JPS6394887A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enable a good-efficiency and high-accuracy transfer, by a method wherein a substrate consists of an anisotropic conductive layer in which a number of electrically conductive fibers arranged parallel in the thickness's direction are interlaced with insulating wefts parallel in the width's direction and these are laid in an insulating resin, a heating resistor layer, a return electrode layer, and an ink separating layer, the latter three which are laminated thereon in order. CONSTITUTION:An anisotropic conductive layer 23 of a substrate 20 forming an ink layer 26 thereon makes use of a material in which an electrical conductivity in the thickness's direction is approximately at least 10 times that in the width's direction and electrically conductive fibers 23a arranged parallel in the thickness's direction are interlaced with insulating wefts 23c to be securely molded with an elastic resin 23b. A heating resistor layer 24 generates heat due to Joule heat by an electric current supplied from a needle electrode to heat an ink for transferring. A return electrode layer 25 serves as an electrode for the diffusion and reflux of an electric current which flowed into the heating resistor layer 24. An ink separating layer 28 adjusts the critical surface tension of its own so that a good ink transfer can be carried out even with a low energy. In this manner, a high-picture quality can be performed with a high efficiency at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a thermal transfer recording medium used for recording on a recording medium by heating and melting or sublimating ink.

"Prior Art" When recording an image corresponding to a predetermined digital image signal on a recording medium, such as plain paper, a recording method using a thermal transfer recording medium such as an ink donor film is widely adopted.

Among these, the thermal head transfer method uses a thermal head in which a large number of heating elements are arranged in a row. In this method, with the ink-coated base film facing the recording paper (plain paper), a thermal head selectively applies heat pulses from the back of the base film to remove the ink from that area. It is transferred onto recording paper by melting or sublimating it (Japanese Unexamined Patent Application Publication No. 1983-1999).
84735, etc.).

On the other hand, the energization transfer method is a method in which a needle electrode is brought into contact with a base film coated with ink, and electricity is selectively applied to the ink to heat the ink using Joule heat.

This method requires the ink layer and the base film to be electrically conductive. In order to impart conductivity to the base film, methods are used in which metals are dispersed in a resin and formed into a film (ribbon), or a highly resistive conductive polymer resin is used.

A material with good conductivity is mixed in the ink layer (Journal of the Institute of Image Electronics Engineers, Vol. 11, No. 1, 1982).

In addition, although it is a similar method, instead of heating the ink by passing a current directly through it, the ink layer is applied on the base film through a heating resistor layer, and the ink is heated by passing current through the heating resistor layer. A method has been proposed to
93585, etc.).

Hereinafter, this will be referred to as a thermal transfer printing method.

This method will be explained using FIG. 4.

In the figure, the thermal transfer recording medium 10 includes a base film 3
It has a structure in which a heating resistor layer 4, a conductive layer 5, and an ink layer 6 are laminated in this order on top.

This base film 3 is given a predetermined electrical conductivity. The needle electrode 1 and the return electrode 2 are brought into contact with the back surface of the thermal transfer recording medium 10. Here, the needle electrodes 1 are arranged in a large number of rows in a direction perpendicular to the plane of this paper, and electric pulses are selectively applied to some of them according to the image signal. Flow like arrow 12
The heat generating resistor layer 4 in the portion indicated by 2 generates heat. This heat melts and softens a portion 8 of the ink layer 6, and the ink 8 is transferred to the recording paper 7.

"Problems to be Solved by the Invention" The above-mentioned conventional techniques each have the following problems.

First, in the thermal head transfer method, heat is transferred from the thermal head to the ink layer via the base film.
There is a time delay in recording due to the time required for heat conduction (time constant 1 m)
5ec), resulting in a slow printing speed.

Furthermore, it is necessary to use inks that transfer less thermal energy and have lower melting points. Therefore, the degree of freedom in selecting the ink material is small, and the transfer control property is also poor. From this,
It is difficult to modulate the density of recording dots, and there is also the drawback that only wax-based materials can be used as ink materials.

Furthermore, the electric transfer method has the disadvantage that it is difficult to produce color images because the conductive material added to the ink makes it difficult to control the color tone. In addition to power loss due to electrical resistance within the base film, there is also loss due to current spread.
There are drawbacks such as poor power efficiency and low positional accuracy of recording dots. Furthermore, if a conductive material is incorporated into the base film, its mechanical properties will also be degraded.

On the other hand, the thermal transfer printing method does not require the ink to be electrically conductive and has a high degree of freedom in selecting ink materials, but the loss due to current spread is large and the positional accuracy of the recording dots is low. This method is no different from the current transfer method.

Further, as is clear from FIG. 4, since the base film 3 needs to have a sufficiently higher resistance than the heating resistor layer 4, the contact resistance with the needle electrode 1 etc. will inevitably become higher. Moreover, since the current reaches the return electrode 2 by following the same path as the needle electrode 1, base film 3, heating resistor layer 4, and conductive layer 5, there are two contact connection parts in the current path. However, there is a drawback that there is a large loss of electrical energy.

The present invention has been made with attention to the above points, and an object of the present invention is to provide a thermal transfer recording medium that can perform efficient and highly accurate transfer.

"Means for Solving the Problems" The thermal transfer recording medium of the present invention heats an ink mainly composed of a thermoplastic polymer substance on a support and transfers the recording onto a recording medium. The support is an anisotropic conductive material in which a large number of conductive fibers arranged parallel to the thickness direction are woven and supported by insulating weft yarns parallel to the width direction, and these are embedded in an insulating resin. The device is characterized in that it is composed of a heating resistor layer, a return electrode scrap, and an ink peeling layer that supports ink, which are laminated in this order on the heating resistor layer.

"Function" In the thermal transfer recording medium described above, the anisotropic conductive layer is provided in order to flow a current with low loss in the direction of the heating resistor layer from the needle electrode in contact with the anisotropic conductive layer. This anisotropic conductive layer is made by weaving conductive fibers with insulating weft threads, and the conductive fibers ensure conductivity in the thickness direction. This structure is suitable for arranging conductive fibers at high density while ensuring insulation in the width direction. The heating resistor layer is a layer that generates heat using Joule heat caused by the current supplied from the needle electrode, and heats and transfers the ink. The return electrode layer serves as an electrode that diffuses and refluxes the current that has flowed into the heating resistor layer. Further, the ink release layer is a layer whose critical surface tension is adjusted so that ink transfer can be performed satisfactorily even at low energy.

With such a configuration, high-quality recording can be performed with high efficiency and high speed.

"Example" (Basic Configuration) FIG. 1 is a longitudinal sectional view showing the basic configuration of the thermal transfer recording medium of the present invention.

This thermal transfer recording medium has an ink layer 26 formed on a support 20. This support 20 includes an anisotropic conductive layer 23 whose conductivity in the thickness direction (direction of arrow X) is higher than conductivity in the width direction (direction of arrow Y), a heating resistor layer 24, and a return electrode. It is composed of a layer 25 and an ink release layer 28.

It is preferable that the conductivity in the thickness direction of the anisotropic conductive layer 23 is about 10 times or more than the conductivity in the width direction, and for example, as shown in FIG. A conductive fiber 23a such as a nickel wire is woven with an insulating weft 23c and fixed in a mold with an elastic resin 23b such as a silicone elastomer.

As the conductive fiber 23a, metal fibers such as stainless steel, nickel, and copper, carbon fibers, etc. can be used. Also,
As the insulating weft, various types of plastic fibers, insulating ceramic fibers, composite fibers made of metal fibers coated with rubber, plastic insulating ceramics, etc. can be used. Further, as the material for filling these gaps, thermoplastic elastomers, rubber materials, etc. are suitable, and adhesive resins, silicone rubber, urethane rubber, neoprene rubber, etc. are generally suitable.

The resistance value of this anisotropic conductive layer 23 in the thickness direction is 200Ω.
Hereinafter, it is preferably selected to be 20Ω or less.

The heating resistor layer 24 is made of a material having heat resistance of 200'C or more, for example, ceramic such as TaN, and its volume resistivity is 10-2 Ω/unit cross-sectional area.
cm to 104Ω・cm, preferably 10Ω
・Select from cm to 103Ω・cm. In addition, from the viewpoint of the mechanical properties of the support, the thickness is from 3000 to 20 μm.
It is preferable to select a range of m.

If the thickness of the heat generating resistor layer 24 is selected within such a range, and its volume resistivity exceeds the above range, high voltage drive will be required to supply the current necessary for heat generation, causing damage to circuits and other parts. Reliability decreases in terms of voltage resistance, etc. On the other hand, when the volume resistivity falls below the above range, it becomes necessary to supply a large current to generate heat, leading to an increase in cost due to an increase in the size of the circuit.

Next, the return electrode layer 25 is formed by vapor deposition of a conductive metal, and its volume resistivity is 5 x 10-' times lower than that of the heating resistor layer 24, preferably I x 10-'.
Select a material that is double the amount and has a heat resistance of 200°C or higher. This return path electrode layer 25 is grounded through an electrode (not shown) or connected to an electrode with a constant bias potential.

The ink release layer 28 is formed of a material having a lower critical surface tension (rc) than the critical surface tension (rc) of the surface of a transfer material such as recording paper so that the ink can be easily transferred when heated. Preferably, it is an extremely thin film. Its thickness is selected to be 10 μm or less, preferably 1 μm or less.

The ink layer 26 is colored by mixing or dissolving a coloring material based on a polymer substance having a glass transition temperature of 130° C. or less.

(Operation) FIG. 3 schematically shows a recording apparatus that performs recording using the thermal transfer recording medium as described above.

The thermal transfer recording medium 30 is conveyed from a supply reel 31 toward a take-up reel 32 . The recording paper 33 is superimposed on this thermal transfer recording medium 30 and is conveyed by a pair of conveyance rollers 3.
4 and transported.

A recording head 35 in which needle electrodes 21 (Fig. 1) are arranged in a row.
is between the pair of conveyance rollers 34, and the back elastic roller 3
6, the thermal transfer recording medium 30 and recording paper 33 are sandwiched together, and electric pulses for recording are applied.

Here, as shown in FIG. 1, when the needle electrode 21 is brought into pressure contact with the anisotropic conductive layer 23 and an electric pulse is applied, the signal current is transmitted to the needle electrode 21, the conductive fiber 23a1, the heating resistor layer 24, and the anisotropic conductive layer 23. It flows in the return path electrode layer 25 like a dashed line arrow. The electrical resistance of the anisotropic conductor 1823 in the X direction is sufficiently low, and the current widely diffuses in the return electrode layer 25, so the electrical resistance is also low here, and most of the electrical energy supplied from the needle electrode 21 is generated as heat. It is converted into thermal energy in the resistor layer 24.

This heat travels through the return electrode layer 25 and the ink peeling layer 28 and reaches the ink layer 26 . In this way, the ink in the ink layer 26 is heated and melted and transferred onto recording paper or the like. At this time, since the return electrode layer 25 and the ink peeling layer 28 are made sufficiently thin, the heat transfer rate is fast and energy loss is small.

The thermal transfer recording medium of the present invention has conductive fibers arranged in high density (5 fibers/mm or more) and high anisotropic conductivity (resistance in the thickness direction of 100 Ω or less, resistance in the width direction of 1010 Ω or more). Since an anisotropic conductive layer having a structure that can be used is adopted, the energy effectively used for recording is 15% or more of the input energy, making it possible to record with extremely high efficiency. Therefore, the energy supplied for recording may be less than 500 erg per dot, and high-speed recording of less than 500 μsec/dot is possible.

Furthermore, by providing the ink peeling layer 28, the ink transfer efficiency is improved, and the amount of dot transfer can be changed by modulating human energy, making so-called multi-gradation recording possible.

More specific examples of the present invention will be described below.

(Specific Example 1) Each part of the thermal transfer recording medium shown in FIG. 1 was manufactured as follows.

■Anisotropic conductive layer 23 First, as shown in Figure 2, the warp yarns 23a have a wire diameter of 30 mm.
Using a μm stainless steel wire, the weft thread 23c has a wire diameter of 30
A cloth-like product is produced by plain weaving using μm polyester fibers. Next, a solution of room-temperature-curing silicone rubber diluted with a solvent and mixed with a curing agent is applied thereto to obtain a sheet-like material as shown in FIG. 2C. After making many of these, Figure 2 d
The resin is laminated without being cured as shown in the figure, and the weight is 2 kg/
A curing treatment is performed by applying a pressure of cm2 and heating at 100°C for 2 hours in an oven. After curing, this was sliced into 2.00 mm thick pieces as shown by the dashed-dotted line in Figure 2d, and the silicone rubber was applied to the end faces and hardened again under pressure, so that both ends of the stainless steel wire appeared on the top and bottom faces. Get a sheet. In this way, the anisotropic conductive layer shown in FIG. 2a is obtained.

The resistance value of this anisotropic conductive layer in the thickness direction is 1.5Ω/c
m2, the resistance value in the width direction was 1014Ω/Cm2 or more.

■ Heat generating resistor layer 24 The anisotropic conductive layer obtained in step (2) was thoroughly washed and dried, and then placed in a vacuum system with a vacuum degree of 3 x 10-6 Torr.
After introducing argon gas to a pressure of X10-3 Torr, a TaN target containing 20 weight percent of 5i02 was sputtered by high-frequency sputtering to form a heat generating layer having a resistance value of 80Ω/10-2 mm2 and a thickness of 2500 mm.

■Return electrode layer 25 On the one obtained in (2), by electron beam vacuum evaporation method,
700 layers of Cr and 2000 layers of Cu were deposited at an ultimate vacuum of 1.5×10 −6 Torr to obtain a return electrode layer.

(2) Ink release layer 28 A 3 μm thick polyfluoroethylene resin film was sintered on the return electrode layer to form an ink release layer.

Its critical surface tension was 2Qdyne/cm.

■Ink layer 26 On top of the above ink release layer, polyester resin (Toyo i
A thermoplastic cyan ink layer having a thickness of 8 μm was formed by mixing 8% of a phthalocyanine pigment in Vylon 200 (manufactured by Co., Ltd.).

The thermal transfer recording medium obtained in this way was set in the apparatus shown in Figure 3, and 8 needle electrodes/mm with a diameter of 95 μm were installed.
Recording was performed using line heads arranged at a density of .

Three types of electric pulses were used for recording: 12 V, 25 V, and 60 V, and all of them were rectangular pulses with a width of 200 μsec.

Plain paper for copying was used as the recording paper, and recording was performed by sandwiching the thermal transfer recording medium and the recording paper by pressing the line head with a pressure of 1000 g/cm2 against an elastic back roller with a rubber hardness of 60. Ta. An electrode was connected to the return path electrode layer 25 so as to continuously apply a rectangular pulse having a width of 5 mm and a frequency of 5 KHz.

In this way, thermal transfer recording was performed in accordance with the image signal, and transferred dots (recorded dots) were evaluated.

(Left below) Table 1 (Specific Example 2) First, as shown in Figure 2, the warp threads 23a have a wire diameter of 26 μm.
A cloth-like product is produced by plain weaving a copper wire with a diameter of 30 μm using a polyester fiber having a wire diameter of 30 μm as the weft thread 23c.

Next, this is immersed in a thermosetting silicone resin liquid, and a second
A sheet-like product shown in Figure C is obtained.

A large number of these were made, and the resin was laminated as shown in Fig. 2 (d) with the resin uncured.
Curing treatment is performed by heating for a period of time. After curing, this was sliced into 3 mm thick pieces as shown by the dashed-dotted line in Figure 2d, the silicone resin was applied to the end surfaces, and the sheets were cured under heat and pressure again to form a sheet with both ends of the copper wires appearing on the top and bottom surfaces. obtain. In this way, the anisotropic conductive layer shown in FIG. 2a is obtained.

This anisotropic conductive layer has copper wires arranged at a density of 18 wires/mm, and the resistance value in the thickness direction is 0.9Ω/mm.
cm2, and the resistance value in the width direction was 10'3Ω/cm2 or more.

Thereafter, a heating resistor layer, a return electrode layer, an ink peeling layer, and an ink layer were formed in the same manner as in the previous example, and transferred dots were evaluated.

Table 2 G "Effects of the Invention" The thermal transfer recording medium of the present invention as described above has the following effects.

(1) High-speed printing is possible The ink layer is close to the heat-generating resistor layer, so heat transfer is fast, and the time constant during printing is small at 300 μsec or less.
If a line head is used, high-speed printing of 1100 cp is also possible.

(2) High-quality images can be obtained.

In the case of the thermal transfer recording medium of the present invention, the ink material need only be thermoplastic, and the degree of freedom in selection is extremely high. For example, when selecting and blending a coloring material into a transparent polymeric material, it is possible to select a wide range of coloring materials (pigments and dyes) with unexpected color tones, and the coloring material is surrounded by the polymeric material. Therefore, the coloring material is less likely to deteriorate or decompose due to direct irradiation with ultraviolet light or contact with oxygen. Therefore, the color tone and fastness of the coloring material can be made to the same level as printing.

(3) High gradation can be obtained.

Since the responsiveness to the input signal is good, the amount of transferred ink can be adjusted by modulating the intensity of the input signal. Therefore, it is possible to express the density of each dot in three or more levels, instead of expressing the gradation using a so-called dot matrix pattern method. Therefore, 6 to 8 pieces/m
While maintaining the high resolution of m, there are 8 to 16 levels of intermediate tones (
Halftone) expression is possible. Of course, full color gradation expression is also possible.

(4) Energy saving can be achieved.

As mentioned above, since the heating resistor layer and the ink layer are close to each other, there is little energy loss due to thermal diffusion.

In addition, the electrical resistance of the current path that guides the current to the heating resistor layer is low, and energy loss due to this is also small. Of course, since fixing processing and the like are not required, there is no wasted energy consumption. From this, if the recording density is 8 dots) 7 mm, 100 to 700 erg per dot.
It is economical to be able to perform recording using less energy.

(5) High reliability.

By managing the resistance value of the heating resistor layer, the amount of heat generated can be controlled.
Furthermore, if a heat-resistant material such as ceramic is used for this heating resistor layer, it can be easily manufactured while controlling its thickness to several tens of angstroms (A). Moreover, the process (recording operation) operates stably in the range of humidity 10 to 90% (Rh) and temperature 5 to 30°C, and high reliability can be obtained. Therefore, there is no need for humidity control when handling powder as in a laser printer or electrostatic recording method, or temperature control for stabilizing ink viscosity as in an inkjet method, and maintenance management is easy.

(6) High-density recording is possible By using conductive fibers as conductors in the anisotropic conductive layer, it is possible to weave and support the conductive fibers and arrange them at a high density of 5 fibers/mm or more. Possible, the thickness direction is 100Ω
- A high conductivity ratio of 1010 Ω·cm or more can be achieved in the width direction of 10 cm or less. Therefore, electrical energy during recording can be supplied to the heating resistor layer with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the thermal transfer recording medium of the present invention, FIG. 2 is a partially cutaway perspective view of the anisotropic conductive layer during each manufacturing process, and FIG.
The figure is a schematic diagram of a recording apparatus using the thermal transfer recording medium of the present invention, and FIG. 4 is a longitudinal cross-sectional view of a conventional thermal transfer recording medium. 20... Support body, 23... Anisotropic conductive layer, 23a... Conductive fiber, 23c... Insulating weft, 24... ... Heat generating resistor layer, 25 ... Return electrode layer, 26 ... Ink layer, 28 ... Ink release layer. Applicant: Fuji Xerox Co., Ltd. Agent

Claims (1)

[Claims] In a device that transfers and records onto a recording medium by heating an ink mainly composed of a thermoplastic polymer substance on a support, the support has a large number of conductive conductors arranged in parallel in the thickness direction of the support. An anisotropic conductive layer in which fibers are woven and supported by insulating weft threads parallel to the width direction and embedded in an insulating resin, and a heating resistor layer laminated in order on the anisotropic conductive layer;
A thermal transfer recording medium comprising a return electrode layer and an ink release layer that carries ink.