JPS61192566A - Thermal printing head for gradation recording - Google Patents

Abstract

PURPOSE:To enable the adjustment of the apparent developed color density of one heat generating dot, by making he distances between electrodes different along the lateral direction of heat generating dots. CONSTITUTION:When power is applied between electrodes 3, 4, the resistance value at the part shortest in the distance between the electrodes 3, 4 becomes min. and a current is flowed to said part in a conc. manner and, therefore, the vicinity thereof generates heat as shown by a numeral 2A. When applied power is increased as compared with heretofore applied one, a current flowing range becomes wide and a heat generating region 2B becomes further wide. If the power applied between electrodes increases and decreases as mentioned above, the heat generating area of one heat generating dot increases and decreases. Therefore, if thermal paper is developed by the heat generating dot, the developed color area thereof can be altered. When the developed color area of each heat generating area is increased and decreased, the developed color density of the character or figure printed by this method changes and, therefore, gradation recording is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal print head for gradation recording.

(Prior Art) As is well known, in a conventional thermal print head, each heating dot made of a resistive heating element has a square or rectangular planar shape. When printing with heat generating dots having such a shape, the shape of the colored dots will be approximately the same as the heat generating dots. By the way, in order to perform gradation recording using such a thermal print head, it is only necessary to change the color density, and to do so, it is necessary to adjust the applied power, but the thermal paper does not rise to a certain temperature. Therefore, it is extremely difficult to adjust the color density by applying electric power.

(Problems to be Solved by the Invention) This invention changes the heating area of each heating dot by adjusting the power applied to each heating dot, thereby increasing the appearance of each coloring dot. The purpose is to adjust the color density of the color.

Means for Solving Problem C) This invention provides that when a heating dot is configured with electrodes for applying power installed at both ends thereof, along the width direction of the heating dot,
The present invention is characterized in that the distances between the electrodes are unequal.

With this configuration, for example, when low power is applied, the shortest distance between the electrodes generates heat due to its low resistance. Furthermore, if the applied power is made larger than this, heat will be generated even in the portion of the distance between the electrodes that is longer than the shortest distance. In other words, the heat generating area of one heat generating dot is adjusted by increasing or decreasing the applied power.

In general, the size of this kind of heat-generating dots is such that the arrangement density is, for example, 6 to 8 dots/m.

Since it is about 100μ x 100μ, when drawing letters, figures, etc. by coloring thermal paper with such heat-generating dots, one colored dot produced by one heat-generating dot is only one point or less when forming letters, etc. do not have.

Therefore, if the coloring area of one coloring dot is changed by changing the heating area of one heating dot using heating dots whose heating area can be adjusted as described above, the density of the letters, figures, etc. can be adjusted. Kake will now be changed upwards. Therefore, by increasing or decreasing the applied power, printing with different densities, that is, gradation recording becomes possible.

This invention will be explained using figures. In Figure 1, 1 is an insulating substrate such as ceramic, 2 is a heating dot,
A plurality of them are arranged in a straight line. Reference numeral 3 designates an electrode that is commonly installed at one end of each heating dot 1, and electrode 4 is installed individually at the other end. If power is applied between the electrode 3 and any selected electrode 4, the heating dots connected to the electrode 4 will generate heat. This is not particularly different from ordinary heating dots of this type.

According to this invention, the shape of 1 heating dot 2 is 1.
The structure is such that the distance between the electrodes at both ends is unequal along the width direction of the heating dot 2. In the example of FIG. 1, as shown in an enlarged view in FIG. 2, the ends of the heating dots 2 are formed into a mountain shape.

(Function) By doing this, when electric power is applied between the electrodes 3 and 4, the resistance value is the smallest in the part where the distance between the electrodes 3 and 4 is the shortest, so the current is concentrated in this part. As the water flows, the area around it starts to generate heat. FIG. 3 shows the state of heat generation, and 2A indicates the heat generation portion. Now, if the applied power is increased more than before, the range through which the current flows becomes wider, and thereby the region where heat is generated becomes even wider, as shown in FIG. 4.

2B shows the heat generating part at that time.

By increasing and decreasing the power applied between the electrodes in this way, 1
The heating area of the heating dots will increase or decrease. Therefore, if the heat-sensitive paper is colored with these heat-generating dots, the coloring area can be changed. By increasing or decreasing the coloring area of each coloring dot, the coloring density of printed characters, figures, etc. can be changed, thereby making gradation recording possible.

The heating dots shown in FIGS. 1 and 2 have a chevron-shaped end, but instead of this, one end of the heating dot 2 may be sloped as shown in FIG. Alternatively, as shown in FIG. 6, both ends may be formed to be inclined in opposite directions. In the case of Figure 2, heat is generated from the center of the heating dot, whereas in the cases of Figures 5 and 6, heat is generated from the edge side where the distance between the electrodes is narrow.
It becomes like this.

Furthermore, as shown in FIG. 7, one or both of the ends (in the example shown, both) of the heating dot may be formed into an arc shape. In this case, since there is a narrow part between the electrodes on both edges, color develops from both edges at the same time.

In the above examples, a head in which heating dots are arranged in a straight line has been described, but the present invention is not limited to this, and the present invention can also be applied to a heating dot in which one heating dot is arranged in multiple rows and columns. It goes without saying that it is applicable.

(Effects of the Invention) As detailed above, according to the present invention, the heating area of one coloring dot by one heating dot can be increased or decreased depending on the electric power applied to it, and therefore, the heating area can be increased or decreased by the increase or decrease in this heating area. It is possible to change the color density of the appearance of printed characters, figures, etc., and this has the effect that gradation recording can be made extremely easily by adjusting the printing force.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the invention, and Fig. 2 is a plan view showing an embodiment of the invention.
FIGS. 3 and 4 are partially enlarged plan views showing heat generating parts, and FIGS. 5 to 7 are partially enlarged plan views showing other embodiments. 2... Heat generating dot, 3, 4... Electrode Figure 2 Figure 3
Figure 4 Figure 5 Figure 6 Figure 11

Claims (1)

[Claims] Electrodes for applying heating power that is adjusted depending on the gradation are installed at both ends of the heating dots, and the distance between the electrodes of the heating dots is varied along the width direction of the heating dots. A thermal print head for gradation recording.