JP2610873B2 - Transfer type thermal recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention has a heat transferable ink layer of a laminated structure, enables clear recording even on a transfer receiving paper having a poor surface smoothness, and reduces dot omission. The present invention relates to a transfer-type heat-sensitive recording medium that gives a clear and high-quality transfer image.

(Prior art)

The transfer type thermal recording method is widely used as a plain paper recording method with a simple apparatus. However, the printing quality is easily influenced by the smoothness of the surface of the transferred paper, and the transfer quality is poor for the transferred paper having a poor surface smoothness. It is difficult to perform clear printing.

Conventionally, in order to improve such a defect, auxiliary means such as magnetic force or electrostatic force is used at the time of transfer for heat treatment after printing. Alternatively, a means has been proposed in which a large amount of an oily substance is added to reduce the melt viscosity at the time of transfer, and a thermally decomposable or thermally expandable substance is added to sensitize the composition.

In addition, a technique for improving the print quality by forming a multi-layer of a heat-fusible ink layer has been conventionally proposed.Layers of a heat-fusible ink having only a slightly different melting point are laminated, and a pigment is applied to one or both of them. Techniques such as providing a layer made of a heat-fusible substance not containing a coloring material on a heat-fusible ink layer to be added have been proposed.

However, in the method of transferring and recording the ink that has become a liquid by being melted in this way, when the smoothness of the surface of the transfer receiving paper is low, compared with the print quality of the transfer receiving paper having a high surface smoothness. Again, only inferior print quality was obtained, and the fundamental problem of transfer-type thermal recording, in which the print quality depends on the smoothness of the surface of the paper to be transferred, could not be solved.

On the other hand, an ink containing a resin having a certain degree of mechanical strength as a main component without exhibiting tackiness when applied with heat energy but being melted into a low-viscosity liquid, has a poor surface smoothness. By using an ink which is adhered to the convex portion of the surface and transferred so as to cover the concave portion, printing can be performed with high quality on a transfer receiving paper having poor surface smoothness.

However, such a resin ink requires a large amount of energy for printing as compared with the conventional wax ink, so that it is necessary to use a support film having particularly excellent heat resistance, and it is also necessary to use a long-life thermal head. It is not preferable because a heat problem occurs.

In order to solve this problem, a hot-melt layer is provided between the support and the resin ink layer, and a high-boiling-point solvent or the like is added in a large amount to the hot-melt layer so that the resin ink has low energy during heating. Various methods have been proposed for improving the cut of the layer. However, even with this method, for example, white spots or dot spots occur on bond paper having a Beck smoothness of 2 to 3 seconds, and a clear transfer image cannot be obtained. was there.

Also, a method of incorporating a tackifier such as a low-molecular-weight styrene resin having a number average molecular weight of about several hundreds in the ink layer, particularly the coloring layer, and further a terpene resin or rosin in order to improve the fixability to a transfer receiving paper. Proposed.

However, although this method improves fixability on low-smoothness paper, it causes printing unevenness and the like, and furthermore, the so-called co-falling phenomenon (printed (A phenomenon in which ink that should not be printed after the image is transferred) occurs.

〔Purpose〕

The present invention enables clear printing with no white spots or missing dots even on a transfer receiving paper having a poor surface smoothness, and the co-falling phenomenon occurs even when applied to a transfer receiving paper having a high surface smoothness. An object of the present invention is to provide a transfer-type thermosensitive recording medium that does not occur.

〔Constitution〕

According to the present invention, on a heat-resistant support, at least a first layer prepared so as to be thermally melted to be a low-viscosity liquid and exhibiting tackiness by heat but being melted to become a low-viscosity liquid. A heat transferable ink layer composed of a second layer prepared so as not to be laminated in that order, and if necessary, the second layer has adhesiveness due to heat on the second layer but melts to become a low-viscosity liquid. In a transfer-type thermosensitive recording medium provided with an adhesive layer mainly containing a resin, at least one of the second layer and the adhesive layer contains a styrene resin having a number average molecular weight of 1,000 to 5,000. A transfer type thermal recording medium is provided.

The transfer type thermosensitive recording medium of the present invention is provided with a heat transferable ink layer on a support, and the ink layer is adjusted to be at least close to the heat resistant support and melted by heat to become a low-viscosity liquid. A first layer (release layer), a second layer (colored layer) adjusted to be tacky by heat but not melt and become a low-viscosity liquid; The adhesive layer is formed of an adhesive layer which exhibits a property but does not melt,
Layer and / or the adhesive layer contains a styrene resin having a number average molecular weight of 1,000 to 5,000, so that sharp and clear printing without white spots can be performed even on a transfer paper having poor smoothness. At the same time, it is possible to form a good transfer image without a dropping phenomenon even on a transfer paper having a high degree of smoothness such as an OHP sheet.

For the first layer of the transfer type thermosensitive recording medium in the present invention, it is preferable to use a substance which has a peak value of the differential thermal analysis of 120 ° C. or less and easily melts by heating to form a low viscosity liquid.

As such a wax, as a natural substance,
Beeswax, whale wax, candelilla wax, carnauba wax,
Rice bran wax, montan wax, ozokerite, and the like, and petroleum waxes include paraffin wax, microcrystalline wax, and the like, as well as various modified waxes, hydrogenated waxes, and long-chain fatty acids. It is appropriate that the used amount is 70% by weight or more of the total amount of the first layer.

In the first layer of the present invention, a binder resin such as polyethylene, polyethylene oxide, polypropylene, ketone resin, and ethylene-vinyl acetate copolymer is used. Is preferably 0 to 30% by weight.

Further, the first layer may further contain a pigment. The pigment as referred to herein is a component that is uniformly dispersed but not dissolved in the hot-melt component and does not melt with the heat energy at the time of recording, and also includes a coloring pigment as a coloring material. By containing pigment,
This has the effect of increasing the stability during storage and high temperature recording. If the pigment is a colored pigment, it also has the effect of increasing the sharpness of printing at the time of recording.

The second layer, unlike the first layer, does not have a definite melting point and generates adhesiveness to the transfer paper due to thermal energy at the time of recording, but a resin or a coloring material that does not melt to become a low-viscosity liquid. It is a layer mainly composed of an agent and a styrene resin having a number average molecular weight of 1,000 to 5,000.

It is necessary to use a styrene resin having a number average molecular weight of 1,000 to 5,000.

If the number average molecular weight is out of the above range, white spots and dot spots occur, and the intended object of the present invention cannot be achieved.

The content of the styrene resin is 10 to 10% based on the total amount of the second layer.
70% by weight, preferably 30-60% by weight.

Examples of the resin which generates tackiness by heat but does not become a low-viscosity liquid include polyester, polyamide, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, ethylene-ethyl acrylate copolymer and the like. Also, terpene resins,
A tackifier or wax such as coumarone resin, rosin and derivatives thereof may be added, but the total amount thereof is desirably 60% by weight or less of the total resin component of the second layer.

Since the second layer is a main component to be transferred at the time of recording, a coloring pigment is contained therein.
Although it can be determined to an appropriate level from the viewpoint of storage performance, print quality, etc., an excessive amount is not desirable, and is desirably 70% by weight or less of the total dry weight of the second layer.

In the present invention, it is desirable to provide an adhesive layer mainly composed of a resin that exhibits tackiness by heat but does not melt to become a low-viscosity liquid, on the second layer.

As such a resin, the resin used in the second layer is used as it is.

This adhesive layer has a number average molecular weight of 1000 as in the second layer.
~ 5000 styrene resins are compounded.

Further, in the present invention, any of the first layer, the second layer, and the adhesive layer may contain a plasticizer or oil. In this case, as the plasticizer, a plasticizer usually used for plastics, paints, and the like is used. Examples of such plasticizers include aliphatic dibasic acid esters such as phthalic acid ester and dioctyl adipate; fatty acid esters such as glycol ester and butyl oleate; and epoxy-based plasticizing agents such as phosphoric acid ester and epoxidized linseed oil. Agents, chlorinated paraffins and the like.

Examples of the oil include liquid paraffin, silicone oil, vegetable oil, animal oil, mineral oil, higher fatty acid, higher alcohol and the like.

The plasticizer or oil is contained in an amount of 5 to 100 parts by weight based on 100 parts by weight of each ink constituting the first layer, the second layer, and the adhesive layer. If the amount of the plasticizer or oil is less than 5 parts by weight, the effect of the addition is almost nil. On the other hand, if the amount of the plasticizer exceeds 100 parts by weight, good printing cannot be obtained because the resolution of recorded characters is reduced or background smearing occurs.

If necessary, additives such as a dispersant, a penetrant, an adhesion modifier, and a flow control agent may be added to the first, second and adhesive layers.

As the support, polyester, polycarbonate,
Plastic films with relatively high heat resistance such as triacetyl cellulose, nylon, polyimide, etc., cellophane, sulfuric acid paper, condenser paper, etc. can be used.If necessary, a silicone resin, a fluororesin,
A heat-resistant protective layer such as a polyimide resin, an epoxy resin, a phenol resin, a melamine resin, or nitrocellulose, or a stick prevention layer such as a wax may be provided.

The thickness of the support is preferably 2 to 6 μm, but 2 to 20 μm if a treatment such as an increase in use conditions or heat transfer efficiency has been performed.
Can be used up to a thickness in the range of

The laminated transfer type thermal recording medium of the present invention as described above,
It can be obtained by applying a component for forming each layer to a support film by a hot melt method, a solvent dispersion coating method, an aqueous emulsion coating method, or the like.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 [Components for forming first layer] Paraffin wax (m.p. 72 ° C) 75 parts by weight Paraffin oil 15 Dispersant 10 The above mixture was dispersed by a hot melt method for 15 hours to form a first layer.
A layer forming solution was obtained.

[Formation Component of Second Layer] Ethylene-vinyl acetate copolymer (vinyl acetate content, 19%) 7 parts by weight Styrene resin (number average molecular weight, 1500) 5 カ ー ボ ン carbon black 3 ト ル エ ン toluene 85 〃 then 3.5 μm thick polyester film
The layer forming solution was applied to a thickness of 5 μm by a hot melt method to form a first layer. Next, the second ink layer forming liquid was applied on the first layer by a wire bar and dried to form a second layer having a thickness of 3 μm, thereby obtaining a transfer type thermosensitive recording medium of the present invention.

Example 2 [Forming component of first layer] Same as in Example 1 [Forming component of second layer] Ethylene-ethyl acrylate copolymer (ethyl acrylate content: 25%) 12.0 parts by weight Carbon black 3.0 ト ル エ ン toluene 85.0 〃 The above mixture was dispersed in a ball mill for 15 hours to obtain a liquid for forming a second layer.

(Formation component of adhesive layer)

Ethylene-vinyl acetate copolymer (vinyl acetate content 35%) 5.0 parts by weight Styrene resin (number-average molecular weight 3000) 5.0 ト ル エ ン Toluene 15.0 オ ク タ Isooctane 75.0 〃 Disperse the above mixture in a ball mill for 15 hours to form an adhesive layer forming solution I got

The first layer forming solution was applied to a 3.5 μm thick polyester film by a hot melt method to a thickness of 4 μm to form a first layer. Then, a forming solution for the second layer is applied on the first layer with a wire bar and dried to form a second layer having a thickness of 3 μm, and a forming solution for the third layer is further formed on the second layer. Was applied and dried with a wine bar to form a third layer having a thickness of 2 μm, thereby obtaining a transfer type thermosensitive recording medium of the present invention.

Example 3 A transfer-type thermosensitive recording medium of the present invention was obtained in the same manner as in Example 2, except that the components for forming the second layer and the components for forming the adhesive layer in Example 2 were changed to the following.

[Formation component of second layer] Ethylene-vinyl acetate copolymer 6 parts by weight Styrene resin (number average molecular weight 4000) 6 カ ー ボ ン Carbon black 3 ト ル エ ン Toluene 85 〃 [Formation component of adhesive layer] Ethylene-ethyl acrylate copolymer Comparative Example 1 A transferable thermal recording medium for comparison was obtained in the same manner as in Example 1 except that the components for forming the second layer were changed to the following.

[Formation Component of Second Layer] Ethylene-vinyl acetate copolymer 7 parts by weight Styrene resin (number average molecular weight 400) 5 {carbon black 3} Comparative Example 2 In Example 1, the components forming the second layer were as follows: A transfer type heat-sensitive recording material for comparison was obtained in the same manner as in Example 1 except that the above-mentioned material was used.

[Formation Component of Second Layer] Ethylene-vinyl acetate copolymer (vinyl acetate content: 28%) 12.0 parts by weight Carbon black 3.0 {toluene 85.0} Comparative Example 3 Styrene which is a constituent component of the adhesive layer in Example 2 A transfer type thermal recording medium for comparison was obtained in the same manner as in Example 2 except that the resin was changed to a terpene resin.

Next, using the transfer-type thermal recording media obtained in Examples and Comparative Examples obtained above, printing was performed on bond paper (Beck smoothness: 4 to 5 seconds) and an OHP sheet by a commercially available thermal printer. Table 1 shows the results.

[Effect] According to the present invention, it is possible to obtain a clear transfer image without white spots even on rough paper having a Beck smoothness of 4 to 5 seconds,
Also, it is possible to form a good transfer image having excellent fixability without dropping on the OHP sheet.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-48590 (JP, A) JP-A-62-77987 (JP, A) JP-A-62-21595 (JP, A) JP-A-59-1984 224392 (JP, A)

Claims (1)

(57) [Claims] 1. A first layer prepared on a heat-resistant support at least so as to be melted by heat to form a low-viscosity liquid, and exhibits a tackiness by heat but does not melt to become a low-viscosity liquid. The heat transferable ink layer composed of the second layer prepared as described above is laminated in this order, and if necessary, the second layer is heat-adhered by heat but does not melt to become a low-viscosity liquid. In a transfer-type thermosensitive recording medium provided with an adhesive layer mainly composed of a resin, at least one of the second layer and the adhesive layer has a number average molecular weight.
A transfer-type thermosensitive recording medium containing 1000 to 5000 styrene resin.