JPH05124237A - Thermal print head - Google Patents

Abstract

PURPOSE:To get rid of printing defects based on misregistration of the position where a heat generating resistor is formed and to make stabilization of the quality of printing possible by performing in advance half-etching of an electrode layer in the neighborhood of a mark formation position for photolithographic positioning of a lead electrode pattern and a heat generating resistor array pattern. CONSTITUTION:After a heat generation array pattern 3a is positioned to an electrode pattern 4a, light exposure, developing and etching are performed to form a heat generating resistor array pattern 3a after peeling a resist off. In this case, as in the neighborhood of the position where a positioning mark 9 for the electrode pattern 4a as standard is formed, the total film thickness is thin by half-etching and the amt. of undercut at the time of etching is small, a clear and sharp pattern is formed and a trapezoid pattern with a gentle slope as the cross-sectional shape of the pattern is obtained. Therefore, the work for photolithoalignment is easily performed and fluctuation caused by the pass sheet can be suppressed and the yield for manufacturing thermal print head can be improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to thermal printheads.

[0002]

2. Description of the Related Art As a conventional method for manufacturing a thermal print head, those shown in FIGS. 5 to 9 are known.

5 and 6 are partially enlarged views of a thermal print head after etching by a conventional manufacturing method.
FIG. 7 is a diagram showing a photolithography manufacturing process of a thermal print head according to a conventional manufacturing method. FIG. 8 is a plan view of a thermal print head according to a conventional manufacturing method.
FIG. 9 is a side cross-sectional view taken along line I-I near the heating resistor array portion in FIG. 7, 8 and 9, 1 is a heat resistant insulating substrate, 2 is glaze glass, 3 is a heating resistor layer, 3a is a heating resistor array pattern, 4 is an electrode layer, 4a is an electrode pattern, 4b is a common electrode. Patterns 4c are individual electrode patterns, 5 is a protective layer, 6 is a photomask, and 7 is a resist.

In the conventional serial type thermal print head shown in FIGS. 8 and 9, the electrode layer 4 is formed on the heating resistor layer 3 formed on the surface of the substrate to a film thickness of several thousand angstroms.
Was laminated to have a thickness of about 1 to 3 μm. At this time, the lead resistance value of the individual electrode pattern 4c is kept as low as possible, the variation in the lead resistance value between the heating resistor elements is small, and the film thickness of the electrode layer 4 is 1.0 μm so as to secure a sufficient current capacity. It is formed to a degree. Since the electrode pattern 4a is patterned by one-time photolithography etching, the film thickness of the electrode pattern 4a is constant.

The thermal print head having the conventional structure has the following problems. As shown in FIG.
For example, when Au is used as the electrode material, it is formed to have a film thickness of about 0.5 μm to 1 μm in order to secure a sufficient current capacity. Furthermore, in order to reduce the cost of the thermal print head, when an inexpensive electrode material such as Al having a high specific resistance value is used as the conductor pattern, the film thickness of the electrode layer 4 needs to be about 2 to 3 μm. When the thickness of the electrode layer 4 is large as described above, the undercut amount 10 becomes large in the electrode pattern shape at the time of photolithography etching, and it is easy to form a pattern with a pattern trapezoidal shape or an extremely trapezoidal sectional shape.

As shown in the manufacturing process diagram of FIG. 7, when a positive resist is used to form the electrode pattern 4a and the pattern is formed by one photolithographic etching after development from alignment, etching solution and plasma are directed to the sample surface in all directions. Since the irradiation is performed from, the etching proceeds isotropically. As the etching progresses, the side surface is exposed, but since this portion is not masked (protected) by the resist 7, the etching progresses in the direction perpendicular to the material surface and in the direction a shown in FIG. As a result, the amount of wraparound under the resist mask 7 is etched by the same thickness as the film thickness of the etched portion, and the thin film pattern cross section after etching becomes a trapezoidal shape. This is because as the film thickness of the electrode layer 4 increases, the amount of wraparound under the resist mask 7 increases, an extreme trapezoidal pattern is likely to be formed, and the pattern accuracy after etching tends to vary. Furthermore, since the heating resistor array pattern 3a is formed,
Photolithography is performed by superimposing a photomask 6 having a heating resistor array pattern 3a formed on the electrode pattern 4a. In this case, since the alignment of the superposition of the photomask 6 on the reference electrode pattern 4a is performed visually, if the reference electrode pattern 4a is thin or has an extremely trapezoidal shape, the electrode pattern 4a and the heating resistor pattern are not formed. There is a problem in that it is difficult to accurately align the photomask for forming 3a.

As shown in FIG. 6, especially when the dot density of the heating resistor array is increased, the pattern shape of the heating resistor array pattern 3a is a special shape such as a meander type or a heat concentration type. In this case, the sub-scanning longitudinal pattern L of the heating resistor array pattern 3a is not symmetrically distributed from the heating resistor center. In such a case, a change in the direction of the current flowing through the heating resistor row pattern 3a and a heating temperature distribution during energization deviate from the center of the heating resistor row pattern 3a. Variation is more likely to occur, which is one of the causes of variations in print quality. Therefore, highly accurate alignment between the electrode pattern and the heating resistor array pattern is required.

[0008]

The problem to be solved is to improve the etching accuracy of a pattern serving as a reference for alignment during photolithographic etching of a thermal print head, and to improve the accuracy of the electrode pattern and the heating resistor array portion. It is to provide a high quality head by performing proper alignment.

[0009]

A thermal print head of the present invention is formed by laminating a heating resistor layer and an electrode layer on the surface of a substrate, and each pattern is formed into a thin film by a photolithographic etching method. It is characterized in that the electrode layers of the lead electrode pattern and the heating resistor row pattern of the thermal print head provided with the heating resistor element are peripherally etched in advance in the photolithography alignment mark forming peripheral portion.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are plan views showing the entire thermal print head according to the present invention. FIG. 2 is a side sectional view of I-I near the heating resistor array portion in FIG. 3 and 4 are diagrams showing a photolithographic etching manufacturing process. The reference numerals of the components 1 to 9 are the same as those in FIG. 8, 8 is a half-etched portion, 9 is a positioning alignment mark, and 10 is an undercut portion.

As shown in FIG. 1, positioning alignment marks 9 used for photolithographic alignment of the electrode pattern 4a and the heating resistor array pattern 3a are formed on both ends of the glaze glass 2 formed on the substrate 1. .. The pattern shape of the half-etched portion 8 is wider than the outer shape of the positioning alignment mark 9 pattern by about 50 to 100 μm so that the entire positioning alignment mark 9 formed on the glaze glass 2 is cured (square shape). Has been created in. Half etching part 8 for the substrate 1
The alignment is performed by aligning the half etching pattern with the outer shape of the glaze glass 2 formed on the substrate 1 and performing photolithography to form the pattern.

As shown in FIG. 2, the heating resistor layer 3 and the electrode layer 4 are laminated on the substrate 1, and a part of the thin film pattern for mask alignment of the electrode layer 4 is half-etched. There is. This thermal print head is manufactured by the following steps. Generally, as a method of manufacturing a thermal print head, a large number of heads are simultaneously manufactured by a photolithography method from one substrate of alumina or the like.

First, a glass frit is printed by a screen printing method and fired to form a heating resistor layer 3 and an electrode layer 4 on a heat resistant insulating substrate 1 on which a glaze glass 2 is formed. To form a film.

FIG. 3 shows that a half-etched portion 8 is formed.
It is a figure which shows the manufacturing process of photolithographic etching. First, a resist 7 is applied on the entire surface of the laminated film on which the heating resistor layer 3 and the electrode layer 4 are formed by a spin coater / roll coater or the like, and prebaking is performed. Next, as shown in FIG.
Photolithography using a photomask 6 having a pattern shown in (b), which is used when forming the electrode pattern 4a and the heating resistor array pattern 3a and in which only the peripheral portion where the alignment mark 9 for photolithography alignment is formed is etched Perform alignment. The alignment of the half-etched portion 8 with respect to the substrate 1 is performed by aligning a pattern for half-etching with the outer shape of the glaze glass 2 formed on the substrate 1 and performing photolithography. After that, exposure, development and etching are performed to form a half-etched portion.

As a half etching method, the electrode layer 4 is formed by a chemical dry etching method which has a smaller amount of undercut (undercut amount) below the resist 7 to be masked, as compared with wet etching by immersion in an etching solution or spraying. Half-etch.

In the normal through-etching up to the surface of the substrate 1, the etching is performed while visually checking the color of the underlying substrate surface. However, in the half-etching of the electrode layer 4, the progress of the etching cannot be visually discerned. As a method, it is desirable to control the etching with time to form the half-etched portion 8. For example, the through etching time when the electrode layer 4 made of NiCr (0.15 μm) / Au (0.5 μm) as the electrode material is patterned on the lead electrode is about 200 sec. In this case, in the case of half-etching the electrode layer 4 having the above-mentioned electrode structure, when the etching time is 100 sec, the electrode layer 4 is partially half-etched to have a total film thickness of about 0.32 μm. It

FIG. 4 is a diagram showing a manufacturing process of photolithography etching for forming the electrode layer 4 partially half-etched on the electrode pattern 4a.

Partially half-etched electrode layer 4
Photomask 6 on which desired electrode pattern 4a is formed
Is used to form the electrode pattern 4a. First, a resist 7 is applied to the entire surface of the electrode layer 4 partially half-etched by a spin coater / roll coater or the like, and prebaking is performed. Next, photolithography alignment is performed using the photomask 6 having the electrode pattern 4a shown in FIGS.

In the photolithographic alignment method in this step, the alignment mark of the electrode pattern 4a is aligned with the outer shape of the glaze glass 2 formed on the substrate 1 for positioning. Next, after exposure and development, the laminated film outside the electrode pattern 4a and the unnecessary portion between the patterns is removed by etching to form the electrode pattern 4a after the resist is removed.

Thereafter, using a photomask having the heating resistor array pattern 3a shown in FIGS. 1A and 1B,
By the same photolithographic method as that used for forming the electrode pattern 4a (not shown), only the electrodes of the heating resistor forming portion of the electrode pattern are removed to form the heating resistor row pattern 3a. The comb-shaped positioning mark 9 formed in the electrode pattern 4a is aligned with the photomask overlay mark in the heating resistor array pattern 3a to position the heating resistor array pattern 3a with respect to the electrode pattern 4a. . After that, exposure, development, and etching are performed, and after the resist is peeled off, the heating resistor array pattern 3a is formed.

At this time, in the periphery where the alignment mark 9 of the reference electrode pattern 4a is formed, the total film thickness is half-etched so that the undercut amount at the time of etching is small. Are formed, and a trapezoidal pattern having a gentle cross-sectional shape is obtained. For this reason, the photolithography alignment work is easy, the variation due to the substrate can be suppressed, and the yield of the thermal print head manufacturing can be improved.

On the contrary, in the case where the amount of undercut is large and the formed pattern has an extremely trapezoidal cross section, when the photomask 6 for the heating resistor row pattern 3a is superposed, the pattern portion and the non-pattern are formed. The boundary between the portions becomes unclear, and the positioning accuracy with respect to the heating resistor pattern 3a of the superposed photomask is likely to vary. When the heat generating resistor pattern 3a is displaced from the electrode pattern 4a, the heat distribution (heat generating peak position) of the heat generating portion b shown in FIG. 6 is disturbed with respect to the lateral (sub scanning side) displacement. Therefore, there is a problem that the dots printed by heat generation are also disordered and non-uniform. Further, as the amount of lateral displacement increases, the difference between the product resistance value of the heat generating resistors that are normally aligned increases, and thus the variation in the average resistance value within one substrate also increases.

Further, in order to reduce the cost of the thermal print head, and when inexpensive Al or the like is used as the electrode material, Al has a higher specific resistance value than Au. It is necessary to make the thickness as thick as about 3 μm. In such a case, the undercut amount (size) during photolithography etching is the processing depth (film thickness).
As the heating resistance increases, the variation in the position where the heating resistor is formed also increases, and as a result, the dots printed by heating are more likely to be disturbed and printing unevenness becomes more noticeable.

Thereafter, as shown in FIG. 2, an insulating heat resistant protective layer 5 having abrasion and oxidation resistance is formed on the laminated thin film pattern by a vacuum thin film apparatus such as sputtering.

[0025]

The thermal print head of the present invention has a structure in which the peripheral portion of the photomask superposition pattern forming portion of the electrode layer formed as a thin film is half-etched so that the total film thickness is partially thin. Therefore, the following points are improved.

(1) Since a trapezoidal reference pattern with a small undercut can be formed at the time of photolithographic etching, the photomask can be accurately aligned with the reference pattern, resulting in a displacement of the heating resistor formation position. Eliminate printing defects (uneven print density)
A thermal print head with stable print quality can be manufactured.

(2) It is possible to solve problems such as dot irregularities and variations in the product resistance value of the thermal print head, which are caused by positional deviation of the pattern that occurs during photolithographic etching, and improve the manufacturing yield of the thermal print head. Has the effect of

[Brief description of drawings]

FIG. 1 is a plan view showing the entire thermal print head according to the present invention.

FIG. 2 is a side sectional view around a heat generating portion of the thermal print head according to the present invention.

FIG. 3 is a diagram showing a photolithography manufacturing process of the thermal print head according to the present invention.

FIG. 4 is a diagram showing a photolithography manufacturing process of the thermal print head according to the present invention.

FIG. 5 is an enlarged view of a part around a heating element portion of a thermal print head having a conventional configuration.

FIG. 6 is an enlarged view of a part around a heating element portion of a thermal print head having a conventional configuration.

FIG. 7 is a diagram showing a photolithography manufacturing process of a thermal print head having a conventional configuration.

FIG. 8 is a plan view showing an entire thermal print head having a conventional structure.

FIG. 9 is a side sectional view around a heat generating portion of a thermal print head having a conventional structure.

[Explanation of symbols]

 1 Heat Resistant Insulating Substrate 2 Glaze Glass 3 Heating Resistor Layer 3a Heating Resistor Row Pattern 4 Electrode Layer 4a Electrode Pattern 4b Common Electrode Part 4c Individual Electrode Part 5 Protective Film Layer 6 Photomask 7 Resist Mask (Resist) 8 Half Etching Part 9 Positioning alignment mark 10 Undercut part

Claims (1)

[Claims] 1. A thermal print head comprising a heating resistor layer and an electrode layer laminated on the surface of a substrate, wherein a plurality of heating resistor elements are provided, each pattern being formed into a thin film by a photolithographic etching method. A thermal print head in which the electrode layers of the lead electrode pattern and the heating resistor array pattern in the peripheral portion of the photolithographic alignment mark formation are pre-etched.