JPH0764123B2 - Thermal transfer sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer sheet, and more specifically, it provides a novel thermal transfer sheet that can easily provide a recorded image with excellent fastness to a recording material. The purpose is to do.

(Prior Art) Conventionally, various thermal transfer methods are known. Among them, a sublimable dye is used as a recording agent, and a sublimable dye is carried on a base material sheet such as paper to form a thermal transfer sheet. A sublimation transfer method is performed in which a sublimable dye is transferred onto a recording material that can be attached, for example, a polyester sheet or a polyester woven cloth, and thermal energy is applied in a pattern from the back surface of the thermal transfer sheet to transfer the sublimable dye to the recording material. ing.

(Problems to be Solved by the Invention) In the sublimation transfer method described above, in the sublimation printing method in which the recording material is, for example, a polyester woven fabric, since the thermal energy is applied for a relatively long time, the recording itself is also As a result of being heated with the applied thermal energy, a relatively good dye transfer has been achieved.

However, due to advances in recording methods, using a thermal head or the like, at high speed, for example, a polyester sheet,
When using recording materials provided with a dye-receiving layer on paper and forming delicate characters or figures or photographic images on these recording materials, the application of heat energy is extremely short, such as seconds or less. Therefore, since the sublimable dye and the recording material are not sufficiently heated in such a short time, an image having a sufficient density cannot be formed.

Therefore, in order to cope with such high-speed recording, a sublimable dye having excellent sublimation property has been developed. However, since the dye having excellent sublimation property generally has a small molecular weight, it can be recorded in a recording material after transfer. In the above, there is a problem in that the dye migrates with time or bleeds on the surface to disturb the image formed at a corner, to make it unclear, or to contaminate surrounding articles.

In order to avoid such a problem, when a sublimable dye having a relatively large molecular weight is used, the sublimation speed is inferior in the above high-speed recording method, so that an image having a satisfactory density as described above cannot be formed. Met.

Therefore, in the thermal transfer method using the sublimable dye,
It is currently strongly desired to develop a thermal transfer sheet that gives a clear image with sufficient density by applying heat energy for an extremely short time as described above, and that the formed image shows various fastnesses. Is.

As a result of earnest research to meet the strong demands of the industry as described above, the present inventor uses a thermal transfer sheet using a sublimable dye having a specific structure, so that even when applying thermal energy for an extremely short time, use The present invention has been completed by finding that the sublimable dyes described above are easily transferred to a recording material to form a recorded image having high density and various fastnesses.

(Means for Solving Problems) That is, the present invention comprises a base material sheet and a dye carrying layer provided on one surface of the base material sheet, and the dye contained in the dye carrying layer has a structure described later. It is a thermal transfer sheet characterized by being at least one sublimable dye selected from the group consisting of formulas a to l.

Next, the present invention will be described in more detail. The dye itself as defined above, which is used in the present invention and mainly characterizes the present invention, is a known dye, and is conventionally used mainly as a disperse dye such as polyester fiber. is there.

Conventionally, various disperse dyes have been diverted as dyes of sublimation transfer method, but in sublimation transfer method, a rapid sublimation speed is required, so that the molecular weight is generally limited to about 300 or less, and a polar group is preferably used. Those that do not have have been selected and used.

However, as described above, such a resin having a relatively low molecular weight and having no polar group has a good transfer rate and color development property, but as described above, an image having low migration resistance and stain resistance can be obtained. It was something to give.

The present inventor, as a result of detailed study of the applicability for thermal transfer of known disperse dyes, which had been completely excluded from the selection for the conventional sublimation transfer method, even if the molecular weight exceeds 350, As long as it has at least one specific polar group in the molecule, that is, a nitro group, a cyano group or a sulfonyl group (may be a linking group), it has an excellent heat sublimation property that cannot be considered from conventional common sense. In addition, it exhibits excellent dyeing property and color development property to the base sheet, and further, migration (bleeding property) and stain property of the dye in the transferred recording material are not observed, and a dye for a thermal transfer sheet. As a result, it has been found that it has extremely ideal properties.

Examples of particularly suitable dyes having the above-mentioned definition used in the present invention include those having the following structures.

Among the dyes exemplified above and the dyes usable in the present invention other than those exemplified above, particularly preferable are dyes represented by the structural formulas a and k, and the molecular weight thereof is about 350 to 700, more preferably 400 to 700. It's 700. If the molecular weight is less than 350, various drawbacks of the prior art are not sufficiently solved,
On the other hand, if the molecular weight exceeds 700, the thermal transfer rate and the color developability become poor, which is not preferable.

Particularly preferred are those in which the dye has two or more groups selected from the group consisting of a nitro group, a cyano group and a sulfonyl group. It is possible to provide an image having the object of the invention, that is, excellent migration resistance and stain resistance.

The thermal transfer sheet of the present invention is characterized by using the specific sublimable dye as described above, and other configurations may be the same as the configurations of conventionally known thermal transfer sheets.

The base sheet used for the constitution of the thermal transfer sheet of the present invention may be any one as long as it has a conventionally known degree of heat resistance and strength, for example, 0.5 to 50 μm,
Paper having a thickness of about 3 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyvinyl alcohol film, cellophane and the like are preferable, and polyester film is particularly preferable.

The dye carrying layer provided on the surface of the substrate sheet as described above is a layer in which the sublimable dye is carried by an arbitrary binder resin.

As the binder resin for supporting the sublimable dye as described above, any conventionally known binder resin can be used, and preferred examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, and cellulose acetate. Cellulose resins such as cellulose acetate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinylpyrrolidone, vinyl resins such as polyacrylamide, polyesters and the like are preferable from the viewpoints of heat resistance and dye migration. .

The dye-carrying layer of the thermal transfer sheet of the present invention is basically formed of the above-mentioned materials, but may also contain various additives similar to the conventionally known ones, if necessary.

Such a dye-carrying layer is preferably a sublimable dye, a binder resin or the like added to a suitable solvent to dissolve or disperse each component to prepare a coating liquid or ink for forming a carrier layer, This is formed by coating and drying on the above-mentioned base material sheet.

The supporting layer thus formed has a thickness of about 0.2 to 5.0 μm, preferably about 0.4 to 2.0 μm, and the sublimable dye in the supporting layer is 5 to 70% by weight of the weight of the supporting layer, preferably
It is preferably present in an amount of 10-60% by weight.

The thermal transfer sheet as described above is sufficiently useful in the present invention as it is, but an anti-adhesion layer, that is, a releasing layer may be further provided on the surface of the dye-carrying layer. By providing such a layer, thermal transfer can be achieved. Prevents the thermal transfer sheet from sticking to the recording material, and uses a higher thermal transfer temperature,
An image having a more excellent density can be formed.

The release layer has a considerable effect even by simply adhering an anti-adhesive inorganic powder, and further, from a resin excellent in release property such as a silicone polymer, an acrylic polymer or a fluorinated polymer, 0.01 to 5 μm, preferably
It can be formed by providing a release layer having a thickness of 0.05 to 2 μm.

The inorganic powder or releasable polymer as described above can bring about sufficient effects even when incorporated in the dye carrying layer.

Further, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet of the present invention in order to prevent adverse effects due to the heat of the thermal head.

The recording material used for forming an image using the thermal transfer sheet of the present invention may be any as long as the recording surface thereof has dye receptivity to the dye, and also the dye receptivity In the case of non-containing paper, metal, glass, synthetic resin, etc., a dye receiving layer may be formed on at least one surface thereof.

Examples of the recording material that does not need to form a dye receiving layer include polyolefin resins such as polyethylene and polypropylene, halogenated polymers such as polyvinyl chloride and polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, and polyacrylic ester. Such as vinyl polymers, polyethylene terephthalate, polyester resins such as polybutylene terephthalate, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene and other vinyl monomers, ionomers,
Cellulose resins such as cellulose diacetate and cellulose triacetate, fibers made of polycarbonate, polysulfone, polyimide and the like, woven fabrics, films, sheets, molded products and the like can be mentioned.

Particularly preferred is a woven fabric, sheet or film made of polyethylene terephthalate.

Further, in the present invention, even a non-dyeing non-recording material such as paper, metal, glass or the like is coated and dried with a solution or dispersion liquid of the above-mentioned dyeing resin on the recording surface, or A recording material can be obtained by laminating these resin films.

Further, even for the recording material having the above dyeing property, a dye receiving layer may be formed on the surface of the recording material from a resin having a more dyeing property as in the case of the above paper.

The dye-receptive layer thus formed may be formed of a single material or a plurality of materials, and may further contain various additives as long as the object of the present invention is not impaired. Of course.

Such a dye receiving layer may have any thickness, but is generally 5 to 50 .mu.m thick. Further, such a dye receiving layer is preferably a continuous coating, but it may be formed as a discontinuous coating by using a resin emulsion or a resin dispersion liquid.

Such a recording material is basically as described above and can be used satisfactorily as it is. However, the recording material or the dye receiving layer thereof may contain an inorganic powder for preventing adhesion. By doing so, even if the temperature at the time of thermal transfer is raised, the adhesion between the thermal transfer sheet and the recording material can be prevented, and more excellent thermal transfer can be performed. Particularly preferred is finely divided silica.

Further, in place of or in combination with the above-mentioned inorganic powder such as silica, the above-mentioned resin having good releasability may be added. Particularly preferable releasing polymer is a cured product of a silicone compound, for example, a cured product of an epoxy-modified silicone oil and an amino-modified silicone oil.
Such releasability is preferably such that it accounts for about 0.5 to 30% by weight of the weight of the dye receiving layer.

Further, the recording material to be used may have the above-mentioned inorganic powder adhered to the surface of the dye receiving layer to enhance the anti-adhesion effect, and the release agent excellent in releasability as described above. You may provide the layer which consists of.

When such a release layer has a thickness of about 0.01 to 5 μm, it exerts a sufficient effect to prevent the thermal transfer sheet from sticking to the dye receiving layer and further improve the dye receiving property.

As the means for applying the thermal energy used when performing the thermal transfer using the thermal transfer sheet of the present invention and the recording material as described above, any conventionally known applying means can be used. For example, a thermal printer (for example, Toshiba ( ), manufactured by the thermal printer TN-5400) a recording device such as by controlling the recording time, by applying heat energy of about 5 to 100 mJ / mm ^2, it is possible to sufficiently achieve the object of the present invention it can.

(Operation / Effect) According to the present invention as described above, as partially described above, the specific dye used in the construction of the thermal transfer sheet of the present invention is a sublimable dye (molecular weight Approximately 150 to 300), it has at least one nitro group, cyano group or sulfonyl group even though it has a remarkably high molecular weight of 350 or more. It exhibits dyeing property and color developability, and does not migrate into the recording material or bleed out to the surface after transfer.

Therefore, the image formed by using the thermal transfer sheet of the present invention has excellent fastness, especially migration resistance and stain resistance, so that the sharpness of the formed image is impaired even if it is stored for a long time, or other The various problems of the prior art have been sufficiently solved, without any contamination of the articles.

In particular, in the case of a dye having at least two polar groups as the specific dye, the fastness as described above becomes more remarkable. Such an excellent effect which has not been heretofore conceivable is remarkable when the dye-receiving portion of the recording material is a material such as polyester, because the dye used in the present invention has many polarities as a whole molecule. Since it has a group, it is considered to be fixed in the polyester by some action due to the correlation with the ester bond which is a polar group in the polyester.

Next, the present invention will be described more specifically with reference to examples. In the text, “part” or “%” is based on weight unless otherwise specified.

Examples 1 to 5 An ink composition for forming a dye-carrying layer having the following composition was prepared and applied to a polyethylene terephthalate film having a thickness of 9 μm and heat-treated on the back surface so that the dry coating amount was 1.0 g / m ^2. It was dried to obtain the thermal transfer sheet of the present invention.

Dyes in Table 1 below 3 parts Polybutyral resin 4.5 parts Methyl ethyl ketone 46.25 parts Toluene 46.25 parts Synthetic paper (Yuji Po FPG # 1 manufactured by Oji Yuka Co., Ltd.) as a base sheet.
50) was used to apply a coating solution having the following composition to one surface thereof at a rate of 4.5 g / m ² when dried, and dried at 100 ° C for minutes to obtain a recording material.

Polyester resin (Vylon103, Toyobo, Tg = 47 ℃) 0.
8 parts EVA polymer plasticizer (Elvalloy 741P, Mitsui Polychemical, Tg = -37 ° C) 0.2 part Amino-modified silicone (KF-857, Shin-Etsu Chemical Co., Ltd.) 0.0
4 parts Epoxy modified Silycorn (KF-103, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.04 parts Methyl ethyl ketone / toluene / cyclohexane (weight ratio 4: 4: 2) 9.0 parts The thermal transfer sheet of the present invention and the recording material described above, The respective dye carrying layers and the dye receiving surface are made to face each other and overlapped, and recording is carried out from the back surface of the thermal transfer sheet with a thermal head under the conditions of a head applied voltage of 10 V and a printing time of 4.0 msec., And the results shown in Table 1 below are obtained. It was

The dye I is the dye of the above formula (a).

Dye II is a dye of formula (b) above.

Dye III is a dye of formula (g) above.

Dye IV is the dye of formula (h) above.

Dye V is a dye of formula (i) above.

Dye VI is the dye of formula (k) above.

Comparative Examples 1 to 5 The dyes shown in Table 2 below were used as the dyes in Examples 1 to 5, and the same results as shown in Table 2 below were obtained in the same manner as in Example 1.

The dye I'is Disperse Red 1.

Dye II 'is Disperse Violet 1.

Dye III 'is Disperse Violet 4.

Dye IV 'is Disperse Violet 28.

Dye V'is Disperse Yellow 7.

Dye VI 'is Disperse Yellow 23.

Dye VII 'is Disperse Blue 26.

The color densities in Tables 1 and 2 are the values measured by a ten sheet meter RD-918 manufactured by Macbeth Co., USA.

For the fastness, the recorded image was left in an atmosphere of 50 ° C for a long time, the sharpness of the image did not change, and the white paper was not colored even if the surface was rubbed with white paper. When the white paper was colored, it was marked with Δ, and the image became unclear, and when the white paper was markedly colored, it was marked with x.

Claims (1)

[Claims] 1. A substrate sheet and a dye carrying layer provided on one surface of the substrate sheet, wherein the dye contained in the dye carrying layer is at least selected from the group consisting of structural formulas a to l below. A thermal transfer sheet comprising one type of sublimable dye.