JPS6151377A - Thermal transfer recording apparatus using liquid ink - Google Patents

Abstract

PURPOSE:To enable good image recording even to recording paper having a rough surface, by destructing the microcapsule on an ink sheet by heating said ink sheet by a thermal head to transfer liquid ink onto recording paper. CONSTITUTION:The m.p. of the film substance of a microcapsule 23 is lower than the b.p. of liquid ink being a core substance and, an ink sheet 11 and recording paper 12 are contacted between a platen roll 13 and a thermal head 14 uner pressure to perform the recording of an image. In this case, the ink sheet 11 is selectively heated from the back surface side thereof, that is, from the side opposite to the coating surface of the microcapsule 23 by the thermal head 14 corresponding to an image to be recorded. At this time, when the ink sheet 11 is heated to temp. equal to or more than the m.p. of the film substance 25 of the microcapsule 23, the film substance 25 is melted by the pressure given from the platen roller 13 and destructed to transfer the liquid ink 24 in microcapsules 31-33 to the recording paper 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal transfer recording device, and particularly to a thermal transfer recording device using microencapsulated liquid ink.

[Technical background of the invention and its problems]

Electrophotography, inkjet recording, and thermal transfer recording are known as methods for recording visible images on plain paper. Electrophotography is currently widely used in copying machines, but since it uses powder toner and requires consumables such as photoreceptors and developers, it poses maintenance problems and equipment problems. It also has the disadvantage of being large.

Furthermore, although the inkjet recording method is superior in terms of energy consumption and miniaturization of the device, a decisive drawback is the problem of clogging of ink nozzles, making stable recording difficult.

On the other hand, the thermal transfer recording method does not have the drawbacks of the first two methods and is the most stable recording method, so it is increasingly being used in printers and the like. However, with the thermal transfer recording method, transfer defects occur on paper with a relatively rough surface, and in order to record a good image with high density, the ink applied to the ink sheet needs to be melted into wax as a binder, and color selection is difficult. There are limits to Furthermore, since it is difficult to record binary images, halftones cannot be recorded.
This also poses a problem in promoting colorization.

[Purpose of the invention]

An object of the present invention is to provide a thermal transfer recording device that is capable of good image recording even on recording paper with a rough surface, that allows selection of a wide variety of colors when colorizing, and that is also capable of gradation recording. be.

[Summary of the invention]

This invention performs thermal transfer recording using an ink sheet coated with microcapsulated liquid ink, whereas conventional thermal transfer recording devices use ink that is solid at room temperature.

That is, the thermal transfer recording device according to the present invention uses ink in which microcapsules containing liquid ink wrapped in a coating material are coated on a sheet-like support, and the ink sheet is placed with the microcapsule-coated surface facing recording paper. In addition, a thermal head for printing is provided on the opposite side of the microcapsule coating surface. Recording is done by destroying the microcapsules on the ink sheet heated by a thermal head.
This is done by transferring liquid ink onto recording paper. Specifically, the coating material of the microcapsules is formed of a material whose melting temperature is lower than the boiling point of the liquid ink, and by melting the coating material of the microcapsules on the heated area, the liquid ink of the microcapsules on the area is melted. transfer onto recording paper.

Alternatively, using a microcapsule coating material with a melting point higher than the boiling point of the ink, the ink sheet is heated to a temperature higher than the boiling point of the liquid ink using a thermal head, causing the liquid ink to bump, destroying the microcapsule coating material and releasing the ink. The image may be transferred onto the recording paper by flying the image.

〔Effect of the invention〕

According to this invention, since liquid ink is used, it is possible to record a good image with sufficient density even on recording paper with a relatively rough surface. Additionally, although liquid ink is used in this way, unlike inkjet recording, the ink is microencapsulated, so there is no problem with ink clogging in the nozzles, which was a problem with inkjet recording. , stable recording becomes possible.

Furthermore, in the case of microencapsulated liquid ink,
Various inks such as water-based inks with vivid colors or pigment-based oil-based inks that could not be used with inkjet recording due to clogging can be used without any restrictions, so they can be used with inkjet recording or at room temperature. Compared to general thermal transfer recording that uses solid ink, a much wider variety of colors can be selected for color recording. Therefore, a high quality color image with excellent color reproducibility can be obtained.

Furthermore, in this invention, by giving the particle size distribution of the microcapsules containing liquid ink, the heating energy (for example, heating time) of the ink sheet by the thermal head can be reduced.
It is possible to selectively transfer only liquid ink in microcapsules with a particle size corresponding to that onto the recording paper. This allows for the expression of halftones, which was considered difficult with thermal transfer recording.
In other words, it is possible to perform gradation recording, and is not only effective in expressing halftones in monochromatic recording, but also very effective in achieving more faithful color reproduction in color recording.

[Embodiments of the invention]

FIG. 1 shows a schematic configuration of a thermal transfer recording apparatus according to an embodiment of the present invention. As shown in the figure, an image is recorded on the recording paper 12 by passing the ink sheet 11 and the recording paper 12 between the platen roller 13 and the thermal head 14 as indicated by an arrow 15. .

As shown in FIG. 2 (aL(b)), the ink sheet 11 is
Microcapsules 23 are coated on a sheet-like support 2) together with an adhesive binder 22. As shown in FIG. 2(C), the microcapsule 23 is a liquid ink 24 wrapped in a coating material 25, and the liquid ink 2
), either water-based ink or oil-based ink can be used, and polymeric materials such as polyester and wax can be used. For example, when the microcapsules 13 are produced by an interfacial polymerization method, if the liquid ink 24 that is the core material is an aqueous ink, an ink containing a hydrophilic monomer is dispersed in the oil phase, and a hydrophobic monomer is added to the system. Microcapsules 13 are formed by adding the monomers. Here, the hydrophilic monomer and the hydrophobic monomer are polyfunctional monomers that undergo polycondensation or polyaddition reaction. Examples of hydrophilic additives include polyamines, glycols, and polyhydric phenols, and examples of hydrophobic additives include polybasic acid halides, bisheroformates, polyisocyanates, and the like. - For example, when a polyamine is used as a hydrophilic upper layer and a polybasic acid halide is used as a hydrophobic upper layer, a polyamide film is formed. When the liquid ink that is the core substance is an oil-based ink, microcapsules of the oil-based ink are generated by dispersing the oil-based ink containing a hydrophobic monomer in water, adding a hydrophilic monomer, and stirring. The produced microcapsules are finally extracted by centrifugation or filtration. In the case of coating materials such as wax and gelatin that cannot be produced from polycondensation or polyaddition reactions, microcapsules are produced by submerged curing coating methods.

The microcapsules 23 produced in this way are shown in FIG.
) As shown in (b), the support 2 is bonded with the adhesive binder 22.
) to form an ink sheet 11. In addition, in FIG. 2 (a>(b), microcapsule 2
The particle size of No. 3 is exaggerated and is actually 50μ, for example.
When microcapsules with a diameter of m are prototyped, the diameter falls within a range of ±10 um100 with respect to the central particle diameter. These particle size distributions generally exhibit a Poisson distribution. The existence of such a particle size distribution of the microcapsules 23 is effective in performing gradation recording as will be described later.

Next, a specific image recording process in the thermal transfer recording apparatus shown in FIG. 1 will be explained with reference to FIGS. 3 and 4. FIG. 3 shows that the melt humidity of the coating material 25 of the microcapsules 23 is lower than the boiling point of the liquid ink 24 which is the core material.
Moreover, the image recording process is shown in which the ink sheet 11 and the recording paper 12 are pressed together between the platen roller 13 and the thermal head 14 to record an image. The ink sheet 11 is selectively heated by the thermal head 14 from the back side, that is, from the side opposite to the coated surface of the microcapsules 23, in a pattern corresponding to the image to be recorded. At this time, when the ink sheet 11 is heated to a temperature higher than the melting temperature of the coating material 25 of the microcapsules 23, the pressure applied from the platen roller 13 causes the microcapsules 23 with the coating material 25 to melt as shown in 31 to 33 in the figure. The liquid ink 24 in the microcapsules 31 to 33 is transferred onto the recording paper 12.

As a result, an ink image corresponding to the heating pattern by the thermal head 14 is recorded on the recording paper 24.

In this case, the liquid ink 24 has a lower viscosity than the ink that is solid at room temperature used in conventional thermal transfer recording, and since it is liquid, it has a capillary phenomenon.
Even when the surface of the recording paper 12 is relatively rough, it penetrates between the irregularities on the surface of the recording paper 12 and adheres well, forming a good image.

Furthermore, if the microcapsules 23 on the ink sheet 11 are distributed within a certain range of particle sizes as described above, the coating material 25 is more likely to be destroyed as the particle size becomes larger. By changing the image density on the recording paper 12, the image density on the recording paper 12 can be changed, and gradation recording becomes possible. That is, among the microcapsules 23, capsules with a large particle size will have their coating material destroyed at a relatively low temperature, but capsules with a small particle size will not have their coating material 25 destroyed unless they are heated to a considerably high temperature. Therefore, for example, if the heating energy is reduced by shortening the recording pulse application time to the thermal head 13, only the liquid ink inside the microcapsules with a relatively large particle size will be transferred onto the recording paper 12, and the image density will be reduced. It gets lower. On the other hand, if the recording pulse application time is lengthened and the heating energy is increased, the image will be transferred onto the microcapsule recording paper 12, resulting in a higher image density.

Furthermore, unlike inkjet recording, the configuration shown in FIG. 1 does not use nozzles, so there is no problem of ink clogging, and stable recording is possible. In addition, liquid ink 24
Since inks of various colors can be selected as inks, color recording with excellent color reproducibility is possible in conjunction with gradation recording.

FIG. 4 shows an image recording process when the ink sheet 11 is heated by the thermal head 14 to a temperature higher than the boiling point of the liquid ink 24 in the microcapsules 23. In this case, the ink sheet 11 and the recording paper 12 do not need to be in close contact with each other as in the case of FIG. 3, but may simply be close to each other. FIG. 4 shows the case where they are close.

When the ink sheet 12 is rapidly heated to a concentration higher than the boiling point of the liquid ink 24 in the microcapsules 23, 4
In the microcapsules on the heated areas shown in 1 to 45, the volume expansion due to boiling of the ink 24 applies a force equal to or higher than the mechanical breaking point to the coating material 25, and the coating material 2
5 destroys.

As a result, the liquid ink 24 in the microcapsules 23 bumps and flies onto the recording paper 12, where it is transferred.

As a result, an ink image is recorded as in the case of FIG. At this time, even if the coating material 25 is a hemolysate nylon capsule membrane that exhibits the highest resistance to expansion and contraction,
Its breaking point is 2520 dine/cm. The energy injected from the thermal head 14 into the microcapsules 3 through the several micrometer thick support 2) on the ink sheet 11 is approximately 40 m Joule/Nn2, and this value is equivalent to the energy injected into the microcapsules 3 with a radius of 50 micrometers. The input energy is enough to boil everything, and the volume expansion coefficient is 1200 times or more. As a result, the covering material of the microcapsules 23 is destroyed, and the ink inside is deposited onto the recording paper 12 in a bumping state. Further, at this time, the binder 22 for adhering the microcapsules 23 onto the support 2) is attached to the recording paper 12 with the coating material 25 in front.
This promotes destruction at the side portions and facilitates the flying and transfer of the ink 24 onto the recording paper 12.

In the image recording process shown in FIG.
FIG. 5 shows how the coating material 25 is destroyed. That is, when the ink sheet 11 is heated by the thermal head 14, the liquid ink 2, which is the core material of the microcapsules 23 on the heated area, is heated as shown in FIG.
4, bubbles 51 are generated, and bubbles 52 are generated as shown in FIG. 4(b).
grows, and as shown in the same figure (C), bubbles 5
3, the coating material 25 is destroyed as shown at 54, and as a result, the ink 24 bumps to the outside of the coating material 25 from the destroyed portion 54, as shown in FIG. 3(d).

According to the image recording process explained in FIG. 4, the same effects as in the case of FIG. 3 can be obtained, and the recording speed can be improved. In other words, conventional thermal transfer recording methods that generally use a thermal head have the disadvantage that if the width of the recording pulse supplied to the thermal head is shortened, the ink is not sufficiently transferred onto the recording paper, resulting in a slow recording speed. .

On the other hand, in the image recording process shown in FIG. 4, the rapid heating of the ink sheet 11 causes the liquid ink 24 in the microcapsules 23 to bump and transfer onto the recording paper 12, so the application of a short recording pulse is enough to produce an image. Density recording becomes possible, and high-speed recording with a period of 2 ms or less, for example, becomes possible.

Note that the present invention is not limited to the above-mentioned embodiments, but uses an ink sheet coated with microcapsules in which liquid ink is wrapped in a coating material, and the liquid ink in the microcapsules on an area heated by a thermal head is used. Various modifications can be made without departing from the gist of recording an image by transferring it onto recording paper.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a thermal transfer recording device using liquid ink according to an embodiment of the present invention, and FIGS. 2(a), (b), and (C) show the structure of an ink sheet used in the same embodiment. FIG. 4 is a diagram showing another image recording process, and FIGS. 5(a) to (d) are diagrams for explaining the image recording process in FIG. 4. FIG. 3 is a diagram showing how a coating material of a microcapsule is destroyed. 11... Ink sheet, 12... Recording paper, 13...
・Platen roller, 14... Thermal head, 2)・
...shi, -to-like, holding body, 22...binder, 2
3...Microcapsule, 24...Liquid ink, 2
5...Coating substance. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 (a) Figure 3 Figure 4

Claims (5)

[Claims] (1) An ink sheet consisting of microcapsules containing liquid ink wrapped in a coating material coated on a sheet-like support, with the surface coated with the microcapsules facing the recording paper; A liquid ink comprising a thermal head that heats from a side opposite to the capsule coating surface, and the liquid ink of the microcapsules on the area of the ink sheet heated by the thermal head is transferred onto the recording paper. Thermal transfer recording device used. (2) The coating material of the microcapsules is formed of a material whose melting temperature is lower than the boiling point of the liquid ink, and by melting the coating material of the microcapsules on the heated region of the ink sheet, the microcapsules on the heated region of the ink sheet are melted. 2. A thermal transfer recording apparatus using liquid ink according to claim 1, wherein the liquid ink is transferred onto recording paper. (3) The ink sheet is heated by the thermal head to a temperature higher than the boiling point of the liquid ink in the microcapsules, and the liquid ink in the microcapsules on the heated area of the ink sheet bursts into boiling water, destroying the coating material and transferring it onto the recording paper. A thermal transfer recording device using liquid ink according to claim 1, wherein the liquid ink is transferred. (4) A thermal transfer recording device using liquid ink according to claim 3, characterized in that a volatile ink is used as the liquid ink. (5) The particle size of the microcapsules is distributed within a certain range, and the liquid ink of the microcapsules with the particle size corresponding to the heating energy from the thermal head is transferred onto the recording paper to perform gradation recording. A thermal transfer recording device using a liquid ink according to claim 1, 2, 3, or 4.