Thermal print head capable of improving both printing quality and service life

Abstract

The present invention proposes a thermal print head that can improve both the printing quality and the service life. A groove is provided on the base along the main printing direction. The groove corresponds to the position of the heating resistor. A first solid material layer and a second solid material layer are provided in the groove from bottom to top. The solid material in the first solid material layer has a preset thermal expansion coefficient, and the solid material in the second solid material layer has a preset elasticity and thermal conductivity. A gap is left between the upper surface of the second solid material layer and the lower surface of the ceramic substrate. After the solid material in the first solid material layer expands, the second solid material layer can be brought into contact with the ceramic substrate, and the heat generated by the heating resistor is conducted to the base through the second solid material layer. The above-mentioned thermal print head can improve the printing concentration by reducing the heat loss in the early stage of printing, and improve the tailing problem of the thermal print head and increase the service life by increasing the heat conduction to the outside in the later stage of printing.

Description

Technical Field

[0001] The invention relates to the technical field of thermal printing, and in particular to a thermal printing head capable of improving both printing quality and service life. Background Art

[0002] As is known to all, a thermal print head includes a substrate made of an insulating material, on which a base glaze layer is provided, and above the base glaze layer, a wire electrode is provided. The wire electrode is divided into individual electrodes and common electrodes. The electrodes connecting the heating resistor and the control IC along the secondary printing direction are called individual electrodes, and the electrodes connecting the heating resistor and the printing power supply along the secondary printing direction are called common electrodes. A heating resistor belt arranged along the main printing direction is formed on the wire electrode, and a protective layer is provided above the wire electrode and the heating resistor belt. The substrate and the PCB are adhered to a metal base with tape, and the connection between the substrate and the PCB is encapsulated with encapsulation glue such as epoxy resin.

[0003] In the early stage of thermal printing, the overall base temperature of the thermal print head is equal to the ambient temperature. Due to the low ambient temperature, the heat generated by the thermal print head during printing is partially transferred to the thermal printing medium, and the rest of the heat is quickly transferred to the base and the surrounding air through the substrate, making the printing density often shallow. After a period of printing, the heat gradually accumulates, the printing density gradually deepens, and the tailing problem occurs; in addition, since the heating element itself is a heating source, the heat accumulates the most, and long-term printing will cause thermal shock to the heating element itself, and the wear resistance of the protective layer above the heating element is also reduced at high temperatures, which can easily reduce the service life of the thermal print head.

[0004] In order to solve the above problems, some solutions have been proposed in the prior art. For example, the invention patent with publication number CN104401135B discloses that a high thermal conductivity interlayer such as ALN, AL2O3, BeO, SiO2, BN, etc. is added between two glaze layers, and the high thermal conductivity interlayer is connected to the base during high-speed printing to dissipate heat quickly, and the connection is disconnected during medium and low-speed printing, thereby increasing the applicable occasions of the print head. However, due to its high thermal conductivity, the high thermal conductivity interlayer added in this solution will still dissipate some heat from the heating element during low-speed printing.

[0005] The utility model patent with publication number CN202271663U discloses a thermal print head with variable thermal conductivity of the bottom glaze layer, which has high thermal conductivity when printing and low thermal conductivity when not printing, so as to improve the printing quality. However, the variable thermal conductivity glaze layer in this scheme switches between low thermal conductivity and high thermal conductivity according to the presence or absence of current, but the switching speed of thermal conductivity is certain, so this scheme is only applicable to a certain range of printing speeds.

[0006] The invention patent with publication number CN101096148B discloses a thermal print head with a glass substrate with a groove under the heating element. The air in the groove can reduce heat loss and improve the printing density. However, although this solution improves the density, long-term heat accumulation will reduce the service life of the thermal print head. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention proposes a thermal print head that can improve both the printing quality and the service life, so as to improve the printing concentration by reducing the heat loss in the early stage of printing, and improve the tailing problem of the thermal print head and increase the service life by increasing the heat conduction to the outside in the later stage of printing.

[0008] In order to achieve the above-mentioned purpose, the present invention proposes a thermal print head that can improve both the printing quality and the service life, including a metal base, a substrate and a PCB made of an insulating material are arranged on the base, an underglaze layer is arranged on the substrate, and a wire electrode is arranged on the underglaze layer, or a wire electrode is arranged on the substrate and the underglaze layer, and the wire electrode is divided into an individual electrode and a common electrode, and a heating resistor is arranged between the individual electrode and the common electrode along the main printing direction, one end of the common electrode is connected to the heating resistor, and the other end thereof is connected to a printing power supply, one end of the individual electrode is connected to the heating resistor, and the other end thereof is connected to a control IC, and A protective layer is provided above the wire electrode and the heating resistor, and a groove is provided on the base along the main printing direction, the groove corresponds to the position of the heating resistor, and a first solid material layer and a second solid material layer are provided in the groove from bottom to top, wherein the solid material in the first solid material layer has a preset thermal expansion coefficient, and the solid material in the second solid material layer has preset elasticity and thermal conductivity, and a gap is left between the upper surface of the second solid material layer and the lower surface of the substrate, and after the solid material in the first solid material layer thermally expands, the second solid material layer can be brought into contact with the substrate, and the heat generated by the heating resistor is conducted to the base through the second solid material layer.

[0009] Preferably, the groove width is 1.2-2 mm.

[0010] Preferably, the upper surface of the second solid material layer is spaced from the lower surface of the substrate by a distance of 1.5 mm to 3 mm.

[0011] Preferably, the thermal expansion coefficient of the solid material in the first solid material layer is greater than 23.3*10 -6 .

[0012] Preferably, the Shore hardness of the solid material in the second solid material layer is ≤80HA.

[0013] Preferably, the thermal conductivity of the solid material in the second solid material layer is ≥10w / m*k.

[0014] The beneficial effect of this solution of the present invention is that the thermal print head that can improve both the printing quality and the service life can reduce heat loss in the initial stage of printing, increase the printing concentration, and after the heat accumulates to a certain extent, it can quickly conduct the heat downward to the base, improve the tailing phenomenon, reduce the thermal shock to the heating resistor, and increase the service life of the thermal print head. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The cross-sectional structure diagram of the thermal print head involved in the present invention is shown.

[0016] Figure 2 The schematic diagram of the top view of the thermal print head involved in the present invention is shown.

[0017] Figure 3 The figure shows the connection relationship between the heating resistor and the lead electrode involved in the present invention.

[0018] Figure numerals: 1-ceramic substrate, 2-base glaze layer, 3-heating resistor, 4-common electrode, 5-individual electrode, 6-protective layer, 7-base, 8-first solid material layer, 9-second solid material layer, 10-packaging glue, 11-PCB, 12-control IC, 13-socket. DETAILED DESCRIPTION

[0019] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0020] like Figure 1-3 As shown, the thermal print head of the present invention which can improve both the printing quality and the service life comprises a ceramic substrate 1, on which a lead-free amorphous glass bottom glaze layer 2 is fully or partially printed, and the ceramic substrate 1 with the bottom glaze layer 2 is sintered at a temperature of 1200°C to 1300°C; then, a conductive paste is printed and sintered on the surface of the ceramic substrate 1 and the bottom glaze layer 2, and the sintering temperature is 800°C to 920°C, and then a common electrode 4 and an individual electrode 5 are formed by photolithography technology, and then strip coating is performed along the main printing direction of the thermal print head, and sintered at a temperature of 780°C to 850°C to form a heating resistor 3 with a thickness of 4μm to 8μm; as shown Figure 3As shown, one end of the common electrode 4 is connected to the heating resistor 3 along the sub-printing direction, and the other end thereof is connected to the printing power supply; one end of the individual electrode 5 is connected to the heating resistor 3 along the sub-printing direction, and the other end thereof is connected to the control IC 12 configured on the PCB 11; finally, glass slurry is coated on the heating resistor 3 and other parts as a protective layer 6, and the ceramic substrate 1 after the above-mentioned process is sintered at a temperature of 810℃-870℃.

[0021] The metal sheet is made into a base 7 according to the design shape of the drawing by a CNC machine tool. A groove is provided on the base 7 along the main printing direction. The groove corresponds to the position of the heating resistor 3, and the groove width of the groove is 1.2-2 mm.

[0022] A first solid material layer 8 and a second solid material layer 9 are sequentially arranged in the groove from bottom to top, wherein the solid material in the first solid material layer 8 has a preset thermal expansion coefficient, and the solid material in the first solid material layer 8 can be a polymer material or a metal material. The solid material in the second solid material layer 9 has a preset elasticity and thermal conductivity, and a gap is left between the upper surface of the second solid material layer 9 and the lower surface of the ceramic substrate 1. The distance between the upper surface of the second solid material layer 9 and the lower surface of the ceramic substrate 1, the thermal expansion coefficient of the solid material in the first solid material layer 8, and the elasticity of the solid material in the second solid material layer 9 are related. After the solid material in the first solid material layer 8 is thermally expanded, the second solid material layer 9 can be brought into contact with the ceramic substrate 1.

[0023] In this embodiment, the upper surface of the second solid material layer 9 is spaced 1.5 mm to 3 mm from the lower surface of the ceramic substrate 1, and the thermal expansion coefficient of the solid material in the first solid material layer 8 is greater than 23.3*10 -6 The Shore hardness of the solid material in the second solid material layer 9 is ≤80HA, and the thermal conductivity is ≥10w / m*k.

[0024] The high elasticity of the second solid material layer 9 is to prevent the high thermal expansion coefficient solid material from excessively expanding due to heat and damaging the upper ceramic substrate 1. The high elasticity and high thermal conductivity solid material can use a high thermal conductivity silicone sheet on the market.

[0025] The ceramic substrate 1 and the PCB 11 are attached to the base 7 with adhesive tape, and the control IC 12 is connected to the individual electrodes 5 on the ceramic substrate 1 by pressure welding or flip-chip welding, and the control IC 12 is connected to the PCB 11. The control IC 12 and the connection between the ceramic substrate 1 and the PCB 11 are sealed with an encapsulating glue 10 such as epoxy resin. The PCB 11 is also provided with a socket 13 for connecting to the printer body.

[0026] In the specific printing process, at the beginning of printing, the ceramic substrate 1 corresponding to the position of the heating resistor 3 does not contact the second solid material layer 9 in the groove, so the heat generated by the heating resistor 3 cannot be conducted downward, the heat is accumulated, and the printing concentration is improved; after printing for a period of time, the heat accumulation causes the overall temperature of the thermal print head to increase, causing the solid material with a high thermal expansion coefficient to expand thermally and increase in volume, thereby causing the second solid material layer 9 above to contact the ceramic substrate 1, and the heat generated by the heating resistor 3 is quickly conducted to the base 7 through the second solid material layer 9, so as to reduce the heat accumulated on the heating resistor 3, reduce the thermal shock to the heating resistor 3, and increase the service life of the thermal print head, while improving the tailing phenomenon and improving the printing quality.

[0027] The thermal print head involved in the present invention, which can improve both the printing quality and the service life, can reduce heat loss in the initial stage of printing and improve the printing concentration. After the heat accumulates to a certain extent, the heat can be quickly conducted downward to the base, improving the tailing phenomenon, reducing the thermal shock to the heating resistor, and improving the service life of the thermal print head.

Claims

1. A thermal print head capable of improving both printing quality and service life, comprising a metal base, a substrate and a PCB made of an insulating material are arranged on the base, an underglaze layer is arranged on the substrate, a wire electrode is arranged on the underglaze layer, or a wire electrode is arranged on the substrate and the underglaze layer, the wire electrode is divided into an individual electrode and a common electrode, a heating resistor is arranged between the individual electrode and the common electrode along the main printing direction, one end of the common electrode is connected to the heating resistor, and the other end thereof is connected to a printing power source, one end of the individual electrode is connected to the heating resistor, and the other end thereof is connected to a control IC, a protective layer is arranged above the wire electrode and the heating resistor, and the characteristics are: A groove is provided on the base along the main printing direction, the groove corresponds to the position of the heating resistor, and a first solid material layer and a second solid material layer are provided in the groove from bottom to top, wherein the solid material in the first solid material layer has a preset thermal expansion coefficient, and the solid material in the second solid material layer has a preset elasticity and thermal conductivity, and a gap is left between the upper surface of the second solid material layer and the lower surface of the substrate, and after the solid material in the first solid material layer is thermally expanded, the second solid material layer can be brought into contact with the substrate, and the heat generated by the heating resistor is conducted to the base through the second solid material layer; wherein the groove width of the groove is 1.2~2mm; the upper surface of the second solid material layer and the lower surface of the substrate are spaced 1.5mm~3mm apart; the thermal expansion coefficient of the solid material in the first solid material layer is greater than 23.3*10 -6 .

2. The thermal print head capable of improving both printing quality and service life according to claim 1, characterized in that: The Shore hardness of the solid material in the second solid material layer is ≤80HA.

3. The thermal print head capable of improving both printing quality and service life according to claim 1 or 2, characterized in that: The thermal conductivity of the solid material in the second solid material layer is ≥10w / m*k.

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