JPH0281667A - Halftone image recording - Google Patents

Abstract

PURPOSE:To record a smooth halftone image onto an ordinary paper with good reproducibility by changing recording energy applied from a heating resistor element in accordance with said image step by step thereby to form a halftone image onto a recording medium. CONSTITUTION:An adhesive layer 3 is applied onto a base material 1 and a powdery color material 2 of thermally melting type is provided onto the adhesive layer 3. Thus, an ink sheet is obtained. An image signal is accumulated on a shift register 7 by a CPU 6 and a gradation signal is set in a strobe pulse control circuit 8 so as to form a halftone image. A heating resistor element 4 in a thermal head is heated step by step in accordance with the digital signal from the shift register 7 and that from the strobe pulse control circuit 8. As a result, the transfer amount of the color material onto a recording paper, i.e., the size and density of a recording pixel can be controlled as a function of a heat generating energy of the thermal head.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal transfer recording method, and in particular to a method that makes it possible to easily record halftone images by controlling the heating temperature and time of the heating resistor element of the print head. The present invention relates to a halftone image recording method.

[Conventional technology]

Conventionally, the ink sheet used for this type of thermal transfer recording method is
It has a structure in which an ink layer is provided directly on the base material, and by one heat generation of the heat generating resistor element, the ink in the heat generating portion of the ink sheet is peeled and transferred onto the recording paper at once. For this reason,
The recorded dots on the recording paper can only obtain two values, black and white.

In recent years, the recording targets required of these recording devices have become more sophisticated, from text to images and from monochrome to color. However, since the above-mentioned conventional technology cannot achieve faithful halftone expression, the above-mentioned requirements have not been met. It is difficult to realize this.

For this reason, as an example of a method for obtaining a halftone image, there is a dye method in which the number of dots constituting one pixel of printing is changed, but a decrease in recording resolution is unavoidable.

The present invention provides a recording method that uses a novel thermal transfer recording ink sheet and applies appropriate recording energy to form halftone images with excellent resolution and good reproducibility even on plain paper.

[Means to solve the problem]

According to the present invention, a print head having a heating resistor element is attached to an ink sheet for thermal transfer recording in which an adhesive layer is provided on a base material and a heat-melting powder coloring material is coated on the adhesive layer. It is possible to reproduce a smooth halftone image on plain paper by applying pressure and heating by changing the recording energy applied from the heating resistor element in stages according to the image.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing the structure of an ink sheet used in the halftone image recording method of the present invention. An adhesive layer 3 is coated on the base material 1, and a heat-melting powder coloring material (
2 (hereinafter referred to as powder coloring material) is provided. Base material 1
Usually, capacitor SA, PET film, etc. are used. The adhesive layer 3 for bonding the base material 1 and the heat-fusible powder coloring material 2 may be made of polyamide resin, polyester resin, or the like. The powder coloring material is generally called a toner and has a diameter of about 2 to 20 μm, and is composed of, for example, a dye in a range of 1 to 2, a binder in a range of 0.1 to IO, a low melting point agent in a range of 1 to 99, It has thermal meltability.

In the configuration diagram of FIG. 1, the powder coloring material 2 has individual particles regularly arranged in a single layer on the substrate, but in reality, when the coloring material is viewed at the particle stage, it is irregularly arranged on the substrate. are arranged to form one layer as a whole. Usually, this layer thickness is on the order of 1 to IO μm.

In the above configuration, the powder coloring material heated by the print head from the substrate side has a different degree of melting depending on the applied recording energy (heating energy of the heating resistor element), and when the energy is high, a large number of Since the powdered coloring material melts more strongly, and when the energy is low, a small number of powdered coloring materials melt more lightly, the extent to which the coloring material is transferred to the recording medium also differs depending on the heat generation energy. . As a result, the amount of dye of the coloring material transferred to the recording paper, that is, the size and density of the recording pixels, can be controlled as a function of the heat generation energy of the thermal head.

Furthermore, by widely distributing the melting point of the powder coloring material within a temperature range that corresponds to the heat generation energy from the heating resistor element, the heat generation energy and the degree of melting of the powder coloring material become correlated over a wide temperature range. Therefore, the stepwise heat generation energy from the heating resistor element corresponding to the pixel corresponds in a wide range to the extent of the dye to be transferred, and as a result, the density reproduction range and density variation on the recording paper can be improved. Can be done.

The melting point of the powdered coloring material can be adjusted by the content of the low melting point substance in the coloring material. That is, by changing the blending ratio of the low melting point agent in the range of about 1 to 99% based on the weight of the powdered coloring material, the melting point of the coloring material itself can be varied in the range of about 80 to 150°C.

On the other hand, since the temperature range depending on the heat generation energy from the heating resistor element is approximately 50 to 400°C, the melting point of the coloring material may be appropriately distributed within this temperature range. As the low melting point substance, commonly known substances such as amide wax can be used. It is also possible to substantially change the melting point by changing the particle size of the coloring material and changing the melting heat energy.

Next, a method of changing heat generation energy by a heat generating resistor element in a stepwise manner according to an image according to the method of the present invention will be described.

Figure 2 shows an example of a circuit diagram for heating the plurality of heating resistor elements in the thermal head in stages. It is connected to a transistor 5 that turns on and off the heat generation of the body element. Reference numeral 6 denotes a CPU, which stores image signals on a shift register 7, and further specifies a gradation signal for forming a halftone image to a strobe pulse control circuit 8. When both the digital signal outputted from the shift register 7 and the digital signal outputted in a pulse form from the strobe pulse control circuit 8 are outputted, a current is transferred from the AND circuit 9 to the transistor 7.
, the potential difference between the emitter and collector of the transistor 5 disappears, and the heating resistor element 4 generates heat.

Halftone images are recorded using the ink sheet and electric circuit configured as described above. In other words, the ink sheet and recording paper are overlapped and moved, and the thermal head inside the printer is moved to the base material of the ink sheet. Halftone image recording is performed by pressing from the side and heating the heating resistor element in the thermal head in stages. At this time, the powdered coloring material is transferred to the recording paper according to the heat generation energy of the thermal head. As a result, the amount of the color material transferred to the recording paper, that is, the size and density of the recording pixels, can be controlled as a function of the heat energy of the thermal head.

Incidentally, generally known means can be used to prepare the ink sheet for thermal transfer recording according to the present invention.

[Example] Three types of microcapsules, yellow, magenta, and cyan, were created by interfacial polymerization.

The obtained powder coloring material has a particle size of 1 to 10 μm and a melting point of 80 to 1
The temperature was about 50°C.

In order to create an ink sheet, polyethylene terephthalate (PET) with a thickness of 6 μm was used as a base material, and polyester resin was coated on top of this in a ball mill using toluene as a solvent.
The mixed solution was coated with a bar coater to a thickness of about 1 μm to form an adhesive layer. The powdered coloring material prepared above was sprinkled on the adhesive layer before it was dry. After removing the excess powder coloring material that did not adhere to the adhesive layer, it was sufficiently dried to obtain an ink sheet for thermal transfer recording.

FIG. 4 shows the sheet obtained. In the figure, 1 is a base material, 10, 11, and 12 are powder coloring materials each containing three primary color materials of yellow, magenta, and cyan, and 3 is an adhesive layer. The ink colors of yellow, magenta, and cyan are distributed within the ink sheet as shown in the figure.

When we performed a solid image printing test on plain paper using a thermal head constructed from the circuit shown in Figure 2, we found that the recording density was affected by the thermal energy generated by the thermal head, as shown in Figure 3. The image changed accordingly, and beautiful midtones were recorded. (The heating temperature was approximately 80 to 200 degrees Celsius.) In other words, the relationship between the width of the energizing pulse to the heating resistor element of the thermal head and the recording density is as shown in Figure 3, as can be seen from the solid line in the figure. In addition, in the ink sheet used in the halftone image recording method of the present invention, by changing the recording energy applied to the heating resistor element in stages, the recording density of the solid image also changes in stages, so that the halftone image can be recorded. Image recording was realized. On the other hand, when using a conventional ink sheet with an ink layer formed directly on the base material, even if the recording energy applied to the heating resistor element is changed stepwise as shown by the dotted line in the figure, Since the recording density did not change accordingly but changed rapidly, it was impossible to record halftone images.

Next, the obtained ink sheet for thermal transfer recording shown in FIG. 4 is superimposed on the recording paper and moved by a paper feeding system, and the ink sheet of the yellow coloring area is first printed using the same device as that used in the above printing test. By forming a yellow halftone image on the recording paper using It was possible to record halftone images with good reproducibility.

[Effects of the Invention] As described above, an ink sheet for thermal transfer recording in which an adhesive layer is provided on a base material and a heat-melting powder coloring material (toner) is coated on the adhesive layer is heated. A smooth halftone image is recorded on plain paper with good reproducibility by pressing a print head having a resistor element and heating it by changing the recording energy applied from the heating resistor element in stages according to the image. This becomes possible.

Further, according to the ink sheet according to the present invention, a complicated device is not required, and the device can be made smaller and lower in cost.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an ink sheet used in the halftone image recording method of the present invention, and Fig. 2 shows stepwise heating of a plurality of heating resistor elements in a thermal head used in the halftone image recording method of the present invention. FIG. 3 is a diagram showing the relationship between the width of the energizing pulse to the heating resistor element of the thermal head and the recording density according to the halftone image recording method used in the embodiment of the present invention, and FIG. 1 is a configuration diagram of an ink sheet for full-color recording used in the halftone image recording method used in the example, in which (a) is a schematic plan view and (b) is a schematic front cross-sectional view. 1... Base material 2... Microcapsule 3... Adhesive layer 4... Heat generating resistor element 5... Transistor 6... CPU 7... Shift register 8... Strobe pulse control circuit 9...AND circuit 10...Microcapsules encapsulating yellow coloring material 11...Microcapsules encapsulating magenta coloring material 12...Microcapsules encapsulating cyan coloring material Patent applicant Canon Corporation company

Claims (1)

[Scope of Claims] 1) Printing having a heating resistor element on a thermal transfer recording ink sheet having an adhesive layer provided on a base material and a heat-melting powder coloring material coated on the adhesive layer. Press the head,
A halftone image recording method, characterized in that a halftone image is formed on a recording medium by heating while changing recording energy applied from the heating resistor element stepwise according to the image. 2) The halftone image recording method according to claim 1, wherein the melting point of the powder coloring material is widely distributed within a temperature range corresponding to the stepwise recording energy from the heating resistor element.