JPH0259389A - Intermediate tone image recording method - Google Patents

Abstract

PURPOSE:To form an intermediate tone image based on density gradation on an ordinary paper by pressing a printing head having heat generating elements against an ink sheet comprising on a base a recording layer comprising a transfer material with a heat-fusible particulate coloring material dispersed therein, and performing heating with variations in heat generating energy. CONSTITUTION:An ink sheet comprises on a base 1 a recording layer comprising a transfer material 3 with a heat-fusible particulate coloring material 2 dispersed therein. The transfer material 3 is transparent, and has the property of dissolving or dispersing the coloring material 2 therein when being melted by heating. The melting temperature of the coloring material 2 is set to be higher than that of the transfer material 3. While the ink sheet and a recording paper are moved in a superposed condition, a thermal head in a printer is pressed against the ink sheet from the base side, and heating is carried out with variations in the heat generating energy of heat generating resistor elements in the head, thereby recording an intermediate tone image. The density of a picture element thus recorded is controlled as a function of the heat generating energy of the head, and is varied according to the amount of the coloring material 2 dissolved into the transfer material 3.

Description

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

(Prior art) Conventionally, ink sheets used in thermal transfer recording methods have a structure in which an ink layer is provided directly on a base material, and one heat generation of a heat-generating resistor element causes the ink in the heat-generating portion of the ink sheet to dry once. It peels off and transfers onto the recording paper. Therefore, the recorded dots on the recording paper can only have a certain density.

Therefore, as an example of a method for obtaining a halftone image, there is a dye method in which the number of dots constituting one printed pixel is changed, but this method poses a problem of a decrease in recording resolution. In addition, the base material
An area gradation method has also been proposed in which the area of printed dots is changed by heating a heating resistor in stages using an ink sheet provided with an ink layer containing a filler in F (Japanese Patent Application Laid-Open No. No. 60-8090, No. 60-212393, etc.).

[Problem to be solved by the invention]

However, since these methods control the area of the dots, when a halftone image is formed, the image appears grainy, making it difficult to use silver halide photography or thermal transfer recording methods using sublimation dyes.

Compared to the density gradation method, which changes the density of pixels, this method has the disadvantage that smooth halftone images cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a halftone image recording method capable of eliminating the above-mentioned drawbacks and forming a smooth halftone image with density gradation on plain paper.

[Means to solve the problem]

The above purpose is to press a print head having a heating element onto a thermal transfer recording ink sheet, which has a recording layer on a base material in which a heat-melting powder coloring material is dispersed in a heat-melting transfer material. This can be achieved by a halftone image recording method in which a halftone image is formed on a recording medium by heating a surface heating element so that its heat generation energy fluctuates.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of an ink sheet used in the halftone image recording method of the present invention. This ink sheet has a recording layer formed of a transfer material 3 in which a heat-fusible powder coloring material (toner) 2 is dispersed on a base material 1.

Base material! Normally, capacitor paper, PET film, etc. are used.

The transfer material 3 is transparent, melts when heated, and has a property of dissolving or dispersing the powder coloring material (toner) 2 in the melted state, and is made of amide wax, carnauba wax, or the like.

The melting temperature of the powder color material 2 is set higher than that of the transfer material 3. It usually has a diameter of about 2 to 20 microns, - Examples include dye 1 to 2, binder 0.1 to 10, and low melting point agent 1 to 99.
A mixture of the following (parts by weight) is used.

The powdered coloring material 2 and the transfer material 3 constituting the recording layer are mixed using a ball mill or the like, and then coated onto the base material 1 using a bar coater coating device. At this time, the thickness of the recording layer is usually within the range of 2 to 8 scales, the proportion of the powdery coloring material 2 in the recording layer is within the range of 10 to 70% by weight, and the powdery coloring material 2 is in the range of 10 to 70% by weight. It is uniformly dispersed within the transfer material 3.

FIG. 2 is a circuit diagram for heating a plurality of heating resistive elements in the thermal head in stages in order to change the amount of heat generation energy of the thermal head. In this circuit, a plurality of heat generating resistive elements 4 in the thermal head are connected to a transistor 5 that turns on and off the heat generated. The image signal is stored in a shift register 7 by the CPU 6, and a gradation signal for forming a halftone image is specified to a strobe pulse control circuit 8. When both the digital signal output from the shift register 7 and the digital signal output in pulse form from the strobe pulse control circuit 8 are output, current flows from the AND circuit 9 to the transistor 5 between the emitter and collector of the transistor 5. The potential difference disappears, and the heating resistor element 4 generates heat.

Using the ink sheet and electric circuit configured as above,
Halftone image recording of the present invention is performed. That is, while moving the ink sheet and recording paper overlappingly, press the bottom of the thermal spatula inside the printer from the base material side of the ink sheet,
A halftone image is recorded by heating the heating resistor element in the thermal head while changing the amount of heat generation energy.

At this time, 30 to 100% of the transfer material 3 on the ink sheet is transferred to the recording paper due to the heat generated by the thermal head. but,
The melting of the powdered coloring material 2 into the transfer material 3 changes in proportion to the heat generation energy of the thermal head.

In other words, when the exothermic energy is low, there is less, and when the exothermic energy is high, there is more. Therefore, the amount of powdered color material 2 transferred to the recording paper, that is, the density of the recording pixels, can be controlled as a function of the heat generation energy of the thermal head. In this halftone image recording method, the transfer material 3 is always transferred to the recording paper, and since the amount of melting of the powder color material 2 in the transfer material 3 is changed, the area of the recording pixels on the recording paper is relatively uniform. Since the density of the recorded pixel changes depending on the amount of the powdered coloring material 2 melted into the transfer material 3, density gradation is realized.

Figure 3 shows the relationship between the micro-density of the recording pixel and the width of the energizing pulse to the heating resistor element of the thermal head when the heat generation energy of the thermal head is gradually changed using the circuit shown in Figure 2. Shown below. As is clear from the solid line in the figure, in the case of the halftone image recording method of the present invention using the above ink sheet, by gradually increasing the recording energy applied to the heating resistor element, the recording pixel micro The density also increases in proportion to this, and density gradation is realized.

In contrast, when using a conventional ink sheet in which an ink layer is formed directly on the base material, it is possible to gradually change the recording energy applied to the heating resistor element as shown by the dotted line in the figure. , the density of the recording pixels changes rapidly, making it impossible to record halftone images.

FIG. 4 shows the structure of an ink sheet when performing full color recording using the halftone image recording method according to the present invention.

This ink sheet has, on a base material 1, a recording layer formed by separately applying a transfer material 3 containing three primary color powder coloring materials of yellow magenta and cyan (10, 11, and 12 in that order).

These ink sheets are stacked on top of the recording paper and moved by a paper feed system. First, a yellow halftone image is formed on the recording paper using the ink sheet of the yellow coloring part, and then the recording paper is returned to the reference position. , then the macenta halftone image,
Furthermore, by forming a cyan halftone image, a halftone image with full color density gradation is reproduced.

FIG. 5 shows another example of an ink sheet used in the halftone image recording method of the present invention.

This ink sheet has a powdered coloring material 2 adhered to a base material 1 through an adhesive layer 13, and a transfer material 3 applied thereon. The adhesive layer 13 is made of polyamide resin, polynisder resin, or the like.

Halftone images are recorded using the ink sheet having the above structure and the electrical circuit shown in FIG. At this time, as in the case shown in FIG. 1, a plurality of powder coloring materials 2 in an amount corresponding to the heat generation energy of the thermal head are melted on the transfer material 3 and transferred onto the recording paper. However, in the case of using the ink sheet shown in FIG.
held on top. This prevents the unmelted powder coloring material 2 from being transferred to the recording paper, thereby improving color light developability, density unevenness, etc. on the recording paper.

Furthermore, in the ink sheet having the configuration shown in FIG. 1 or FIG. 5, the melting point of the powder coloring material 2 is widely distributed within a temperature range corresponding to various amounts of heat generation energy from the heating resistor elements. , the density expression range and density variations on the recording paper are improved.

〔Effect of the invention〕

As explained in detail above, a print head having a heating element is attached to a thermal transfer recording ink sheet in which a recording layer in which a heat-fusible powder coloring material is dispersed in a heat-fusible transfer material is provided on a base material. By pressing and heating the surface heating element so that its heat generation energy changes, it has become possible to form a smooth halftone image with density gradation on plain paper.

Furthermore, since this method employs a density gradation method based on an improved ink sheet, 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, FIG. 2 is a circuit diagram for stepwise heating a plurality of heating resistive elements in a thermal head used in the method, and FIG. The figure is a diagram showing the relationship between the current pulse width to the heating resistor element of the thermal head and the micro density of the recording pixel according to this method, and FIG. FIG. 5 is a sectional view of another example of an ink sheet used in the method. 2: Powder color material 3: Transfer material 4: Heat generating resistor element 5 Nidorangistaro: CPU 7: Shift resistor rope pulse control circuit: AND circuit 0: Yellow powder Color material 1: Magenta powder Coloring material 2 Nijian powdered coloring material 3: Adhesive layer

Claims (1)

[Scope of Claims] 1) A print head having a heating element on a thermal transfer recording ink sheet having a recording layer on a base material in which a heat-melting powder coloring material is dispersed in a heat-melting transfer material. A halftone image recording method in which a halftone image can be formed on a recording medium by pressing the heating element and heating the heat generating element so that its heat generation energy fluctuates. 2) The halftone image recording method according to claim 1, wherein the base material and the powdery coloring material are bonded to each other via an adhesive layer provided on the base material. 3) The halftone image recording method according to claim 1, wherein the melting point of the powder coloring material is distributed within a temperature range corresponding to the fluctuating heat energy from the heating element.