JPS62156373A - Thermal transfer sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thermal transfer sheet, and more specifically, provides a novel thermal transfer sheet that can easily provide a recorded image with excellent durability on a transfer material. The purpose is to

(Prior Art) Various thermal transfer methods have been known in the past, but among them, a sublimation dye is used as a recording agent, this is carried on a base sheet such as paper to form a thermal transfer sheet, and the dye is dyed with a sublimation dye. A sublimation transfer method is used in which the thermal transfer sheet is layered on a transferable material such as polyester woven cloth, and heat energy is applied in a pattern from the back side of the thermal transfer sheet to transfer the sublimable dye to the transfer material.

(Problems to be Solved by the Invention) In the above-mentioned sublimation printing method, in which the material to be transferred is, for example, a polyester woven fabric, heat energy is applied for a relatively long time, so the material to be transferred is As a result, relatively good dye migration is achieved as a result of the heat applied to the dye.

However, with the advancement of recording methods, thermal hefed etc. are used to record at high speeds, such as polyester sheets,
When using transfer materials with a dye-receiving layer on paper and forming delicate letters, figures, or photographic images on these transfer materials, the application of thermal energy is extremely short, on the order of seconds or less. Therefore, in such a short time, the sublimable dye and the transfer material are not sufficiently heated, and an image of sufficient density cannot be formed.

Therefore, in order to cope with such high-speed recording, sublimable dyes with excellent sublimation properties were developed, but dyes with excellent sublimation properties generally have small molecular weights, so they do not dissolve in the transferred material after transfer. Problems have arisen in that dyes migrate over time or bleed onto one surface, resulting in distorted or unclear images or contaminating surrounding articles.

In order to avoid such problems, if a sublimable dye with a relatively large molecular weight is used, the sublimation speed will be inferior in the high-speed recording method as described above, so it will not be possible to form an image with a satisfactory density as described above. Met.

Therefore, in thermal transfer methods using sublimable dyes,
At present, there is a strong demand for the development of a thermal transfer sheet that can provide sufficiently dense and clear images by applying thermal energy in an extremely short period of time as described above, and also exhibits excellent fastness of the formed images. It is.

As a result of intensive research in response to the strong demands of the industry as described above, the inventor of the present invention discovered that in the conventional sublimation printing method for polyester woven fabrics, etc., the surface of the woven fabric is not smooth, so the thermal transfer sheet and the transfer material cannot be used. Some woven fabrics do not adhere well, so the dye used must be sublimable or vaporizable (i.e. capable of moving through the space between the thermal transfer sheet and the woven fabric). However, when the transfer material is a polyester sheet with a smooth surface, a surface-treated paper, etc., the thermal transfer sheet and the transfer material come into close contact during thermal transfer, so only the sublimation and vaporization properties of the dye are affected. is not an absolute requirement, but the ability of the dye to migrate through the interface between the two in close contact with each other by heat is also extremely important.The thermal migration property of such an interface depends on the melting point of the dye used, and whether it is inorganic or organic. By selecting a dye with an appropriate melting point and inorganic/organic value (hereinafter referred to as I10 value), it is possible to achieve a level that is considered unusable by conventional common sense. It was discovered that even dyes with a molecular weight have good thermal transfer properties. By using a thermal transfer sheet that carries a dye selected according to the melting point and I10 value of the dye, the dye used can be easily transferred to the transfer material even if thermal energy is applied for an extremely short time. However, the present invention was completed based on the finding that a recorded image having high density and excellent fastness can be formed.

(Means for Solving the Problems) That is, the present invention comprises a base sheet and a dye-supporting layer formed on one side of the base sheet, and the dye included in the dye-supporting layer is as follows. This is a thermal transfer sheet characterized by using an anthraquinone dye represented by the general formula.

However, R1, R2 and R3 in the formula are alkyl groups such that the molecular weight of the entire dye is 350t-1,
X represents 0 or an NH group, and R1 and R2 may be hydrogen atoms.

It is.

Next, to explain the present invention in more detail, the inventor of the present invention explained that in the anthraquinone dye having the basic structure as shown in the above general formula, R1, R2 and R3 in the general formula, especially R2, is the molecular weight of the entire dye. If R is selected to be more than 350, preferably 380 or more, it deviates from the conventional selection criteria based on the molecular weight of dyes for thermal transfer;
1. As the number of carbon atoms in R2 and R3, especially R2, increases, the melting point or I10 value of the dye tends to decrease, and when used as a dye for thermal transfer, the heat transfer rate increases, and it has excellent fastness after transfer. This is the result of the discovery that it is possible to obtain images of the same degree.

The anthraquinone dye represented by the above general formula can be obtained by a conventionally known production method.

In the anthraquinone dye of the above general formula, R1,
The alkyl group represented by R2 and R3 is a linear or branched alkyl group, and examples of these alkyl groups include methyl group, ethyl group, propyl group,
Butyl group, pentyl group, cyclohexyl group, hexyl group, heptyl group, octyl group, decyl group, undecyl group,
Alkyl groups such as lauryl group, tridecyl group, tetradecyl group, pentadecyl group, cetyl group, heptadecyl group; alkanol groups such as ethanol group, propatool group, butanol group, pentanol group, heptatool group, octatool group; methoxymethyl group, methoxyethyl group, methoxypropyl group, methoxybutyl group, methoxypentyl group, methoxyhexyl group, methoxyheptyl group, methoxyoctyl group, in place of these methoxy groups, ethoxy,
Alkoxyalkyl groups having other flukoxy groups such as propoxy, butoxy, pentoxy: N-methylamino,
Ethyl, propyl, butyl, pentyl having 7 alkylamino groups such as N-ethylamino, N-propylamino, N-butylamino, N-pentylamino, and N-hexylamino 7.

Examples include N-fulkylaminoalkyl groups such as hexyl and octyl groups. Among these alkyl groups, R1
It is preferable to select a hydrogen atom or an alkyl group of 01 to C4 as R3, and select an alkyl group of 04 or more as R2.

In the anthraquinone dye of the present invention represented by the above general formula, R1, R2, and R3 in the formula are determined so that the molecular weight of the entire dye exceeds 350, preferably 380 or more. It is necessary to select an I10 value of 1.2 or less.

The rI10J value referred to in the present invention is based on "Organic Conceptual Diagram - Basics and Applications" by Yoshio Koda (published by Sankyo Publishing).

That is, according to the detailed research of the inventor, in the dye of the above general formula, substituents R1, R2 and R3, especially R
By selecting an alkyl group with a large number of carbon atoms as 2, the molecular weight of the dye increases, and the molecular weight exceeds 350 or 380. However, the melting point of these dyes tends to decrease, and when used as dyes for thermal transfer, the rate of heat transfer of the dye from the thermal transfer sheet to the transfer material decreases even when heated for a very short time with a thermal head etc. It was found that the image quality was increased and images with excellent fastness were obtained.

Furthermore, as R1, R2 and R3, especially R2, are used as alkyl groups with a large number of carbon atoms, the I10 value decreases, and as the alkyl group, one having a polar group such as a hydroxyl group, an ether bond, or an amide bond is used. However, in the dyes of the present invention, the selection of R1, R2 and R3, especially R2, increases the I10 value of the dye to 1.
It has been found that, when adjusted to a range of 2 or less, such a dye having a suitable I10 value is very useful as a dye for thermal transfer.

That is, in the case of a dye for thermal transfer, as mentioned above, it is required to transfer heat to the transfer material in an extremely short period of time, but the dye of the present invention can be used in the methyl ethyl ketone and ethanol used when preparing the thermal transfer sheet. The solubility in general-purpose organic solvents such as toluene, isobrobyl alcohol, tetrahydrofuran, cyclohexanone, dimethylformamide, formamide, dimethyl sulfoxide, etc., or their mixed solvents is significantly improved, making it suitable for thermal transfer and dye-carrying layers formed on sheets. , the dye can exist in a non-crystalline state or in a low crystalline state, and the dye can be easily transferred to the transferred material with a significantly lower amount of heat than in a highly crystalline state, as is the case with conventional dyes. It was possible.

The thermal transfer sheet of the present invention is characterized by using the above-mentioned specific dye, and other than that, the structure may be the same as that of conventionally known thermal transfer sheets.

The base sheet used for constructing the thermal transfer sheet of the present invention containing the above-mentioned dye may be any conventionally known material having a certain degree of heat resistance and strength, for example, 0.5 to 50, wm. Preferably, paper with a thickness of about 3 to 10 pm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyvinyl alcohol film, cellophane, etc. are preferred, and polyester film is particularly preferred.

The dye-carrying layer provided on the surface of the base sheet as described above is a layer in which the dye of the general formula is supported by an arbitrary binder resin.

As the binder resin that supports the above-mentioned dye,
Any conventionally known ones can be used, and preferred examples include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose acetate butyrate, polyvinyl alcohol, and polyacetic acid. Vinyl resins such as vinyl, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylamide, polyesters, and the like are preferred from the viewpoint of heat resistance, dye migration, and the like.

The dye-carrying layer of the thermal transfer sheet of the present invention is basically formed from the above-mentioned materials, but may also contain various conventionally known additives as required.

Preferably, such a dye-supporting layer is prepared by adding the dye, binder resin, and other optional components in a suitable solvent, dissolving or dispersing each component, and preparing a coating solution or ink for forming the dye-supporting layer. It is formed by coating and dry-exploding the above-mentioned base material sheet.

In particular, the above-mentioned dyes are more sensitive to solvents such as methyl ethyl ketone, ethanol, toluene, isopropyl alcohol, tetrahydrofuran, cyclohexanone, dimethyl formamide, formamide, dimethyl sulfoxide, etc. or mixed solvents thereof used in preparing the transfer sheet than conventional dyes. Since it has a high solubility, for example, 3% and preferably 5%, it is easy to prepare an ink for forming a dye-carrying layer, and the dye is Since it exists in a dissolved state or a state close to it, it exhibits the advantage of exhibiting an excellent heat transfer rate with a small amount of thermal energy. The support layer formed in this way has a thickness of about 0.2 to 5.0 Lm, preferably 0.4 to 2 OJLm, and the dye in the support layer is It is suitably present in an amount of 5 to 70% by weight, preferably 10 to 60% by weight.

The thermal transfer sheet of the present invention as described above is fully useful for thermal transfer as it is, but it is also possible to provide an anti-adhesive layer, that is, a release layer, on the surface of the dye-carrying layer. This prevents adhesion between the thermal transfer sheet and the transfer material during thermal transfer, allows use of a higher thermal transfer temperature, and forms images with even better density.

As this mold release layer, even if an inorganic powder with anti-adhesive properties is simply attached, it has a considerable effect. It can be formed by providing a release layer of 0.01 to 5 m, preferably 0.05 to 27 m.

Incidentally, the above-mentioned inorganic powder or releasable polymer exhibits a sufficient effect even when included in the dye-carrying layer.

Furthermore, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet in order to prevent adverse effects caused by the heat of the thermal head.

The transfer material used to form an image using the thermal transfer sheet as described above may be any material as long as its recording surface has dye receptivity to the above-mentioned dyes. If the material is paper, metal, glass, synthetic resin, etc., which does not have a dye, a dye-receiving layer may be formed on at least one surface thereof.

Examples of transfer materials that do not require the formation of 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. vinyl polymers such as polyethylene terephthalate, polyester resins such as polybutylene terephthalate, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene with other vinyl monomers, ionomers,
Examples include m-fibers, woven fabrics, films, sheets, and molded products made of cellulose resins such as cellulose diacetate and cellulose triacetate, polycarbonate, polysulfone, and polyimide.

Particularly preferred are sheets or films made of polyester or processed paper provided with a polyester layer. In addition, even if the transfer material is non-dyeable such as paper, metal, glass, etc., a solution or dispersion of a dyeable resin such as those mentioned above is coated on the recording surface and dried, or the resin is By laminating the film, it can be used as a transfer material.

Furthermore, even if the transfer material has the dyeability described above, a dye-receiving layer may be formed on the surface thereof from a resin having better dyeability, as in the case of the paper described above.

The dye-receiving layer formed in this manner may be formed from a single material or from a plurality of materials, and may also contain various additives as long as the intended purpose is not hindered. Of course.

Such a dye-receiving layer may be of any thickness, but typically has a thickness of 5 to 504 m. Although such a dye-receiving layer is preferably a continuous coating, it may also be formed as a discontinuous coating using a resin emulsion or resin dispersion.

Such a transfer material is basically as described above and can be used as is, but it is possible to incorporate an inorganic powder for anti-adhesion into the transfer material or its dye-receiving layer. In this way, even if the temperature during thermal transfer is increased, adhesion between the thermal transfer sheet and the material to be transferred can be prevented, and even better thermal transfer can be performed. Particularly preferred is finely powdered silica.

Furthermore, in place of or in combination with the inorganic powder such as silica, the above-mentioned resin having good mold releasability may be added. Particularly preferred release polymers include cured products of silicone compounds, such as cured products of epoxy-modified silicone oil and amino-modified silicone oil.

Such release agents may be present in an amount of about 0.5 to 3 by weight of the dye-receiving layer.
A ratio of 0% by weight is good.

In addition, the transfer material to be used may have an inorganic powder as described above attached to the surface of the dye-receiving layer to enhance the anti-adhesive effect, or a mold release agent with excellent mold release properties as described above. A layer consisting of may be provided.

Such a release layer exhibits a sufficient effect at a thickness of about 0.01 to 5 gm, and can further improve dye receptivity while preventing adhesion to the dye receptive layer of the thermal transfer sheet.

Any conventionally known means for applying thermal energy can be used to apply thermal energy when performing thermal transfer using the thermal transfer sheet of the present invention as described above and the recording material as described above, such as a thermal printer (e.g. By controlling the recording time using a recording device such as Toshiba's thermal printer TN-5400), 5 to 100
By applying thermal energy on the order of mJ/mm', the intended purpose can be fully achieved.

(Functions/Effects) As described above, the dye used in the present invention has excellent heat transferability to the transferred material, similar to conventional dyes with a low molecular weight, for example, a molecular weight of 300 or 350 or less. The various fastness properties of images produced by such dyes, especially sublimation resistance and light fastness, are extremely excellent due to the relatively low molecular weight.

Therefore, the thermal transfer sheet of the present invention solves various problems of the prior art.

Next, the above will be explained in more detail with reference to Examples and Comparative Examples. In the text, parts or % are based on weight unless otherwise specified.

Example 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 JLm and having undergone heat-resistant treatment on the back side.
A thermal transfer sheet of the present invention was obtained by coating and drying to give a coating composition of g7rn'.

Dyes in Table 1 (Example) 1 part Polybutyral resin 4.5 parts Methyl ethyl ketone 23.35 parts Toluene
25.35 parts dimethylformamide
43.80 copies Next, using synthetic paper (Yubo FPG #150, manufactured by Tamago Yuka Co., Ltd.) as a base sheet, a coating liquid having the following composition was applied to one side of the paper at a drying rate of 4.5 g/m'. A transfer material was obtained by coating at a ratio of 100° C. and drying at 100° C. for 1 minute.

Polyester resin (Vy1on103, manufactured by Toyobo, Tg=47°C) 0.
8 parts EVA polymer plasticizer (Elvaloy 741P, manufactured by Mitsui Polychemicals, Tg=-
37°C) 0.2 part Amine-modified silicone (KF-857, manufactured by Shin-Etsu Chemical) 0.04 part Epoxy-modified silicone (KF-103, manufactured by Shin-Etsu Chemical) 0.04 part Methyl ethyl ketone/toluene/cyclohexanone (by weight Ratio 4:4:2) 9, 0 parts The thermal transfer sheet of the present invention and the transfer material described above are placed one on top of the other with their respective dye-supporting layers and dye-receiving surfaces facing each other. Applied voltage 10V, printing time 4.
Recording was performed with a thermal head under the condition of 0 m5ec, and the results shown in Table 1 below were obtained.

Comparative Examples Using the dyes listed in Table 1 below as dyes in Examples,
Otherwise, the results shown in Table 1 below were obtained in the same manner as in the examples. However, the composition of the ink composition for forming the dye-carrying layer was as follows.

Dyes listed in Table 1 below 3 parts Polybutyral resin 4.5 parts Methyl ethyl ketone 48.25 parts Toluene
46.25 parts The color density in Table 1 is the value measured with Tensheet Meter RD-918 manufactured by Macbeth, USA.

Fastness is rated O when the sharpness of the image does not change after the recorded image is exposed for a long time in an atmosphere of 50' (!), and the white paper does not become colored even when the surface is rubbed with white paper. 0 if the sharpness is lost and the white paper is slightly colored.
, the sharpness is lost and the blank paper becomes colored.
The image became unclear and the white paper was markedly colored, which was marked with an "x".

(Left below) R1, H 5R2; Dodecyl 474R3; H X; NH ICH 6R2; Dodecyl 487R3, Methyl X, NH (Comparative example below)

Claims (3)

[Claims] (1) Consisting of a base sheet and a dye-supporting layer formed on one side of the base sheet, the dye included in the dye-supporting layer is an anthraquinone dye represented by the following general formula. Thermal transfer sheet. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [However, R1, R2, and R3 in the formula are alkyl groups that cause the molecular weight of the entire dye to exceed 350, and
represents an O or NH group, and R1 and R2 can be hydrogen atoms. ] (2) R1, R2 and R3 are the molecular weight of the entire dye,
380 or more claims (1)
) Thermal transfer sheet described in section. (3) The thermal transfer sheet according to claim (1), wherein R1, R2, and R3 are selected such that the inorganic/organic value of the dye is 1.2 or less.