JPS5941877B2 - Electric heating sheet for recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrified heat generating sheet for recording, and more particularly to an improved energized heat generating sheet for recording used in a thermosensitive recording method in which electricity is supplied from a recording electrode.

Various methods have been proposed for recording electrical signals as characters or figures on recording paper.

Among these methods, the thermal recording method has recently attracted particular attention as a recording method for facsimiles, computer printing devices, and the like. This is due to the advantages that the thermal recording method is a primary coloring method that does not require liquid or powder ink, that the printing section is easy to maintain, and that the thermal recording paper, which is a consumable material, is inexpensive. However, the thermal recording method
Since the heat-sensitive recording head used as a recording heat source has a slow thermal response speed, it has the disadvantage of a slow recording speed.

On the other hand, the so-called current-carrying thermal recording method, in which the recording paper has heat-sensitive color development and conductivity, and electricity is passed directly to the recording paper from the recording electrode, and the generated Joule heat is used as the heat source, is a simple method, but the cost of the recording paper is high. There was a problem with the price being high. The present inventors have previously proposed a recording method that incorporates the advantages of both the thermal recording method and the current-conducting thermal recording method. We proposed a heat-sensitive recording method that uses an electrically conductive heat-generating sheet for recording, which is composed of laminated conductive layers that produce a desired electrically conductive state.

As shown in FIG. 1, an electrically conductive heating sheet 1 for recording used in the electrically conductive recording system which forms the background of the present invention is comprised of a conductive layer 2 and a resistive layer 3. As the conductive layer 2, a metal foil having a thickness of 5 to 20 microns is used. As the resistance layer 3, a coating film of a conductive paint or a vapor deposited film of a semiconductor having a resistance value one or more orders of magnitude higher than that of the conductive layer 1 is used. As shown in Fig. 2, the recording principle is that a recording signal source 4 generates a voltage of 10 to 20 volts and a pulse width of 1 between the recording electrode 5 and the return electrode 6 (frequency 4 to 10 kHz).
A pulse signal of 00 to 250 microseconds is applied to locally generate heat in the energized heating sheet 1 under the recording electrode 5.

The generated heat is transmitted to the coloring layer 8 of the thermal paper 1 that is in close contact with the energized heat generating sheet 1, and forms a recorded image 9. At this time, the temperature of the energized heat generating sheet 1 is raised to 300 to 400° C. for several milliseconds.
Alternatively, the temperature of the energized heat generating sheet 1 is locally increased by movement of the recording electrode 5 during recording. Therefore, the material for the energizing heat generating sheet 1 is required to be able to withstand such temperature rise. On the other hand, since it is necessary to reduce the heat transfer resistance at the interface with the heat-sensitive paper 7 as much as possible for the energized heat-generating sheet 1, the recording electrode has a weight of 1 kg/CT! Apply a load of l.

Therefore, the heat generating sheet 1 is also required to be made of a flexible material. As the material for the conductive layer 2, the metal foil mentioned above satisfies these conditions, but the conductive coating film or semiconductor vapor deposited film, which is the material for the resistive layer 3, satisfies these conditions and is suitable for industrial production. Suitable examples include conductive coatings using carbon black as the conductive agent. However, vinyl polymers such as vinyl acetate and vinyl acrylate are used as binders in conventional conductive paints, and when a coating film of these conductive paints is used for the resistive layer 3, localized It cannot withstand the target temperature rise and causes thermal damage. Therefore, it is essential to use a conductive coating film using a binder that is resistant to electrical and thermal deterioration as the material for the resistive layer. From this point of view, the present inventors have previously invented an electrically heated recording sheet using a heat-resistant polyimide polymer as a binder for the resistance layer. However, the above-mentioned polyimide polymers require the use of organic solvents harmful to the human body, such as toluene and xylene, as paint solvents, which poses a problem for industrial mass production. In consideration of the above, the present inventors prototyped an electric heating sheet using a water-soluble polyesterimide polymer as a binder, which is a heat-resistant polymer that can use water as a solvent, which is harmless to the human body.
A recording experiment was conducted.

As a result, this energized heating sheet heated up to 300~
Can withstand temperature rise of 400℃, applied voltage 15~2
It was discovered that it is resistant to electric discharges that occur at 0 volts, has excellent flexibility, and can provide high-quality recording, and is comparable to electric heating sheets that use polyimide-based polymer as a binder, leading to the completion of the present invention. Ivy. This invention improves work safety and sanitary environment in industrial production by using a water-soluble polyesterimide polymer as a binder for the resistance layer, and improves the flexibility and instantaneous heat resistance of the coating film. To provide an electrified heat-generating sheet for recording, which is improved so that it does not suffer thermal damage during use, provides high-density, uniform, and high-quality records, and can be used repeatedly. be.

The above-mentioned water-soluble polyesterimide polymers include water-soluble polyesterimide (continuous use temperature: 200°C), water-soluble polyesteramide-imide (continuous use temperature: 18°C)
etc. can be mentioned.

The thickness of the conductive layer 2 of the current heating sheet for recording is 5 to 20 mm.
Micron metal foils such as aluminum foil, tin foil, titanium foil, etc. are used, but aluminum foil is the most preferred in terms of cost. The thinner the conductive layer 2 is, the less thermal diffusion occurs and a high quality recorded image can be obtained, but from the viewpoint of mechanical strength, it is preferably about 10 microns. Commercially available carbon black can be used as the conductive agent for the resistance layer 3, but grafted carbon with improved compatibility with resin is preferred. A water-soluble heat-resistant polymer is used as a binder for the resistance layer 3, and water-soluble polyesterimide is particularly preferred because it has excellent heat resistance (heat resistance temperature of up to 210°C during continuous use) and can provide recorded images with strong contrast. preferable. The thinner the resistance layer 3 is, the higher the thermal efficiency is, and a higher recording density can be obtained even with the same recording energy. Therefore, in consideration of mechanical strength, a film thickness of about 10 to 30 microns is preferable. The present invention will be explained in detail below with reference to Examples.

Example 1 A water-soluble polyester imide varnish containing 35% by weight of carbon black was dissolved in an equal amount of water and dispersed in a ball mill overnight on the top surface of a 110 micron aluminum foil. It was applied using the wire bar method.

After drying indoors, it was heated in an electric oven at 200° C. for about 3 hours to form a coating film of about 20 microns to obtain an electrically heated recording sheet 1. Next, the energized heat generating sheet 1 was attached to a metal frame 6 which also served as a return electrode as shown in FIG. The drum 10 was rotated at a speed of 360 rpm while applying a pulse signal with a voltage of 10 volts, a frequency of 4 kHz, and a pulse width of 100 microseconds using a recording electrode 5 made of a copper wire with a diameter of 1 mm and a polished round tip. As a result, a recorded image 9 of dot lines having a resolution of 4 lines/7!1 m was obtained. Obtained recorded image 9
It was of good quality and had a uniform D density of 0.9 to 1.0. It was also possible to use it repeatedly several dozen times. Example 2 A water-soluble polyester amide imide varnish containing 30% by weight of carbon black was dissolved in an equal amount of water and dispersed in a ball mill for a day and night on the top surface of a 10 micron tin foil.
．． The coating was carried out using a wire bar method using an enameled wire of 3 mm diameter.

After drying at room temperature, it was heated in an electric oven at 200° C. for about 6 hours to cure crosslinking and form a coating film of about 30 microfron to obtain an electrically heated recording sheet. Next, a recording experiment was conducted in the same manner as in Example 1, and as a result, a good quality recorded image with a uniform density at a D density of 0.7 to 0.8 was obtained.

It was also possible to use it repeatedly several dozen times. Reference Example Polyvinyl butyral containing 35% by weight of carbon black was dissolved in an equal amount of ethyl alcohol and dispersed in a ball mill overnight on the top surface of a 10 micron aluminum foil, and then the wire bar method was applied using a 0.2 mm diameter enameled wire. It was applied by.

It was air-dried indoors to form a coating film of about 20 microns, and an electrically heated sheet for recording was obtained. Next, a recording experiment was conducted in the same manner as in Example 1, and as a result, when continuous pulse signals were applied, heat was accumulated in the energized heating sheet, and eventually thermal destruction occurred and holes were formed in the sheet. The recorded image of that part was missing. From the above, the current heating sheet for recording using the water-soluble heat-resistant polymer according to the present invention as the binder of the resistance layer can be heated at temperatures of 300 to 400°C for several milliseconds during recording or discharging.
It has become clear that not only does it withstand temperatures up to

Furthermore, it has excellent flexibility and can reduce the heat transfer resistance with the thermal paper, making it possible to obtain clear recorded images with high D density.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an energizing heat-generating sheet used in the energizing recording method which is the background of this invention, FIG. 2 is a block diagram showing the recording principle of FIG. 1, and FIG. FIG. 2 is a configuration diagram showing an experimental apparatus.

Claims (1)

[Claims] 1. An electrically conductive heating sheet for recording, comprising 90 to 60% by weight of a water-soluble polyesterimide polymer or a water-soluble polyesteramide polymer as a binder for a resistive layer that is laminated on a conductive layer and generates local heat.