JP3797511B2 - Thermal head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal head .
[0002]
[Prior art]
Thermal heads are widely used in inexpensive and simple printers, taking advantage of the convenience of thermal paper or transfer paper that does not require refilling with ink or the like. Recently, high-quality printing and high-speed printing have also been demanded for printers used for these thermal heads. Further, there is a demand for a high-density thermal head such as 600 dpi to 1200 dpi, which is miniaturized before being used in a color printer system using a thermal transfer system, an index printer of a photo lab automation minilab that emphasizes high image quality, and the like.
[0003]
However, in the thermal head, it is necessary to consider the temperature increase and heat dissipation so that the heat generating portion of the heat generating resistor is rapidly heated to instantaneously raise the temperature and heat is quickly dissipated to prevent bleeding. For rapid temperature increase, heat concentrates on the heat generating part and does not escape around, and rapid heat dissipation requires a conflicting thermal response characteristic that heat of the heat generating part escapes quickly.
[0004]
That is, the following items are basically required for the thermal head.
1) Light, thin and small 2) Low cost 3) Large screen for A3, etc. 4) Low power consumption 5) High speed 6) High-density, clear, so-called high-definition image print 7) Uniformity without color unevenness Screen 8) Maintenance-free with no dirt remaining As an example of such a thermal head, in Japanese Patent Laid-Open No. 5-64905, as shown in FIG. 6, peeling for peeling on a substrate 30 having a flat surface is provided. A wear-resistant layer 32, a protective layer 33, a heating resistor 34, an electrode 35, and a heat storage layer 36 made of polyimide resin are formed in this order via the layer 31, and then a substrate 38 is bonded with an adhesive 37 to peel off the substrate 30. A method is disclosed in which the printing surface 40 is formed flat by a method of manufacturing a thermal head in which both are peeled off at the interface with the layer 31.
[0005]
In this thermal head, since the wear-resistant layer 32 is formed on the plane of the substrate 30, the surface that contacts the recording paper such as thermal paper becomes smooth, and no space is formed between the recording paper and the thermal efficiency is improved. To do.
[0006]
[Problems to be solved by the invention]
However, as described in the above publication, the thermal head using a resin such as polyimide resin for the heat storage layer 32 and the surface (printing surface) of the wear-resistant layer 32 formed flat has the following problems.
(1) The recording paper is strongly pressed onto the head by a roller. However, if the heat generating portion is planar, including its periphery, the contact surface of the head is relatively expanded, and the pressing pressure against the head is reduced. As a result, it is susceptible to roller deformation and wear.
(2) In order to solve such a problem, if the heat generating portion is formed so as to be raised, the pressing force of the roller is concentrated on the heat generating portion. Since the resin is exposed to a high temperature due to the heat generated in the heat generating portion, it softens, and the surface of the head dents and deforms when used for a long time. As a result, printing becomes unclear.
(3) In order to improve the printing quality, a thermal head that is tough against mechanical deformation stress is required. However, according to the prior art, if the heat generating part is made convex to increase the printing efficiency, Further, it has been impossible to provide a thermal head having a long life due to deformation due to mechanical stress.
[0007]
In view of the above problems, the present invention can exhibit the original characteristics of a thermal head that does not impair the print quality over a long period of time and does not require maintenance, and further achieves pixel miniaturization, large print screen, and high speed. An object of the present invention is to provide a thermal head that can achieve low power consumption.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the thermal head of the present invention is a thermal head comprising a protective layer covering the surface of the heating resistor, and an electrode that is in contact with the heating resistor and forms a heating portion together with the heating resistor.
The surface of the protective layer is formed with a convexly raised printing surface, and the back surface of the heat generating portion is provided with a reinforcing body made of glass that is filled in the back surface of the heat generating portion and melted and re-solidified , and the reinforcing body is a resin. Or it is covered with the support body which consists of resin which mixed the inorganic material powder | flour (Claim 1).
[0009]
In the present invention, in addition to the glass, a rod-like body filled in and fixed to the back surface of the heat generating portion ( Claim 2 ) is used. Moreover, the structure ( Claim 3 ) which provides a heat storage layer between a heat generating part and a reinforcement body or between a reinforcement body and a support body is also employ | adopted.
[0010]
[Action]
In the thermal head of the present invention, since the reinforcing body is embedded in the back surface of the heat generating portion formed in a raised convex shape, the heat generating portion is not deformed by pressing of the roller during printing. In addition, since the reinforcing body is interposed between the heat generating portion and the support made of resin, the degree of the temperature rise of the resin can be reduced, and the support is reinforced by the reinforcing body, so that the head is heated and heated by the roller. Deformation is prevented.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A is a cross-sectional view showing an embodiment of a thermal head according to the present invention with respect to a heat generation laminated portion. As shown in FIG. 1 (A), the heat-generating laminated portion includes a protective layer 1 that acts as a wear-resistant layer, a heat-generating resistor 2, a common electrode 3a that is provided on the heat-generating resistor 2 in an overlapping manner, and It is interposed between the individual electrode 3b, the support 4, the heat generating part 5 formed by the electrodes 3a, 3b and the heating resistor 2, and the support 4, thereby preventing the diffusion of substances from the support 4. The barrier layer 8 includes a reinforcing body 9 embedded between the barrier layer 8 and the support 4 on the back surface of the heat generating portion 5.
[0012]
As the protective layer 1, a SiC compound, SiB compound, SiN compound, AlN compound, BN compound, or the like is used. In particular, the surface layer is made of SiB having a small friction coefficient, high hardness, and chemically stable, and the back layer on the side of the heating resistor 2 is made of SiO ₂ having high electrical resistance. This is preferable in terms of ensuring electrical insulation. As a method of forming the protective layer 1, conventionally used methods such as plasma CVD can be employed.
[0013]
As the heating resistor 2, Nb—SiO ₂ , Ni—Cr, Ta, TiO ₂ , BN, or the like can be used. As a method for forming the heating resistor 2, LPCVD (low pressure CVD), plasma CVD, sputtering, or the like can be used.
[0014]
Each heating resistor 2 needs to be etched so as to be formed for each heating dot. As this etching method, dry etching such as RIE (reactive ion etching) is preferably used, but wet etching can also be used. Moreover, as an etcher (reactive gas) for dry etching, SF ₆ , CF ₄ , Cl ₂ , O _{2, and the} like are generally used, and these can be mixed and used.
[0015]
As the electrodes 3a and 3b, one or more kinds of metals such as Al, Cu, Au, Ta, W, and Mo can be used in an overlapping manner. Among them, Al is inexpensive, and can easily obtain adhesion with other layers without the need for a special layer, the process becomes simple, and the electric resistance is low. It is preferable in that it is easy to obtain. As a film forming method, vapor deposition, sputtering, or the like is used.
[0016]
As an etching method for obtaining the patterns of these electrodes 3a and 3b, dry etching can be used, but wet etching is preferably used. As an etchant (etching solution) for wet etching, H ₂ SO ₄ , HNO _{3 and the} like are generally used. In particular, when Al is etched, a mixed solution in which H ₃ PO ₄ , C ₂ H ₄ O ₂ , and HNO ₃ are mixed may be used.
[0017]
Using SiO _2, SiN, or the like in the barrier layer 8. As a film forming method, LPCVD, plasma CVD, sputtering, or the like can be used. As an etching method, either dry etching or wet etching may be used. When wet etching is performed, HF or a mixed solution of HF and NH ₄ F is generally used as an etchant.
[0018]
Glass is used as the reinforcing member 9 . When glass is used for the reinforcing body 9, low-melting glass having a softening point of 450 ° C. or lower (more preferably, a softening point of 400 ° C. or lower) is used as the glass. When Al is used, the electrode can be prevented from being oxidized or altered, and the electrodes 3a and 3b can be used. Moreover, when using low melting glass for the reinforcement body 9, the softening point of the glass used for the reinforcement body 9 is 300 degreeC or more in the meaning which prevents the reinforcement body 9 by the heating in the manufacturing process after formation of the reinforcement body 9. More preferably, it is 350 ° C.
[0019]
When this low melting point glass is used for the reinforcing body 9, as a coating method thereof, a screen printing method or a dispenser is used, and this is baked at 350 ° C. to 400 ° C. As the composition of the lead glass, it is preferable to use, for example, those of _PbO-B 2 _{O 3} -based or _PbO-B 2 O 3 -ZnO system.
[0020]
Further, as the reinforcing body 9, a structure in which a rod-shaped body made of ceramic or glass is fixed by an epoxy resin, an acrylic resin, or the like can be employed.
[0021]
As resin used for the support body 4, heat resistant resin, such as a polyimide resin and an epoxy resin, can be used. Moreover, it is also possible to adjust mechanical strength and heat conductivity by making these resin contain ceramic powders, such as an alumina and a silica, and inorganic powders, such as a metal powder. The support 4 can be a thermal head substrate, and if the support 4 made of resin is provided, it is less expensive than using a ceramic substrate or a glaze substrate. If necessary, this thermal head can be bonded to a heat sink such as Al or Cu.
[0022]
FIG. 2 is a process diagram showing a reference example of a method for manufacturing a thermal head according to the present invention . In this example , first, as shown in FIG. 2A, a groove 7a is formed on the surface of the substrate 7 by grinding and wet etching. The width of the groove 7a was 700 μm and the depth was 300 μm. The groove shape is a rounded trapezoidal shape or an arc shape.
[0023]
Next, as shown in FIG. 2B, the protective layer 1 is formed on the substrate 7 including the groove 7a. As the 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. Further, as the protective layer 1, a SiB layer and a SiO ₂ layer were sequentially formed in an atmosphere of about 400 ° C. by plasma CVD. The thickness of the SiB layer was 7 μm, and the thickness of the SiO ₂ layer was 3 μm.
[0024]
After forming the protective layer 1, as shown in FIG. 2C, an Nb—SiO ₂ layer to be the heating resistor 2 is formed to a thickness of 0.1 μm by sputtering at a temperature of 300 ° C. to 350 ° C. The individual heating resistors 2 were separated and formed by RIE. The pitch of the heating resistors 2 was 167 μm, and the spacing between the heating resistors 2 was 10 μm. The Nb—SiO ₂ layer is a mixture of metal Nb, Nb silicide, and oxide in an amorphous SiO ₂ layer. After providing the heating resistor 2 in this way, heat treatment may be performed at about 400 ° C. in order to improve the TCR of the heating portion 5.
[0025]
Next, as shown in FIG. 2D, an Al layer as electrodes 3a and 3b is formed by vapor deposition at a temperature of 100 ° C. to a thickness of 0.5 μm, and H ₃ PO ₄ , C ₂ H ₄ O ₂ , HNO ₃ was used as an etchant, and a common electrode 3a and an individual electrode 3b were formed by overlapping a part of them on the heating resistor 2.
[0026]
Next, as shown in FIG. 2E, a SiO ₂ layer as the barrier layer 8 was formed to a thickness of 0.3 μm by LPCVD. Then, the barrier layer 8 was formed by etching the formed SiO ₂ layer using HF as an etchant.
[0027]
Next, as shown in FIG. 2 (F), in order to form the reinforcing body 9, a paste in which silica particles are mixed with a binder is applied along the recesses on the back surface of the heat generating portion 5 and baked at 150 ° C. for 2 hours. Thus, a reinforcing body 9 in which the particles are consolidated is obtained.
[0028]
Next, as shown in FIG. 2G, the support 4 was formed by applying a paste containing a polyimide resin and curing it at 350 ° C. for 2 hours.
[0029]
Thereafter, the portion below the substrate 7 was covered with an etching resist and immersed in HF solution to dissolve the substrate 7. Thereby, as shown in FIG. 2 (H), the protective layer 1 having a smooth surface formed on the substrate 7 can be exposed. When the substrate 7 is removed, the substrate 7 is removed by mechanical grinding to a depth before reaching the protective layer 1 of the substrate 7, and then the substrate 7 is not deepened until reaching the protective layer 1 or until the entire substrate 7 is removed. By performing wet etching with a liquid or the like, the substrate 7 can be efficiently removed.
[0030]
Further, the substrate 7 may be removed so that the printing surface 1 corresponding to the heat generating portion 5 of the protective layer 1 is exposed as shown in FIG. If the substrate 7 is left in this way, the strength of the thermal head can be increased.
[0031]
FIG. 3 is a perspective view showing the thermal head having the reinforcing member 9 together with the roller 10 and the recording paper 11, and the reinforcing member 9 is arranged in an elongated shape under the region where the heat generating portions 5 are arranged in a horizontal row. By providing the groove-like depression on the back surface of the raised heat generating part 5 as the reinforcing body 9 made of ceramic or glass, the pressing force by the roller 10 is dispersed in the longitudinal direction of the reinforcing body 9. Thereby, the intensity | strength of a heat-generation laminated part can be improved, and even when hard particles, such as sand, are bitten, damage can be avoided. Further, it is not deformed by the pressing pressure of the roller. Therefore, a clear print can be made. The reinforcing body 9 reinforces even when the temperature of the heat generating part rises and the resin softens the support 4.
[0032]
In addition, since the heat generating portion 5 is formed so as to rise up in a convex shape, the heat generating portion is intensively pressed against the recording paper, and it is not necessary to apply useless pressing pressure, thereby simplifying the roller pressing structure. it can. Further, since the heat generating portion 5 is formed in a convex shape, the convex portion serves as a rib to increase the strength of the thermal head, and the bending in the longitudinal direction can be reduced. Further, if the substrate 7 is left as shown in FIG. 1B, the strength of the thermal head is further increased.
[0033]
FIG. 4A shows an example of a mounting structure of the driving IC 12 in the thermal head of the present invention. In this example, the driving IC is flip-chip between the individual electrode 3b formed on the back surface of the protective layer 1 and the connection electrode 13. The drive IC 12 is disposed on the back surface of the print surface 6 by being connected by bonding and embedded in the support 4 made of resin. The connection electrode 13 is connected to the external connection portion 14.
[0034]
Thus, since the driving IC 12 is arranged on the opposite side of the printing surface, the printing surface 6 and the printing surface 6 can be prevented from coming into contact with the recording paper 11 as in the conventional structure in which the driving IC is provided on the same surface as the printing surface 6. There is no need to separate the drive IC 12 from the drive IC 12, and the thermal head can be downsized. Further, there is no contact between the drive IC 12 and its external connection electrode 13 and the recording paper 11 and the like, and it is possible to eliminate the risk of occurrence of problems such as disconnection or short circuit of the electric system. In addition, since the support 4 made of resin can be used for fixing the driving IC 9, the number of parts and the number of processes can be reduced.
[0035]
In addition, this miniaturization can increase the number of thermal heads obtained from one collective substrate. As a result, a large number of films can be formed at one time, and the thermal head manufacturing efficiency can be improved. The cost of the thermal head can be reduced.
[0036]
In the reference example of FIG. 2, an inexpensive glass plate is used as the base 7, and the protective layer 1 is directly formed on a temporary substrate. After the formation of each layer on the base 7 and the mounting of the driving IC 12, The base 7 is removed by dissolving, but when an expensive plate material is used as the base 7, a sacrificial layer such as MgO is formed on the base 7, and the layers are formed as described above, and the driving IC is formed. After fixing, the sacrificial layer may be dissolved with phosphoric acid or the like to peel off the substrate 7 from the heat-generating laminated portion 2 and the substrate 7 may be reused.
[0037]
Further, the electrodes 3a, 3b, and 13 may be formed before the formation of the heating resistor 2, instead of being formed after the heating resistor 2 is formed.
[0038]
FIG. 4B is a cross-sectional view showing another embodiment of the thermal head of the present invention with respect to the heat generating laminated portion. In this embodiment, the barrier layer 8 is formed in a limited region immediately below the heat generating portion 5. In addition, a heat storage layer 15 as a partial glaze layer made of low-melting glass is provided, and the reinforcing body 9 is provided thereunder. As described above, by combining the heat storage layer 15 having a suitable material and thickness for the reinforcing body 9, the heat storage performance can be selected appropriately. The heat storage layer 15 may be provided on the back side of the reinforcing body 9.
[0039]
FIG. 5A is a cross-sectional view showing another embodiment of the present invention. In this embodiment, a rod-shaped reinforcing body 9 as shown in FIG. 5 is fixed to the groove-like portion. The same effect can be obtained by this embodiment.
[0040]
【The invention's effect】
According to the first and second aspects, since the reinforcing body is embedded in the back surface of the heat generating portion, the strength of the thermal head can be improved in combination with the fact that the heat generating portion is formed in a convex shape. Can provide a thermal head with high strength.
[0041]
Also, since the printing surface is prevented from being deformed by pressing the roller, the printing quality is not impaired over a long period of time, and it does not deform even if the printing surface rises and presses strongly, making contact with the recording paper in a small area. As a result, the pixels can be miniaturized, and the screen can be enlarged, the speed can be increased, and the power consumption can be reduced.
[0042]
According to the third aspect , in addition to the effects of the first and second aspects, by combining the heat storage layer with the reinforcing body, it is possible to obtain an effect that it is easy to obtain a thermal head having a heat storage action corresponding to a product.
[Brief description of the drawings]
FIG. 1A is a sectional view showing an embodiment of a thermal head according to the present invention, and FIG. 1B is a sectional view showing another embodiment of the thermal head of the present invention.
FIGS. 2A to 2H are diagrams showing a reference example of the manufacturing process of the thermal head of the present invention .
3A is a perspective view of the thermal head of the embodiment of FIG. 1A. FIG.
4A is a cross-sectional view showing an arrangement example of drive ICs in the embodiment of FIG. 1A, and FIG. 4B is a cross-sectional view showing another embodiment of the thermal head of the present invention.
5A is a sectional view showing another embodiment of a thermal head according to the present invention, and FIG. 5B is a perspective view showing an example of a reinforcing member used in the thermal head of FIG.
FIG. 6 is a cross-sectional view showing an example of a conventional thermal head.
[Explanation of symbols]
1: protective layer, 2: heat generating resistor, 3a: common electrode, 3b: individual electrode, 4: support, 5: heat generating part, 6: printing surface, 7: substrate, 7a: groove, 8: barrier layer, 9 : Reinforcing body, 10: Roller, 11: Recording paper, 12: Drive IC, 13: Electrode, 14: External connection part, 15: Heat storage layer, 16: Adhesive

Claims (3)

In a thermal head comprising a protective layer covering the surface of the heating resistor, and an electrode that is in contact with the heating resistor and forms a heating portion together with the heating resistor,
The surface of the protective layer is formed with a convexly raised printing surface, and the back surface of the heat generating portion is provided with a reinforcing body made of glass that is filled in the back surface of the heat generating portion and melted and solidified , and the reinforcing body is a resin. Alternatively, a thermal head characterized by being covered with a support made of a resin mixed with inorganic powder. In claim 1,
As the reinforcing body , a rod-shaped body filled and fixed on the back surface of the heat generating portion is used instead of the glass . In claim 1 or 2 ,
A thermal head, characterized in that a heat storage layer is provided between the heat generating part and the reinforcing body or between the reinforcing body and the support.

Images