JPH1134374A - Thermal head and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make heat of a heat-generating resistance body act immediately on a recording paper thereby carrying out printing in a short time and enabling highly fine printing, by forming a printing face which is a front face of a protecting layer covering a front face of the heat-generating resistance body in a shape to smoothly swell like a projection from the periphery and forming the protecting layer of a heat-generating part in a uniform thickness. SOLUTION: A heat-generating laminate part of a thermal head comprises a protecting layer 1 acting as an abrasion resistive layer, a heat-generating resistance body 2, a common electrode 3a and an individual electrode 3b overlapping via a space with the heat-generating resistance body 2, and a supporting body 4. A printing face 6 including a heat-generating part 5 constituted of the common electrode 3a, individual electrode 3b and the heat-generating resistance body 2 is formed to swell like a projection from the periphery. The protecting layer 1 has a uniform thickness and a front face of the protecting layer 1, namely, the printing face 6 is formed smooth. Accordingly heat of the heat- generating resistance body 2 acts immediately on a recording paper, thus enabling printing in a short time. Moreover, paper stain, etc., is never allowed to stay and therefore clear printing is maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal head and a method for manufacturing the same.

[0002]

2. Description of the Related Art Thermal heads are widely used as inexpensive and simple thermal printers and thermal transfer printers. Recently, high image quality, high speed, and low power consumption have been demanded.

In order to increase the speed of the thermal head, it is possible to increase the temperature of the heat generating resistor rapidly by suppressing heat dissipation, and at the same time, to reduce the temperature in a short time by releasing the heat quickly. In general, it is necessary to balance the opposing thermal responses of heating and cooling. For this reason, conventionally, a device such as providing a heating resistor on a ceramic substrate with a heat storage layer interposed therebetween has been devised.

In addition to the above, the following items are basically required of the thermal head. 1) Lighter, thinner and shorter 2) Inexpensive 3) Large screen for A3 etc. 4) Low power consumption 6) High-density, clear, so-called high-definition image print 7) Uniform screen without color unevenness 8) Dirt In conventional thermal heads, heat is deposited on an alumina substrate in the order of a heat storage layer, a heating resistor, electrodes, and a protective layer, and a heating section is formed between the common electrode and individual electrodes. Even if the printing surface is made to have a convex structure with a partial grace structure (a structure in which a heat storage layer is formed only below the heat generating portion of the alumina substrate), the heat efficiency decreases because the heat generating portion in contact with the recording paper is depressed. However, there is a problem that power consumption cannot be reduced. To solve this, Japanese Patent Application Laid-Open No. 62-109
No. 665 proposes a thermal head having a structure as shown in FIG.

As shown in FIG. 4A, a heat storage part (partial glaze) 32 made of glass having a melting point of, for example, about 1000 ° C. is provided on a part of an alumina substrate 31 which also serves as a heat radiator (heat sink). A heating resistor 33 is provided on the heat storage section 32 and the substrate 31. Reference numerals 34a and 34b denote a common electrode and an individual electrode for forming the heat generating portion 35. The surfaces of these electrodes 34a and 34b and the heat generating resistor 33 are protected from oxidation by the oxidation of the heat generating resistor 33 and the like. 36, and a wear-resistant layer 38 for preventing abrasion by thermal paper or thermal transfer paper 37 or the like. 39 is a roller.

At the top of the center of the heat storage layer 32 made of glass, a projection 32a is provided to prevent the surface of the wear-resistant layer 38 from being dented due to the lack of the electrode layer between the electrodes 34a and 34b. It is formed.

According to this structure, since the heating resistor 33 is provided on the surface of the ceramic substrate 31 having good heat conduction with the heat storage section 32 interposed therebetween, the heat of the heat generation section 35 is transferred to the heat storage section 3.
2, the heat generating portion 35 can be heated with relatively low power without escaping directly to the substrate 31. Moreover, the heat generating portion 3 is provided on the convex portion 32a at the center of the heat storage portion 32 which has been raised.
5, the heat generating portion 35 is in good contact with recording paper such as thermal paper or thermal transfer paper.

[0008]

However, according to the structure described in the above publication, the heat generating portion 35 of the thermal head is provided on the convex portion 32a of the heat storage portion 32, but the heat resistant portion 3
6 and the heat-generating resistor 33 and the electrode 3 serving as the base of the wear-resistant layer 38
The concave portion 40 remains on the printing surface of the thermal head under the influence of the irregularities 4a and 34b.

As described above, since the concave portion 40 is formed on the printing surface, paper dust or heat-sensitive paint adheres to the printing surface as the use time elapses, thereby soiling the recording paper. For this reason, the heat generating part 35 must be appropriately cleaned.

Since the heat storage section 32 is formed by applying glass, it is necessary to smooth the surface of the heat storage section 32 by polishing or the like after the formation of the heat storage section 32. Also, the recess 4
In order to eliminate 0, it is necessary to polish the printing surface until a polished smooth surface 41 appears as shown by a broken line in FIG. In this case, the abrasion-resistant layer formed with great thickness is polished, so that the thickness of the abrasion-resistant layer is reduced by an amount corresponding to the shaving allowance, and becomes non-uniform (t2 <t1).

SUMMARY OF THE INVENTION In view of the above problems, the present invention can respond to finer patterns, does not require maintenance such as cleaning to remove stains on recording paper even after the use time has elapsed, and smoothes the printed surface by polishing. It is an object of the present invention to provide a thermal head that does not require any operation and a method of manufacturing the same.

[0012]

In order to achieve this object, a thermal head according to the present invention comprises a protective layer covering the surface of a heating resistor, and an electrode which is in contact with the heating resistor and forms a heating section together with the heating resistor. In the thermal head provided with the above, the printing surface formed of the surface of the protective layer is formed to be convex from the periphery and formed smoothly, and the protective layer of the heat generating portion is formed with a uniform thickness. (Claim 1).

Further, the thermal head according to the present invention is characterized in that a support is formed on the back surface of the heat generating portion via a heat generating resistor and a barrier layer for preventing diffusion of impurities to the electrodes. ).

Further, in the thermal head according to the present invention, a heat storage layer is formed between the back surface of the heat generating portion or the back surface of the barrier layer and the support.

According to the method of manufacturing a thermal head of the present invention, a step of forming a groove on the surface of the temporary substrate, a step of forming a protective layer on the temporary substrate including the groove, Forming a heating resistor, forming an electrode connected to the heating resistor before or after forming the heating resistor, and forming a support covering the heating resistor and the electrode; And (c) forming a heat-generating laminate on the temporary substrate, and then removing or separating the temporary substrate.

[0016]

According to the thermal head of the present invention, the printing surface including the heat generating portion is formed so as to protrude from the periphery, and the protective layer is formed to have a uniform thickness and the surface is formed smoothly. No dust or heat-sensitive paint adheres, no blurring of print quality occurs, clear printing can be performed for a long time, and maintenance is unnecessary. Further, since the printing surface is formed so as to be raised, the heat of the heating resistor immediately acts on the recording paper, so that printing can be performed in a short time.

According to the method of manufacturing a thermal head of the present invention, a groove is formed on a temporary substrate, and a printing surface is formed by using the groove. A protective film surface having a smooth and uniform film thickness such as a shape or a convex R shape, that is, a printing surface can be formed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a sectional view showing an embodiment of a thermal head according to the present invention with respect to a heat generating laminated portion.
FIG. 1B is a cross-sectional view illustrating a heat-generating laminated portion of a thermal head according to another embodiment.

As shown in FIG. 1A, the heat-generating laminated portion is
A protective layer 1 acting as a wear-resistant layer, a heating resistor 2,
The support 4 includes a common electrode 3 a and an individual electrode 3 b which are provided on the heating resistor 2 at intervals. A heating section 5 is formed by the heating resistor 2 between the common electrode 3a and the individual electrode 3b. As shown in the drawing, the printing surface 6 including the heat-generating portion 5 is formed so as to protrude from the periphery, and as described later, the protective layer 1, the heat-generating resistor 2, the electrodes 3a, 3b The protective layer 1 has a uniform thickness and the surface of the protective layer 1, that is, the printing surface 6 is formed smoothly by a method of sequentially forming the support 4.

As the protective layer 1, a SiC-based compound,
SiB-based compounds, SiO-based compounds, SiON-based compounds and the like are used. In particular, the surface layer of the protective layer 1 is made of SiB having a low coefficient of friction, high hardness and chemically stable, and the back layer on the side of the heating resistor 2 is made of SiO ₂ having a high electric resistance. It is preferable from the viewpoint of securing electric insulation between the above. As a method of forming the protective layer 1, conventionally used methods such as plasma CVD can be adopted.

The heating resistor 2 is made of Nb-SiO.
_2, Ni-Cr, may be used Ta, or TiO _2, BN and the like. As a method of forming the heating resistor 2, L
PCVD (low pressure CVD), plasma CVD, sputtering, or the like can be used.

Each heating resistor 2 needs to be etched so as to be formed for each heating dot. As this etching method, it is preferable to use dry etching such as RIE (reactive ion etching). But,
It is also possible to use wet etching. Also,
As an etcher (reactive gas) for dry etching, SF ₆ , CF ₄ , Cl ₂ , O _{2, and the} like are generally used, and a mixture thereof can be used.

The electrodes 3a and 3b are made of Al, C
One or a plurality of metals such as u, Au, Ta, W, and Mo can be used repeatedly. Above all, Al is inexpensive and can easily obtain the adhesion to other layers without the need of interposing a special layer, and the process is simplified.
Further, since the electric resistance is low, it is preferable in that a fine pattern can be easily obtained. In addition, as a film forming method, vapor deposition, sputtering, or the like is used.

As an etching method for obtaining the patterns of the electrodes 3a and 3b, dry etching can be used, but wet etching is preferable. As an etchant (etching solution) for wet etching, H ₂ SO ₄ , HNO _{3 and the} like are generally used. In particular, when etching Al, H ₃ PO ₄ ,
A mixture of C ₂ H ₄ O ₂ and HNO ₃ may be used.

The support 4 can be made of a resin such as polyimide or silicon, or a cement type inorganic adhesive.
Further, an optimal material is appropriately selected and used according to the required high speed of transient thermal characteristics and power consumption, such as using a substrate made of ceramic or metal as a part of the support.

In this configuration, the heating resistor 2 generates Joule heat by the current flowing into the heating resistor 2 from the electrodes 3a and 3b to heat the heating portion 5, but the printing surface 6 including the heating portion 5 has a convex shape. (Trapezoidal shape), the heat of the heating resistor 2 immediately acts on the recording paper, and printing can be performed in a short time.

Further, since there is no concave portion on the surface of the protective layer 1 in the portion of the heat generating portion 5, no stain on the paper is accumulated. Therefore, extremely clear printing can be maintained for a long period of time.

FIG. 2 is a process chart for explaining a method of manufacturing the thermal head of the embodiment shown in FIG. In this example, first, as shown in FIG. 2A, a trapezoidal groove 7a having a smooth surface was formed on a temporary substrate 7 by machining and wet etching. As the temporary substrate 7, a 0.7 mm thick borosilicate glass plate (manufactured by Nippon Electric Glass Co., Ltd., trade name: BLC), which is inexpensive and easily available, was used.

As shown in FIG. 2B, the temporary substrate 7
The protective layer 1 was formed thereon including the groove 7a. As the protective layer 1, the SiB layer and the SiO ₂ layer
The layers were sequentially formed in an atmosphere of 350 to 400 ° C. by VD. The thickness of the SiB layer was 7 μm, and the thickness of the SiO ₂ layer was 3 μm.

[0030] After forming the protective layer 1, as shown in FIG. 2 (C), the Nb-SiO ₂ layer serving as a heat generating resistor 2, 300 ° C.
At a temperature of ~ 350 ° C, the temperature is reduced to 0.
It was formed to a thickness of 1 μm, and separated into individual heating resistors 2 by RIE. The pitch of the heating resistor 2 is 167μ.
m, and the interval between the heating resistors 2 was 10 μm. The Nb—SiO ₂ layer is a layer in which metal Nb or silicide or oxide of Nb is mixed in an amorphous SiO ₂ layer.

Next, as shown in FIG. 2D, the electrodes 3a,
An Al layer 3b was formed to a thickness of 0.5 μm by vapor deposition at a temperature of 100 ° C., and H ₃ PO ₄ , C ₂ H ₄ O ₂ ,
Using a mixed solution obtained by mixing HNO ₃ as an etchant,
The common electrode 3a and the individual electrode 3b were formed by overlapping a part of them on the heating resistor 2.

Next, as shown in FIG. 2E, a paste made of a polyimide resin as the support 4 is printed,
Cured at ° C.

Next, as shown in FIG.
The lower portion was covered with an etching resist, and immersed in an HF solution to dissolve the temporary substrate 7. Thereby, the protective layer 1 having a smooth surface formed on the temporary substrate 7 can be exposed.

In the embodiment shown in FIG. 2, an inexpensive glass plate is used as the temporary substrate 7, the protective layer 1 is formed directly on the temporary substrate, and Substrate 7
Is dissolved by dissolving, but when an expensive plate material is used as the temporary substrate 7, MgO
And the like, and as described above, film formation of each layer, drive I
After the fixing of C, the temporary substrate 7 may be reused by dissolving the sacrificial layer with phosphoric acid or the like to separate the temporary substrate 7 from the heat-generating laminated portion.

The electrodes 3a and 3b may be formed before the heating resistor 2 is formed, instead of after the heating resistor 2 is formed.

In the embodiment shown in FIG. 1B, the raised surface of the printing surface 6 which is the surface of the protective layer 1 is formed not in a trapezoidal shape but in a convex R shape. Further, a barrier layer 8 is formed on the back surface of the heating resistor 2 and the electrodes 3a and 3b constituting the heating unit 5, and a heat storage layer 9 is formed on the back surface of the heating unit 5 via the barrier layer 8. The support 4 is formed on the substrate.

The barrier layer 8 is made of SiO ₂ , SiN or the like. LPCVD, plasma CV
D, sputtering or the like can be used. Either wet etching or wet etching may be used as an etching method. In the case of performing wet etching, HF or HF and NH ₄ are used as etchants.
Generally, a mixed solution with F is used.

The heat storage layer 9 has, for example, a melting point of 30.
A low melting point glass of 0 ° C to 450 ° C is used. As a method for forming the heat storage layer 9, a screen printing method or the like is used.
Bake at 50-400 ° C. As described above, if the low-melting glass is used for the heat storage layer 9, the firing temperature can be low. Therefore, when Al is used for the electrodes 3a and 3b, the deterioration and oxidation due to the growth of Al crystal grains can be prevented. The characteristics of the heating resistor 2 are not changed. The support 4
When using polyimide resin or epoxy resin as
The mechanical strength of the heat generating part 5 can be improved.

When a resin is used as the support 4,
By stacking this on the heat storage layer 9 made of glass, the heat storage effect is increased, and a thermal head with low power consumption can be provided. As a matter of course, a part of the support 4 may be made of alumina or a metal substrate as in the above embodiment.

The presence of the barrier layer 8 causes the heat storage layer 9
For example, there is no possibility that the contained material of the low-melting glass or the contained material such as the support 4 diffuses into the heat generating portion 5 to deteriorate the characteristics such as increasing the resistance value.

FIG. 3 is a manufacturing process diagram for realizing the heat-generating laminated structure shown in FIG. 1 (B). As shown in FIG. 3 (A), an R-shaped temporary substrate 7 made of the glass plate is provided. A groove 7b is formed. The subsequent steps of FIGS. 3B to 3D correspond to FIG.
This is the same as the steps from (B) to FIG. 2 (D). After forming the electrodes 3a and 3b as shown in FIG. 3D, the barrier layer 8 was formed as shown in FIG. Thereafter, as shown in FIG. 3 (F), the heat storage layer 9 made of the low melting point glass is transferred to the heat generating portion 6.
Printing or application with a dispenser over a slightly wider range than the length of the paper
It was formed by firing at 350 ° C to 400 ° C.

Next, in order to form the support 4 made of epoxy resin, as shown in FIG. 3G, a paste containing the resin is printed so as to cover the entire heat storage layer 9 made of the low melting glass. Then, it was heated and cured at 150 ° C.

As shown in FIG. 3H, the temporary substrate 7 was removed by wet etching to expose the printing surface 6 in the same manner as in the above embodiment. As a result, a smooth surface having no convex R-shaped concave portion was obtained as the printing surface 6. By forming the convex R-shaped surface as the printing surface 6 in this way, the recording paper can more smoothly hit the printing surface 6 and the area of the recording paper that hits the surface can be reduced, so that clearer printing can be achieved. It becomes possible.

The thermal head according to the present invention includes the support 4
Is used as a resin.
A structure in which a driving IC is molded, a structure in which a driving IC is mounted on or fixed to the support 4, or a structure in which a chip of a heat generation stack including the support 4 is mounted on a substrate together with a driving IC, etc. can do.

[0045]

According to the first aspect of the present invention, the printing surface, which is the surface of the protective layer, is formed so as to protrude from the periphery in a convex manner and to be formed smoothly.
The heat of the heat generating resistor immediately acts on the recording paper to enable printing in a short time, thereby enabling high resolution.

Further, since the printing surface is formed as a smooth surface having no concave portion, no dust of paper or heat-sensitive paint adheres to the printing ground, no blurring of printing quality occurs, and clear printing is achieved. Maintenance is not required because it is possible over a long period of time.

Further, since the protective layer does not have a locally polished portion and has a uniform thickness, the wear life and reliability of the protective layer can be improved.

Further, when the printing surface is formed in a convex R shape, the recording paper can be further smoothly fed, and the contact area of the recording paper is narrowed, so that a further higher fineness can be achieved.

According to the second aspect, on the back surface of the heat generating portion,
Since the support is formed via the heat-generating resistor and the barrier layer for preventing diffusion of impurities into the electrode, in addition to the effect of claim 1, the material contained in the heat storage layer or the support diffuses into the heat-generating portion to reduce the resistance value. The effect of not deteriorating the characteristics, such as changing, is obtained.

According to the third aspect, the heat storage layer is formed between the back surface of the heat-generating portion or the back surface of the barrier layer and the support. By selecting the thermal head, an effect that a thermal head having desired heat storage and heat radiation characteristics can be easily obtained is obtained.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a thermal head.
Since a groove is formed in the temporary substrate and each layer below the protective layer is formed in the groove to form the heat generating portion, the print surface formed of the surface of the protective layer is formed to be convexly convex from the periphery and formed smoothly. In addition, a thermal head in which a protective layer of a heat-generating portion is formed with a uniform thickness can be easily obtained, and high-quality fine print quality and a thermal head that does not require cleaning of a print surface require polishing or the like. And can be obtained inexpensively.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views showing an embodiment of a thermal head according to the present invention, with respect to a heat generating laminated portion.

FIGS. 2A to 2F are manufacturing process diagrams of the embodiment of FIG. 1A.

3 (A) to 3 (H) are manufacturing process diagrams of the embodiment of FIG. 1 (B).

FIG. 4A is a cross-sectional view illustrating an example of a conventional thermal head, and FIG. 4B is a diagram illustrating polishing for smoothing the thermal head.

[Explanation of symbols]

1: protective layer, 2: heating resistor, 3a: common electrode, 3b:
Individual electrodes, 4: support, 5: heating section, 6: printing surface, 7:
Temporary substrate, 7a, 7b: groove, 8: barrier layer, 9: heat storage layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Hirabayashi 1-1-13 Nihonbashi, Chuo-ku, Tokyo Inside TDC Corporation (72) Inventor Jun Hagiwara 1-13-1 Nihonbashi, Chuo-ku, Tokyo No. Inside TDK Corporation

Claims (4)

[Claims] In a thermal head having a protective layer covering a surface of a heating resistor and an electrode which is in contact with the heating resistor and forms a heating portion together with the heating resistor, a printing surface formed by a surface of the protection layer is provided. A thermal head, wherein the thermal head is formed so as to protrude from the periphery so as to be smooth, and the protective layer of the heat generating portion is formed with a uniform thickness. 2. A thermal head according to claim 1, wherein a support is formed on a back surface of said heat generating portion via a heat generating resistor and a barrier layer for preventing diffusion of impurities into electrodes. 3. The thermal head according to claim 1, wherein a heat storage layer is formed between a back surface of the heat generating portion or a back surface of the barrier layer and a support. 4. A step of forming a groove on the surface of the temporary substrate, a step of forming a protective layer on the temporary substrate including the groove, and a step of forming a heating resistor on the protective layer. Forming an electrode connected to the heating resistor before or after forming the heating resistor, and forming a support over the heating resistor and the electrode to form a support on the temporary substrate. A method of manufacturing a thermal head, further comprising a step of removing or separating the temporary substrate after forming the heat generating laminated portion.