JPH0530632B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head of a thermal transfer printing device.The present invention relates to a thermal head of a thermal transfer printing device. It is an object of the present invention to provide a thermal head for a thermal transfer printing device, in which, for example, an excellent transferred image can be obtained by configuring the head to have at least two heat transfer paths using one heating element.

[Prior art]

As shown in FIG. 1, the principle of a thermal transfer type printing device is that recording paper 1 and transfer paper 2 are brought into close contact with each other and are fed between a pressure roller 3 and a thermal head 4. When the transfer paper 2 is heated by passing a current through the resistors to make each heating resistor generate heat, the hot-melt ink 2' applied to the transfer paper 2 at a constant thickness melts, and the recording paper 1 Hot-melt ink 2' is applied to the paper, and the recording paper printed in this way is cut into an appropriate shape to become a printed matter, and the unnecessary transfer paper passes through a guide roller and is wound up on a take-up roller. It is like being disposed of.

The thermal head used in the multi-tone recording method in conventional thermal transfer printing is
As shown in the figure and FIG. 3, it is composed of a lead wire 5 and a rectangular or square heating element 6.
In addition, methods for producing gradations include using the thermal head described above and controlling the number of dots to produce the desired gradation, or controlling the size of the dots to produce the desired gradation. is the mainstream.

[Problems with conventional technology]

A method of producing a desired gradation by controlling the number of dots using the thermal head having the above configuration is described, for example, in the third method.
In the case of using the thermal head shown in the figure, if the heat generated at a certain point is blocks A and C in the heat generating element 6, the transfer of the portion that comes into pressure contact with the blocks A and C will be recorded as dots on the recording paper. become.

By the way, according to the above method, in order to reduce the size of the dots when a pale color is to be expressed on the recording paper, the transfer dots of blocks A and C in the above example are made small. Therefore, the distance between the transferred patterns on the recording paper is too wide, resulting in a recording with coarse grains.

On the other hand, a method for producing a desired gradation by controlling the size of dots using the thermal head having the above configuration is as follows:
For example, when using the thermal head shown in FIG. 3, each block A,
By controlling the amount of current applied to blocks A, C, D, etc., the heat generation conditions of each block A, B, C, D, etc. are controlled to produce the shade of color on the recording paper. In the case of recording with
Therefore, there is a drawback that variations occur in the heat generation conditions and unevenness occurs in the recorded dots.

[Means for solving problems]

The thermal head of the thermal transfer printing device is configured such that there are at least two heat transfer paths by one heating element to the transfer paper used during thermal transfer printing, and the width of each heat transfer path is set at the center thereof. By controlling the area of the heating part at an appropriate temperature that exceeds the melting point of the transfer paper during transfer, and by utilizing the spread of the melting point due to the thickness of the transfer paper and the heat conduction effect in the high temperature range, the above-mentioned non-conformity can be achieved. The object is to also enable transfer on conductive parts.

[Example 1] FIGS. 4 and 5 show the structure of a thermal head of a thermal transfer printing apparatus according to the present invention and its transfer pattern.

In FIG. 4, 11 is the same lead wire as shown in FIGS. 2 and 3, 12 is a heating element,
12a and 12b are heat generating parts divided by a non-conductive part 13, which will be described later, and constitute one heat generating element 12 of the thermal head.

Reference numeral 13 denotes a gap, that is, a non-conductive portion, formed in a portion that becomes a high temperature region when the heating element 12 generates heat under a certain heat generation condition.

That is, in the above configuration, the heat generating portions 12a and 1
There are two heat transfer paths, as described above: the heat generated from 12a and 12b of one heating element 12 is transferred to the transfer paper, and the heat generated from 12a and 12b of one heating element 12 is transferred to the transfer paper. .

FIG. 5 shows the transfer pattern transferred onto the recording paper by the thermal head when a predetermined current is applied to the heating element 12 having the above configuration and the heating time is increased sequentially.

In the figure, the upper side (a side in the figure) is the low temperature transfer pattern, and the lower side (the e side in the figure) is the high temperature transfer pattern.

That is, when transfer printing is performed using a thermal head by applying a predetermined current to the heating elements 12 shown in FIG. 13
Among the left and right conductive parts divided by , that is, the heat generating parts 12a and 12b, the narrowest part (the part surrounded by the dashed line in the figure) generates a large amount of heat,
This part quickly reaches the appropriate temperature for transfer. The transfer pattern in this state is as shown in Figure 5a.
It will be transferred as the smallest dot.

As the heating time for each heating element 12 increases sequentially, the appropriate temperature range for transfer of the heat generating portions 12a and 12b, which reached the appropriate temperature for transfer first in the initial heating stage, gradually expands to the periphery.
As shown in Figures b, c, d, and e, it can be seen that the shape of the transferred pattern expands with the length of the current application time (temperature rise) at each heating stage.

By the way, in enlarging the transfer pattern mentioned above,
Looking at the transfer patterns from Figure 5 d to Figure 5 e,
Heating is also carried out in the gap region of the non-conductive part 13, which is not normally directly heated by the heat-generating parts 12a and 12b shown in FIG. The pattern is Figure 5e
The transfer pattern is then completely integrated.

This is because the heat generated by the left and right heat generating portions 12a and 12b is transmitted to the transfer paper over time.

Incidentally, heat generation in each of the heat generating portions 12a and 12b is caused by the following equation: P=I ² R.

Therefore, if the width of each heat generating portion 12a, 12b is kept constant, by narrowing the central portion, the electrical resistance can be increased and the amount of heat generated can be increased.

Incidentally, the larger the non-conductive portion 13 is and the thinner the central portion of the left and right heat generating portions 12a and 12b, the more a transfer pattern of small dots can be obtained.
When the surrounding area reaches the appropriate temperature, the center area may burn.

In other words, the amount of heat generated is P = I ² R and is proportional to the resistance, but if the heating element has the same thickness and the amount of heat generated per unit area ΔS is considered, the current density in the narrow part of the heating element is inversely proportional to the width. However, if we assume that the thickness of the heating element is the same, the electrical resistance per unit area will be the same everywhere, so the partial heating value ∝ (current density) ² , which is inversely proportional to the square of the width of the heating element. .

From the above, in the above example, the ambient temperature is set to 20
℃, and in order to prevent the transfer paper from burning in the center and to narrow down the smallest dot, the width ratio of the heating element at the end in contact with the lead wire and the center should be 3:1 to 3:3. It can be said that it is extremely desirable to set the value between 2 and 3.

[Embodiment 2] FIG. 6 shows a second embodiment of a thermal head of a thermal transfer printing apparatus according to the present invention.

The thermal head shown in the figure has the heating element 12 of the first embodiment made slightly wider and has two gaps, that is, non-conductive parts 13, 13 formed therein.

In the thermal head constructed in this way, the heating element 12 is divided into three parts by the non-conductive parts 13, 13 to form the heating parts 12a, 12b, 12c. When a pattern is determined, three dots can be transferred at once using one heating element 12, and images, etc., can be efficiently recorded using small-grained particles.

[Embodiment 3] FIG. 7 shows a third embodiment of a thermal head of a thermal transfer printing apparatus according to the present invention.

The thermal head shown in the same figure is constructed by connecting a large number of heating elements 12 in the first embodiment with the heating elements 12 folded down, and heating portions 12a, 12b of each heating element 12, 12, . . .
are arranged above and below.

The thermal head configured in this way can be heated by increasing or decreasing the number of heating elements 12, 12, etc. installed in parallel depending on which lead wire 11 is selected, so that the number of transferred patterns can be increased or decreased. Of course,
It is easy to control the energization conditions, and it is possible to efficiently record images using small particles.

Although the third embodiment has been described as a case in which a large number of heating elements 12 in the first embodiment are connected, a similar structure may be adopted using the heating elements 12 in the second embodiment, and in particular, the above-mentioned It is not limited to the examples.

Moreover, one heating element as referred to in the present invention includes the same terminals of the current path applied to the heating element, and is not limited to the configurations of Examples 1 to 3 above.

〔effect〕

As described above, the thermal head of the thermal transfer printing device according to the present invention has at least two heat transfer paths from one heating element to the transfer paper used in thermal transfer printing. In addition, since the width of each heat transfer path is narrowest at the center, the number of dots obtained with one heating element is smaller than that obtained with one conventional heating element. This is at least twice as large, making it superior to images produced by conventional thermal heads, even when printing television images, for example, where it is impossible to print a sufficiently large number of dots due to the pixel limitations of the video signal. It is possible to obtain images with high resolution.

Also, even when controlling the number of dots as a method of producing multiple gradations, compared to conventional thermal heads,
The thermal head of the thermal transfer printing device according to the present invention is a head that can produce a very large number of dots as described above, so it can be used, for example, when expressing a pale color and narrowing down the dots to a small size. However, the distance between the dots is not too wide, and it is possible to produce multiple gradations using very fine particles.

Moreover, even when controlling the size of dots as a method of producing multiple gradations, the thermal head of the thermal transfer printing apparatus according to the present invention having the above-mentioned configuration is
It is very easy to control the heating amount of each heating element by energizing, so even if you want to express a light color and narrow down the dots, you can heat them evenly at precise positions and avoid uneven dots. I never tighten it.

Furthermore, at least twice as many heating elements are required to obtain the number of dots obtained with the thermal head of the thermal transfer printing apparatus of the present invention using conventional heating elements. Moreover, since the same number of ICs for controlling the heating temperature of the heating element are required, the thermal head is not only difficult to manufacture but also extremely expensive. In comparison, the thermal head of the thermal transfer printing device according to the present invention is
Regardless of the increase in the number of dots, the number of heating elements and ICs can be the same as those used in conventional thermal heads, so it has various excellent features such as being inexpensive.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the principle of a thermal transfer printing device, Figure 2
3 and 3 are explanatory diagrams of a heating element used in a conventional thermal head, FIG. 4 is an enlarged view of a main part of a heating element used in a thermal head of a thermal transfer printing apparatus according to the present invention, and FIG. FIG. 4 is an explanatory diagram of the transfer pattern recorded by the heating element, and FIGS. 6 and 7 are main parts of the heating element of other embodiments of the heating element used in the thermal head of the thermal transfer printing apparatus according to the present invention. It is an enlarged view. 12... Heat generating element, 12a, 12b, 12c... Heat generating portion, 13... Non-conductive portion.

Claims (1)

[Claims] 1. The thermal head of the thermal transfer printing device is configured so that there are at least two heat transfer paths by one heating element to the transfer paper used in thermal transfer printing, and the width of each heat transfer path is set at the center thereof. A thermal head for a thermal transfer printing device, characterized in that the head is configured to have the narrowest width.