JPH05124239A - Preparation of thermal head - Google Patents

Abstract

PURPOSE:To ensure electric and physical strength by controlling distribution of heat generation without needing fine processing of a heat generating resistor. CONSTITUTION:A required distribution of heat generation is obtd. by irradiating a required part 52 and 52' of the heat generating resistor 5 formed on an insulating substrate 1 with a laser light with such a power that can decrease the value of resistance and thereby controlling partially the value of resistance of the heat generating body 5. It is therefore possible to control the distribution of heat generation without especially performing fine processing and using a complex process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thermal head used in a recording device such as a thermal printer or a facsimile as an output device of a word processor, a personal computer or the like.

[0002]

2. Description of the Related Art Thermal heads are widely used because they have advantages such as low noise during printing and easy handling because they do not require a developing / fixing process. Figure 2
Reference numeral 0 is a perspective view of a main part of a conventional thermal head, showing a broken-away perspective view, showing a common electrode 3 and an individual electrode 4 on an insulating substrate 1 having a glaze layer 2 deposited thereon. A heating resistor 5 that forms a unit heating portion is formed by bridging 3 and the individual electrode 4. This type of thermal head is called an individual-separation type thermal head, and the size of the unit heating portion constituted by the heating resistor 5 is generally one dot for printing.

A wear resistant layer 6 is deposited on the heating resistor 5, the common electrode 3 and the individual electrode 4, and the recording medium comes into contact with the wear resistant layer 6. In such a thermal head, heat is generated by connecting the plurality of individual electrodes 4 arranged in a row on the glaze layer 2 of the insulating substrate 1 and the common electrode 3 arranged corresponding to the tips of the individual electrodes 4 to each other. A heating current is applied to the resistor 5 via the individual electrode 4 and the common electrode 3 selected by the print information, and the heating resistor 5 is heated to perform thermal recording (printing). ing. The print quality depends on the shape and heat distribution of the heating resistor.

Usually, the heat generating resistor constituting the unit heat generating portion of this type of thermal head has a rectangular shape, and the heat distribution is uniform over the entire surface thereof and generally has no heat generating spot. Instead of the individual separation type heating resistor as described above, a large number of individual electrode groups and common electrode groups are arranged in one direction, and band-shaped heating resistors are formed so as to cross these electrode groups. An electrode type thermal head is also known. In this type of thermal head, one heating element dot (printing dot) is printed by using a heating resistor portion defined by one individual electrode and common electrodes arranged on both sides thereof as a unit heating portion.

On the other hand, in recent years, thermal printers have been improved in image quality, and in particular, in order to realize halftone (multi-tone) printing without deteriorating image quality, so-called gradation is obtained by the area of print dots. A thermal head capable of printing with a dot tone has been proposed. A sublimation type thermal transfer method is known as a printer that realizes dot gradation, but if it is controlled by a method that changes the width of the heating current pulse that applies the printing dot area using a heat concentration type heating resistor The dot gradation is also possible by the fusion type thermal transfer system and the direct thermal system.

In the sublimation type thermal transfer system, it is also known that halftone printing is performed by adjusting the density of each dot. In this method, the transfer amount of the sublimation dye from the ink donor film (IDF) holding the sublimation dye layer is adjusted by the pulse width. in this case,
Unlike the type that adjusts the size of each dot,
If the size of 1 dot is constant regardless of the pulse width,
Better image quality can be obtained. Therefore, it is possible to obtain better printing quality by using a heat dispersion type heating resistor as the resistor of the sublimation transfer type thermal head.

When the heating energy, that is, the heating current is applied to the thermal head, the above-mentioned heat-concentration type heating resistor is perpendicular to the current direction (in the individual separation type thermal head, the main scanning direction is alternated with the main scanning direction). In the type electrode type thermal head, the direction perpendicular to the main scanning direction, hereinafter referred to as the sub-scanning direction), and the current direction (the main scanning direction in the individual facing type thermal head, the sub-scanning direction in the alternating electrode type thermal head). Or a heating resistor having a heating spot in the center of both.

The heat dispersion type heating resistor means a heating resistor which has a uniform heat distribution over the entire unit heating resistor portion when heating energy, that is, a heating current is applied to the thermal head. FIG. 21 is an explanatory diagram of a heat generation distribution of a conventional thermal head having a normal rectangular heating resistor, in which a predetermined voltage is applied to the rectangular heating resistor forming the unit heating portion and the driving current is gradually increased. (Heating current) When the heating energy is increased by increasing the pulse width, the heat generation distribution curve of the heat generating resistor rises as →→ in the figure.

As shown, the temperature distribution curve has a flat top. And the width d of the flat region
The width of the portion ₂ does not change much depending on the width of the driving current pulse, that is, the heating energy. 21. Assuming that the color development temperature of the thermal paper which is the recording medium or the temperature at which the color material of the ink donor film begins to melt is T _O , FIG.
When the heating energy of 1 is reached, the thermal paper starts to develop color (or the coloring material starts to melt) and print dots start to be formed. At this time, the print dot width is the width shown by d ₂ in the figure, but even if heating energy is applied, the dot width is d ₃
Since it is nothing but gradation, almost no gradation can be obtained. Further, the print dots shown in the figure are very unstable, and the printed result lacks sharpness.

FIG. 22 is an explanatory diagram of heat generation distribution in the case of a heat concentration type heat generating resistor having a heat generating spot at the center of the heat generating resistor constituting the above-mentioned unit heat generating portion.
In this case, as the heating energy is increased, the heat generation distribution curve gradually rises as →→, but the temperature distribution curve does not have a flat top, so the print dot width is d ₁ → d ₂ → d It gradually becomes ₃ and wider. That is, by using a thermal head having a heating spot at the center of the heating resistor, it is possible to control heating energy and perform multi-gradation printing.

The prior art relating to the above heat concentration type heat generating resistor is disclosed, for example, in JP-A-60-58877 and JP-A-6-58877.
No. 0-58876, JP-A-60-184858, or JP-A-60-78768. These thermal heads are formed by microfabrication of the heating resistor into a shape other than rectangular,
Alternatively, it is realized by shortening the heating resistor size.

Further, as described with reference to FIG. 21, in a thermal head having a normal rectangular heating resistor, a predetermined voltage is applied to the rectangular heating resistor to gradually increase the width of the drive pulse. As the heating energy is increased by increasing the heating energy, the heat distribution curve of the heating resistor rises as →→ in the figure. In this case, since the temperature distribution curve has a relatively flat top, the change in dot size due to the pulse width is smaller than that in the case of the heat concentration type resistor, but it is slightly changed. That is, assuming that the color development temperature of the thermal paper (or the temperature at which the color material starts to melt or sublime) is T ₀ , the thermal paper starts to develop color (or the color material starts to melt or sublime when the heating energy shown in FIG. 22 is reached). ), Print dots start to be formed. At this time, the print dot width is the size shown by d ₂ in the figure, but when the heating energy is set to, the dot width becomes the size shown by d ₃ in FIG.

Therefore, there has been proposed a method of stabilizing the print dot shape by reducing the difference between d ₂ and d ₃ . For example, in the thermal head described in JP-A-3-15563, the heat generating resistor is finely processed to make the heat distribution uniform. Also,
In the thermal head disclosed in Japanese Unexamined Patent Publication No. 64-22567, the heat generation distribution is made uniform by thinning the underglaze layer near the center of the heat generating resistor. As described above, the thermal heads disclosed in the above publications are intended to realize uniform heat generation distribution by finely processing the heat generating resistors or the vicinity thereof.

[0014]

In the above-mentioned prior art, in order to realize a heat concentration type thermal head,
The heating resistor forming the unit heating portion is finely processed into a shape other than a rectangle, or the resistor size is reduced.
For example, JP-A-60-58877, JP-A-60-
In Japanese Patent No. 184858, the width of the central portion of the heating resistor in the current direction is narrowed so that a heating spot is provided in the central portion of the heating resistor. In addition, JP-A-6
According to Japanese Patent Laid-Open No. 0-58876, the width of the heating resistor in the direction perpendicular to the current direction is narrowed so that the heating resistor has a heating spot at the center in the current direction.

The above-mentioned heat concentration type thermal heads are
Since a part or the whole of the width of the heating resistor in the direction perpendicular to the current direction is narrowed, there is a problem that electrical strength and physical strength are lower than those of a normal rectangular heating resistor. If the shape of the heating resistor is not uniform as described above, the resistance value variation and the printing dot variation are affected by the processing accuracy during microfabrication of the heating resistor, as compared with the normal rectangular heating resistor. There was a problem that was easy to occur.

Further, in the above-mentioned prior art, in order to realize a distributed type thermal head, the heating resistor or its periphery is finely processed. For example, JP-A-3-
In the device disclosed in Japanese Patent No. 15563, the electrical or physical strength is lower than that of an ordinary rectangular resistor. Further, in order to realize the thermal head disclosed in Japanese Patent Laid-Open No. 64-22567, there is a problem that its manufacturing process becomes complicated and difficult.

Therefore, the first object of the present invention is to reduce the electrical or physical strength of the rectangular rectangular heating resistor and to require a highly precise microfabrication as compared with the ordinary rectangular heating resistor. To obtain a thermal head having a heating resistor. A second object of the present invention is to obtain a thermal head provided with a heat dispersion type heating resistor without requiring a complicated manufacturing process and without requiring special fine processing precision.

[0018]

In order to achieve the above first object, the present invention irradiates a required portion of a heating resistor constituting a unit heating portion with laser light having a power that reduces the resistance value by irradiation. In this way, the resistance value of the heating resistor of the required portion is lower than the resistance value of the heating resistor of the other portion which does not irradiate the laser beam, and the heating resistor constituting the substantially rectangular unit heating portion is provided. According to this, a heat concentration type thermal head having a region (heat generation spot) having a partially high current density in the required portion at the time of heat generation of the heat generating resistor is obtained.

That is, according to the present invention, in a method of manufacturing a thermal head in which a heating resistor is formed on an insulating substrate, laser light having a power that reduces the resistance value by irradiation is formed after the heating resistor is formed. By irradiating the central portion of the unit heat generating portion formed of the heating resistor, a region having a low resistance value is formed in the central portion.

Further, after the heating resistor is formed, laser light having a power that reduces the resistance value by irradiation is irradiated over the whole area near the central portion in the current direction of the unit heating portion constituted by the heating resistor. A region having a low resistance value is formed in the entire region near the central portion in the current direction. Although the heating resistor has a rectangular shape, the present invention is not limited to this, and may be applied to a heating resistor having a shape other than the rectangular shape described in the publication disclosing the prior art, or The present invention is not limited to the individual-separation-type heating resistor, and the present invention is applied to an alternating-electrode-type thermal head in which common electrodes and individual electrodes are alternately arranged in the main scanning direction and a heating resistor is formed between these electrodes. As a result, the necessary heat concentration type thermal head can be obtained.

That is, in a method of manufacturing a thermal head having a heating resistor formed in a strip shape so as to cross a plurality of pairs of power supply electrodes on an insulating substrate, the heating resistor is formed on the insulating substrate, and then the resistance is applied by irradiation. By irradiating a required portion of the heating resistor forming the unit heating portion of the heating resistor with a laser beam having a power that reduces the value, the resistance value of the heating resistor in the required portion does not emit laser light. It is characterized in that a region lower than the resistance value of the heating resistor of a part is formed.

In order to achieve the second object,
The present invention relates to a method of manufacturing a thermal head in which a heating resistor is formed on an insulating substrate. After the heating resistor is formed, laser light of a power that reduces the resistance value by irradiation is applied to the heating resistor. A region having a low resistance value is formed in the entire area near the central portion in the direction perpendicular to the current direction by irradiating the entire unit heating portion near the central portion in the direction perpendicular to the current direction. ..

Further, after forming the heating resistor, by irradiating laser light having a power that reduces the resistance value by irradiation over the entire area in the vicinity of both side edges in the current direction of the unit heating portion constituted by the heating resistor. A region having a low resistance value is formed in the entire region near both side edges in the current direction. Furthermore, after forming the heating resistor,
Laser light of power that reduces the resistance value by irradiation,
By irradiating the whole area near the central portion in the direction perpendicular to the current direction of the unit heating portion composed of the heating resistor and the entire area near both side edges in the current direction, the entire area near the central portion in the direction perpendicular to the current direction. And a region having a low resistance value is formed in the entire region near both side edges in the current direction.

Although the heating resistor has a rectangular shape, the present invention is not limited to this. For a heating resistor having a shape other than the rectangular shape described in the above-mentioned prior art publication, the heating resistor is not limited to the rectangular shape. Alternatively, the present invention is not limited to the individual-separation-type heating resistor, and the present invention may be applied to an alternating-electrode-type heating resistor in which common electrodes and individual electrodes are alternately arranged in the main scanning direction and a heating resistor is formed between these electrodes. By applying the above, the necessary heat dispersion type thermal head can be obtained.

[0025]

When the heating resistor is irradiated with laser light, the resistance value of the irradiated resistor in the irradiated portion changes. FIG. 6 is an explanatory diagram of the power of the laser light to be radiated and the rate of change in resistance value of the heating resistor. As shown in FIG. 6, when the power of the laser light is gradually increased from 0, a certain area A In the area B, the rate of change in resistance becomes negative, and in the other areas B, this becomes positive.

When a desired portion of the heating resistor is irradiated with a laser beam having such a power that the resistance value change rate becomes negative, that is, a laser beam having a power that reduces the resistance value by irradiation, the irradiation is performed. The resistance value of the part becomes lower than the resistance value of the other part which is not irradiated with the laser beam. As a result, without changing the shape of the conventional rectangular heating resistor, the electrical or physical strength of the conventional rectangular heating resistor is not reduced, and particularly the resistance value is adjusted. It is possible to realize a heat concentration type thermal head having a heat generation spot at a required portion of the heat generating resistor facing the recording medium, without requiring highly precise microfabrication.

Further, according to the present invention described above, it is not necessary to change the shape of the ordinary rectangular resistor, so that the electrical or physical strength is not reduced as compared with the ordinary rectangular resistor.
In particular, a heat dispersion type thermal head can be realized without requiring fine processing precision.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a plane of a main part of a heating resistor portion of a thermal head for explaining one embodiment of a method of manufacturing a heat concentration type thermal head according to the present invention.
The heating resistor size and the laser beam irradiation position of the thermal head used in this example are shown, and 1 is an insulating substrate (actually, as shown in FIG. 19, a glaze layer is formed on the upper surface of the insulating substrate 1. 3 is a common electrode, 4 is an individual electrode, 5 is a heating resistor, 51 is a heating resistor portion that does not emit laser light, and 52 is a heating resistor portion that emits laser light (required portion). Is. Further, here, a 10-dot / mm MOD thermal head was used.

In FIG. 1A, the irradiation width of laser light is 26.
Schematic diagram when laser light is irradiated to the entire surface in the sub-scanning direction with μm, (b) shows a laser light having a diameter of 2 at the center of the heating resistor.
It is a schematic diagram at the time of irradiating a substantially circular area of 6 μm.
FIG. 2 shows that when the irradiation width D of the laser light is set to 26 μm,
Explanatory drawing showing the results of measuring the relationship between the laser light power and the resistance value change rate (%). FIG. 3 shows the laser light power and resistance value change rate (%) when the irradiation width D of the laser light is 13 μm. It is explanatory drawing which shows the result of having measured the relationship of.

The power of the laser beam is shown by the input of the excitation lamp of the laser (current A ampere). The laser light used for the measurement in FIGS. 2 and 3 is the output light of the laser cut by 32% by a filter.
As shown in FIGS. 2 and 3, the resistance value of the heating resistor irradiated with the laser light does not change at all until the power of the laser light reaches a certain value, but as the power of the laser light is increased, the heating resistance is increased. The rate of change in the resistance value of the body becomes negative and the resistance value gradually decreases, and then the rate of change in the resistance value becomes positive and the resistance value starts to increase.

The resistance value of the heating resistor begins to increase only when the rate of change in resistance value which starts to increase becomes positive, that is, when the excitation lamp input of the laser is about 13 A in FIGS. 2 and 3. Further, as can be seen by comparing FIG. 2 and FIG. 3, when the irradiation width of the laser beam is narrow, the way the resistance value decreases and the way the resistance value decreases become smaller, but the power at which the resistance value starts to decrease from the initial resistance value and The power to start rising is the same regardless of the laser beam irradiation width.

Therefore, the central portion of the heating resistor of the ordinary thermal head manufactured as described below is irradiated with the laser light of the excitation lamp input 13A which is the power that lowers the resistance value, and the heat-concentrated thermal of the present invention is used. I made a head. In manufacturing a thermal head, first, a glaze ceramic substrate 1 is prepared, and a MOD resistor containing iridium oxide or ruthenium oxide as a main component is formed on the surface of the glaze ceramic substrate 1 by screen printing and firing. Next, an electrode layer is formed by screen printing and firing using a MOD gold paste, and then patterned by a photolithographic etching method to form the common electrode 3, the individual electrode 4, and the rectangular heating resistor 5. After that, the basic structure of the thermal head is obtained by forming an overglaze layer by screen printing and firing using an overglaze paste.

Next, as described above, the power of the excitation lamp input 13A is linearly formed in the central portion (predetermined portion) of the heating resistor 5 in the main scanning direction in the printing current direction (here, the sub-scanning direction) with a width of 26 μm. Was irradiated with laser light. FIG. 4 is a schematic diagram for explaining the resistance value configuration of the heating resistor after laser light irradiation. In FIG. 4A, the heating resistor 5 includes a portion 51 not irradiated with laser light and a laser as described above. As shown in (c) and (d) of the figure, the resistance value of the portion 51 not irradiated with the laser light maintains the initial high resistance value r ₁ , The resistance value of the portion irradiated with the laser light becomes the resistance value r ₂ which is lowered, and as shown in FIG. 7B, an equivalent parallel circuit of r ₁ , r ₂ and r ₁ should be constructed. become. Therefore, when a drive current is passed through the individual electrode 4 and the common electrode 3, the current density in the portion of low resistance r ₂ increases.

That is, the specific resistance of the portion 52 in FIG. 4A decreases, and the current density of this portion increases. As shown in the figure, the heating resistor 5 is divided into two regions 51 which are not irradiated with laser light and one region 52 which is irradiated with laser light. The combined resistance value R ′ of the heating resistor 5 configured in this way is determined by the region 5 not irradiated with laser light.
When the resistance value of ₁ is r ₁ and the resistance value of the region 52 irradiated with the laser beam is r ₂ , R ′ = r ₁ r ₂ / (r ₁ + 2r ₂ ) ... (Equation 1).

On the other hand, the resistance value R of the heating resistor 5 when not subjected to laser light irradiation treatment _{is, R = r 1/2 ··············} ( Equation 2) The From FIG. 2, when the laser beam having the power of the excitation lamp input 13A is irradiated in a line shape with a width of 26 μm, the resistance value change rate is −16%, so (1-R ′) / R = 0.16. ··· (Equation 3) From (Equation 1), (Equation 2), and (Equation 3), r ₂ / r ₁ = 0.64 (Equation 4)

Therefore, when a voltage V is applied to the heating resistor, the heating resistor applies an electrode W ₁ in a region not irradiated with laser light and an electrode W ₂ in a region irradiated with laser light. and, respectively, because it is _{W 1 = V / r 1,} W 2 = V / r 2 ····· ( equation 5), (equation 4) and (equation _{5), W 2 / W 1} = r ₁ / r ₂ = 1.57 (Equation 6) That is, in FIG. 4A, the heating resistor in the region (laser light irradiation region) 52 irradiated with laser light is not irradiated with laser light. No area (non-laser light irradiation area) 5
1.57 times the electric power of the resistor of No. 1 is applied.

As a result, a heating spot having a peak is generated near the center of the heating resistor in the main scanning direction, and the size of this heating spot can be controlled by the energy of the driving current applied to perform multi-gradation printing. .. FIG. 5 is an explanatory diagram of the relationship between the laser light irradiation width and the resistance value change rate when laser light is irradiated with the excitation lamp input being kept constant at 13 A as the laser power for reducing the resistance value.

From the relationship shown in the figure, it can be seen that at a current value of 13 A for the excitation lamp input of the laser, the resistance change rate decreases substantially in proportion to the laser beam irradiation width. Therefore, if the irradiation width of the laser beam is adjusted according to the variation in the resistance value, the resistance value trimming of the heating resistor can be performed at the same time. Further, FIG. 1 (b) shows the excitation lamp input 13
The schematic diagram of the heating resistor when the laser beam of the power of A is irradiated to the circular area 52 ′ having a diameter of 26 μm in the central portion of the heating resistor 5 ′ is shown. Reference numeral 51 'indicates a heating resistor in a region not irradiated with laser light.

The specific resistance of the circular region 52 'in the figure is reduced by 36% from the above (Equation 4), and the current path during heat generation of this resistor is the direction perpendicular to the current direction of the heat generating resistor (here Then, in the sub-scanning direction) As in the case of narrowing the width of the central part,
The current density in the central part of the heating resistor increases. As a result, a heat spot is generated near the center of the resistor, and multi-tone printing can be performed. Needless to say, the shape of the region irradiated with the laser light is not limited to the above-mentioned circular shape and may be any shape.

In the above embodiment, the laser light irradiation region is set in the direction parallel to the current direction of the heating resistor or in the vicinity of the central portion of the heating resistor, but instead, in the vicinity of the central portion of the heating resistor. By irradiating the region parallel to the direction perpendicular to the current direction with the laser beam, it is possible to obtain a heat dispersion type thermal head having heating spots near both ends of the heating resistor in the current direction.

That is, FIG. 7 is a schematic view showing the plane of the main part of the heating resistor portion of the thermal head for explaining the embodiment of the method for manufacturing the heat dispersion type thermal head according to the present invention.
The heating resistor size and the laser beam irradiation position of the thermal head used in this example are shown, and 1 is an insulating substrate (actually, as shown in FIG. 19, a glaze layer is formed on the upper surface of the insulating substrate 1. 3) is a common electrode, 4 is an individual electrode, 5 is a heating resistor, 51 (51-1, 2, 3, 3)
4, 5) are heating resistor parts which are not irradiated with laser light, 5
Reference numeral 2 (52-1, 2, 3, 4, 5) is a heating resistor portion (required portion) for irradiating laser light. Further, here, an individual separation type MOD thermal head of 10 dots / mm was used. In the case of the alternating electrode type thermal head, the heating resistor 5 extends in a strip shape across the common electrode and the individual electrode, but since the principle of heating of the heating resistor is the same, the description with the drawings is omitted. ..

FIG. 8 is a schematic diagram for explaining the laser light irradiation position of the heating resistor constituting the unit heat generating portion. (A) shows the laser light irradiation width at 26 μm, and (b) shows the laser light irradiation width. The case where the thickness is 13 μm is shown. 9 and 10 show 26 μm and 1 μm, respectively, as shown in FIGS.
It is explanatory drawing of the relationship of the power of a laser, and a resistance value change rate when irradiating a laser beam to the whole central part of an electric current direction (sub scanning direction in an individual opposing type | mold) with an irradiation width of 3 micrometers.

Here, the power of the laser was changed by the input of the excitation lamp. The laser light is cut by 32% by a filter. 9 and 1
As can be seen from 0, the resistance value of the heating resistor does not change at all up to a certain value of the laser power (near 12 A in the figure), but gradually starts decreasing from the above value and then starts increasing. When the resistance value starts to rise and the rate of change of the resistance value becomes positive, that is, in the figure, the resistor begins to be cut for the first time near the excitation lamp input of the laser of about 15A.

As can be seen by comparing FIGS. 9 and 10, in FIG. 10 (corresponding to (b) of FIG. 8) where the laser irradiation width is small, the decrease and increase of the resistance value are small. The laser power at the point where the resistance value starts to fall and the point where the resistance value starts to rise is the same regardless of the irradiation width of the laser light. Therefore, a laser of the power of the excitation lamp input 13A is formed in a line shape with a width of 26 μm in the central portion in the current direction (main scanning direction in the individual separation type) of the heating resistor forming the unit heating portion, that is, the central portion in the direction perpendicular to the current. From the change in resistance value when light is irradiated, the rate of change in sheet resistance due to laser irradiation is obtained.

FIG. 11 is an explanatory diagram of an equivalent circuit diagram of the heating resistor. (A) is a heating resistor in an area not irradiated with laser light and its equivalent circuit, and (b) is heat generated in an area irradiated with laser light. The resistor and its equivalent circuit, (c) shows the entire heating resistor constituting the unit heating portion corresponding to the heating resistor of FIG. 8 (a) and its equivalent circuit. First, as shown in FIG. 9A, the heating resistor 51 in the region not irradiated with the laser beam.
The resistance value of -4 is r ₁ , and the resistance value of the heating resistor 52-4 in the region irradiated with the laser beam is r ₂ . Therefore, as shown in (c), in the heating resistor 5 that constitutes the unit heating portion, there are two regions 51-4 that are not irradiated with laser light and one region 52-4 that is irradiated with laser light. Then, the specific resistance of the region 52-4 irradiated with the laser beam is lowered, and the current density of this portion is increased.

Assuming that the resistance value of the region not irradiated with laser is r ₁ and the resistance value of the region irradiated with laser is r ₂ , the heating resistor 5 is as shown in the equivalent circuit of FIG. because represented by a parallel circuit of a resistor, the resistance value R of the whole heating resistor 5 becomes _{R = r 1 r 2 / (} r 1 + 2r 2) ····· ( equation 7).

Meanwhile, the resistance value R of the heating resistor 5 when not at all irradiated with a laser beam becomes R = r _1/3 ····· (Equation 8). Further, from FIG. 9, the rate of change in resistance is 16% when the laser beam with the power of the excitation lamp input 13A is irradiated in a line shape with a width of 26 μm over the central portion of the heating resistor in the current direction. R 3 /R=0.16 (Equation 9)

From the above (formula 7), (formula 8) and (formula 9), r ₂ / r ₁ = 0.64 (formula 10). That is, since the widths of the heating resistor portions corresponding to the resistance values r ₁ and r ₂ are both 26 μm and equal to each other, from the above (Equation 10), when the above laser light is irradiated, the irradiation portion has a sheet resistance of It can be seen that the area is 0.64 times as large as the area not irradiated with light.

Next, a method of manufacturing the thermal head will be described based on the above description. In manufacturing a thermal head, first, a glaze ceramic substrate is prepared, and a MO film containing iridium oxide or ruthenium oxide as a main component is formed on the surface by screen printing and firing.
Form a D resistor. Next, an electrode layer is formed by screen printing and firing using a MOD gold paste, and then a lead electrode (individual electrode, common electrode) and a rectangular resistor are formed by a photophosphor etching method. Then, an overglaze layer is formed by screen printing and firing using an overglaze paste. The manufacturing of the alternating electrode type thermal head is similar to that of the individual opposing type thermal head except that the heating resistor is formed in a band shape crossing the individual electrode and the common electrode.

With respect to the heating resistor formed as described above, as shown in FIG. 7A, the size of the heating resistor 5 forming the unit heating portion is 160 μm in the current direction.
m, when the current is set to 78 μm at right angles, the irradiation width is 32
Current and vertical direction in μm (main scanning direction in case of individually opposed type)
A laser beam was applied to the entire central portion. In this case, laser light is applied to a region of only 1/5 of the length of the heating resistor 5 in the current direction, and the sheet resistance of this region is 0.
Since it is 64 times, (5-4.64) / 5 × 100 =
The resistance should drop by 7.2 or 7.2%.

FIG. 12 is an explanatory diagram of the actual measurement value of the resistance value change rate when the irradiation width of the laser light is increased by 3 μm.
As shown in the figure, the resistance value decreases as the irradiation width of the laser beam increases, and the resistance value change rate becomes 7.0% at the laser irradiation width of 33 μm, which is close to the above calculated value.

As described above, since the sheet resistance value in this laser light irradiation region is about 0.64 times, the sheet resistance in the non-laser light irradiation region where laser light is not irradiated is r _{sq 1} and laser light irradiation is performed. If the sheet resistance of the region is r _sq2 , the applied power W ₁ per unit area of the non-laser light irradiation region and the applied power W ₂ per unit area of the laser irradiation region are W ₁ = r _sq1 I ² W ₂ = r _sq2 I ² (Equation 11) is obtained.

Therefore, W ₂ / W ₁ = r _sq2 / r _sq1 = 0.64 (Equation 12) As a result, the calorific value per unit area of the laser light irradiation area is 0.64 times that of the non-laser irradiation area.

FIG. 13 is an explanatory diagram of the temperature distribution of the unit heating element when the laser beam is not irradiated, and FIG. 14 is an explanatory diagram of the temperature distribution of the heat dispersion type thermal head obtained by irradiating the laser beam. As is clear from comparison between FIG. 13 and FIG. 14, the temperature distribution in the current direction (the sub-scanning direction in the individual separation type) of the heating resistor obtained by irradiating the laser light is as shown in FIG. Compared with the heating resistor shown in FIG. 13, which does not irradiate the laser beam, the central portion in the current direction (sub scanning direction in the individual facing type) is slightly lower, but the temperature peak is pushed to both ends and the both ends of the temperature distribution stand out. , In FIG. 14 →
When the temperature is increased as shown by →, the width of the printed dots in the current direction (sub-scanning direction in the individual separation type) is d ₂
→ Changes to d ₃ . Therefore, as can be seen by comparing with the change of the width d ₂ → d ₃ of the print dot in the current direction (sub-scanning direction) when the temperature is increased in the order of →→ in FIG. By irradiating the laser beam, the change in the printed dot width due to the applied energy is small.

As a result, it is possible to obtain a heat dispersion type thermal head which can obtain a more stable dot shape regardless of gradation. Next, as shown in FIG. 7B, the irradiation width 1 is applied to the entire area in the current direction near both ends of the heating resistor 5 in the current direction (in the individual facing type, the direction perpendicular to the main scanning direction: the sub-scanning direction).
The case where the above-mentioned laser light is irradiated at 3 μm will be described.

In this case, the voltage applied per unit area of the heating resistor 5 constituting the unit heating portion is the same in both the laser irradiation area and the non-laser irradiation area, so let V be the unit area of the non-laser irradiation area. The applied power W ₁ per unit area and the applied power W ₂ per unit area of the laser irradiation area are W ₁ = V ² r _sq1 W ₂ = V ² r _sq2 (Equation 13).

Therefore, W ₂ / W ₁ = r ₁ / r ₂ = 1.57 (Equation 14) From this, the calorific value per unit area of the laser light irradiation region is 1 in the non-laser irradiation region. .57 times. FIG. 15 is a temperature distribution chart of a heating resistor forming a unit heating portion of a heat dispersion type thermal head obtained by irradiating a laser beam.

As shown in FIG. 15, the temperature distribution in the direction perpendicular to the current of the heating resistor 5 shown in FIG. Compared with, the temperature near the center is slightly lower, but the temperature peaks are pushed to both ends and the both ends of the temperature distribution rise, so when the temperature is raised as →→ in FIG. The width (in the main scanning direction in the individual separation type) changes as d ₂ → d ₃ .

Therefore, as can be seen by comparing with the change d ₂ → d _{3 in} the width of the print dot in the current direction (sub-scanning direction in the individual separation type) in →→ in FIG.
When the laser irradiation as shown in FIG. 7B is performed, the change in the printed dot width due to the applied energy is small.
As a result, it is possible to obtain a heat dispersion type thermal head that can obtain a more stable dot shape regardless of the gradation.

FIG. 7C is an explanatory view of a heat dispersion type thermal head obtained by laser light irradiation in which the above-mentioned two methods are combined, and the laser light having a power capable of lowering the resistance value is used as a unit. Irradiation is performed in the current direction (sub-scanning direction in the individual separation type) near the central portion of the heating resistor forming the heat generating portion with the irradiation width of 32 μm in the direction perpendicular to the current (main scanning direction in the individual separation type), and at the same time, the laser light Is irradiated in the width of 13 μm in the direction perpendicular to the current (main scanning direction in the individual separation type) near both ends in the current direction (sub scanning direction in the individual separation type).

FIG. 16 is a temperature distribution diagram of the heating resistors constituting the unit heating portion of the thermal dispersion type thermal head obtained by irradiating the laser beam as shown in FIG. 7C. In this case, due to the above reason, the temperature distribution of the resistor is as shown in FIG. 16, and the current and the vertical direction (the main scanning direction in the individual separation type) and the current direction (the sub scanning direction in the individual separation type) are The change in print dot width due to applied energy is reduced.

As a result, it is possible to obtain a heat dispersion type thermal head which can obtain a more stable dot shape regardless of gradation. Further, the same effect as described above can be obtained with a normal thin film resistor. FIG. 17 shows an example of an individually separated thin film resistor.
It is explanatory drawing of the relationship between the power of the laser obtained by irradiating a laser beam in the whole electric current direction (sub-scanning direction in an individual separation type) with an irradiation width of μm, and the resistance value change rate.

Compared with FIG. 9 showing the same relationship regarding the MOD resistor, although there is a difference in the falling width of the resistance value, the MO
As in the case of the D resistor, the resistance value is the lowest near the excitation lamp input 13A. Therefore, both the MOD resistor and the thin film resistor were irradiated with the laser light from the excitation lamp input 13A, and the relationship between the irradiation width and the resistance value change rate was measured.

FIG. 18 is an explanatory view of the relationship between the irradiation width of the laser light with which the MOD resistor is irradiated and the rate of change in resistance value. The laser excitation lamp input is 13 A and the current and the vertical direction (the sub-scanning direction in the individual separation type). The case where the whole area is irradiated is shown.
Further, FIG. 19 is an explanatory diagram of the relationship between the irradiation width of the laser beam with which the thin film resistor is irradiated and the rate of change in resistance value. As in the case of FIG. The case where the entire area is irradiated in the sub-scanning direction) is shown.

As can be seen by comparing both FIG. 18 and FIG. 19, the rate of decrease of the resistance value of the thin film resistor is about ⅓ of MOD, and considering the degree of freedom of resistance value control,
MOD resistors are more effective than ordinary thin film resistors. By irradiating the laser light irradiation area to the entire heating resistor or to a specific part, it can be applied to various heating resistors other than heat concentration type or thermal dispersion type thermal heads or resistance value trimming of resistors. Is.

[0066]

As described above, according to the present invention,
By irradiating the required area of the heating resistor with a laser beam with a power that lowers the resistance value, a heat-concentrating heating resistor can be formed without changing the shape of the heating resistor. A centralized thermal head can be obtained. Therefore, it is possible to provide a heat-concentration type thermal head without lowering the electrical or physical strength as compared with an ordinary rectangular heating resistor, and without requiring highly precise microfabrication. You can

Further, according to the present invention, a heat dispersion type thermal head can be manufactured in the same manner without processing the heat generating resistor and the periphery of the heat generating resistor. Without decreasing the physical strength
Further, it is possible to realize a heat dispersion type thermal head without requiring a particularly complicated process. As described above, it goes without saying that the present invention is not limited to the individual separation type thermal head, but can be applied to the heat concentration type thermal head and the heat dispersion type thermal head provided with the alternating electrode type strip heating resistors.

[Brief description of drawings]

FIG. 1 is a schematic view showing a main part plane of a thermal head for explaining an embodiment of a method for manufacturing a thermal head according to the present invention.

FIG. 2 is an explanatory diagram showing the results of measuring the relationship between laser power and resistance value change rate (%) when the irradiation width D of laser light is set to 26 μm.

FIG. 3 is an explanatory diagram showing the results of measuring the relationship between the laser light power and the resistance value change rate (%) when the irradiation width D of the laser light is set to 13 μm.

FIG. 4 is a schematic diagram illustrating a resistance value configuration of a heating resistor after laser light irradiation.

FIG. 5 is an explanatory diagram of a relationship between a laser light irradiation width and a resistance value change rate when laser light is irradiated with the excitation lamp input being kept constant at 13 A as laser power for reducing the resistance value.

FIG. 6 is an explanatory diagram of the power of laser light to be irradiated and the rate of change in resistance value of a heating resistor.

FIG. 7 is a schematic view showing a plane of a main part of a heating resistor portion of a thermal head for explaining an embodiment of a method for manufacturing a heat dispersion type thermal head according to the present invention.

FIG. 8 is a schematic diagram illustrating a laser light irradiation position of a heating resistor that forms a unitary heating unit.

FIG. 9 is an explanatory diagram of a relationship between a laser power and a resistance value change rate when laser light is applied to the entire central portion in the current direction with an irradiation width of 26 μm.

FIG. 10 is an explanatory diagram of a relationship between a laser power and a resistance value change rate when a laser beam is applied to the entire central portion in the current direction with an irradiation width of 13 μm.

FIG. 11 is an explanatory diagram of an equivalent circuit diagram of a heating resistor,
8A is a heating resistor in a region not irradiated with laser light and its equivalent circuit, FIG. 8B is a heating resistor in a region irradiated with laser light and its equivalent circuit, and FIG. 8C is a heating resistor in FIG. 8A. The whole heating resistor which comprises the unit heating part corresponding to a body and its equivalent circuit are shown.

FIG. 12 is an explanatory diagram of an actual measurement value of a resistance value change rate when the irradiation width of laser light is increased by 3 μm.

FIG. 13 is an explanatory diagram of a temperature distribution of a unit heating element when laser light is not irradiated.

FIG. 14 is an explanatory diagram of a temperature distribution of a heat dispersion type thermal head obtained by irradiating a laser beam.

FIG. 15 is a temperature distribution diagram of a heating resistor forming a unit heating portion of a heat dispersion type thermal head obtained by irradiating a laser beam.

FIG. 16 is a temperature distribution diagram of a heating resistor forming a unit heating portion of a heat dispersion type thermal head obtained by irradiating a laser beam as shown in FIG. 7C.

FIG. 17 is an explanatory diagram of a relationship between a laser power and a resistance value change rate obtained by irradiating an individual separation type thin film resistor with a laser beam with an irradiation width of 26 μm in the entire current direction.

FIG. 18 is an explanatory diagram of the relationship between the irradiation width of the laser light with which the MOD resistor is irradiated and the rate of change in resistance value, showing the case where the excitation lamp input of the laser is 13 A and the current and the entire vertical direction are irradiated.

FIG. 19 is an explanatory view of the relationship between the irradiation width of the laser light with which the thin film resistor is irradiated and the rate of change in resistance value, showing the case where the laser excitation lamp input is 13 A and the entire area in the vertical direction is irradiated, as in FIG. Show.

FIG. 20 is a perspective view in which a main part is broken for explaining the configuration of an example of a conventional thermal head.

FIG. 21 is an explanatory diagram of heat generation distribution of a conventional thermal head having a rectangular heating resistor.

FIG. 22 is an explanatory diagram of heat generation distribution in the case of a heat concentration type heat generating resistor having a heat generating spot at the center of the resistor.

[Explanation of symbols]

1 ... Insulating substrate, 3 ... Common electrode, 4 ...
Individual electrodes, 5 ... Heating resistors, 51, 51 '...
-Non-laser light irradiation area, 52, 52 '... Laser light irradiation area.

Claims (6)

[Claims] 1. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, laser light of a power that reduces the resistance value by irradiation is applied to the heating resistor. A method of manufacturing a thermal head, wherein a region having a low resistance value is formed in the required portion by irradiating the required portion. 2. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, laser light having a power that reduces the resistance value by irradiation is applied to the heating resistor. A method of manufacturing a thermal-concentration type thermal head, characterized in that a region having a low resistance value is formed in the central portion by irradiating the central portion of the unit heat generating portion. 3. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, the heating resistor is irradiated with laser light having a power that reduces the resistance value by irradiation. A method for manufacturing a heat concentration type thermal head, characterized in that a region having a low resistance value is formed in the entire area in the vicinity of the central portion in the current direction by irradiating the entire area in the vicinity of the central portion in the current direction of the unit heat generating portion. 4. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, the heating resistor is irradiated with laser light having a power that reduces the resistance value by irradiation. By irradiating the entire area near the central portion in the direction perpendicular to the current direction of the unit heat generating portion, a low resistance area is formed in the entire area near the central portion in the direction perpendicular to the current direction. A method for manufacturing a heat dispersion type thermal head. 5. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, the heating resistor is irradiated with laser light having a power that reduces the resistance value by irradiation. A method of manufacturing a heat dispersion type thermal head, characterized in that a region having a low resistance value is formed in the entire area in the vicinity of both side edges in the current direction by irradiating the entire area in the vicinity of both side edges in the current direction of the unit heat generating part. 6. A method of manufacturing a thermal head comprising a heating resistor formed on an insulating substrate, wherein after the heating resistor is formed, the heating resistor is irradiated with laser light having a power that reduces the resistance value by irradiation. By irradiating the whole area near the central portion in the direction perpendicular to the current direction of the unit heat generating portion and the entire area near both side edges in the current direction, and the entire area near the central portion in the direction perpendicular to the current direction and the current direction. A method of manufacturing a thermal dispersion type thermal head, characterized in that a region having a low resistance value is formed in the entire region near both side edges.