JPH11115232A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fine dot stably. SOLUTION: This thermal head 21 comprises at least a pair of electrodes 23 to which an identical driving voltage is applied and a resistor body 27a provided between the pair of electrodes 23 to be connected thereto. The resistor body 27a is divided into a plurality of resistor elements. The area of one resistor element of the resistor body 27a is greater than that of the other resistor element, then the resistance value of one resistor element of the resistor body 27a is less than that of the other resistor element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film head and a thick-film head type thermal head mounted on a thermal printer, and more particularly to a thermal head for generating heat at a plurality of heating portions by the same driving voltage. is there.

[0002]

2. Description of the Related Art A thermal head for a thermal printer includes a thin-film head and a thick-film head having different heat-generating portions, and the thin-film head further includes a slit head provided with a slit in the heat-generating portion.

A general thin film head 1 shown in FIG.
A resistor (heater) 5 is provided between a plurality of pairs of electrodes 3 opposed to each other in units of one dot. Therefore, by applying a voltage to the predetermined resistor 5 through the selected pair of electrodes 3, the resistor 5 can generate heat as one dot.

Further, a slit head 7 shown in FIG.
Is between a plurality of pairs of electrodes 3 opposed to each other in units of one dot.
A divided resistor 5a divided into two equal parts by a slit 9 is provided,
The pair of electrodes 3 are connected in parallel. Therefore, by applying a voltage to the selected pair of electrodes 3, it is possible to simultaneously generate heat from the pair of divided resistors 5a by one driving power supply.

On the other hand, the thick film head 11 shown in FIG.
Arranges a plurality of parallel common electrodes 13 at equal intervals on the same plane, and at a central position between adjacent left and right common electrodes 13,
An individual electrode 15 that is substantially parallel to the common electrode 13 is arranged to face each other, and a linear resistor 17 is connected across the common electrode 13 and the individual electrode 15. Therefore, by applying a voltage to the selected individual electrode 15, this individual electrode 1
The resistor portion 7a between the common electrode 13 and the common electrode 13 adjacent to the left and right can generate heat as one dot.

[0006]

In FIG. 8 (c),
There are two lines of the printable limit value th in the case where the threshold for dot formation has fluctuated due to some disturbance. FIG. 8B shows an example of dot formation in that case. A white circle indicates a case where the printable limit value th becomes low and a printable limit value th becomes low. Therefore, it is preferable that the difference between the white circle and the black circle is small.

However, the conventional thermal head described above, when printing a large dot having a dot percentage of 30%, as shown in FIGS.
As shown in FIGS. 6 to 8C, each resistor generates heat equal to or higher than the printable limit value th, so that printing is performed reliably. However, for example, when the dot percentage is 5%, 10%
When printing a fine dot of%, the driving voltage is lowered and the heat generation amount fluctuates near the printable limit value th, so that the dot formation becomes unstable. Further, when the driving voltage decreases and the resistor generates heat at the lower limit of the fluctuation range, the heat generation amount does not reach the printable limit value, and when the dot percentage in FIGS. 6B and 8B is 10%, and As shown in FIG. 7B when the dot percentage is 5%, dots may not be formed.

[0008] When such dot missing occurs, the printed image becomes rough, and the image quality is degraded.

In order to solve such a problem, for example, as shown in FIG.
There is a thermal head of the slit head type in which the number of dots is increased by providing a. However, since the electric characteristics of the divided resistors 5a are the same, the voltages of the divided resistors are similarly set near the printable limit value th. Due to the fluctuation, fine dots cannot be stably formed yet.

The present invention has been made in view of the above circumstances, and has as its object to obtain a thermal head capable of stably forming fine dots.

[0011]

A thermal head according to the present invention includes at least a pair of electrodes to which the same drive voltage is applied, and a resistor connected between the pair of electrodes. One or both of the electrode and the resistor are substantially divided, and one of the divided resistors has a lower resistance value than one of the other resistors.

This thermal head includes a pair of electrodes to which the same drive voltage is applied, and a resistor connecting between the electrodes. At least one of the plurality of divided resistors is replaced with another resistor. Since the resistance value is lower than that of the resistor, when printing fine dots, even if the driving voltage drops and the amount of heat generated fluctuates near the printable limit value, the other resistor is connected to the resistor with the smaller resistance value. Larger current flows than the body,
The heat energy that has been equally distributed in the past concentrates on one resistor, and the heat generated by one resistor always reaches the printable limit value, and a dot is formed.

In the thermal head having the above-mentioned structure, a low resistance value is realized by making a substantial width of at least one of the substantially divided resistors larger than a width of the other resistors. can do.

Further, the thermal head according to the present invention is characterized in that the parallel common electrodes are arranged in the same direction on the same plane, and the common electrodes are arranged between the common electrodes substantially in parallel with the common electrodes and are adjacent to the left and right. An individual electrode approaching any one of the common electrode and the individual electrode, and a strip-shaped resistor having a uniform width connected to one surface of the common electrode and the individual electrode in a direction substantially orthogonal to the common electrode. One of the plurality of divided resistors has a lower resistance value than one of the other resistors.

In this thermal head, an individual electrode is provided so as to approach one of the left and right common electrodes, and one of the resistors sandwiched between the individual electrode and the left and right common electrodes is provided. Since the resistance value of the resistor part is smaller than the other resistance value, when printing fine dots, the driving voltage drops, and even if the heat generation value fluctuates near the printable limit value, the resistance value A larger current flows through the smaller resistor part than the other resistor part, and the heat energy previously divided equally is concentrated on one resistor part, and the heat generated by one resistor always reaches the printable limit value. And the dots will be formed.

In the thermal head having the above-mentioned structure, at least one of the resistors divided into a plurality of resistors is made substantially shorter than the other resistors to reduce a low resistance value. Can be realized.

The structure of the thermal printer according to the present invention is as follows.
The thermal head having the above configuration is provided, and printing is performed by forming dots on recording paper by causing the resistor of the thermal head to generate heat. In this thermal printer, the thermal head having the above-described configuration is provided, and a dot is formed on recording paper by performing heating of the resistor of the thermal head to perform printing.
Even if the calorific value fluctuates near the printable limit, dots can always be formed with one resistor,
High-quality printing without roughness is possible.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a thermal head according to an embodiment of the present invention. FIG. 1 is an explanatory diagram showing the configuration (a), dot size (b), and resistor temperature distribution (c) for each dot percentage of the thermal head according to the first embodiment of the present invention, and FIG. FIG. 3 is an explanatory view showing a modification of the electrode and the resistor of the thermal head, and FIG. 3 is an explanatory view showing another modification of the electrode and the resistor of the thermal head of FIG.

In this embodiment, a case where the thermal head is a thin film head type will be described as an example. In the thermal head 21 of this embodiment, a plurality of pairs of electrodes 23 are arranged to face each other in units of one dot, and the same drive voltage is applied to each pair of electrodes 23.

Each opposing portion 23a of the pair of electrodes 23
Between them, divided resistors 27a divided by slits 25 are connected in parallel. The divided resistor 27a is formed to have a uniform thickness and a uniform resistance value in the thickness direction at an arbitrary position in the surface direction. That is,
The resistance value of the split resistor 27a is inversely proportional to its surface area. The split resistor 27a is
Is divided unequally, so that one divided resistor 2
7a (right) has a lower resistance value than the other divided resistor 27a (left).

In the thermal head 21 configured as described above, when printing a fine dot having a dot percentage of, for example, 5%, the driving voltage is reduced and the heat generation is reduced to the printable limit value t.
h, even though the resistance fluctuates in the vicinity of h, a larger current flows through the divided resistor 27a having a smaller resistance value than the other divided resistor 27a, and the heat energy which has been equally divided in the past is divided into one divided resistor 27a. As shown in the case of the dot percentage of 5% in FIG. 1C, the heating value of one of the divided resistors 27a always reaches the printable limit value, and a dot is formed.

In this example, for example, when the dot percentage is 10%, the divided resistor 27a having the larger resistance value is used.
Although the heat generation amount does not reach the printable limit value, the heat generation amount of the other divided resistor 27a is sufficiently ensured, and a large dot is formed to make the roughness less noticeable.

As described above, according to the thermal head 21 described above, the divided resistors 27a unequally divided by the slits 25 are provided in parallel between the pair of electrodes 23, and the divided resistors 27a are provided in parallel. Is smaller than the other resistance value, so that the calorific value is smaller than the printable limit value th.
Even when printing a fine dot that fluctuates in the vicinity of, the heat generation energy can be concentrated on the divided resistor 27a having a small resistance value so that the heat generated by one of the divided resistors 27a can be always equal to or larger than the printable limit value. . As a result, dots are always formed, and roughness of a printed image can be prevented to improve image quality.

As described above, the thermal head 21 concentrates heat energy, which has been conventionally equally supplied to a plurality of heat generating portions of the resistor, to one heat generating portion, and generates heat of one of the heat generating portions. Since the energy is set to be equal to or higher than the printable limit value, the configuration need not be limited to the above-described configuration as long as such an action is generated.

That is, as a modified example of the thermal head 21 having the same operation and effect as described above, as shown in FIG. 2 (a), a split resistor 27a is divided by a slit 25a bent in a crank shape. As shown in FIG. 2B, a slit 25 is formed between one of the opposing electrodes 23 and the resistor 27b to divide the electrode 23 and the resistor 27b unequally, and FIG. As shown in FIG.
2A and 2B, the slits 25 for dividing the resistor 27c are inserted into both of them, and the two electrodes 23 are unequally branched.
As shown in FIG. 2 (e), a cutout portion 29a having a closed contour is provided at a position other than the center of the resistor 27d to make the heating area in the surface direction of the resistor 27d non-uniform. The body 27e and the electrode 23 divided unequally,
As shown in FIGS. 2F and 2G, the arc-shaped slit 25b
It is conceivable that the dividing resistors 27f and 27g are divided by the above.

Further, in the above-described thermal head 21, the resistor provided between the pair of electrodes 23 is divided or cut out by the slit 25 and the cutout portion 29a. As a modified example of the thermal head 21 that plays, as shown in FIG.
7e is not divided, and only the electrode 23 may be unequally branched by the slit 31 to divide the facing portion 23a. In this case, the resistor 27e in the facing portion 23a
And the connection cross-sectional area is different. As a result, in the same manner as described above, the heat generation energy can be concentrated on one heat generation portion of the resistor, and the heat generation energy of this heat generation portion can be increased to a printable limit value or more.

Next, a thermal head according to a second embodiment of the present invention will be described. FIG. 4 shows the configuration (a) and the dot size (b) of the thermal head according to the second embodiment of the present invention, and the resistor temperature distribution for each dot percentage (c).
FIG. In this embodiment, a case where the thermal head is a thick film head type will be described as an example.

In the thermal head 41 of this embodiment, parallel strip-shaped common electrodes 43 arranged in the same direction are arranged on the same plane. Between the common electrodes 43, individual electrodes 45 arranged substantially parallel to the common electrode 43 and approaching one of the common electrodes 43 adjacent to the left and right are arranged facing each other. On one surface of the common electrode 43 and the individual electrode 45, a band-shaped resistor 47 having a uniform width, which intersects the common electrode 43 and the individual electrode 45 in a substantially orthogonal direction and is connected to the common electrode 43 and the individual electrode 45, is provided. It is provided.

Therefore, by applying a voltage to the selected individual electrode 45, the thermal head 41 causes the resistor portion 47a between the individual electrode 45 and the adjacent common electrode 43 to generate heat as one dot. be able to.

In the thermal head 41 configured as described above, when printing a fine dot whose halftone dot percentage is, for example, 5%, the driving voltage is reduced and the heat generation is reduced to the printable limit value t.
Even if the value f changes in the vicinity of h, a larger current flows through the resistor portion 47a having a smaller resistance value than the other resistor portion 47a, and the heat energy which has been equally divided in the prior art is reduced to the one resistor portion 47a. As shown in the case of the dot percentage of 5% in FIG. 4C, the heating value of one resistor portion 47a always reaches the printable limit value, and a dot is formed. .

In this example, for example, when the dot percentage is 10%, the resistor portion 47a having the larger resistance value is used.
Although the dot size becomes smaller, the dot size of the other divided resistor 27a becomes sufficiently large and the roughness becomes less noticeable.

As described above, according to the above-described thermal head 41, the individual electrode 45 is disposed so as to approach one of the common electrodes 43 adjacent to the left and right. The resistance value of one of the resistor portions 47a of the resistor 47 sandwiched between them is smaller than the other resistance value, so that when printing a fine dot whose calorific value fluctuates near the printable limit value th. Also, heat energy is concentrated on the resistor portion 47a having a small resistance value,
The amount of heat generated by one of the resistor portions 47a can always be equal to or larger than the printable limit value. As a result, dots are always formed, and roughness of a printed image can be prevented to improve image quality.

[0033]

Next, a description will be given of the results of actually manufacturing a thermal head based on the above-described embodiment, mounting the thermal head on a printing apparatus, performing printing, and comparing printing unevenness with a conventional thermal head. . The printing and evaluation conditions are shown below.

<Printing Apparatus> A FIRST PROOF printer manufactured by Fuji Photo Film Co., Ltd. is used. <Materials> Fuji Photo Film Co., Ltd. ・ FIRST PROOF proof ribbon J ・ Uses the same receiver sheet A3WL.

<Evaluation Method> A conventional thin film head, a conventional equally divided slit head, and an unequally divided slit head manufactured based on the above-described embodiment and having an area ratio of 3: 7 are mounted on a printing apparatus, respectively. A tone patch was printed. X-rit
The halftone percent of each patch was measured by e938, and the degree of roughness of each patch was visually evaluated. The results are shown in Table 1 as “out of acceptable range”, “in acceptable range”, and “good”.

[0036]

[Table 1]

As is clear from the results shown in Table 1 above, the dot percentage of the conventional thin film head is 5%, 10%.
%, The sample is not good even at 20%, and the dot percentage of the slit head is 5%, which is unacceptable.
%, Whereas the thermal head of the example had good dot percentages of 10%, 20%, and 30%, and was satisfactory even at 5%.

Further, the uneven slit ratio was changed, and the degree of roughness of each patch was evaluated by visual observation.
It was shown to.

[0039]

[Table 2]

As is clear from the results shown in Table 2 above, the preferred area ratio of the unequal slit is 10:90 to 4
It turns out that it is 5:55.

Although the above example shows the case where the resistor is divided into two by one slit, the resistor may be divided into three by two slits as shown in FIG. That is, as such a modification, FIG.
As shown in (a) and (b), two slits 25, 25
5c, the resistor 27g is divided into two by the slit 25 as shown in FIG. 5C, and the resistor 27g is cut out by the cutout portion 29b.

In the above example, the area is changed in order to make a difference in the resistance value. However, the resistance value may be changed by other means such as thickness and material.

In the thermal heads 21 and 41 according to the above-described embodiments, the case of a thermal head for heating a resistor has been described as an example. However, the configuration of the thermal head according to the present invention is different from that for heating a resistor. The present invention can also be applied to a printing method, for example, a printing method such as an LED print head. Also in this case, by connecting a plurality of LEDs having substantially different resistance values to the common electrode, the luminous energy, which has been conventionally equally divided, is concentrated on a part of the luminous energy. The effect of enabling only the part to emit light can be obtained.

[0044]

As described above, according to the thermal head of the first or third aspect of the present invention, a pair of electrodes to which the same drive voltage is applied and a resistor for connecting the electrodes to each other. And at least one of the plurality of divided resistors has a lower resistance value than the other resistors. The calorific value of the body can be equal to or higher than the printable limit value. As a result, dots are always formed, and roughness of a printed image can be prevented to improve image quality.

According to the thermal head of the second or fourth aspect, the individual electrode is disposed so as to approach one of the common electrodes adjacent to the left and right, and the individual electrode is disposed between the individual electrode and the left and right common electrodes. Since the resistance value of one of the interposed resistors is smaller than that of the other, the heat is concentrated on the resistor with the smaller resistance, and the heat value of this resistor is printed. It can be higher than the possible limit. As a result, dots are always formed,
The image quality can be improved by preventing the roughness of the printed image.

According to the thermal printer of the present invention,
A thermal head according to claim 1 or 2,
Since printing is performed by forming dots on the recording paper by causing the resistor of the thermal head to generate heat, it is possible to perform high-quality printing without roughness. It should be noted that since the drive circuit can be completely the same as the conventional head, the head cost does not increase.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration (a) and a dot size (b) of a thermal head according to a first embodiment of the present invention and a resistor temperature distribution (c) for each dot percentage.

FIG. 2 is an explanatory view showing a modification of the electrodes and resistors of the thermal head of FIG. 1;

FIG. 3 is an explanatory view showing another modification of the electrodes and resistors of the thermal head of FIG. 1;

FIG. 4 is an explanatory view showing a configuration (a) and a dot size (b) of a thermal head according to a second embodiment of the present invention, and a resistor temperature distribution (c) for each dot percentage.

FIG. 5 is an explanatory diagram showing a configuration example of a thermal head having three or more divisions.

FIG. 6 is an explanatory diagram showing a configuration (a) and a dot size (b) of a conventional thin film head and a resistor temperature distribution (c) for each dot percentage.

FIG. 7 is an explanatory diagram showing a configuration (a) and a dot size (b) of a conventional slit head and a resistor temperature distribution (c) for each dot percentage.

FIG. 8 is an explanatory diagram showing a configuration (a) and a dot size (b) of a conventional thick film head and a resistor temperature distribution (c) for each dot percentage.

[Explanation of symbols]

 21, 41 Thermal head 23 Electrode 27a, 47 Resistor 43 Common electrode 45 Individual electrode

Claims (5)

[Claims] 1. A semiconductor device comprising: at least one pair of electrodes to which the same drive voltage is applied; and a resistor connected between the pair of electrodes, wherein one of the electrode and the resistor is provided. A thermal head, wherein both are substantially divided, and one of the divided resistors has a lower resistance value than one of the other resistors. 2. A common electrode which is arranged in the same direction on the same plane and which is parallel to the common electrode, and which is arranged substantially in parallel with the common electrode and approaches one of the common electrodes adjacent to the left and right. An electrode, comprising a band-shaped resistor having a uniform width and intersecting the common electrode and the individual electrode in a substantially orthogonal direction and connected to the one surface of the common electrode and the individual electrode; A thermal head, wherein one of the resistors has a lower resistance value than one of the other resistors. 3. The thermal device according to claim 1, wherein a low resistance value is realized by making a substantial width of at least one of the plurality of substantially divided resistors larger than a width of another resistor. head. 4. The low resistance value according to claim 2, wherein a substantial resistance of at least one of the plurality of substantially divided resistors is made shorter than a length of the other resistors. Thermal head. 5. A thermal printer comprising the thermal head according to claim 1 or 2, wherein the resistor is heated to form dots on recording paper to perform printing. .