copolymer, which is a forming component of the heat-softening colored layer in Example 1, was replaced with polyester resin, and the isooctane, which was a forming component of the heat-softening fine particulate colorless layer, was replaced with naphtha. A thermosensitive recording medium was produced in the same manner as in Example 1 except for the above. When this surface was observed using a microscopic photograph, the presence of fine particulate matter was observed on the uppermost surface as in Example 1, and the surface was uneven.

Comparative Example 1 A heat-sensitive recording medium was prepared in the same manner as in Example 1, except that isooctane, which was a forming component of the heat-softening fine particle colorless layer in Example 1, was replaced with toluene.

Comparative Example 2 Example 1 except that liquid paraffin, which is a forming component of the heat-fusible layer in Example 1, was replaced with dioctyl adipate.
A thermosensitive recording medium was prepared in the same manner.

Comparative Example 3 A heat-sensitive recording medium was produced in the same manner as in Example 1, except that the drying temperature of the heat-softening fine particulate colorless layer forming liquid in Example 1 was changed to 100°C.

When the surfaces of the three types of heat-sensitive recording media prepared in Comparative Examples were observed using microscopic photographs, the presence of fine particulate matter was observed on the top surface in Comparative Example 2, but the presence of fine particulate matter on the top surface was observed in Comparative Example 1.3. 6. Printing was performed on Lancaster bond paper (Beck smoothness: 1 to 2 seconds) using the thermal recording media of the Examples and Comparative Examples using a commercially available thermal transfer printer. As a result, in Example 1.2, a clear image with no white spots or background smudges was obtained, but in Comparative Example 1.3, there was no background smudge, but there were white spots and an image with poor sharpness. In Comparative Example 2, only images with noticeable background stains were obtained.

[Effects] The thermal transfer recording medium of the present invention is capable of printing with low energy and high sharpness without line breakage on transfer paper with poor surface smoothness, and also does not cause background smearing. . It also has excellent storage stability and is suitable for high-speed printing due to its high sensitivity.

Claims (4)

[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 a transfer-type heat-sensitive recording medium in which a heat-transferable ink layer consisting of the prepared heat-softening colored layer is laminated in that order, a layer is further added on top of the heat-transferable ink layer that exhibits tackiness when heated but does not melt into a low-viscosity liquid. The prepared heat-softening fine particle-like colorless layer is provided, and the heat-melting layer has a viscosity of 100c at 40°C.
1. A thermal transfer recording medium comprising an oil containing methane group hydrocarbons and naphthenes as main components and having a viscosity of 20 cst or less at 100°C. (2) The heat-sensitive transfer recording medium according to claim 1, wherein the heat-fusible layer contains 10 to 50% by weight of oil. (3) The thermal transfer recording medium according to claim 1 or 2, wherein the content of methane group hydrocarbons in the oil is 50% by weight or more. (4) The heat-sensitive transfer recording medium according to claim 1, wherein the heat-softening fine particulate colorless layer has an average particle size of 0.1 to 10 μm, and the layer does not contain a colorant.