JPS62216790A - Ink sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To obtain an ink composition having high filming rigidity and high transfer sensitivity to permit low energy printing without causing scumming by selecting a thermally fusable material containing an ester oligomer having specific range of melting point and molecular weight as main component of a thermally fusable ink composition. CONSTITUTION:A thermally fusable material contains more than 40wt% of ester oligomer having a number-average molecular weight of 500-6,000 and a melting point in the range of 60-110 deg.C. Consequently, scumming caused by lowering the melting point of the thermally fusable material such as wax necessary for low energy printing can be prevented. The ester oligomer to be employed is synthesized through polycondensation reaction of polyhydric alcohol and polyhydric carboxylic acid, preferably dioxy compound and dibasic acid or an acid anhydride of dibasic acid so as to have a low degree of polymerization, to be suitable as a thermally fusable material for heat transfer ink and to be fused at relatively low melting point within narrow temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ink sheet for thermal transfer recording, and particularly to an ink composition forming a coloring material layer (ink layer) thereof.

[Conventional technology and problems]

Thermal transfer recording ink sheets are made by coating at least one coloring material layer on a support such as paper or plastic film, and perform recording by thermally melting solid ink and transferring the ink onto the recording paper. . As for the heating method, heating may be performed using a heating element from the side opposite to the coated surface or from the coated surface side via the recording paper, or heating may be performed by energization by providing a resistive layer on one layer constituting the ink sheet. The coloring material layer is made of a heat-fusible substance containing a pigment or dye as a coloring agent.

As the heat-melting substance, heat-melting materials such as carnauba wax and paraffin wax are used. As the support, polyethylene terephthalate film, polycarbonate film, etc., which have excellent surface smoothness and dimensional stability, are generally used.

When recording a transferred image on plain paper or the like using such a thermal transfer recording ink sheet, for example, a thermal transfer printer equipped with a thermal head is generally used, but it is desirable to keep the thermal energy required for printing as low as possible. It will be done. By suppressing the thermal energy required for printing to a lower level than before, this technology shortens the head heating and cooling cycle time, enabling faster printing, as well as preventing thermal deterioration of the head and reducing power supply for line printers. This is because miniaturization becomes possible.

It can also compensate for the lack of heat resistance of the base film.

However, if the melting point of the ink composition is designed to be low in order to increase the transfer sensitivity of the thermal transfer ink sheet, when printing on plain paper, background stains will occur due to the low melting point components of the wax, and the fixation and fastness of the print will deteriorate. In addition to the decrease in temperature, a so-called blocking phenomenon also occurs when the environmental temperature rises during storage, so it is not easy to realize this.

In order to solve these problems, attempts have been made to add various thermoplastic polymer compounds, such as polyethylene wax (Japanese Patent Application Laid-open No. 101094-1982), ethylene-alkyl acrylate copolymer (Japanese Patent Application Laid-open No. 60-1988), 12009
No. 2), 1,2-polybutadiene (JP-A-60-12)
7193) and the like in an ink composition to perform low-energy printing without background smudge.

All of these methods use a thermoplastic resin as an additive to a low-melting wax as a main component, and use the polymer network structure to increase the strength of the coating film and prevent surface staining. There is a limit.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventors have conducted extensive research and found that by selecting an ester oligomer having a specific melting point range and molecular weight range as the main component of a heat-melting ink composition as a heat-melting material, It has been found that an ink composition with high transfer sensitivity that has fastness and enables low-energy printing without background smearing can be obtained.

That is, the present invention provides an ink sheet for thermal transfer recording having a coloring material layer containing a colorant or (and) an inorganic or organic fine powder and a heat-melting material, wherein the heat-melting material has a number average molecular weight of 5.
The present invention provides an ink sheet for thermal transfer recording, characterized in that it contains 40% by weight or more of an ester oligomer having a temperature range of 0.00 to 6000°C and a melting point range of 60 to 110°C.

The present invention is designed to have a low melting point of a heat-melting material such as wax for low-energy printing, and instead of the conventional method of adding a small amount of a high-melting-point thermoplastic resin to prevent background smudges. The above objective was achieved by selecting an ester oligomer having a melting point range of 60 to 110°C and a number average molecular weight of 500 to 6000.

Further, the present invention provides an ink sheet for thermal transfer recording having a coloring material layer containing a heat-melting substance on a support, by containing 40% by weight or more of the above-mentioned ester oligomer in the heat-melting substance. It achieves the purpose,
If this content is less than 40% by weight, the ester oligomer cannot exhibit high transfer sensitivity.

The ink sheet for thermal transfer recording of the present invention has at least one coloring material layer on a base film that is a support, and the coloring material layer contains at least one type of ester oligomer.

The coloring material layer contains at least one kind of coloring agent or (and) inorganic or organic fine powder, and the coloring agent includes various conventionally known dyes or pigments such as yellow, red, blue, and black, with special restrictions. Can be used without. For example, for black pigments, carbon blanks and oil blanks are used. Further, the fine powder used in the present invention may be magnetic powder, other metal powder, or conductive fine powder depending on the purpose.

The ester oligomer used in the present invention is synthesized by a polycondensation reaction between a polyhydric alcohol and a polycarboxylic acid, preferably a dioxy compound and a dibasic acid, or an acid anhydride of a dibasic acid, and is synthesized from a conventional polyethylene terephthalate polyester. It is an ester oligomer that has a relatively low melting point and melts in a narrow temperature range, making it suitable as a heat-melting material for thermal transfer inks. The number average molecular weight and melting point of this ester oligomer are usually 300 to 10,000 calculated from the terminal group and 40 to 120°C, but preferably 500 to 6,000 and a ring and ball method melting point range of 60 to 110°C. The synthesis method may be any known method.

Examples of dibasic acids include adipic acid, azelaic acid, sepatic acid, succinic acid, dodecanedioic acid, etc., and examples of dioxy compounds include ethylene glycol, 1,4-butanediol, 1,5-bentanediol, 1,6 -Hexanediol, 1,8-octanediol, 1,9-nonanediol, 1. Examples include IO-decanediol and neopentyl glycol.

The ester oligomer used in the present invention may be used alone, or in combination with two or more types of ester oligomers, or waxes that have been widely used in the past such as paraffin and carnauba wax, rosin derivatives such as hydrogenated rosin and ester gum, It may be used in combination with polyethylene wax, ethylene-alkyl acrylate, etc. Further, the ink sheet for thermal transfer recording of the present invention has at least one coloring material layer of the present invention applied in contact with a base film or a coating layer on the base film, and in addition, an overcoat layer or a resistive layer for heating by electricity. etc. may be included as other constituent layers.

The support used in the ink sheet for thermal transfer recording of the present invention is preferably a support that has heat resistance strength, high dimensional stability and surface smoothness. In addition to polyethylene terephthalate, which is mainly used, resin films made of polycarbonate, polyethylene, polystyrene, polypropylene, polyimide, etc. and having a thickness of 2 to 20 μm are preferably used.

〔Effect of the invention〕

As described above, according to the ink sheet for thermal transfer recording of the present invention, since an ester oligomer with a low melting point range (60 to 110°C) is used as a heat melting material, the transfer sensitivity is high and low energy printing is possible. Therefore, it is suitable for speeding up printing. In addition, there is no uneven transfer, the fastness of printing does not deteriorate, and since the content of components with low melting points below 55° C. is extremely small, there is no fear of blocking.

〔Example〕

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Polydecamethylene adipate (number average molecular weight 1600,
Melting point 73°C) 80 parts Ester Gum 11S (Arayo Kagaku) 5 Carbon Black 15 The above composition was kneaded with 200 parts of toluene in a ball mill for 12 hours to obtain a uniform coating solution. This coating liquid was applied with a wire bar onto a 6μ thick polyethylene terephthalate film (Toshi, Lumirror), and after drying, a color material layer with a thickness of 3.5μ was provided to create a thermal transfer ink sheet. did. In this way, the created thermal transfer recording ink sheet was printed on a line-type thermal transfer printer (NIP 5234°9.4 dots/m
m, Nihon Denki type) plain paper (BEKK160 seconds)
The density of the transferred image was measured. In order to investigate the relationship between printing energy and transferred image density, operate the density adjustment lever to adjust the pulse width of the applied voltage from 0.65 to 0.85.
Macbeth Densitometer (RD514)
(type). As a result, the pulse width of the applied voltage necessary to obtain a transferred image with a density of 1.2 was 0.66 seconds.

No scumming was observed during printing.

In order to examine blocking resistance, five thermal transfer ink sheets were stacked and stored in an environment of 500 g/cm'' for one week, and then the sheets were taken out and observed for the presence or absence of blocking, but no blocking was observed.

Example 2 Polyhexamethylene sebacate (number average molecular weight 3200
, melting point 75°C) 80 parts Ester gum 1) S (Arayo Kagaku) 5 Carbon black 15 Regarding the above composition,
A thermal transfer ink sheet was created in the same manner as in Example ■,
I tried printing.

As a result of measuring the density after transfer using a Macbeth densitometer (model RD514), the pulse width of the applied voltage necessary to obtain a transferred image with a density of 1.2 was 0.66 seconds.

Comparative example Paraffin wax 60 parts Carnauba wax 25 Carbon black
15 The above composition was dispersed in an attritor at 100°C for 4 hours, and this ink was hot-melt coated on the 6μ polyethylene terephthalate film used in Example 1 to a film thickness of 3.5μ to form a thermal transfer ink sheet. Created.

When printing was attempted on this thermal transfer ink sheet in the same manner as in Example 1, the pulse width of the applied voltage was 0.65.
In the case of seconds, only a transferred image with a density of 0.20 was obtained. Further, the pulse width of the applied voltage necessary to obtain a transferred image with a density of 1.2 was 0.85 seconds.

Claims (1)

[Claims] In an ink sheet for thermal transfer recording having a coloring material layer containing a colorant or (and) an inorganic or organic fine powder and a heat melting material, the heat melting material has a number average molecular weight of 500 to 6000.
and an ester oligomer with a melting point range of 60 to 110°C.
An ink sheet for thermal transfer recording, characterized in that the ink sheet contains 0% by weight or more.