JP3761968B2 - Heating element resistance adjustment method for thin film thermal print head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for adjusting a heating element resistance value of a thin film thermal print head, and more specifically to a technique for adjusting a resistance value of a heating element formed in a thin film as desired.
[0002]
[Prior art]
2. Description of the Related Art A thermal print head for performing printing by a thermal method or a thermal transfer method is configured by arranging a large number of heating elements that can be individually driven to generate heat on an insulating substrate. The thermal print head can be classified into a thick film type and a thin film type according to the heating element forming method. In the thick film type thermal print head, the heating element is formed by a thick film printing method. On the other hand, in a thin film type thermal print head, the heating element is formed into a thin film by CVD or sputtering.
[0003]
A thick film type thermal print head can be manufactured relatively easily and at a low cost. On the other hand, since each heating element is thick, the printing dots are blurred, and the printing density cannot be increased beyond a predetermined level. Thin-film thermal print heads are suitable for high-speed printing because they have a thin film shape with a heat generation of 500-1500 mm, so the printed dots are less blurred and have excellent thermal responsiveness. However, there is a disadvantage that the manufacturing cost is high because the film forming process and the photolithography process by CVD and sputtering are repeated.
[0004]
For example, when a thermal print head is configured to print on an A4 size recording paper at a printing density of 200 dpi, 1728 heating elements are arranged in a line. And, it is desirable that the resistance value of each of these heating elements is constant in order to improve the printing quality. However, when the heating elements are formed on the substrate, the resistance value of each heating element inevitably varies. Arise. This is because variations occur in the pattern size and thickness of the heating element.
[0005]
In the case of a thick film type thermal print head, resistance value adjustment called pulse trimming is performed in order to correct the variation in resistance value of each heating element as described above. That is, while a measurement probe is brought into contact with an appropriate part of the substrate and the resistance value of each heating element is monitored, a pulse current is passed through the heating element so that the measured resistance value of the heating element falls within a predetermined range.
[0006]
[Problems to be solved by the invention]
However, in the thin film type thermal print head, since the thickness of the heating element is as extremely thin as 500 to 1500 mm as described above, the resistance value adjustment by the pulse trimming as described above is impossible.
[0007]
By the way, in recent years, attempts to perform color printing with a thermal print head have been actively made. In this case, in order to obtain a print quality of a certain level or more, a thin film type thermal print head is often employed. In color printing by a thermal print head, overprinting is performed using a sublimation ink ribbon having an area of Y (yellow), M (magenta), C (cyan), or B (black) in addition to this. . The sublimation ink ribbon can change the amount of ink transferred to the recording paper in accordance with the applied heat, and accordingly, the printing energy given to the heating element when printing each color is changed in multiple stages. Thus, multi-tone color printing can be performed. When such multi-tone printing is performed, it is more strongly required to suppress variation in resistance value of each heating element of the thermal print head within a predetermined range. This is because, as is well known, when color printing is performed, even if the blending ratio of each color slightly changes, the color tone changes greatly. However, if there is a large variation in the resistance value of the multiple heating elements that make up the thermal print head, even if each heating element is driven under the same conditions, the generated printing energy will differ from one heating element to another. Therefore, the quality of color printing is remarkably deteriorated.
[0008]
When a thin film thermal print head is formed by a normal manufacturing process, it is said that it is difficult to suppress the variation in resistance value between the heating elements within ± 10% even if the film forming process is improved. ing. Such a variation in the resistance value between the heating elements is too large for the above color printing to be performed with high quality.
[0009]
The present invention has been conceived under the circumstances described above, and provides a thin film resistor that reduces manufacturing costs and has a variation in resistance value between heating elements within a predetermined range. That is the issue.
[0010]
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present invention takes the following technical means.
[0011]
The method of adjusting the heating element resistance value of a thin film thermal print head according to the present invention is a thin film thermal print head in which a plurality of heating elements made of thin film resistors formed by CVD or sputtering are arranged on an insulating substrate. A method of adjusting the resistance value of each of the heating elements by irradiating each of the heating elements with an excimer laser beam, wherein each of the plurality of strip-like regions extending in the entire width direction of the heating element The resistance value of each heating element is adjusted by simultaneously irradiating the entire width direction of the heating element with a strip-shaped excimer laser beam extending in the entire width direction and having a smaller area than the surface area of the heating element. It is said.
[0012]
In a preferred embodiment, by repeating the irradiation of the strip of excimer laser light with respect to band-like region of the positions are different from each other said plurality of locations in the length direction of the heating body, the excimer laser with respect to the entire surface of the heating body surface Irradiate light .
[0013]
In a preferred embodiment further irradiation, after irradiation of the excimer laser light to the entire surface of the heating body surface, a strip of the excimer laser beam extending across the width direction of the heating body to one or more positions As a result, the resistance value of each heating element is adjusted.
[0014]
An excimer laser is a laser that can oscillate ultraviolet rays. Excimer laser light has a high photon energy and a short pulse width compared to laser light oscillated from other lasers such as YAG laser and CO ₂ laser. It has the characteristic of having a high peak output. The inventor of the present application lowers the resistance value of a thin film resistor made of, for example, TaSiO ₂ as desired by selecting the irradiation area and irradiation position of the excimer laser beam having such characteristics and the combination thereof. I found out that I can do it.
[0015]
According to the adjustment method of the heating element resistance value of the thin film type thermal printhead according to the present invention, by the irradiation of excimer laser light to the entire surface of the heating body surface lever, it is possible to change the resistance value of the large heating element Further , according to the irradiation of the belt-like or line-like laser beam to one or a plurality of belt- like regions extending in the width direction of the heating element, a large amount of heat is generated by selecting the total irradiation area for the heating element. The resistance value of the body can be changed, or the resistance value of the heating element can be changed small.
[0016]
In particular, when the ratio of the irradiation area to the surface of the heating element is, for example, TaSiO ₂ or the like whose resistance value is reduced by excimer laser light irradiation as the material of the heating element, it is reduced by approaching the desired resistance value. If the resistance value of each heating element is adjusted, the resistance value of the heating element can be changed greatly until it approaches the desired resistance value, and the resistance value of the heating element is gradually increased as it approaches the desired resistance value. Can be changed to small. Finally, the excimer laser light is irradiated to an extremely small area and fine adjustment is performed, so that the resistance value of the heating element can be adjusted with high accuracy.
[0017]
Further, by performing by the energy density of the excimer laser beam applied to the heating body surface to decrease hand little is as it approaches the desired resistance value, stepwise resistance value of the heating element toward the desired resistance value Can be changed to small. Ultimately, the resistance value of the heating element can be finely adjusted with high accuracy by irradiating the excimer laser beam with an extremely low energy density. Further, the resistance value can be easily finely adjusted by combining the selection of the area to be irradiated with the excimer laser light and the selection of the energy density.
[0018]
[0019]
[0020]
Preferably, after stabilized by a heat treatment on the Symbol heating element adjusts the resistance value of each heating element by the irradiation of excimer laser light. The heating element once stabilized by the heat treatment does not change its resistance value greatly at a high temperature when the protective film is formed.
[0021]
Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.
[0023]
FIG. 1 shows a typical cross-sectional structure of the heat generating portion 2 of the thin film thermal print head 1 with emphasis in the thickness direction. FIG. 2 shows a planar arrangement of the heat generating part 2. A partial glaze 4 is formed on an insulating substrate 3 made of alumina ceramic or the like to increase the pressure concentration on the recording paper and to impart heat storage to the heat generating portion 2. The partial glaze 4 is formed by printing and baking using a glass paste, and has a smooth bow shape due to fluidization of glass components during baking.
[0024]
A thin film resistor layer 5 is formed on the surface of the insulating substrate 3 or the partial glaze 4. The resistor layer 5 is formed in a thin film shape of 500 to 1500 mm by, for example, a CVD method using TaSiO ₂ or sputtering. Conductor layers 6 a and 6 b are formed on the upper side of the resistor layer 5 so as to expose the resistor layer 5 over a predetermined range at the top of the partial glaze 4. The conductor layers 6a and 6b are formed to a thickness of 500 to 2000 mm, for example, by sputtering using Al. A portion of the resistor layer 5 that is exposed without being covered with the conductor layers 6 a and 6 b near the top of the partial glaze 4 functions as the heating element 7.
[0025]
As shown in FIG. 2, the resistor layer 5 and the conductor layers 6a and 6b are provided with slits 8 so that each heating element 7 can be driven independently. The conductor layers 6a that extend to the left in FIGS. 1 and 2 with respect to the respective heating elements 7 and are separated from each other by the slits 8 function as individual electrodes, and are output pads of a drive IC (not shown). Are electrically connected to each other. The conductor layers 6b extending to the right in FIGS. 1 and 2 with respect to the respective heating elements 7 are connected to each other and function as a common electrode.
[0026]
In FIG. 1, reference numeral 9 denotes an oxidation resistant layer made of, for example, SiO ₂ , and reference numeral 10 denotes a protective layer made of, for example, Ta ₂ O ₅ or Si ₃ N ₄ , both of which are formed by CVD or sputtering. The thickness of the oxidation resistant layer 9 is set to 3000 to 6000 mm, for example, and the thickness of the protective layer 10 is set to 2 to 4 μm, for example.
[0027]
In the above configuration, when any one of the individual electrodes 6a is turned on, the heating element 7 including the resistor layer 5 exposed without being covered with the conductor layers 6a and 6b is individually driven to generate heat.
[0028]
The thin film thermal print head 1 having the above-described configuration of the heat generating portion 2 is manufactured through the following processes, for example.
[0029]
First, as shown in FIG. 3, after forming the partial glaze 4 on the insulating substrate 3, the resistor layer 5 and the conductor layer 6 are sequentially formed into a thin film by CVD or sputtering. The materials and suitable thicknesses of the resistor layer 5 and the conductor layer 6 are as described above.
[0030]
Then, as shown in FIG. 4, the 1st photolithography process, to the resistor layer 5 and the conductor layer 6, forming a circuit pattern by the child form the slits 8 extending in the width direction of the partial glaze 4 To do.
[0031]
Next, as shown in FIG. 2, only the conductor layer 6 is edged by the second photolithography process, and the underlying resistor layer 5 is exposed. The resistor layer 5 thus exposed functions as the heating element 7 as described above.
[0032]
Preferably, each layer on which the circuit pattern is formed as described above is stabilized by performing a heat treatment so as not to cause a change in the resistance value with respect to a high temperature when the protective layer 10 is formed.
[0033]
Next, the oxidation resistant layer 9 and the protective layer 10 are formed by CVD or sputtering. The materials and suitable thicknesses of the oxidation resistant layer 9 and the protective layer 10 are as described above. Also, as shown in FIG. 12, an auxiliary resistor 11 not formed with the protective layer 10 is provided on the extension of the individual electrode 6a so that the resistance value of the heating element 7 after the protective layer 10 is formed can be adjusted. You may design.
[0034]
For example, in achieving a print density of 200 dpi, the heating element 7, as shown in FIG. 6, the longitudinal direction dimension L is 182Myuemu, a rectangular dot shape having a width dimension W is 112Myuemu, the thickness is e.g. 540 mm, and arranged in the longitudinal direction of the partial glaze 4 at a pitch of 125 μm. As the material for the heating element 7, TaSiO ₂ is suitable as described above, and its sheet resistance is 358Ω / □. In the present invention, such adjustment of the resistance value of the heating element 7 is performed as follows in the stage before the oxidation resistant layer 9 and the protective layer 10 are formed.
[0035]
That is, a probe (not shown) is brought into contact between the common electrode 6b and the individual electrode 6a, and the resistance value of the heating element 7 corresponding to the individual electrode 6a is monitored, as shown in FIG. This is performed by irradiating the target portion of the heating element 7 selected by the energy.
[0036]
The KrF excimer laser having a wavelength of 280 nm is used for the heating element 7 formed by the TaSiO ₂ resistor described above, the irradiation energy density is 60 to 200 mJ / cm ² , the irradiation pulse frequency is 10 to 200 Hz, and the number of shots is 1 to 500. As a result of performing energy irradiation to the entire surface of the heating element under the conditions of the rotation, the resistance value of the heating element 7 decreased by about 40% at the maximum.
[0037]
At this time, irradiation in the width direction having a smaller area than the surface area of the heating element 7, for example, irradiation to a band-like region having an area of 1/10 of the total surface area extending in the width direction of the heating element 7 as shown by the oblique lines in FIG. When the energy irradiation is performed on the entire surface of the heating element while changing the irradiation position in the longitudinal direction of the heating element 7, the resistance value is larger than that when the energy irradiation is performed on the entire surface of the heating element at one time. The rate of change per unit time was small.
[0038]
In addition, when energy irradiation is performed on a band-like region having an area of 1/10 of the total surface area extending in the width direction of the heating element 7 as shown by the oblique lines in FIG. 9, the resistance value of the heating element 7 is the maximum. It decreased by about 4%.
[0039]
Based on the above results, the inventor increased the energy density stepwise under the same conditions as the above-described operating conditions, and as shown in FIG. After substantially reducing the resistance value of the heating element 7 by irradiating the energy of the band-shaped laser light extending in the width direction of the heating element 7 to each of the three portions of the band-like area having a tenth area, the same condition is applied. The resistance value of the heating element 7 can be reduced by irradiating the band-shaped laser beam energy extending in the width direction of the heating element 7 to one place of the band-like area having a tenth area other than the area irradiated under the above. Minor adjustments were made. 11, 8, and 10 are schematic diagrams of a change in resistance value of the heating element 7 under the above operating conditions and a temperature distribution at the time of voltage application in the longitudinal section of the central portion in the width direction of the heating element 7.
[0040]
As is clear from FIG. 11, the resistance value of the heating element 7 is significantly reduced by the energy irradiation to the three regions shown in FIG. 7, and then the energy irradiation to the one region shown in FIG. As a result, the rate of decrease in the resistance value of the heating element 7 was reduced. R ₀ is an initial resistance value of the heating element 7 and R is a desired resistance value. The solid line represents the resistance value, and the alternate long and short dash line represents the energy density.
[0041]
From this result, when forming a thin-film thermal print head by a normal manufacturing process, it is difficult to suppress the variation in resistance value between the heating elements within ± 10% even if the film forming process is improved. However, by adjusting the resistance value of each heating element 7 by the above operation, the variation of the resistance value between each heating element is within ± 10%, and within a smaller range, specifically, It becomes possible to suppress variations in resistance value within ± 1%. That is, it is possible to provide a print head having a small variation in resistance value between the heating elements 7, and color printing with higher resolution than before can be realized.
[0042]
Moreover, the temperature distribution at the time of voltage application of the heating element 7 before the irradiation of the excimer laser light indicated by the broken line in FIGS. 8 and 10 is high in the central portion of the heating element 7 and ends in the longitudinal direction. The temperature is getting lower as it gets closer to. As shown by a solid line in FIG. 8, by applying energy to the heating element 7 while gradually increasing energy in the three regions, it is possible to apply a voltage in the heating element 7 compared to before irradiation. The temperature distribution became smaller. Furthermore, as shown by a solid line in FIG. 10, the temperature distribution during voltage application in the heating element 7 is further reduced by irradiating energy in a region where the temperature in the heating element 7 is high during voltage application.
[0043]
That is, by adjusting the resistance value of the heating element 7 using an excimer laser as in the present embodiment, it is possible to provide a good heating element 7 with a small temperature distribution in the heating element, and the resistance between the heating elements 7. A print head with a small variation in value can be provided.
[0044]
The protection performs resistance value adjustment of the heating element 7 by the method, necessary to adjust the resistance value after forming the protective layer 10 is when occurred, provided urchin individual electrodes by shown in FIG. 12 the auxiliary resistor 11 which does not form a layer 10, may be performed to adjust the resistance value of the heating element 7 by a child irradiation with excimer laser light.
[0045]
In addition, the resistance value after forming the protective layer 10 on the heating element 7 changed only by 0.5% at maximum as compared with the resistance value after adjusting the resistance value of the heating element 7. Further, the power durability before and after adjusting the resistance value of the heating element 7 hardly changed.
[0046]
Note that the graphs shown in FIGS. 8, 10, and 11 merely schematically show the tendency of the experimental results, and do not necessarily exactly match the experimental results.
[0047]
In this embodiment, the resistance value of the heating element formed by the TaSiO ₂ resistor whose resistance value is reduced by the excimer laser light irradiation is adjusted. However, the resistance value adjustment of the heating element according to the present invention is performed. The method is not limited to the TaSiO ₂ type resistor, but has the same effect on other metal-insulator composites and polysilicon material resistors whose resistance value is increased by irradiation with excimer laser light. Needless to say.
[0048]
In addition, as in the present embodiment, energy irradiation to three places of a band-shaped region having a one-tenth area of the entire surface area extending in the width direction of the heating element 7 and a band-shaped one-tenth area other than the region where the irradiation is performed. It is not necessary to adjust the resistance value of the heating element 7 by combining with energy irradiation to one place in the region, and various design changes can be made. For example, after performing the irradiation of excimer laser light on the entire surface of the heating element surface, subjected to irradiation of d excimer lasers light to one place of the band-like region of one area of the 10 minutes of heating element surface area extending in the width direction of the heat generating element Or other combinations may be used. Further, the area of the belt-like region is not limited to one-tenth of the surface area of the heating element, and other areas may be used, and the density of irradiation energy does not necessarily need to be increased stepwise as in the present embodiment.
[0049]
Figure 13 is a schematic configuration diagram showing an example of the excimer laser device 20 for adjusting the heating element resistance value of the thin film type thermal printhead by Ekishimare laser light as described above. On the XYZ stage 21 that can be precisely driven, an intermediate product of the thin-film thermal print head at the stage where the heating element 7 is formed as described above is installed as a workpiece W. Excimer laser light from the reduction projection lens 22 is irradiated onto the workpiece W. The laser light is oscillated by a laser oscillator 24 connected to the gas supply device 23. The oscillation pulse frequency and irradiation pulse of the excimer laser light oscillated by the laser oscillator 24 can be controlled by the control unit. The laser light oscillated by the laser oscillator 24 travels through the light adjusting optical system 25 and the variable attenuator 26, is changed in direction by the reflection mirror 27, and is introduced into the reduction projection lens 22. In this example, a mask 28 is interposed between the light control optical system 25 and the reflection mirror 27. The mask 28 has a window hole corresponding to a selected region to be irradiated with laser light on the surface of the heating element 7, that is, a window hole corresponding to the shaded portion in FIGS. Above the reflection mirror 27, an optical system 30 for monitoring the work W illuminated by the irradiation light from the light source 29 is disposed. In addition, although illustration is abbreviate | omitted, the resistance value of the heat generating body 7 which should adjust resistance value on the thin film type thermal print head as the workpiece | work W is monitored by making a predetermined probe contact an individual electrode and a common electrode. . The mask 28 can also be disposed at an appropriate position between the workpiece W and the reduction projection lens 22.
[0050]
While driving the XYZ stage 21 and step-feeding the thin-film thermal print head 1 as the work W in the arrangement direction of the heating elements 7, each heating element 7 is irradiated with excimer laser light, and the resistance value of the heating elements 7. The operation of adjusting the value to a desired value is sequentially performed. As a method for adjusting the resistance value of the heating element 7, there is a method of changing the irradiation area and position of the laser beam as described above. In the configuration shown in FIG. 13, the work W is stepped and the resistance value of each heating element 7 is adjusted. However, the work W is fixed and the reduction projection lens 22 is stepped and the resistance value of each heating element 7 is adjusted. Adjustments can also be made.
[0051]
Of course, the scope of the present invention is not limited to the embodiment described above. For example, as a gas for the excimer laser, it is needless to say that ArF or XeCl can be selected in addition to KrF as described above. In addition, the form of the heat generating part of the thin film type thermal print head is not only the form having the partial glaze as shown in the figure, but the form in which the heat generating elements are arranged on the entire glaze, or the so-called folded as the individual electrode pattern. Some of them have patterns, and appropriate resistance value adjustment can be similarly performed for these.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing the structure of a heat generating portion of a thin film thermal print head as a target for resistance value adjustment by the method of the present invention, with emphasis in the thickness direction.
FIG. 2 is an enlarged plan view of a heat generating portion of the thin film thermal print head shown in FIG.
3 shows a manufacturing process of the thin film thermal print head shown in FIG. 1, and shows a stage in which a partial glaze, a resistor layer, and a conductor layer are formed on an insulating substrate.
4 shows a manufacturing process of the thin film thermal print head shown in FIG. 1, and shows a stage in which slits are formed in the resistor layer and the conductor layer.
5 shows a manufacturing process of the thin film type thermal print head shown in FIG. 1, and shows a stage in which a part of the conductor layer is removed by edging and a part of the resistor layer is exposed to form a heating element.
FIG. 6 is a schematic plan view showing details of a planar form of a heating element.
FIG. 7 is a diagram for illustrating an irradiation position and an area of excimer laser light on a heating element.
FIG. 8 is a graph for explaining the operation of the present invention.
FIG. 9 is a diagram for illustrating an irradiation position and an area of excimer laser light on a heating element.
FIG. 10 is a graph for explaining the operation of the present invention.
FIG. 11 is a graph for explaining the operation of the present invention.
FIG. 12 is an enlarged plan view of a heat generating portion of a thin film thermal print head provided with an auxiliary resistor.
FIG. 13 is a schematic configuration diagram of an example of an apparatus for carrying out resistance value adjustment in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thin film type thermal print head 2 Heat generating part 3 Insulating substrate 4 Partial glaze 5 Resistor layer 6 Conductive layer 6a Individual electrode 6b Common electrode 7 Heating unit 8 Slit 9 Oxidation resistant layer 10 Protective layer 20 Excimer laser device

Claims (6)

In each thin film type thermal print head in which a plurality of heating elements made of thin film resistors formed by CVD or sputtering are disposed on an insulating substrate, the respective heating elements are irradiated with excimer laser light and the resistance values of the respective heating elements. Is a method of adjusting
For each of a plurality of strip-like regions extending in the entire width direction of the heating element,
The resistance value of each heating element is adjusted by simultaneously irradiating the entire width direction of the heating element with a strip-shaped excimer laser beam extending in the entire width direction of the heating element and having a smaller area than the surface area of the heating element. A method of adjusting a heating element resistance value of a thin film thermal print head. By repeating the irradiation of the strip of excimer laser light with respect to the band region of the position in the length direction are different from each other said plurality of positions of said heating elements, performs irradiation of the excimer laser beam to the entire surface of the heating body surface, The heating element resistance value adjusting method of the thin film type thermal print head according to claim 1. After irradiation of excimer laser light to the entire surface of the heating body surface, of each heating element by irradiating the excimer laser beam of the strip extending across the width direction of the heating body to one or more positions The heating element resistance value adjusting method for a thin film type thermal print head according to claim 2, wherein the resistance value is adjusted.   The heating element resistance value adjustment of the thin film type thermal print head according to claim 3, wherein the resistance value of each heating element is adjusted by reducing the ratio of the irradiation area to the surface of the heating element as it approaches a desired resistance value. Method.   The heat generation of the thin-film thermal printhead according to any one of claims 1 to 4, wherein the surface of the heating element is irradiated with excimer laser light by decreasing the energy density as it approaches a desired resistance value. Body resistance adjustment method.   6. The heating element resistance of a thin film thermal print head according to claim 1, wherein after the heating element is stabilized by heat treatment, the resistance value of each heating element is adjusted by irradiation with an excimer laser beam. Value adjustment method.

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