JP2006001018A - Thermal head and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head which can attain a long life by suppressing a decrease of sealing performance that results from diffusion of conductive components from an upper layer to a lower layer in the thermal head equipped with both the lower layer and the upper layer with conductive properties as a protecting layer, and to provide its manufacturing method. <P>SOLUTION: In the thermal head, a heating resistor 5, an electrode 3 for energizing the heating resistor 5, and the protecting layer 6 formed to cover at least the heating resistor 5 are set on a substrate 1. The protecting layer 6 consists of the lower layer 6A and the upper layer 6B. At the same time, the upper layer 6B has the conductive properties. A thickness t1 of the lower layer is made not smaller than three times of a thickness t2 of the upper layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal head used as a component of a thermal printer and a manufacturing method thereof.

  A conventional thermal head is shown in FIG. 6 (see, for example, Patent Document 1). In the illustrated thermal head B, a glaze layer 92 made of glass or the like is formed on an insulating substrate 91, and an electrode 93, a heating resistor 95, and a protective layer 96 are further laminated. The protective layer 96 includes an insulating layer 96A formed by printing and baking glass so as to cover the heating resistor 95 and the electrode 93, and a conductive component such as a metal oxide added to cover the insulating layer 96A. It is composed of a two-layer structure with a conductive layer 96B formed by printing and baking glass. A platen roller P is provided at a position facing the heating resistor 95.

  When performing the printing process using the conventional thermal head B, the thermal recording paper S, which is an example of a printing medium, is pressed against the protective layer 96 by the platen roller P, and the thermal recording paper S is moved in the sub-scanning direction. While being moved, the heat generated in the heating resistor 95 is transmitted to the thermal recording paper S through the protective layer 96 and colored, whereby printing is performed. When the thermal recording paper S is moved while being pressed against the protective layer 96 in this way, static electricity is generated due to contact friction between the protective layer and the thermal recording paper. In the thermal head B, since the upper layer side of the protective layer 96 is the conductive layer 96B, static electricity is efficiently released without being charged. Therefore, as compared with a thermal head of a type that does not include the conductive layer 96B, the problem that the heating resistor is destroyed due to electrostatic discharge charged in the protective layer and heat generation becomes impossible can be avoided.

  However, in the conventional thermal head B, when the conductive layer 96B is formed, the insulating layer 96A softens, and the conductive component of the conductive layer 96B may diffuse into the lower insulating layer 96A. When such diffusion of the conductive component occurs, bubbles existing around the conductive component are also diffused into the insulating layer 96A, and the sealing performance of the heating resistor 95 is deteriorated. As a result, the deterioration of the heat generating resistor 95 is promoted, and as a result, there is a problem that the life of the thermal head B is shortened.

JP 2001-47652 A

  The present invention has been conceived under the circumstances described above, and is caused by diffusion of a conductive component from an upper layer to a lower layer in a thermal head having a lower layer and a conductive upper layer as a protective layer. It is an object of the present invention to provide a thermal head capable of suppressing a decrease in sealing performance and prolonging the life and a manufacturing method thereof.

  In order to solve the above problems, the present invention takes the following technical means.

  The thermal head provided by the first aspect of the present invention includes a heating resistor, an electrode for energizing the heating resistor, and a protection formed to cover at least the heating resistor on the substrate. The protective layer is composed of a lower layer and an upper layer, and the upper layer is a thermal head having conductivity, and the thickness of the lower layer is at least three times the thickness of the upper layer. It is characterized by that.

  According to such a configuration, since the thickness of the lower layer is sufficiently larger than the thickness of the upper layer, it is possible to suppress a decrease in sealing performance due to diffusion of the conductive component. Specifically, the degree to which the conductive component diffuses into the lower layer varies depending on the firing temperature for forming the upper layer and the formation conditions of the protective layer such as the softening point of the glass forming the upper layer and the lower layer. On the other hand, in order to prevent the upper layer from peeling from the lower layer, it is required to ensure the adhesion between the upper layer and the lower layer. For this reason, when forming the upper layer, at least one of the lower layer or the upper layer needs to be sufficiently softened. Here, when the lower layer is softened, the conductive component contained in the upper layer is likely to diffuse into the lower layer. Even if the conductive component diffuses into the lower layer in this way, according to the present invention, the thickness of the lower layer is sufficiently larger than three times the thickness of the upper layer. The conductive component does not diffuse in most regions except the upper portion of the lower layer. Therefore, the original function of the lower layer of insulation protection of the heating resistor is appropriately maintained, and the life of the thermal head can be extended.

  In preferable embodiment of this invention, the thickness of the said lower layer is 2 micrometers-13 micrometers. According to such a configuration, it is possible to cope with high-speed printing while ensuring the durability of the thermal head. In other words, if the thickness of the lower layer is too small, the heating resistor is likely to be exposed due to wear, and the durability is lowered. On the other hand, if the thickness of the lower layer is too large, the thermal response of the heating resistor is deteriorated. The thickness of the lower layer is preferably 2 μm to 13 μm because the printing speed is reduced or printing is not appropriately performed. When the thickness of the lower layer is set in such a range, it is possible to achieve appropriate durability and increase the printing speed.

  The thermal head manufacturing method provided by the second aspect of the present invention is formed on a substrate so as to cover at least the heating resistor, an electrode for energizing the heating resistor, and the heating resistor. The protective layer is a thermal head manufacturing method comprising a lower layer formed by baking glass and an upper layer formed by baking glass added with a conductive component. The firing temperature for forming the upper layer is lower than the softening point of the glass for forming the lower layer.

  According to such a manufacturing method, when the upper layer is formed, most of the lower layer is not softened, so that the conductive component contained in the upper layer can be efficiently prevented from diffusing into the lower layer. Therefore, it is possible to effectively suppress a decrease in the sealing performance of the heating resistor. Therefore, the original functions of the lower layer such as insulation protection of the heating resistor are appropriately maintained, and the life of the thermal head can be extended.

  Other features and advantages of the present invention will become more apparent from the following description of the embodiments of the invention.

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

  1 and 2 show an example of a thermal head according to the present invention. The thermal head A of this embodiment includes a substrate 1, a glaze layer 2, a common electrode 3, a plurality of individual electrodes 4, a heating resistor 5, and a protective layer 6. In FIG. 1, the protective layer 6 is not shown.

  The substrate 1 has an insulating property, and is made of, for example, alumina ceramic. The glaze layer 2 serves as a heat storage layer and serves to smooth the surface on which the common electrode 3, the individual electrode 4, and the like are formed and to increase the adhesive force thereof, and is formed over substantially the entire surface of the substrate 1. Has been.

  The common electrode 3 has a plurality of extending portions 3a protruding in a comb shape. The plurality of individual electrodes 4 are arranged in such a manner that one end portion thereof enters between the adjacent extending portions 3a. The other end of each individual electrode 4 is a bonding pad 4a, and each of these bonding pads 4a is in a conductive state with respect to an output pad of a driving IC (not shown).

  The heating resistor 5 is provided in a band shape having a constant width extending in a certain direction of the substrate 1 so as to straddle the plurality of extending portions 3a and the plurality of individual electrodes 4 in series. When the individual electrodes 4 are selectively energized by a driving IC (not shown), a region 50 (for example, a portion shown by cross-hatching in the figure) sandwiched between the extending portions 3a adjacent to each other in the heating resistor 5 Is configured to generate heat and form one heating dot.

  The protective layer 6 is provided so as to cover the surfaces of the common electrode 3, the individual electrode 4, and the heating resistor 5, and has a two-layer structure including a lower layer 6 </ b> A and a conductive upper layer 6 </ b> B. The thickness t1 of the lower layer is set to be three times or more the thickness t2 of the upper layer. As an example of these specific numerical values, the thickness t1 is 7 μm and the thickness t2 is 2 μm.

  Next, an example of a method for manufacturing a thermal head according to the present invention will be described.

  First, the substrate 1 on which the glaze layer 2, the common electrode 3, the individual electrode 4, and the heating resistor 5 are stacked is prepared. The glaze layer 2 is formed by printing and baking a glass paste. The common electrode 3 and the individual electrode 4 are formed by, for example, printing and baking a resinate gold paste and removing unnecessary portions by etching using a photolithography method. The heating resistor 5 is formed, for example, by printing and baking a ruthenium oxide paste. FIG. 3 is a cross-sectional view of the main part showing a state in which the glaze layer 2, the common electrode 3, the individual electrode 4 and the heating resistor 5 are formed on the substrate 1.

Next, as shown in FIG. 4, a lower layer 6 </ b> A is formed so as to cover the common electrode 3, the individual electrode 4, and the heating resistor 5. The lower layer 6A is formed by printing and baking an amorphous glass paste mainly composed of SiO ₂ and PbO. The softening point of the amorphous glass is, for example, 745 ° C. The firing temperature for forming the lower layer 6A (hereinafter referred to as “lower layer firing temperature”) is, for example, 800 ° C. Since the firing temperature of the lower layer (800 ° C.) is 55 ° C. higher than the softening point (745 ° C.) of the amorphous glass, the viscosity of the amorphous glass becomes small during firing and the fluidity is sufficient. Become bigger. As a result, the air bubbles inherent in the amorphous glass disappear, and the lower layer 6A having excellent sealing properties is formed.

Next, as shown in FIG. 5, an upper layer 6B is formed on the lower layer 6A. The upper layer 6B is formed by printing and baking a conductive glass paste in which a conductive component such as ruthenium oxide is added to amorphous glass mainly composed of PbO, B ₂ O ₃ and SiO ₂ . The softening point of the amorphous glass forming the upper layer 6B is, for example, 590 ° C. The firing temperature for forming the upper layer 6B (hereinafter referred to as “upper layer firing temperature”) is, for example, 680 ° C. The upper layer firing temperature (680 ° C.) is 65 ° C. lower than the softening point (745 ° C.) of the amorphous glass forming the lower layer 6A. For this reason, most of the lower layer 6A is not softened during firing of the upper layer 6B, and the conductive component contained in the upper layer 6B is efficiently suppressed from diffusing into the lower layer 6A. Therefore, it is possible to effectively suppress a decrease in sealing performance of the heating resistor 5. Therefore, the original function of the lower layer 6A such as insulation protection of the heating resistor 5 is appropriately maintained, and the life of the thermal head A can be extended. Further, the upper layer firing temperature is 90 ° C. higher than the softening point (590 ° C.) of the amorphous glass forming the upper layer 6B. Improved adhesion.

  In the thermal head A of the present embodiment, the thickness t1 of the lower layer is sufficiently larger than three times the thickness t2 of the upper layer. For this reason, even if the conductive component diffuses into the lower layer 6A when forming the upper layer 6B, the sealing performance of the heating resistor 5 is hardly affected. Specifically, unlike the manufacturing method described above, when the firing temperature of the upper layer is higher than the softening point of the glass forming the lower layer 6A, the lower layer 6A is softened during the firing of the upper layer 6B and the fluidity is increased. Then, the conductive component contained in the upper layer 6B may diffuse into the lower layer 6A beyond the boundary between the upper layer 6B and the lower layer 6A. Even in such a case, since the thickness t1 of the lower layer is sufficiently larger than the thickness t2 of the upper layer, the diffusion of the conductive component remains at the upper part in the lower layer 6A, and most of the regions excluding the upper part in the lower layer 6A. In this case, the conductive component does not diffuse. Therefore, the original function of the lower layer 6A, ie, insulation protection of the heating resistor 5 is appropriately maintained, and the life of the thermal head A can be extended.

  Further, when firing for forming the upper layer 6B, if the firing temperature of the upper layer is lower than the softening point of the glass forming the lower layer 6A as in the manufacturing method described above, the lower layer of the conductive component as described above. Diffusion to 6A is efficiently suppressed. As a result, it is possible to more effectively suppress a decrease in the sealing performance of the heating resistor 5, which is more suitable for extending the life of the thermal head A.

  By the way, if the thickness t1 of the lower layer is too small, the heat responsiveness of the heat generating resistor 5 to the printing medium is improved and high-speed printing is possible, but the heat generating resistor is easily exposed by wear and the durability is lowered. Resulting in. On the other hand, if the thickness t1 of the lower layer is too large, the durability is improved, but the thermal responsiveness of the heating resistor 5 is deteriorated, and the printing speed must be reduced or the printing is not appropriately performed. For this reason, the thickness t1 of the lower layer is preferably 2 μm to 13 μm. When the lower layer thickness t1 is set within such a range, it is possible to achieve appropriate durability and increase the printing speed.

  Since the upper layer 6B contains a conductive component, static electricity generated during the printing process is efficiently discharged without being charged. Moreover, since the upper layer 6B contains a conductive component, it is excellent in mechanical strength, and is superior in wear resistance as compared to the case where it does not contain a conductive component. Here, if the thickness t2 of the upper layer 6B is too small, the predetermined wear resistance cannot be obtained, and the adhesion with the lower layer 6A is deteriorated, and the upper layer 6B is likely to be peeled off or chipped. From this, the thickness t2 of the upper layer is preferably 0.5 μm to 4 μm. When the thickness t2 of the upper layer is set in such a range, the wear resistance and the adhesion with the lower layer 6A are appropriately ensured.

  For the upper layer 6B, for example, when ruthenium oxide particles having a particle diameter of 0.001 to 1 μm are added as a conductive component in a weight percentage of 0.3 to 30 wt% with respect to the conductive glass paste, The flow of the glass component is suppressed by the conductive component. For this reason, bubble marks are generated around the conductive component, which becomes a gap. As a result, the upper layer 6B is formed in a porous shape. When the upper layer 6B is porous as described above, the surface of the upper layer becomes uneven, so that many gaps are generated at the boundary between the upper layer 6B and the print medium during the printing process, and these adhesions are suppressed. Is done. Therefore, the printing medium is smoothly fed, which is preferable. When crystallized glass is used as the glass for forming the upper layer 6B, the upper layer 6B becomes more uniform and porous, which is more preferable.

  The present invention is not limited to the contents of the above-described embodiment. The specific configuration of each part of the thermal head according to the present invention can be variously modified without departing from the spirit of the invention.

  For example, the thickness of the lower layer and the upper layer may not be in the range shown in the above embodiment, and can be appropriately changed as long as the thickness of the lower layer is three times or more the thickness of the upper layer. The form of the glaze layer may be a form having a raised portion in addition to the planar form shown in the above embodiment. Also, the type of thermal head such as thin film type or thick film type is not questioned.

It is a principal part schematic plan view which shows an example of the thermal head which concerns on this invention. It is II-II sectional drawing of FIG. It is principal part sectional drawing which shows an example of the method of manufacturing the thermal head which concerns on this invention. It is principal part sectional drawing which shows an example of the method of manufacturing the thermal head which concerns on this invention. It is principal part sectional drawing which shows an example of the method of manufacturing the thermal head which concerns on this invention. It is principal part sectional drawing which shows the conventional thermal head.

Explanation of symbols

A Thermal head 1 Substrate 3 Common electrode 4 Individual electrode 5 Heating resistor 6 Protective layer 6A Lower layer 6B Upper layer t1 Lower layer thickness t2 Upper layer thickness

Claims (3)

The substrate has a heating resistor, an electrode for energizing the heating resistor, and a protective layer formed to cover at least the heating resistor. The protective layer includes a lower layer and an upper layer. And the upper layer is a thermal head having conductivity,
The thermal head according to claim 1, wherein the thickness of the lower layer is at least three times the thickness of the upper layer.   The thermal head according to claim 1, wherein the lower layer has a thickness of 2 μm to 13 μm. On the substrate, a heating resistor, an electrode for energizing the heating resistor, and a protective layer formed to cover at least the heating resistor,
The protective layer is a method for producing a thermal head comprising a lower layer formed by firing glass and an upper layer formed by firing glass added with a conductive component,
The method for producing a thermal head, wherein the firing temperature for forming the upper layer is lower than the softening point of the glass for forming the lower layer.

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