JPS59165696A - Thermal multiple-time transfer sheet and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled sheet easily and inexpensively without generating any toxic gas, by a method wherein an emulsified material comprising a heat- fusible ink composition dispersed in a solid film layer of a water-soluble polymer or a water-dispersible type resin is prepared by a specified method, and is then applied onto a film base. CONSTITUTION:A heat-fusible ink composition (the first composition) comprising a coloring mterial (e.g., carbon black or a pigment) and a low melting point material (e.g., wax) acting as a binder for the coloring material is kneaded (a), and while heating and agitating (b) the first composition, the second composition consisting of an aqueous composition of a water-soluble polymer (a water-dispersible type resin) is added (c) to the first composition together with a surface active agent to obtain the first emulsified material (d) wherein the second composition is dispersed in the first composition. Further, the emulsified material is gradually cooled (e) so that it is converted in phase (f) into the second emulsified material (g) wherein the first composition is dispersed in the second composition, and then the second emulsified material (g) is applied (h) onto a film base, followed by drying (i) to obtain the objective transfer sheet (j).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal multiple transfer sheet used in a printing device such as a thermal printer that performs printing by thermal transfer, and a method for manufacturing the same.

[Prior art]

Conventionally, this type of heat-sensitive transfer sheet has simply applied a heat-melting ink composition consisting of a colorant and its binder to a base material, and once it is used for printing, the ink composition in that area is transferred onto the surface of the recording paper. It was impossible to use the same transfer sheet for printing more than once. Therefore, such transfer sheets have to be discarded after being used once, which is extremely uneconomical.

In order to solve this uneconomical problem, the following attempts have recently been made to provide a transfer sheet that can be printed multiple times using the same transfer sheet.

(1) For example, print 4! There is a method in which the ink composition is reapplied onto the substrate. However, the transfer sheet of this type requires a complicated mechanism to be built into the printing device or the ribbon cassette, resulting in a large-scale device and high costs.

(2) There is also a multi-transfer sheet made by mixing an ink composition consisting of a soluble dye and a low melting point agent with a cohesive powder such as carbon black, and applying this to a base material (Unexamined Japanese Patent Publication No. (Sho 57-160691). However, in such a transfer sheet, powder such as carbon black does not contribute to the formation of a printed image at all, and the molten M+! A printed image is formed by dye r1. Therefore, considering that printed images formed with dyes are highly susceptible to discoloration, there is a problem in the fastness of the printed images and they lack archival stability. In addition, organic solvents are used as solvents for ink compositions, and therefore there is a high risk that toxic gases will be generated when removing the organic solvents from the ink compositions applied to the substrate. As a result, the cost of the transfer sheet increases as a result.

(3) Furthermore, there is a transfer sheet in which a heat-resistant resin layer having many continuous micropores is formed on a base material, and a heat-melting ink is contained in the micropores of the heat-resistant resin layer (
JP-A-55-105579). However, such transfer sheets require complicated operations to form a porous resin layer on the base material, and furthermore, it is difficult to efficiently and uniformly impregnate hot-melt ink into the porous resin layer. It is something. Therefore, with such a transfer sheet, the density of the printed image becomes uneven, and the printing quality is unsatisfactory.

(4) After coating the base material with the heat-melting ink dispersed and dissolved in the resin solution, the solvent is evaporated and removed to continuously inject the heat-melting ink into the fine pores of the resin. There is an impregnated transfer sheet (Japanese Patent Laid-Open No. 54-68
No. 253). However, since this transfer sheet uses a mechanical method to disperse solid ink into a resin solution, the shape and size of the ink particles become non-uniform, which causes uneven density in the printed image. As a result, deterioration in print quality is unavoidable. Moreover, dispersion by such a mechanical method requires a large amount of time, and the production efficiency cannot be said to be favorable.

[Purpose of the invention]

The present invention improves the above-mentioned conventional drawbacks, and provides a low-cost thermal multi-transfer sheet that can produce uniform printed images, does not generate toxic gases, is easy to manufacture through simple operations, and the like. To provide a manufacturing method.

[Configuration of Example]

Embodiments of the present invention will be described in detail below with reference to FIG.

FIG. 1 shows a schematic cross-sectional view of a heat-sensitive multiple transfer sheet according to this embodiment, and the transfer sheet is formed by coating a film base material 1 with a heat-melting ink-containing layer 2. The film base material 1 used in this example has a heat resistance temperature of 150
Examples include films made of polyester, polyimide, polycarbonate, polysulfone, polyether sulfone, polyether-ether ketone, etc., or papers such as capacitor paper and glassine paper with a thickness of about 3 to
It is desirable that the thickness be in the range of 20μ. In addition, as shown in Figure 2, in order to prevent sticking even with films such as polyethylene whose heat resistance temperature is lower than 150°C, the surface opposite to the coated surface of the heat-melting ink-containing layer 2 is made of epoxy resin or the like to prevent sticking. Once layer 3 is formed, it can be used. The heat-melting ink-containing layer 2 used in this example is a water-soluble polymer - a water-based composition or a water-dispersible resin.
An emulsion obtained by heating and stirring a water-based composition, a colorant, and a low-melting point agent that acts as a binder for the colorant in the presence of a surfactant is used as the main emulsion. It is an ingredient.

Water-soluble polymer (water-dispersed resin) - In the water-based composition, carboxycellulose, methyl cellulose, hydroxyethyl cellulose, hydro-1 dipropyl cellulose, polyvinyl alcohol, etc. are used, and the water-dispersed resin As the material, water-based urethane resin, water-based acrylic resin, water-soluble epoxy compound, water-soluble polyester, etc. are used. In addition, pigments such as carbon black, lake red, and alkali blue are suitable as coloring agents in hot-melt ink compositions. It is effective if it is included as an adjuvant. Examples of low melting point agents include water-insoluble waxes having a melting point of about 40 to 100°C, such as paraffin wax, microcrystalline wax, carnauba wax, montan wax, beeswax, polyethylene wax, oxidized polyethylene wax, castor wax, and beef tallow. Hardened oil, carbowax, wood wax, spermaceti wax, lanolin, etc. are used, and a mixture of two or more of the above waxes may be used as a low melting point agent to adjust the melting point and viscosity.

Such a low melting point agent has a binder action of dissolving the fine particles of pigment and aggregating the fine particles to form heat-melting ink particles having an appropriate particle size. Furthermore, when mixing such a colorant and a low-melting point agent to prepare a hot-melt ink composition, a dispersing agent such as lecithin is added to promote dispersion of the colorant into the low-melting point agent. Good too.

Water-soluble polymer (water-dispersed resin) prepared in this way
An emulsion of both of these acids can be obtained by emulsifying the aqueous composition and the hot-melt ink composition by heating and stirring them in the presence of a surfactant. At this time, the surfactant acts to promote emulsification of both acids, and in this example, stearic acid, stearic acid monoglyceride, sorbitan monostearate, and
Sorbitan distearate or the like is used, and such a surfactant is mixed in advance into the hot-melt ink composition. Further, the heating temperature for emulsification is set to at least a temperature higher than the melting point of the low melting point agent contained in the hot melt ink composition. This is to perform emulsification in a liquid-liquid system and to ensure that emulsification is performed uniformly throughout the system.
Set to 0℃. Furthermore, the stirring operation is important for adjusting the particle size of the heat-melting ink after emulsification to the optimum particle size and for making the particle size uniform throughout the system. is adjusted to be 0.2 to 15μ.

Here, the explanation will be given again based on FIG. 1. The emulsion obtained as described above is applied to the film base material 1 using a coating device such as a reverse coater, a roll coater, or a doctor blade. If the coating thickness at this time is too thick or too thick, it will cause problems in multiple transfers, so in this example, the coating thickness was set at 5 to 30 μm.
Good results were obtained by using In addition, as shown in FIG. 3, the acrylic resin has affinity with the emulsion.

An undercoat bonding layer 6 made of vinyl chloride resin or the like may be provided. The emulsion coated on the film base material 1 is placed in a dryer to evaporate and remove the water contained therein. At this time, the drying temperature is set at 80 to 120°C. This is because if the emulsion is only coated on the film base material 1, it is difficult to uniformly disperse the heat-melting ink particles 4 contained in the emulsion throughout the heat-melting ink-containing layer 2. Therefore, after application, a temperature higher than the melting point of the low melting point agent contained in the ink particles 4 is applied again to make the dispersion state of the ink particles 4 uniform, and as shown in FIG. This is done to form a continuous phase of ink particles 4 in layer 2. As a result, the heat-sensitive multiple transfer sheet according to this example has a film base material 1.
Above, a thermofusible ink-containing layer 2 in which thermofusible ink particles 4 are uniformly and continuously dispersed in a solid film layer 5 of water-soluble polymer (water-dispersible resin) with approximately the same particle diameter. It is made by holding the.

Next, a method for manufacturing the heat-sensitive multiple transfer sheet according to this example will be explained based on FIG. 4.

(1) Kneading step of first composition First, a heat-melting ink composition containing a colorant and a low melting point agent (hereinafter referred to as the first composition for convenience) and a surfactant are mixed with at least a low melting point agent. temperature above the melting point of, for example about 70
Crosstalk occurs at temperatures above ℃. For kneading, a commonly used kneading machine such as a ball mill such as a three-roll mill, a rently mill, or a sand mill, or a resolver is used. At this time, heating the kneading temperature to a temperature higher than the melting point of the low melting point agent is to make the low melting point agent liquid and to make the colorant more uniformly dispersed. In addition,
It is preferable to mix the above-mentioned dispersant in order to promote dispersion of the colorant into the low melting point agent during kneading.

(2) Step of producing the first emulsion The first composition kneaded as described above is stirred with a stirrer in a tank whose temperature is controlled to the kneading temperature, while the water-soluble polymer (water Dispersion type resin)-aqueous composition (hereinafter referred to as the second composition for convenience) is added dropwise little by little until a predetermined ratio is reached. As a result, a so-called W2O type first emulsion in which the second composition is dispersed in the first composition is obtained. Note that the reason why the first composition is added dropwise little by little is to make the second composition uniformly dispersed in the first composition.

(3) Phase inversion step of first emulsion Subsequently, the temperature of the first emulsion obtained in the above step is gradually lowered in the temperature controlled tank to disperse the first composition in the second composition. The phase is inverted to form a so-called O/W type second emulsion. The phase inversion temperature depends on (a) the type of surfactant;
(b) Dispersed particle size, (C) Amount ratio of both phases, etc., and in the case of this example, approximately 50 to 65
Phase inversion occurred within the range of ℃. Furthermore, the reason why the temperature is gradually lowered during phase inversion is to eliminate the risk of phase separation occurring if the temperature is lowered rapidly.

(4) Step of applying the second emulsion The second emulsion obtained as described above is slowly stirred and the temperature is lowered to room temperature to obtain a fluid slurry-like second emulsion. . In this state, the hot-melt ink composition has returned to a solid state, and its particles are dispersed in a water-soluble polymer (water-dispersible -l+- resin) solution.

This slurry-like second emulsion is applied to the film base material 1 using the appropriate coating device described above. The coating thickness at this time needs to be set slightly thicker in consideration of the fact that water as a solvent will be evaporated and removed in the next drying step. In this example, by setting the coating thickness to about 100 .mu.m, a heat-fusible ink-containing layer 2 having a thickness of 5 to 30 .mu.m was obtained on the film base material 1.

(5) At the end of the drying process, a second
The emulsion coated product is heated to 80 to 120°C as described above.
Place it in a dryer set at a temperature of 100 mL to evaporate the remaining water as a solvent. Such drying not only removes water but also uniformly disperses the heat-melting ink particles 4 in the solid film layer 5 of the water-soluble polymer (water-dispersible resin) remaining on the film base material 1 as described above. This is done to form a continuous phase of ink particles 4.

After the above steps are completed, a heat-sensitive multiple transfer sheet as shown at 12- in FIGS. 1 to 3 is obtained.

Next, a specific experimental example of this example will be shown below.

A heat-sensitive multiple transfer sheet was prepared by the method described above using a composition comprising the above components. When printing was performed as described below using such a transfer sheet, it was found that printing could be performed up to about 10 times at the same location on the transfer sheet, and the density of the printed image remained the same as that of the first printing until the fifth printing. Although the image density was almost the same and the density gradually decreased after the 6th printing, the printed image density was still sufficient to withstand use even in the 10th printing.

[Operation of the embodiment]

Here, based on FIG. 5, the printing operation when printing is performed using the thermal multiple transfer sheet according to this embodiment will be explained.

FIG. 5 is a schematic sectional view showing the printing state, and the transfer sheet produced by the above method is applied to a thermal transfer type printing device such as a thermal printer. In the figure, the transfer sheet is coated with the heat-melting ink-containing layer 2 and is brought into contact with the heating element 8 of the thermal head 70 of the printing device, and the surface coated with the ink-containing layer 2 is Print paper 9 mounted on a platen (not shown) is opposed. When the heating element 8 of the thermal head 7 is selectively driven in accordance with the print information, thermal energy 15- emitted from the heating element 8 is transmitted to the ink-containing layer 2 via the film base material 1. The transferred thermal energy melts the ink particles 4 only in the portion where the heating element 8 is in contact, and the melted ink adheres to the opposing printing paper 9, thereby forming a predetermined dot 10. . these dots 10
A predetermined character, symbol, etc. is printed by collecting a large number of characters.

At this time, as described above, the ink particles 4 of the transfer sheet are uniformly dispersed in the solid film layer 5 of the water-soluble polymer (water-dispersible resin) and are held in a state where they form a continuous phase.
In this state, the solid film layer 5 of water-soluble polymer (water-dispersed resin) acts as a barrier when the molten ink particles 4 seep out toward the printing paper 9 side. Therefore, the molten ink particles 4 do not ooze out at once during one printing, and the barrier effect of the solid film layer 5 allows multiple transfers. Incidentally, since the ink particles 4 exist as a continuous phase in the solid film layer 5, the ink particles 4 or 18- on the film base material 1 side are used for printing without waste.

As explained above, in the transfer sheet according to this embodiment, the solid film layer 5 of the water-soluble polymer (water-dispersed resin) has a barrier effect against leaching of the melted ink particles 4, so the film The ink particles 4 on the base material 1 do not fall off during one printing, and therefore, it is possible to print more times than with the same transfer sheet. Therefore, this transfer sheet is much more economical than conventional transfer sheets that can only be used once, and the costs associated with the printing device can be reduced.

In addition, in this transfer sheet, since the heat-melting ink-containing layer 2 is generated by emulsifying the first composition and the second composition, the overall particle size of the heat-melting ink particles 4 in the first composition is Therefore, it is possible to obtain a printed image having constant printing quality without uneven printing density.

Furthermore, since water can be used as a solvent, no toxic gas is generated during its production compared to conventional methods that use organic solvents, and it is completely harmless. There is no need for equipment to detoxify the product, and workers involved in manufacturing can carry out their work with peace of mind.

(Effects of the Invention) As explained above, the present invention provides a heat-sensitive multi-transfer sheet that has uniform print density, can be manufactured by simple operations without generating toxic gases, and is low in cost, and a method for manufacturing the same. can be provided, and its effects are great.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a transfer sheet showing one embodiment of the present invention, FIG. 2 is a schematic sectional view of a transfer sheet showing an embodiment of the present invention, and FIG. 3 is a schematic sectional view of a transfer sheet showing another embodiment. 4 is a flowchart showing the manufacturing process, and FIG. 5 is a schematic sectional view showing the state of printing by the transfer sheet. In the figure, 1 is a film base material, 2 is a heat-melting ink-containing layer,
4 is an ink particle, and 5 is a solid film layer of water-soluble polymer (water-dispersible resin). Figure 4

Claims (1)

[Scope of Claims] 1. A heat-melting ink composition comprising: a water-soluble polymer-water composition or a water-dispersible resin-water composition; and a low melting point agent that acts as a binder for the colorant. The ink composition is emulsified by heating and stirring in the presence of a surfactant, and the emulsion is applied to a film base material and dried to form the ink composition in the solid film layer of the water-soluble polymer or water-dispersible resin. A heat-sensitive multiple transfer sheet characterized by dispersing substances. 2. kneading a first composition which is a heat-melting ink composition containing a spring coloring agent and a low melting point agent that acts as a binder for the colorant; and heating and stirring the first composition while adding a surfactant to the composition. A step of obtaining a first emulsion in which the second composition II is dispersed in the first composition by adding a second composition which is a water-soluble polymer-water composition or a water-dispersible resin-water composition together with the step. and a step of inverting the phase of the first emulsion to a second emulsion in which the first composition is dispersed in a second composition by cooling the first emulsion, and after applying the second emulsion to the film base material. A method for producing a heat-sensitive multiple transfer sheet, characterized by comprising a step of drying.