JPH04279360A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent the generation of the irregularity in the accumulation quantity of heat of a heating body part between thermal heads. CONSTITUTION:A protruding glaze layer 2 is formed on the substrate constituting the base of a heating body part and a plurality of heating bodies 3 are arranged on the glaze layer 2 in one row. Current supply electrodes 4 are connected to the heating bodies 3 and a pulse voltage is applied to the heating bodies 3 through the current supply electrodes 4. In this case, the applied voltage is set to the magnitude corresponding to the thickness of the glaze layer 2 and the average resistance value of the heating bodies 3. Therefore, even when there is irregularity in the thickness of the glaze layer 2 or the average resistance value of the heating bodies 3, the rise of the peak temp. of the heating bodies 3 becomes uniform between thermal heads and, therefore, it is unnecessary to adjust printing history control between the thermal heads. As a result, uniform peak temp. is always obtained and the lowering of density or sticking is not generated and stable printing grade can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for thermal transfer recording.

0002

[Prior Art] Conventionally, in a thermal head that performs high-speed printing, attention is paid to the past printing history of a heating element for printing, and the first dot that has no previous printing history is printed with a predetermined printing energy. , there is a device that prints with lower printing energy than the previous printing if there is a previous printing history (see Japanese Patent Application Laid-Open No. 130527/1982).
.

FIG. 2 is a diagram showing the principle of a conventional thermal head in which heating elements are arranged in one row. As shown in the figure, taking the dot-shaped thermal heads in rows Y1 to Y7 as an example, the thermal heads are relative to the recording paper, that is, the image receiving paper, in the space direction (direction perpendicular to the arrangement direction of the heating elements). be moved to. At this time, when a pulse voltage corresponding to the character pattern is applied to the heating element to generate heat in each of the X1 to X5 columns, a 5×7 dot character pattern as shown in the printing example is printed.

In this case, the row under the most severe application conditions for the thermal head is the Y4 row, in which pulse voltages are continuously applied, followed by the Y7 row, and the other rows have relatively easy application conditions. That is, in a character pattern in which dots are continuous, a heating element is driven at each application cycle, causing the thermal head to repeatedly generate and dissipate heat, and this thermal cycle shortens the life of the thermal head. Therefore, a heating pulse with a long pulse width is applied when printing the first dot of consecutive dots or a dot that is not continuous with the preceding and succeeding dots, and a heating pulse with a longer pulse width is applied when printing dots other than the first dot of consecutive dots. A low power warming pulse with a short pulse width is applied.

FIG. 3 is a time chart of applied pulses and temperature changes of a conventional thermal head. As shown in Figure 2, S1 is a pulse applied to the heating elements in row Y4, which is the all mark, S2 is a pulse applied to heating elements in rows Y1 to Y3, Y5 and Y6, and S3 is a pulse applied to the heating elements in row Y4. This is the temperature change.

That is, as shown in pulse S1, Y4
A heating pulse A having a pulse width t is applied to the X1 column of dots at the beginning of a row of consecutive dots. The pulse width t and voltage E of this heating pulse A are the same values as those of a normal applied pulse. Next, for consecutive dots in rows X2 to X5, the pulse width t' is shorter than the pulse width t of heating pulse A.
A warming pulse B having a temperature is applied.

Therefore, the temperature change of the heating element in row Y4 draws a curve as shown in S3, and the thermal head, which was first heated by heating pulse A, then repeats small temperature fluctuations (ripples) by heating pulse B and reaches the threshold. Maintain the temperature above. As a result, the Y4 row becomes
It is printed as a line connecting the dots of rows to X5, and there is no large temperature fluctuation in the thermal head at this time, and a stable printing state can be maintained. Also, Y
Pulse S is applied to the heating elements in rows 1 to Y3, Y5 and Y6.
As shown in FIG. 2, a heating pulse A having a pulse width t is applied to the dots in the X1 column and the X5 column.

[0008] In this way, temperature fluctuations in the heating element due to past printing history are prevented, printing quality is improved, and the load on the thermal head can be reduced.

[0009]

[Problems to be Solved by the Invention] However, with the above-mentioned conventional thermal head, it is difficult to perform high-speed printing of 5 ms or less per line, for example, or to perform high-output printing (for example, thermal transfer printing on paper with low smoothness). , twice as much energy is required as in the case of printing on thermal paper), the difference in the amount of heat stored in the heating element portion between the thermal heads becomes noticeable.

That is, if printing history control is performed at the same rate for all thermal heads, the thermal head with a small amount of heat storage will not raise the temperature of the heating element sufficiently, making it impossible to obtain the necessary thermal transfer recording density. In addition, with a thermal head that stores a large amount of heat, the temperature of the heating element may rise too much, causing the transferred ink to return to the donor film, or the ink to be transferred to the image receiving paper to soak into it, reducing the density, or the donor film may become thermally It may adhere to the surface of the head and cause sticking. Therefore, stable printing quality cannot be obtained for all thermal heads.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional thermal heads described above and to provide a thermal head in which the amount of heat stored in the heating element portion does not vary between thermal heads.

0012

[Means for Solving the Problems] To this end, in the thermal head of the present invention, a convex glaze layer is formed on the substrate constituting the base of the heating element portion, and a convex glaze layer is formed in a row on the glaze layer. A plurality of heating elements are arranged. A power supply electrode is connected to the heating element, and when a pulse voltage is applied, the temperature of the heating element rises, and the ink on the transfer film is transferred.

The pulse voltage applied to the power supply electrode is set to a value corresponding to the thickness of the glaze layer and the average resistance value of the heating element.

[0014]

[Operation] According to the present invention, a convex glaze layer is formed on the substrate constituting the base of the heating element portion as described above, and a plurality of heating elements are arranged in a row on the glaze layer. It is now possible to do so. Therefore, when a pulse voltage is applied to the heating element to selectively generate heat, a dot pattern image can be printed on the image receiving paper.

[0015] A power supply electrode is connected to the heating element, and the pulse voltage is applied via this power supply electrode. In this case, the applied pulse voltage is set to a magnitude corresponding to the thickness of the glaze layer and the average resistance value of the heating element. Therefore, it is possible to suppress variations in the amount of heat stored in the heating element portion between the thermal heads.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a structural diagram of a heating element portion of a thermal head according to the present invention. In the figure, 1 is an alumina substrate constituting the base of the heating element part, 2 is a convex glaze layer disposed on the alumina substrate 1, and 3 is a coating on the alumina substrate 1 and the glaze layer 2. heating element,
4 is a power supply electrode connected to the heating element 3 and applies a predetermined pulse voltage to the heating element 3; 5 is a protective film.

In a thermal printer using a single-line thermal head (see FIG. 2), in the case of a serial type thermal head, the thermal head moves relative to the receiver paper in the space direction; In this case, printing is performed while the platen roll rotates and moves the image receiving paper and ink film relative to the thermal head. In thermal transfer recording, if the surface smoothness of the image-receiving paper used is low, the contact area between the ink and the image-receiving paper decreases, and the ink transfer rate decreases. Therefore, it is necessary to increase the heat generation temperature and lower the viscosity of the ink to improve the transfer rate, which increases the required electric power.

The glaze layer 2 is formed into a convex shape by printing and baking a glass paste, and serves as a heat resistance layer, that is, a heat insulating layer. Therefore, the heating element portion also becomes convex, and the contact pressure between the heating element 3, the film, and the image receiving paper increases, reducing the power required for printing. By the way, the glaze layer 2 formed at the bottom of the heating element 3 constitutes a heat insulating layer and is designed to store heat. However, if there is variation in the thickness of the glaze layer 2, the thermal head Variations in the amount of heat storage occur between the two.

For example, in a device having a partial glaze structure formed in a convex shape on the alumina substrate 1, the variation in the thickness of the glaze layer 2 is generally ±10 μm between thermal heads. FIG. 4 is a diagram showing the relationship between the thickness of the glaze layer and the peak temperature of the heating element, and FIG. 5 is a diagram showing the relationship between the peak temperature of the heating element and the transfer rate.

In FIG. 4, seven pulses are applied continuously, and when the heating element portion has sufficiently accumulated heat, the heating element 3
The peak temperature of glaze layer 2 and the thickness of glaze layer 2 are shown. As shown in the figure, if the thickness of the glaze layer 2 differs by 1 μm, the heating element 3
It can be seen that the peak temperatures differ by 3°C. Therefore, by reducing the variation in the thickness of the glaze layer 2, it is possible to reduce the variation in the amount of heat storage between thermal heads.

Further, FIG. 5 shows the transfer rate and the peak temperature of the heating element 3 when printing is performed on image receiving paper having a smoothness of about 30 seconds. In order to eliminate the visual roughness of images when solid black printing is performed, the transfer rate should be set to 9.
It is necessary to make it 3% or more, and for this purpose, it is desirable to make the peak temperature of the heating element 3 higher than 340°C. In addition, although the variation in the smoothness of the image receiving paper is about ±10 seconds, the peak temperature of the paper with high smoothness is 380°.
If it exceeds C, the density of the transfer ink will decrease.

Therefore, the peak temperature of the heating element 3 is
The temperature is preferably 60±20°C. From this, the thickness of the glaze layer 2 can be ranked, and the error can be calculated as ±
If the thickness is 6 μm, the peak temperature of the heating element 3 can be kept within the above temperature range. Furthermore, energy efficiency can be optimized by ranking the average resistance value of the heating elements 3 and setting the difference in pulse voltages applied between the thermal heads to within ±1%.

Therefore, by combining the ranking of the thickness of the glaze layer 2 and the ranking of the average resistance value of the heating element 3, it is possible to always obtain the same peak temperature of the heating element 3. For example, for a thermal head with a thin glaze layer 2 and a low heat storage capacity, the resistance value of the heating element 3 can be ranked higher than the standard rank, so that an extra pulse voltage is required. , the peak temperature of the heating element 3 can be increased. In addition, for thermal heads with a thick glaze layer 2 and a large amount of heat storage,
By lowering the rank of the resistance value of the heating element 3 and lowering the applied pulse voltage, the peak temperature of the heating element 3 can be lowered.

FIG. 6 is a diagram showing the relationship between the rank of the thickness of the glaze layer, the rank of the resistance value of the heating element, and the applied pulse voltage. From this figure, we can see that the manufactured heating element part is the glaze layer 2.
The pulse voltage applied between the power supply electrodes 4 can be determined based on the ranks of the heating elements 3 and 3 based on the average resistance value of the heating element 3.

Reference resistors having resistance values representative of each rank of the thickness of the glaze layer 2 and each rank of the resistance value of the heating element 3 are provided, and a predetermined resistor is provided for each rank of the heating element. The required pulse voltage can be formed by selecting a resistor and mounting it on the thermal head. Alternatively, the pulse voltage may be directly adjusted without ranking, taking into account the thickness of the glaze layer 2 and the average resistance value of the heating element 3.

[0026] Furthermore, the value of the print history control rate is generally RO
Since it becomes M, it is difficult to make adjustments between thermal heads, and complex control algorithms are required even when performing environmental temperature correction, gradation correction, etc., so it is better to keep them constant. Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0027]

As described above in detail, according to the present invention, a convex glaze layer is formed on the substrate constituting the base of the heating element portion, and a plurality of convex glaze layers are formed in one row on the glaze layer. A heating element is installed. A power supply electrode is connected to the heating element, and a pulse voltage is applied via the power supply electrode. In this case, the applied pulse voltage is set to a magnitude corresponding to the thickness of the glaze layer and the average resistance value of the heating element.

Therefore, even if there are variations in the thickness of the glaze layer or the average resistance value of the heating element, the rise in the peak temperature of the heating element will be uniform among the thermal heads, so it is possible to adjust the printing history control between the thermal heads. There is no need to do this. Therefore, a uniform peak temperature can always be obtained, and stable printing quality can be obtained without causing a decrease in density or sticking.

Furthermore, since there is little variation in heat generation between thermal heads, the reproducibility of gradation is improved in gradation printing control as well.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a heating element portion of a thermal head according to the present invention.

FIG. 2 is a principle diagram of a conventional thermal head in which heating elements are arranged in one row.

FIG. 3 is a time chart of applied pulses and temperature changes of a conventional thermal head.

FIG. 4 is a diagram showing the relationship between the thickness of the glaze layer and the peak temperature of the heating element.

FIG. 5 is a diagram showing the relationship between the peak temperature of the heating element and the transfer rate.

FIG. 6 is a diagram showing the relationship between the rank of the thickness of the glaze layer, the rank of the resistance value of the heating element, and the applied pulse voltage.

[Explanation of symbols]

1 Alumina substrate 2 Glaze layer 3 Heating element 4 Power supply electrode 5 Protective film

Claims (1)

[Claims] 1. A thermal head that prints a dot pattern image by applying a pulse voltage, comprising: (a) a substrate constituting a base of a heating element portion; (b)
a convex glaze layer disposed on the substrate; (c) a plurality of heating elements disposed in a row on the glaze layer;
d) a power supply electrode connected to the heating element; and (e) means for applying a pulse voltage of a magnitude corresponding to the thickness of the glaze layer and the average resistance value of the heating element to the power supply electrode. Features a thermal head.