JP2005153253A - Method for manufacturing thermal head, thermal head and printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fully display the effect of tapering the peripheral edge part of a common electrode in a thermal head used for thermal recording in various kinds of printing devices such as a video printer, a facsimile machine and a ticket vending machine. <P>SOLUTION: This method for manufacturing a thermal head comprises a process to form the common electrode 7 on a substrate 3; a process to form a resist 10 on the common electrode 7; a process to form a gap 12 between the common electrode 7 and the resist 10 by partially removing an interface between the common electrode 7 and the resist 10 by BHF; and a process to etch the peripheral edge part 7a of the common electrode 7 in a tapering fashion by infiltrating an etching liquid into the gap 12. As a protecting film need not be formed thick by tapering the peripheral edge part 7a of the common electrode 7, it is possible to avoid the deterioration of printing efficiency or an increase in the film formation cost due to the thickening of the protecting film. In addition, time and cost for the manufacture of the thermal head are curtailed and the rectilinear propagation of a pattern is ameliorated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermal head used for thermal recording of various printing apparatuses such as a video printer, a bar code printer, a label printer, a card printer, a facsimile machine, and a ticket vending machine, a method for manufacturing the thermal head, and a print incorporating the thermal head. It relates to the device.

  In this type of thermal head, the common electrode is as thick as 3 to 20 μm, and the peripheral edge of the common electrode is an edge (almost right angle). Therefore, if it is going to cover all the common electrodes with a protective film, the protective film must be formed very thick. This is because when the protective film is formed, the base common electrode is flat and the film can be formed with a uniform thickness, but if there is a portion perpendicular to the base common electrode, that portion is sufficient. This is because the film thickness is not formed. For example, in normal non-bias sputtering, even if a film is formed with a thickness of 8 μm on a flat part, only about 2 μm can be formed on a vertical part.

  Further, since the peripheral edge portion of the base common electrode is an edge, micro-cracks are easily formed on the edge portion of the protective film covering this portion, causing the common electrode to corrode. At this time, the thinner the protective film is, the greater the ratio of the depth of the microcracks to the total thickness of the protective film is, so that it is easier to induce peeling or chipping of the protective film. Therefore, from this point, the protective film must be formed thick.

  However, if the protective film is formed thick due to such circumstances, the protective film covering the heating element is inevitably thick, which causes problems such as a decrease in printing efficiency and an increase in the cost of forming the protective film. .

  In order to avoid such a problem, it has been proposed to etch the peripheral portion of the common electrode into a tapered shape (see, for example, the paragraph [0011] in Patent Document 1, FIG. 1). That is, if the peripheral edge portion of the common electrode is tapered, the protective film covering the peripheral edge portion is almost the same as the flat portion, so that it is not necessary to form the protective film so thickly. Further, the edge of the protective film becomes obtuse as the peripheral edge of the common electrode is tapered, and microcracks are less likely to enter the edge, so that it is not necessary to form a thick protective film. As a result, it is possible to avoid a decrease in printing efficiency and an increase in the deposition cost of the protective film due to the increase in the thickness of the protective film.

In addition, four methods (hereinafter referred to as first to fourth taper methods) have been proposed as conventional methods for forming the peripheral edge portion of the common electrode in a tapered shape. The first taper method is a method using a low-viscosity etching liquid whose viscosity is adjusted (see, for example, the paragraph [0017] in Patent Document 1, FIG. 3). The second taper method is a method of forming a common electrode into a plurality of layers (for example, refer to the paragraph [0020] in Patent Document 1, FIG. 4). The third taper method is a method of changing the crystal grain size of the common electrode in the thickness direction (see, for example, the paragraph [0022] in Patent Document 1, FIG. 5). The fourth taper method is a method in which the peripheral edge of the common electrode is etched in two stages (see, for example, the paragraphs [0024] and [0026] in Patent Document 1, FIGS. 6 and 8).
JP-A-8-127143

  However, these conventional taper methods have the following disadvantages.

  In the first taper method, etching takes time because the viscosity of the etching solution is low. On the other hand, when the film thickness is 3 μm or more, as shown in FIG. 8A, the overetch 13 becomes excessive, and the predetermined patterning cannot be stably formed. That is, the pattern straightness is inferior.

  In the second taper method, the number of types of electrode materials increases, and it takes time to form a film, so that the manufacturing cost increases.

  In the third taper method, it is troublesome to adjust the sputtering power, leading to an increase in cost.

  In the fourth taper method, the manufacturing process of the thermal head increases and the manufacturing cost increases. Further, a step is formed at the peripheral edge of the common electrode, and the taper effect cannot be sufficiently obtained.

  In view of such circumstances, the present invention is a thermal head capable of fully exhibiting the effect of tapering the peripheral edge of the common electrode, reducing the time and cost for manufacturing, and improving the straightness of the pattern. An object of the present invention is to provide a manufacturing method, a thermal head, and a printing apparatus.

First, the invention according to claim 1 includes a step of forming a common electrode on a substrate, a step of forming a resist on the common electrode, and an interface between the common electrode and the resist partially with a pretreatment liquid. A step of providing a gap between the common electrode and the resist by removing, and a step of etching the peripheral portion of the common electrode into a tapered shape by allowing an etchant to enter the gap. .
According to a second aspect of the present invention, the common electrode is formed so that the crystal grain size increases in the stacking direction.
According to a third aspect of the present invention, the taper angle of the peripheral edge of the common electrode is adjusted by setting the treatment conditions with the pretreatment liquid.
According to a fourth aspect of the present invention, only the peripheral edge of the common electrode on the nip region side is etched in a tapered shape.
According to a fifth aspect of the present invention, only the peripheral edge of the common electrode opposite to the nip region is etched in a tapered shape.
According to a sixth aspect of the present invention, the peripheral edges of the common electrode on the nip region side and the opposite sides are etched into a tapered shape.
The invention according to claim 7 is configured such that a taper angle of a peripheral edge portion of the common electrode is 15 to 45 °.
The invention according to claim 8 is configured such that a taper angle of a peripheral edge portion of the common electrode is 15 to 30 °.
The invention according to claim 9 is manufactured by the method for manufacturing a thermal head according to any one of claims 1 to 8.
Further, the invention according to claim 10 includes the thermal head according to claim 9.

  According to the present invention, since the protective film does not need to be thickly formed by tapering the peripheral edge of the common electrode, the printing efficiency decreases due to the increase in the protective film thickness, and the protective film deposition cost increases. Can be avoided.

  In addition, compared with the conventional taper method, it is possible to reduce the time and cost for manufacturing and improve the straightness of the pattern.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a thermal head 2 is incorporated in the video printer 1, and the thermal paper 4 is heated to cause the color to develop, thereby printing images such as characters and images on the thermal paper 4. can do.

As shown in FIG. 2, the thermal head 2 has an insulating substrate 3 made of alumina ceramic having a thickness of 1 mm, and a glass glaze 5 having a thickness of 40 μm is formed on the substrate 3. Yes. On the glaze 5, a heating element 6 made of a Poly-Si (polysilicon) thin film having a thickness of about 0.2 μm doped with B (boron) is formed. An Al-based (Al or Al alloy) common electrode 7 having a thickness of 3 to 20 μm is formed on the heating element 6, and an Al-based individual electrode 8 having a thickness of about 0.6 μm is formed on the heating element 6. The film is formed so that electric power can be supplied to the film. A protective film 9 made of SiO ₂ or SiON and having a thickness of 3 to 10 μm is formed so as to cover the heating element 6, the common electrode 7 and the individual electrode 8. Here, the peripheral portions 7a and 7b on both sides (the nip region side and the opposite side) of the common electrode 7 are tapered with a predetermined taper angle α (for example, α = 20 °) as shown in FIG. It is formed in a shape.

  Next, the manufacturing process of the thermal head 2 will be described with reference to FIGS. In FIG. 3, the glaze 5, the heating element 6, the individual electrode 8, and the protective film 9 are not shown.

  First, as shown in FIG. 2B, the glaze 5 is formed on the substrate 3, and the heating element 6 is formed on the glaze 5 by LP-CVD (low pressure CVD) or the like.

  Next, the common electrode 7 is formed on the heating element 6 by sputtering or vapor deposition. Thereafter, a photoresist is applied, and exposure and development are performed using a photomask to form a pattern of the common electrode 7.

  And the pattern edge part of this common electrode 7, ie, peripheral part 7a, 7b, is formed in a taper shape. For this purpose, as shown in FIG. 3A, first, a novolac positive resist 10 is formed on the common electrode 7. Next, this is immersed in BHF (buffered hydrofluoric acid) as a pretreatment liquid for a certain period of time (for example, 2 to 8 minutes) to replace with pure water. At this time, the optimum concentration of BHF is 5% hydrofluoric acid and 50% ammonium fluoride, but is not limited to this concentration. Then, as shown in FIG. 3B, the resist 10 is dissolved and the interface with the common electrode 7 is partially removed, and a gap 12 is formed between the common electrode 7 and the resist 10. Therefore, as shown in FIG. 3C, the peripheral portions 7a and 7b of the common electrode 7 are etched by allowing an etching solution such as phosphoric acid, acetic acid, and nitric acid to enter the gap 12. Then, as shown in FIG. 3D, the peripheral portions 7a and 7b of the common electrode 7 are formed in a tapered shape with a predetermined taper angle α.

  In addition, since the depth of the gap 12 between the common electrode 7 and the resist 10 changes when the processing conditions (BHF concentration, temperature, immersion time, etc.) with the pretreatment liquid are changed, the peripheral portions 7a and 7b of the common electrode 7 are changed. The taper angle α increases or decreases. For example, if the immersion time in BHF becomes longer, the gap 12 becomes deeper and the taper angle α becomes smaller. In order to confirm this, it was experimentally determined how the taper angle α changes when the immersion time in BHF is changed within a range of 0.3 to 11 minutes. As a result, as shown in FIG. 4, it was confirmed that the taper angle α tends to decrease as the immersion time in BHF increases. Therefore, the pretreatment has good controllability of the taper angle α, and the taper angle α can be easily adjusted by setting the immersion time in BHF. Similarly, the taper angle α can be easily adjusted by setting the concentration and temperature of BHF.

  Next, the resist 10 is removed from the common electrode 7, and as shown in FIG. 2B, the individual electrode 8 is formed on the heating element 6 by sputtering or the like. Thereafter, a photoresist is applied, exposed and developed using a photomask, Al is etched, the length of the heating element 6 is defined, and the pattern of the individual electrodes 8 is formed. Again, using a photolithography process, the Poly-Si is etched to define the width of the heating element 6.

  Finally, a protective film 9 is formed so as to cover the heating element 6, the common electrode 7, and the individual electrode 8.

  Here, the manufacture of the thermal head 2 is completed.

  In the thermal head 2 manufactured in this way, the peripheral portions 7a and 7b of the common electrode 7 are tapered. Therefore, particularly when the taper angle α is 30 ° or less, the thickness of the protective film 9 is almost equal to the flat portion. Be the same. Therefore, it is not necessary to form the protective film 9 so thick.

  Further, as the peripheral portions 7a and 7b of the common electrode 7 are tapered, the edge portion of the protective film 9 becomes obtuse, and microcracks are less likely to enter the edge portion. In order to confirm this, an experiment was conducted to determine how the crack generation rate changes when the taper angle α is changed within a range of 5 to 90 °. As a result, as shown in FIG. 5, when the taper angle α exceeds 45 ° and approaches 90 ° (right angle), the crack generation rate increases rapidly, whereas when the taper angle α is 45 ° or less, When the crack occurrence rate was 2% or less and the taper angle α was 30 ° or less, the crack occurrence rate was zero. Therefore, it is not necessary to form the protective film 9 thick in this respect.

  Thus, since the protective film 9 does not need to be thickly formed by tapering the peripheral portions 7 a and 7 b of the common electrode 7, the printing efficiency decreases due to the increase in the film thickness of the protective film 9 and the protective film 9 An increase in film formation cost can be avoided.

  Further, it was experimentally determined how the pattern straightness changes when the taper angle α is changed within a range of 5 to 90 °. Here, as shown in FIG. 8, the pattern straightness means the waviness (waving) amount W of the pattern end surface when the pattern of the common electrode 7 is formed. The smaller the waviness W is, the more the pattern straightness is. It becomes good. As a result, as shown in FIG. 6, when the taper angle α is 90 °, the pattern straightness is ± 6 μm, whereas when the taper angle α is 15 to 81 °, the pattern straightness is ± 5 μm or less. became. In particular, when the taper angle α is 20 to 65 °, the pattern straightness is ± 1 μm or less.

  And unlike the 1st taper method mentioned above, the low viscosity etching liquid which adjusted the viscosity is not necessarily used. Therefore, the viscosity of the etching solution does not decrease and etching does not take time. Even with a film thickness of 3 μm or more, as shown in FIG. 8B, overetching does not become excessive and predetermined patterning can be stably formed. That is, the pattern straightness is excellent.

  In addition, unlike the above-described second taper method, the common electrode 7 is not formed in a plurality of layers, so that the types of electrode materials do not increase. Therefore, the film formation does not take time, and the manufacturing cost can be suppressed.

  In addition, unlike the above-described third taper method, the crystal grain size of the common electrode 7 is not changed in the thickness direction, so that it is possible to avoid a troublesome adjustment of the sputtering power and suppress an increase in cost.

  Further, unlike the above-described fourth taper method, the peripheral portions 7a and 7b of the common electrode 7 are not etched in two stages. Therefore, there is no fear that the manufacturing cost of the thermal head 2 increases and the manufacturing cost increases. In addition, since no step is formed in the peripheral edge portions 7a and 7b of the common electrode 7, a taper effect can be sufficiently obtained.

  The common electrode 7 may be formed so that the crystal grain size increases in the stacking direction. In this case, since the taper becomes difficult to taper due to the effect of increasing the etching rate as the crystal grain size is small, the peripheral portions 7a and 7b of the common electrode 7 are sufficiently tapered by a method of increasing the BHF processing time. be able to.

  The material of the common electrode 7 and the individual electrode 8 may not be Al-based, and may be Cu, Ag, or the like. Further, the materials of the insulating substrate 3, the glaze 5, and the heating element 6 are not limited to those described above.

  In the above-described embodiment, the case where the peripheral portions 7a and 7b on both sides of the common electrode 7 on the nip region side and the opposite side are etched in a tapered shape has been described. However, as shown in FIG. 7A, only the peripheral portion 7b on the nip region side of the common electrode 7 may be etched into a tapered shape. Further, as shown in FIG. 7B, only the peripheral edge portion 7a opposite to the nip region of the common electrode 7 may be etched into a tapered shape.

  In the above-described embodiment, as shown in FIG. 2B, the individual electrodes 8 are patterned so as to cover the common electrode 7. However, as shown in FIG. Alternatively, the individual electrodes 8 may be patterned.

  In the above-described embodiment, BHF is used as the pretreatment liquid. However, one that dissolves the resist 10 (for example, methanol or xylene) or one that erodes the interface between the common electrode 7 and the resist 10 (hydrofluoric acid). Etc.), the interface between the common electrode 7 and the resist 10 can be removed, so that a substitution is possible.

  In the above-described embodiment, the novolac positive resist 10 is used, but other resists (for example, a polyvinyl cinnamate negative resist or a cyclic rubber negative resist) may be used.

  In the above-described embodiment, the video printer 1 has been described. However, the present invention may be applied to a printing apparatus other than the video printer 1 (for example, a barcode printer, a label printer, a card printer, a facsimile machine, a ticket vending machine, etc.). it can.

1 is a perspective view showing an embodiment of a video printer which is a printing apparatus according to the present invention. It is a figure which shows the principal part of the thermal head which concerns on this invention, Comprising: (a) is the top view, (b) is an expanded sectional view by the BB line of (a). It is process drawing which shows the manufacturing method of the thermal head concerning this invention. It is a graph showing the relationship between the processing time by a pre-processing liquid, and a taper angle. It is a graph showing the relationship between a taper angle and a crack generation rate. It is a graph showing the relationship between a taper angle and pattern straightness. It is sectional drawing which shows another 3 embodiment of the thermal head based on this invention. It is explanatory drawing explaining the superiority or inferiority of pattern straightness.

Explanation of symbols

1. Video printer (printing device)
2 ... Thermal head 3 ... Substrate 4 ... Thermal paper 5 ... Glaze 6 ... Heating element 7 ... Common electrode 7a, 7b ... Perimeter 8 ... Individual electrode 9 ... Protective film 10 ... Resist 12 …… Gap α …… Taper angle

Claims (10)

Forming a common electrode on the substrate;
Forming a resist on the common electrode;
Providing a gap between the common electrode and the resist by partially removing the interface between the common electrode and the resist with a pretreatment liquid;
A method of manufacturing a thermal head, comprising: etching a peripheral portion of the common electrode into a tapered shape by allowing an etchant to enter the gap.   2. The method of manufacturing a thermal head according to claim 1, wherein the common electrode is formed so that a crystal grain size is increased in a stacking direction.   3. The method of manufacturing a thermal head according to claim 1, wherein a taper angle of a peripheral portion of the common electrode is adjusted by setting a processing condition with the pretreatment liquid. 4.   4. The method of manufacturing a thermal head according to claim 1, wherein only the peripheral edge of the common electrode on the nip region side is etched in a tapered shape. 5.   4. The method of manufacturing a thermal head according to claim 1, wherein only the peripheral edge of the common electrode opposite to the nip region is etched in a tapered shape. 5.   4. The method of manufacturing a thermal head according to claim 1, wherein peripheral portions on both sides of the nip region side and the opposite side of the common electrode are etched in a tapered shape. 5.   The method of manufacturing a thermal head according to claim 1, wherein a taper angle of a peripheral edge portion of the common electrode is 15 to 45 °.   The thermal head manufacturing method according to claim 1, wherein a taper angle of a peripheral edge portion of the common electrode is 15 to 30 °.   A thermal head manufactured by the method for manufacturing a thermal head according to claim 1. A printing apparatus comprising the thermal head according to claim 9.

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