JPS61261091A - Thermal recording medium - Google Patents

Abstract

PURPOSE:To contrive a higher thermal efficiency in recording, by using a thermal recording medium comprising a thermally transferrable ink and an ink transfer assistant capable of being transferred to a recording paper at a temperature lower than the temperature at which the ink is transferred. CONSTITUTION:The thermal recording medium 11 basically comprises an ink layer 11B provided on one side of a base 11A, which are covered by heat-fusible layers 11C, 11D on both side. The ink layer 11B starts to be melted at about 70-90 deg.C, while the heat-fusible layers 11C, 11D start to be melted at a lower temperature of about 50-70 deg.C. Accordingly, at a part where a heating element of a thermal head is energized to generate heat, the heat-fusible layer 11D between the head surface and the base 11A and the heat-fusible layer 11C between the ink layer 11B and a recording paper are first liquefied, whereby the gap between the head surface and the base 11a is filled with a liquid substance, resulting in favorable thermal transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a thermal recording medium used in a thermal recording device using heating means such as a thermal head.

``Prior Art'' With the spread of office equipment such as computers and facsimile machines, recording of various types of information has become more and more commonplace.

There are various recording methods for recording such various information. Among these, thermal recording devices that perform recording or display using thermal pulses have an excellent feature in that they can be manufactured inexpensively and compactly, and are widely used.

In thermal recording devices, a thermosensitive color recording method or a thermal transfer recording method is often used as a recording method.

In these recording methods, recording is performed by applying heat pulses to thermal recording paper or a thermal recording medium using a heating means such as a thermal head. Among these, in the thermosensitive color recording method, recording is performed directly on thermal recording paper, and in the thermal transfer recording method, recording is performed on recording paper (plain paper) superimposed on a thermal recording medium.

FIG. 4 shows the main parts of an example of a thermal recording device that performs recording using a thermal transfer recording method. An ink donor film (thermal recording medium) 3 is placed between a line type thermal head 1 and a counter roll 20 arranged in parallel thereto.
and recording paper 4 are supplied in a superimposed state. As shown, the opposing roll 2 comes into contact with the recording paper 4 and serves to press it against the thermal head 1 via the ink donor film 3.

FIG. 5 shows the structure of a conventionally used ink donor film. The ink donor film 3 is composed of a base material 3A such as capacitor paper and an ink layer 3B formed on the surface of the base material 3A. The thickness of the base material 3A is 8 to 1
The thickness is approximately 5 μm, and a heat-resistant processed layer is provided if necessary. The thickness of the ink layer 3B is usually about 3 to 7 μm. The ink constituting the ink layer 3B has the property of melting or sublimating when heated, and is composed of a binder, a colorant, and an additive, and its composition (% by weight) is, for example, as follows.

Ink composition example (Part 1) Binder Ester wax 50% Paraffin wax 20% Colorant Carbon black 15% Additives
Composition example of oil 15% ink (Part 2) Binder Ester wax 40% Carnauba wax 10% Paraffin wax 20% Colorant Pigment (red) 15% Additive
Oil 15% Now, when a heat pulse is applied to the base material 3A side of the ink donor film 3 by the thermal head 1, ink in a corresponding portion is transferred to the recording paper 4. Opposing roll 2 is 1
Each time a line is recorded, it is rotated by a small angle in the direction of the arrow in the figure, thereby performing sub-scanning. As the sub-scanning progresses, the ink donor film 3 is unwound from the supply roll paper tube 5, and the portion used for recording is sequentially wound onto the take-up roll paper tube 6. The recording paper on which recording has been completed and the ink donor film are separated when passing through a drive roll 7 and a pinch roll 8, and the recording paper is also discharged to a discharge tray (not shown).

However, such a thermal recording device has a problem in that the thermal energy utilization efficiency is quite low. For example, of the thermal energy generated by the thermal head 1, only 10% is transmitted to the ink layer 3B and used to sufficiently reduce the viscosity of the ink and transfer it to the recording paper 4.
It is said that it is less than that. One of the reasons for this is
The fact is that about 30% of the total thermal energy is wasted between the thermal head 1 and the ink donor film 3. This is because the surface of the abrasion resistant layer of the thermal head l and the surface of the ink donor film 3 do not constitute completely smooth surfaces, so there are many gaps between them, and it is as if a thin air layer is forming on the thermal head. It is thought that this is because the ink donor film 1 and the ink donor film 3 are in a state of being covered.

Therefore, JP-A-59-196293 proposes a method of supplying a liquid phase medium into this gap. In this proposal,
The gaps are filled with a liquid such as silicone oil to ensure uniform thermal energy transfer and efficient heat conduction in these areas.

However, this proposed method requires a special device to stably supply these liquids to the recording section, which increases the size of the thermal recording device and increases the price and running costs of the device. There was a problem. There is also the problem that the addition of a device containing liquid reduces the reliability of the entire device.

On the other hand, Japanese Patent Application Laid-open No. 114098/1983 proposes to improve the ink transfer efficiency which occurs between the recording paper and the thermal recording medium. In this proposal, as shown in FIG. 6, an ink donor film 9 in which a heat-melting ink layer 9B is formed on a base material 9A and a heat-melting wax layer 9C is formed thereon is used as a thermal recording medium. . The heat-melting ink layer 9B of this ink donor film 9 has a diameter of about 70 to
It softens at a temperature of 90 degrees Celsius, and the heat-fusible wax layer 9C softens at a temperature lower than this, for example, 50 to 70 degrees Celsius. Therefore, during thermal transfer recording.

First, a portion of the hot-melt wax layer 9C is melted, which helps the hot-melt ink to soak into the recording paper. In other words, in this proposal, even if the surface of the recording paper has some unevenness, the wax plays a role in smoothing it out, thereby eliminating blurring of the image and loss of density. In other words, the utilization efficiency of the thermal energy output by the thermal head 1 can be increased.

``Problems to be Solved by the Invention'' However, according to the latter proposal, it was not possible to increase the thermal efficiency of a thermal recording medium coated with thermal sublimation ink. Furthermore, thermal recording media coated with heat-melting ink still have the problem of poor thermal efficiency between them and the thermal head. Thermal efficiency during recording is related to the size of the power source and the recording speed, and it is essential to improve it in order to create a low-cost, high-speed thermal recording device.

In view of these circumstances, it is an object of the present invention to provide a thermal recording medium that can further improve the thermal efficiency for recording.

"Means for Solving the Problems" In the present invention, in addition to the thermal transfer ink used for recording, a thermal recording medium is constructed using an ink transfer auxiliary material that transfers to the recording paper at a lower temperature. do. (2) This ink transfer auxiliary material may be melted (fluidized) or sublimated by heating. (2) The ink and the ink transfer aid may be formed as separate layers on the base material, or (2) may be formed as an integrated layer on the base material.

Further, (1) the ink transfer aid may be placed on both sides of the substrate, or (2) the ink transfer aid may be placed only on one side. (2) The ink transfer aid may be housed in a capsule that melts or bursts when heated, or (2) it may be housed in a capsule that melts or bursts when pressurized.

■If the ink transfer aid is colorless or light-colored, it will not adversely affect the color reproduction of the ink. (2) The ink transfer aid may be impregnated into the base material itself.

The ink transfer auxiliary material starts transferring to the recording paper before the ink and helps the ink transfer, so that it is possible to efficiently utilize the thermal energy output from the heating means such as the thermal head.

"Example" The present invention will be described in detail below with reference to Examples.

"First Embodiment" FIG. 1 shows the structure of a thermal recording medium in a first embodiment of the present invention. Thermal recording medium 11 is base material 11A
The basic structure is such that an ink layer 11B is arranged on one side of the ink layer 11B, and these are covered with a heat-melting layer 11C and an LID from both sides. The thickness and composition (% by weight) of each layer are as follows.

Base material 11A (6 μm thickness) Polyethylene terephthalate ink layer 1
1F3 (3 μm thick) Carnauba wax 20% Ester wax 40% Pigment fucarbon black, etc.) 20% Oil 20% Heat melting layer 11C, LID (ink transfer aid) (both 1
μm thickness) paraffin wax 80% oil
20% In this thermal recording medium 11, the ink layer 11B starts melting at about 70 to 90 degrees Celsius. Further, the heat-melting layer 11C111D starts melting at about 50 to 70 degrees Celsius, which is lower than this. Therefore, the areas where the heating element of the thermal head generates heat due to energization are between the head surface and the base material 11Δ, and between the ink layer 11
The clearly molten layer 11C1LID between B and the recording paper liquefies first. As a result, the gap between the head surface and the base material 11A is filled with the liquid substance, improving heat transfer. Further, a liquid substance such as wax penetrates into the gaps between the fibers of the recording paper, and then the ink in the liquefied ink layer 11B is caught by this and efficiently transferred to the recording paper.

Since the heat-melting layer 11C is almost colorless and transparent, this does not cause a decrease in recording density. On the contrary, since both transfer efficiency and transfer uniformity are improved, image contrast becomes better, and color reproducibility is significantly improved in thermal recording media used for color recording.

"Second Embodiment" FIG. 2 shows the structure of a thermal recording medium in a second embodiment of the present invention. Thermal recording medium 12 of this example
The thermal recording medium 11 has basically the same structure as the thermal recording medium 11 in the first embodiment, but the thermal melting layer 12D on the side that contacts the thermal head is composed of a large number of microcapsules 13.

The thickness and composition (% by weight) of each layer are as follows.

Base material 12A (8 μm thick) Capacitor paper ink layer 12B (4 μm thick) Paraffin wax 40% Ester wax 40% Pigment (carbon black, etc.) 15% Oil 5% Heat-melting layer 12C (ink transfer aid) (1 μm thick) Paraffin wax 80% oil
20% Thermal melting layer 12D (ink transfer aid) (1 μm thick) Film material: Gelatin capsule containing material: Silicone oil Even in this thermal recording medium 12, the ink layer 12B has a thickness of approximately 70 to 90%.
The melting layer 12C starts melting at a temperature of 50 to 70 degrees Celsius, which is lower than this temperature. The effect of the heat-melting layer 12C on the recording paper is the same as in the first embodiment. On the other hand, in the heat-melting layer 12D made of microcapsules 13, gelatin as a membrane material is turned into a sol by heating with a thermal head, and the silicone oil is discharged. The silicone oil fills the gap between the thermal head and the thermal recording medium 12, making heat conduction more efficient and uniform. This makes it possible to achieve a significant improvement in image quality.

Note that it is also possible to store other liquids such as water in the microcapsules 13. The membrane material may be other than gelatin as long as it melts (fluidizes) or ruptures due to temperature or pressure from opposing rolls in the recording section. For example, synthetic polymers such as urea resin, melamine resin, polyurea, polyurethane, polyamide, etc.
-situ combustion method) or interfacial polymerization method.

"Modification" The thermal recording medium of the present invention described above may be manufactured as a roll paper having approximately the same width as one side of the recording paper, or may be manufactured as a band-shaped ribbon. Of course, it is also possible to commercialize the product as cut paper that is pre-cut to the size of recording paper.

By the way, the structure of the thermal recording medium of the present invention can be modified in various ways. FIG. 3 shows a thermal recording medium 14 as an example of this.
The base material 14A on the side where the ink layer 14B is not formed is impregnated with a liquefied substance (ink transfer aid) 15 that causes liquid to ooze out when heated or pressurized. As such a liquefied substance 15, for example, microcapsules containing silicone oil or wax infiltrated into paper fibers are suitable. Liquefied substance 15
The impregnated paper portion can be considered as the heat-melting layer of the present invention.

In addition, in the above embodiment, a substance that melts or becomes fluidized by heating is used as the ink constituting the ink layers 11B and 12B, but it is understood that sublimable dyes that sublimate by heating can also be used in the thermal recording medium of the present invention. Of course. In addition, the heat melting layer 11C112C114C is the ink layer 11
B, 12B, 14B need not be formed independently, both are mixed and formed as a single layer on the base materials 11A, 12A, 1.
It is also possible to form it on 4A.

"Effects of the Invention" As described above, according to the present invention, since the ink transfer auxiliary material assists ink transfer, stable and good recording can be performed even on various types of paper having different smoothness. Furthermore, since the energy applied to the thermal head can be reduced, recording speed can be increased and the life of the head can be extended.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a thermal recording medium in a first embodiment of the present invention, FIG. 2 is a structural diagram of a thermal recording medium in a second embodiment of the present invention, and FIG. 3 is a modification of the present invention. 4 is a schematic configuration diagram showing an example of a conventional thermal recording device, FIG. 5 is a structural diagram of a conventionally used thermal recording medium, and FIG. 6 is a thermal recording medium proposed previously. FIG. 2 is a structural diagram of a recording medium. 11Δ, 12A, 14A...Base material, 11B, 1
2B, 14B... Ink layer, 11c, 12C,
14C... Heat melting layer (ink transfer aid), 13... Microcapsule, 15... Liquefiable substance (ink transfer aid). Applicant: Fuji Xerox Co., Ltd. Representative
Person Patent Attorney Umeo Yamauchi 1st Session 2nd School Figure 3

Claims (1)

[Claims] 1. A base material, and an ink formed on the base material that melts or sublimates upon heating and transfers to the opposing recording paper;
A thermal recording medium comprising an ink transfer aid that melts or sublimates at a lower temperature or pressure than the ink and transfers to the recording paper to assist in the transfer of the ink to the recording paper. 2. The thermal recording medium according to claim 1, wherein the ink and the ink transfer aid are formed as different layers on the base material. 3. The thermal recording medium according to claim 1, wherein the ink and the ink transfer aid are formed as an integrated layer on the base material. 4. The thermal recording medium according to claim 1, wherein the ink transfer assisting material is arranged in layers on both sides of the base material. 5. The thermal recording medium according to claim 1, wherein the ink transfer aid is arranged in a layer on one side of the base material. 6. The heat according to claim 1, characterized in that a minute capsule that melts or ruptures when heated contains a liquid therein and constitutes at least a part of the ink transfer aid. recoding media. 7. A microcapsule that melts or ruptures under pressure contains a liquid therein, and constitutes at least a part of the ink transfer aid. thermal recording medium. 8. The thermal recording medium according to claim 2, wherein the heat-melting layer composed only of the ink transfer auxiliary material is colorless or light-colored. 9. The thermal recording medium according to claim 5, wherein the base material is made of a porous material, and one side of the base material is impregnated with an ink transfer aiding material.