JP4367771B2 - Thermal head - Google Patents

Description

The present invention relates to a thermal head used as a component of a thermal printer.

  FIG. 6 shows a conventional example of a thermal head. 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 and a heating resistor 95 are formed on the glaze layer 92. A protective layer 96 is formed by printing and baking amorphous glass so as to cover the heating resistor 95 and the electrode 93. A platen roller P is provided at a position facing the heating resistor 95. During the printing process, the heat-sensitive recording paper S, which is an example of a print medium, is pressed against the protective layer 96 by the platen roller P, and the heat-generating resistor 95 generates heat while moving the heat-sensitive recording paper S in the sub-scanning direction. The generated heat is transmitted to the heat-sensitive recording paper S through the protective layer 96 and colored, whereby printing is performed.

  By the way, in a printing process using a thermal head, a so-called sticking phenomenon may occur. Sticking is a phenomenon in which the thermal recording paper sticks to the surface of the protective layer and the feeding of the thermal recording paper becomes irregular. Due to this sticking, there may be a printing defect such as white streaks on the thermal recording paper. In order to eliminate sticking, it is preferable that the surface of the protective layer is smooth so that the frictional resistance caused by sliding between the thermal recording paper and the protective layer can be reduced. Since amorphous glass is excellent in surface smoothness, it has been said that the use of amorphous glass for the protective layer as in the conventional thermal head B is suitable for suppressing sticking.

  As another example of a conventional thermal head, there is a protective layer having a two-layer structure in which different types of layers are stacked. For example, the lower layer of the two layers is a crystallized glass having excellent wear resistance. It is known that the upper layer is formed of amorphous glass (see, for example, Patent Document 1). According to such a structure, while maintaining the surface of a protective layer smooth, compared with the case where the whole protective layer is comprised with an amorphous glass, the abrasion resistance of a protective layer can be improved.

  However, even when the surface of the protective layer is smooth as described above, sticking may occur. If the surface of the protective layer is smooth, the friction coefficient of the surface of the protective layer can be reduced in a state where the printing process is not performed. However, when the printing process is performed, since the thermal recording paper is conveyed while being pressed against the protective layer, the adhesion of the thermal recording paper to the protective layer is enhanced. Further, when the protective layer or the thermal recording paper component is softened by the heat generated in the heating resistor, the adhesion is further enhanced. For this reason, it is considered that the thermal recording paper is unlikely to be separated from the surface of the protective layer, and sticking is likely to occur. As a means for suppressing sticking, a means for reducing the force for pressing the thermal recording paper against the protective layer may be considered. However, according to such a means, heat transfer to the thermal recording paper is not sufficiently performed, and the print quality is reduced. This causes a problem such as lowering.

JP-A-63-74658

The present invention has been conceived under the circumstances described above, and it is an object of the present invention to provide a thermal head capable of suppressing the occurrence of sticking and improving the quality of printing.

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

Thermal head that is in the onset Ming Thus provided, on a substrate, a heating resistor, an electrode for performing energization to the heating resistor, the protection is formed thereon so as to cover at least the heat-generating resistor and a layer, the protective layer includes a lower layer first protective layer, a thermal head which is formed by the upper second protective layer, the first protective layer, the amorphous glass And the second protective layer is formed of a crystallized glass and is porous, and the second protective layer is formed of a porous glass. The surface is characterized by unevenness .

According to such a configuration , the second protective layer, which is the upper layer side of the protective layer, is formed in a porous shape , and the surface of the second protective layer is formed in an uneven shape. The adhesion with the protective layer is reduced, and as a result, the occurrence of sticking can be suppressed. That is, as described above, conventionally, in order to reduce the frictional resistance caused by sliding between the thermal recording paper and the protective layer, the surface of the protective layer is preferably smooth. However, sticking occurred even when the surface of the protective layer was smooth. Therefore, contrary to the conventional case, the surface of the protective layer is formed in an uneven shape so that the contact area between the thermal recording paper and the protective layer during the printing process is reduced. did. The thermal print head of the present invention uses crystallized glass for the second protective layer, and is fired at a temperature not higher than 50 ° C. below the softening point, whereby the flow of the glass is suppressed by the crystal component, and the second protective layer is porous. Jo the formed, thereby, it is possible to form the surface of the second protective layer uneven. Therefore, it is not necessary to add another process such as a surface treatment process after firing the second protective layer, and the thermal head according to the present invention can be obtained by the same process as that of the prior art. Therefore, it is possible to suppress the occurrence of sticking while suppressing an increase in manufacturing cost. Moreover, since the first protective layer is made of amorphous glass, it has excellent sealing properties, and can properly exhibit its original function of protecting the heating resistor and the electrode. Note that in the case of performing the printing process using the thermal head according to the present invention, there is no need to take measures such to reduce the force for pressing the example recording paper as sticking measures the protective layer, to improve the quality of the printing Can be planned.

  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. It is formed over substantially the entire surface. 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 common electrode 3 and the individual electrode 4 are formed, for example, by printing and baking a resinate gold paste. 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. For example, a ruthenium oxide paste is printed. -It is formed by firing. 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 includes a first protective layer 6 </ b> A made of amorphous glass and a second protective layer 6 </ b> B made of crystallized glass. Is a two-layer structure. The second protective layer 6B is a porous layer formed so as to cover the first protective layer 6A.

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

  First, the substrate 1 on which the glaze layer 2, the common electrode 3, the individual electrode 4, and the heating resistor 5 are formed is prepared. 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, the first protective layer 6 </ b> A is formed so as to cover the common electrode 3, the individual electrode 4, and the heating resistor 5. The first protective layer 6A is formed by printing and baking an amorphous glass paste mainly composed of SiO ₂ , B ₂ O ₃ and PbO. The softening point of the amorphous glass is 680 ° C. The firing temperature for forming the first protective layer 6A (hereinafter referred to as “first firing temperature”) is 760 ° C. Since the first firing temperature (760 ° C.) is a temperature that is 80 ° C. higher than the softening point (680 ° C.) of the amorphous glass, the viscosity of the amorphous glass decreases during firing, and its fluidity is Become big enough. As a result, the air bubbles inherent in the amorphous glass disappear, and the first protective layer 6A having excellent sealing properties is formed.

Next, as shown in FIG. 5, a second protective layer 6B is formed on the first protective layer 6A. The second protective layer 6B is formed by printing and baking a crystallized glass paste mainly composed of SiO ₂ , ZnO, and CaO. The softening point of the crystallized glass is 785 ° C. The firing temperature for forming the second protective layer 6B (hereinafter referred to as “second firing temperature”) is 760 ° C. The second protective layer 6B is made of crystallized glass, and the second baking temperature (760 ° C.) is a temperature near the softening point (785 ° C.) of the crystallized glass. At the time of firing, since the crystal component suppresses the flow of the crystallized glass, the air bubbles inherent in the crystallized glass remain, and this becomes a void. As a result, the second protective layer 6B has a porous shape having a large number of voids. In addition, since the softening point (680 ° C.) of the amorphous glass for forming the first protective layer 6A is 80 ° C. lower than the second baking temperature (760 ° C.), the second protective layer 6B is When firing, the first protective layer 6A is sufficiently softened to improve the adhesion with the second protective layer 6B. In addition, according to the present embodiment, since the first baking temperature and the second baking temperature are substantially the same, it is necessary to change the baking temperature when forming the first protective layer 6A and the second protective layer 6B. Absent.

  According to such an embodiment, the second protective layer 6B of the thermal head A is formed in a porous shape, and the surface of the second protective layer 6B is uneven. Therefore, when the thermal head A is used to perform the printing process on the thermal recording paper, the occurrence of sticking is suppressed. Since the second protective layer 6B is porous, even if the second protective layer 6B is slightly worn due to sliding contact with the heat-sensitive recording paper during the printing process, the surface of the second protective layer 6B has an uneven shape and suppresses sticking. The effect can be maintained appropriately. Further, it is not necessary to add another process such as a sandblasting process to form the surface of the second protective layer 6B in an uneven shape, and the thermal head A can be obtained by a process similar to the conventional one. Therefore, according to the said embodiment, generation | occurrence | production of sticking can be suppressed, suppressing the raise of manufacturing cost. Further, it is not necessary to reduce the force for pressing the heat-sensitive recording paper against the protective layer 6 during the printing process, and the printing quality can be improved.

  When the second baking temperature is in the temperature range from 20 ° C. lower to 50 ° C. higher than the softening point of the crystallized glass for forming the second protective layer 6B as in the above embodiment, the second protection At the time of firing the layer 6B, although the flow of the entire glass is suppressed by the crystal component, the viscosity of the crystallized glass becomes small. Thereby, the 2nd protective layer 6B is formed as a porous shape with the size of a cavity part, and the distribution of the cavity part in the whole layer more uniform, and can suppress generation | occurrence | production of sticking more effectively.

  When the softening point of the amorphous glass for forming the first protective layer 6A is not more than 50 ° C. lower than the second baking temperature as in the above embodiment, the second protective layer 6B is fired. In addition, since the first protective layer 6A is sufficiently softened, the adhesion between the first protective layer 6A and the second protective layer 6B is improved. Therefore, the problem that the second protective layer 6B peels off from the first protective layer 6A during the printing process is suppressed, and the durability of the thermal head A is improved.

  As in the above embodiment, the softening point of the amorphous glass for forming the first protective layer 6A should be lower than the temperature lower by 50 ° C. than the softening point of the crystallized glass for forming the second protective layer 6B. For example, even if the second firing temperature is set to a temperature near the softening point of the second protective layer 6B, the first protective layer 6A can be sufficiently softened when the second protective layer 6B is fired. Therefore, the adhesiveness between the first protective layer 6A and the second protective layer 6B can be improved while suppressing the manufacturing cost by setting the second baking temperature low.

  According to the embodiment, since the first firing temperature and the second firing temperature are substantially the same, the temperature management in the manufacturing process is simplified, and as a result, the productivity of the thermal head A is improved.

  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 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 first protective layer 6B second protective layer

Claims (1)

The substrate has a heating resistor, an electrode for energizing the heating resistor, and a protective layer formed in an upper layer so as to cover at least the heating resistor. a first protective layer side, a thermal head which is formed by a second protective layer on the upper layer side,
The first protective layer is made of an amorphous glass, and is formed so that the bubbles inherent in the amorphous glass disappear.
The thermal head is characterized in that the second protective layer is made of crystallized glass and is formed in a porous shape, and the surface of the second protective layer is uneven .

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