JPH0281646A - Thermal head - Google Patents

Abstract

PURPOSE:To record a sharp medium contrast image without generating the deterioration of image quality largely by forming two or more kinds of heating resistors made different in a heat value or resistance value so that said resistors are respectively arranged in a combination arrangement predetermined at every predetermined arrangement unit. CONSTITUTION:The dot recorded by a heating resistor 11a is larger than the dot recorded by a heating resistor 10a. The same result is also obtained with respect to heating resistors 10b-10n and 11b-11n. That is, a thermal head constitutes a 2X1 matrix preliminarily and the sizes of the dots recorded at every pixel in the matrix are different and the driving part of this thermal head performs the control of driving using the matrix as one unit. Therefore, when dummy gradation recording is performed by this thermal head using the 2X1 matrix, three gradations and four gradations of 'dot-less' can be expressed. By this method, many gradations can be expressed by using a reduced number of dots and a medium contrast image can be recorded without lowering the resolving power too much.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal head used, for example, in a thermal recording device.

(Prior Art) FIG. 3 is a diagram showing a general configuration of a conventional thermal head. This thermal head has a plurality of rectangular heating resistors 28 to 2n having the same resistance value arranged in parallel at regular intervals on an insulating substrate 1 made of, for example, ceramics or alumina, and these heating resistors 2a. First lead electrodes 3a to 3n and second lead electrodes 4a to 4n having the same width as the heating resistors 2a to 2n and rectangular shapes are provided at both ends of the heating resistors 2a to 2n.
are provided one on top of the other. In addition, 5a to 5n
and 6a to 6n are the first and second lead electrodes 3
The first and second connected to a to 3n and 4a to 4n
This is an external terminal.

According to such a thermal head, dot printing can be performed by driving the heating resistors 2a to 2n with electricity through the first and second external terminals 5a to 5n and 6a to 6n.

Nowadays, there are many opportunities to record images with gradations (halftone images), such as photographs, using thermal recording devices and the like. This halftone image is recorded by the above-mentioned thermal head by changing the voltage applied to each of the heating resistors 2a to 2n depending on the brightness and darkness of the dots to be recorded. However, in this method, each of the plurality of heating resistors 2a to 2n must be driven and controlled, which increases the circuit scale and makes the control difficult. These are miniaturized devices.

This becomes an impediment to lower prices.

Therefore, when recording a halftone image using the above-mentioned thermal head, a dither method or the like is used, for example, to express the halftone in a pseudo manner. However, this pseudo-halftone expression method is a method of obtaining pseudo-gradations by devising the dot distribution per pixel. For example, in the dither method, n dots are required to obtain n gradations, and the resolution is extremely high. There is a problem that the value decreases.

(Problems to be Solved by the Invention) As mentioned above, conventional thermal heads are formed by arranging a plurality of heating resistors with the same resistance value, There was a problem in that the image quality deteriorated drastically when the tone expression method was used.

The present invention has been made in consideration of these circumstances, and its purpose is to solve the problem that even if recording is performed using a pseudo-halftone expression method to record a halftone image, a large deterioration in image quality occurs. To provide a thermal head capable of recording a clear halftone image without any trouble.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for arranging a plurality of types of heating resistors having different heat generation amounts or resistance values in a predetermined combination arrangement for each predetermined arrangement unit. I tried to form it.

(Function) By taking such a measure, heating resistors having different resistance values generate different amounts of heat when the same voltage is applied, so that the sizes of recorded dots differ. Therefore, when recording is performed using the pseudo halftone expression method, the same number of gradations can be expressed with fewer dots than with conventional thermal heads.

(Embodiment) Hereinafter, a thermal head according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1(a) is a diagram showing the configuration of the thermal head. The same parts as in Fig. 1(a) are given the same reference numerals.
A detailed explanation thereof will be omitted.

This thermal head has two types of heating resistors 10a to 10n (resistance value -XΩ) and lla to 11 having different resistance values.
n (resistance value - YΩ, here the relationship is set to [X>Y]) are arranged alternately. Here, the heating resistors 10a and 11a, 10b and 11b.=, and 10n and lin each form one array unit. Lead electrodes 12a-12n and 14a-14n are provided on both ends of each heating resistor 108-1on, respectively, and lead electrodes 13a-13n and 15a-15n are provided on both ends of each heating resistor 118-11n. are provided one on top of the other. Furthermore, lead electrodes 12a~
12n, lead electrodes 13a13a to 13n, lead electrodes 14a to 14n, and lead electrodes 15a to 15n, respectively, have external terminals 16a, 16Ω, external terminals 17a to 17n,
External terminals 18a to 18n and external terminals 19a to 19n are connected, respectively. Note that the heating resistors 11a to ll
n and the heating resistors 12a to 12n are set to different resistance values by changing the film thickness or material.

In the thermal head constructed as described above, when a voltage is applied to the heating resistor 10a but no voltage is applied to the heating resistor 11a, dots as shown in FIG. 1(b) are recorded, for example. Furthermore, if a voltage is applied to the heating resistor 11a without applying a voltage to the heating resistor 10a, for example, the first
Dots as shown in Figure (c) are recorded. As can be seen by comparing FIG. 1(b) and FIG. 1(c), the resistance value X of the heating resistor 10a is greater than the resistance value Y of the heating resistor 11a, so the same type and pressure When applied, the current flowing through the heating resistor 11a is higher than that flowing through the heating resistor 10a.
is larger. Therefore, the dots recorded by the heating resistor 11a shown in FIG. 1(c) are larger than the dots recorded by the heating resistor 10a shown in FIG. 1(b). Then, the heating resistor 10a and the heating resistor 11
When a voltage is applied to both a and a, for example, dots as shown in FIG. 1(d) are recorded. Note that the heating resistor 10b~
The same applies to Ion and the heating resistors 11b to 11n.

That is, this thermal head has a 2.times.1 matrix configured in advance, and the size of the dot recorded is different for each pixel in this matrix. The driving section (not shown) of this thermal head controls the driving of the matrix as one unit. Therefore, when performing pseudo gradation recording using a 2×1 matrix, this thermal head records three gradations shown in FIGS. Can express the tone. On the other hand, the third
If recording is performed using the dither method using a 2×1 matrix with the conventional thermal head shown in the figure, for example, a 4×4 matrix (16 dots) is required when expressed using the dither method with the conventional thermal head. On the other hand, with the present thermal head, for example, a 2×3 matrix (6 dots) is sufficient.

As described above, according to this embodiment, many gradations can be expressed with a small number of dots, and a halftone image can be recorded without significantly reducing the resolution.

FIG. 2 is a diagram showing the configuration of a thermal head according to another embodiment of the present invention. Note that the same parts as in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

Here, this thermal head has heating resistors 20 with different widths.
By alternately arranging a to 2On and 21a to 21n, the resistance value is made different from that of the adjacent heating resistors.

However, according to this embodiment, it is possible to obtain effects completely similar to those of the previously described embodiment.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, two types of heat generating resistors having different resistance values are alternately arrayed, but heat generating resistors having three or more types of resistance values may be arrayed. Further, the arrangement order of the heat generating resistors is not limited to being arranged alternately, and may be further arranged two-dimensionally. Furthermore, the shape of the heating resistor is not limited to a rectangle, and may be any other shape. other than this. Various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] According to the present invention, a plurality of types of heating resistors having different heat generation amounts or resistance values are arranged in a predetermined combination arrangement for each predetermined arrangement unit. The same number of gradations can be expressed with fewer dots than the conventional halftone recording using the dither method, and therefore a decrease in resolution can be suppressed.

[Brief explanation of the drawing]

FIG. 1(a) to FIG. 1(d) are diagrams explaining a thermal head according to an embodiment of the present invention, FIG. 1(a) is a diagram showing the configuration, and FIG. 1(b) to FIG. FIG. 1(d) is a diagram showing an example of recorded dots, FIG. 2 is a diagram showing the configuration of a thermal head according to another embodiment of the present invention, and FIG. 3 is a diagram showing the configuration of a conventional thermal head. It is a diagram. 10a~1on, 20a~2On...heating resistor, 1
1a to lln, 21a to 21n... heating resistors. Applicant's agent Patent attorney Takehiko Suzue i2 diagram

Claims (2)

[Claims] (1) A thermal head characterized in that a plurality of types of heat generating resistors having different amounts of heat are arranged in a predetermined combination arrangement for each predetermined arrangement unit. (2) A thermal head characterized in that a plurality of types of heating resistors having different resistance values are arranged in a predetermined combination arrangement for each predetermined arrangement unit.