Multi-color printing thermal print head and printing method

Abstract

The present invention relates to the technical field of manufacturing thermal printing devices, specifically a multi-color printing thermal print head and a printing method that can meet the different hair color temperature requirements in multi-color printing and can significantly improve the printing quality. It is characterized in that the heating element includes two rows of heating resistor bodies parallel to each other, and two bottom glaze layers corresponding to each other and parallel to each other are provided for the bottom glaze layer. Among them, a first bottom glaze layer is provided below the first heating resistor body, and a second bottom glaze layer is provided below the second heating resistor body. The first bottom glaze layer and the first heating resistor body are arranged close to the paper feeding side, and the second bottom glaze layer and the second heating resistor body are arranged close to the paper discharging side. The thickness of the first bottom glaze layer is at least 1.5 times the thickness of the second bottom glaze layer, and the width of the first bottom glaze layer is greater than the width of the second bottom glaze layer.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal printing device manufacturing, and specifically relates to a multi-color printing thermal printing head and a printing method that can meet the different color development temperature requirements in multi-color printing and can significantly improve the printing quality. Background Art

[0002] As is well known, a thermal printing head includes an insulating substrate made of an insulating material. A base layer is made on the insulating substrate, and there are wire electrodes above the base layer. The wire electrodes are divided into individual electrodes and common electrodes. The ones connecting the heating resistor strip and the control IC along the sub-printing direction are called individual electrodes, and the ones connecting the heating resistor and the conductive pattern along the sub-printing direction are called common electrodes. A heating resistor strip arranged along the main printing direction is formed on the wire electrodes, and there is a protective layer above the conductive pattern and the heating resistor strip.

[0003] Thermal multi-color printing uses a thermal printing head to provide different color development temperatures to achieve different color displays on the thermal printing medium. By controlling the heating of the thermal printing head to provide different color development temperatures, different color displays on the thermal printing medium are achieved. The existing thermal printing head has a fixed thermal printing structure and a fixed power according to the printing speed. Therefore, when performing multi-color printing, different printing temperatures are achieved by adjusting the opening time of the heating points. For low temperature, a short opening time is required, and for high temperature, a long opening time is required. Since the high-temperature color development layer has a high heating temperature at the heating point, it will reach the color of the low-temperature color development layer during the cooling process. To reduce the color interference of the low-temperature layer, the thermal printing head needs to have a fast heat dissipation speed; while the low-temperature color development layer requires a low printing heat temperature and a short opening time of the thermal printing head. To ensure the printing quality, the cooling speed of the thermal printing head should be slowed down. Therefore, for the same printing medium, the high-temperature heating layer and the low-temperature heating layer have different structural requirements for the thermal printing head. However, the existing thermal printing head only has a fixed single-row heating element structure and cannot meet the multi-color layer temperature printing requirements.

[0004] The thermal printing head in the patent document JP2010-201693 is provided with a double-row heating resistor. The double-row heating resistor can perform two printings at the same position on the printing paper. Since it is heated in two steps, heat concentration can be avoided and damage to the medium can be reduced. However, this technical solution essentially shortens the ON time required for printing and realizes high-speed printing without reducing the gray scale. The two rows of heating resistors are arranged side by side tightly with equal volume and specifications. During printing, the opening time of the two rows of heating resistors changes, but the power of the single-row heating resistor does not change. When applied to multi-color printing, it still cannot overcome the problem of multi-color bleeding caused by heat accumulation. Summary of the Invention

[0005] In view of the disadvantages and deficiencies existing in the prior art, the present invention provides a multi-color printing thermal print head and a printing method with double rows of heating elements and double rows of local heat storage layers, which can overcome the problems of insufficient color development of the low-temperature color development layer or bleeding of the high-temperature color development layer in multi-color printing, and effectively extend the service life of the thermal print head.

[0006] The present invention is achieved by the following measures:

[0007] A multi-color printing thermal print head is provided with an insulating substrate, on which a bottom glaze layer and electrode leads are provided. A common electrode and individual electrodes are provided on the surface of the insulating substrate and the bottom glaze layer. The heating element is arranged between the common electrode and the individual electrodes. One end of the common electrode is connected to the heating resistor body, and the other end is connected to the power supply; one end of the individual electrode is connected to the heating element, and the other end is connected to the control IC. The control IC is connected to the other end of the power supply; the control IC is used to control the on / off state of a single heating point in the heating element. It is characterized in that the heating element includes two rows of heating resistor bodies parallel to each other, and two bottom glaze layers parallel to each other are correspondingly arranged on the bottom glaze layer. A first bottom glaze layer is arranged below the first heating resistor body, and a second bottom glaze layer is arranged below the second heating resistor body. The first bottom glaze layer and the first heating resistor body are arranged close to the paper feeding side, and the second bottom glaze layer and the second heating resistor body are arranged close to the paper discharging side. The thickness of the first bottom glaze layer is at least 1.5 times the thickness of the second bottom glaze layer, and the width of the first bottom glaze layer is greater than the width of the second bottom glaze layer.

[0008] In the present invention, the distance between the two rows of heating resistor bodies on the insulating substrate ranges from 0.75 mm to 1.25 mm.

[0009] In the present invention, the first heating resistor body is located at the center of the first bottom glaze layer or deviated towards the paper discharging side, and the second heating resistor body layer is located at the center of the second bottom glaze layer or deviated towards the paper feeding side. Since the same rubber roller is used during printing, this structure can effectively increase the local pressure of the contact between the rubber roller and the two parts of the heating elements, thereby ensuring the color development quality.

[0010] In the present invention, corresponding to the two rows of heating resistor bodies, two control ICs are provided. The common electrode is arranged between the two rows of heating resistor bodies and is respectively connected to the first heating resistor body and the second heating resistor body on both sides. The two control ICs are respectively arranged on the paper feeding side of the first heating resistor body and the paper discharging side of the second heating resistor body to be respectively connected to the first heating resistor body and the second heating resistor body.

[0011] The first underglaze layer and the first heating resistor of the present invention are close to the paper feeding side and are used to print the low-temperature color-developing layer. The second underglaze layer and the second heating resistor are close to the paper discharging side and are used to print the high-temperature color-developing layer. The thickness and width of the first underglaze layer are greater than the width and thickness of the second underglaze layer. The thickness of the first underglaze layer is more than 1.5 times that of the second underglaze layer. Thickening the first underglaze layer can slow down the heat dissipation, and thinning the second underglaze layer can accelerate the heat dissipation speed and reduce the bleeding caused by the low-temperature color-developing layer.

[0012] An insulating protective layer is also provided on the insulating substrate of the present invention. The insulating protective layer covers the surfaces of the heating resistor, the common electrode, and the individual electrodes. Two parts of the control IC and a printed circuit board are also provided on the insulating substrate, and the insulating substrate is arranged on the base.

[0013] The present invention also provides a printing method for the multi-color printing thermal print head as described above, which is characterized in that when multi-color printing is performed, the following steps are executed:

[0014] Step 1: Determine the multi-color printing content in the current printing line, and group the printing control data according to the multi-color printing content. Among them, the printing control data for low-temperature color development is divided into the first group, and the printing control data for high-temperature color development is used as the second group;

[0015] Step 2: The first group of printing control data is sent by the control IC connected to the first heating resistor to complete the low-temperature color development printing through the first heating resistor close to the paper feeding side; the second group of printing control data is sent by the control IC connected to the second heating resistor to complete the high-temperature color development printing through the second heating resistor close to the paper discharging side. The second group of printing control data is delayed by a time △T as a whole compared with the first group, where △T = L / V, L is the distance between two rows of heating resistors, and V is the printing speed, and the printing speed is the paper feeding speed of the rubber roller;

[0016] Step 3: Repeat Step 1 to Step 2 until the entire page of printing content is completed.

[0017] The present invention further provides a three-color printing method. When multi-color printing is performed, the printing control data for low-temperature color development and high-temperature color development is grouped according to the color development temperature range, and the printing control data of the current printing line is divided into two levels according to the low-temperature color development temperature and the high-temperature color development temperature, which specifically includes the following steps:

[0018] Step 1: Determine the three-color printing content in the current printing line, and group the printing control data according to the three-color printing content. Among them, the color development temperatures of the three colors are 90°C, 130°C, and 170°C respectively. The printing control data corresponding to 90°C and 130°C is used as the first group of printing control data, and the printing control data for 170°C color development is used as the second group;

[0019] Step 2: By sending print control data, control the first heating resistor and the second heating resistor to generate heat respectively to achieve three-color printing. Specifically:

[0020] Step 2-1: Complete the printing of the printing content corresponding to the medium-low temperature coloring temperature:

[0021] The first set of print control data is sent by the control IC connected to the first heating resistor to complete low-temperature coloring printing through the first heating resistor near the paper feeding side. Among them, the first set of print control data is sent in two times. The low-temperature coloring printing content is realized by the print control data sent for the first time in the first set of print control data. The medium-temperature coloring printing content is realized by sending the data in the first set of print control data twice. After the first heating resistor accumulates to reach above the medium-temperature coloring temperature under the control of the two print data, it prints and colors.

[0022] Among them, the opening time corresponding to the data sent for the second time in the first set of print control data is at least 60% lower than the opening time of the first time.

[0023] Step 2-2: Complete the printing of the printing content corresponding to the high-temperature coloring temperature: After an interval of ΔT time, the second set of print control data is sent by the control IC connected to the second heating resistor to complete high-temperature coloring (170 °C) printing through the second heating resistor near the paper discharging side. In order to reduce the mutual interference between different colors and improve the printing speed, it is necessary to heat to above the coloring temperature at one time. Among them, ΔT = L / V, L is the distance between two rows of heating resistors, and V is the printing speed, and the printing speed is the feeding speed of the rubber roller.

[0024] Step 3: Repeat Step 1 to Step 2 until the printing of the entire page content is completed.

[0025] In the multicolor printing thermal print head proposed by the present invention, the low-temperature coloring layer and the high-temperature coloring layer are printed separately, removing the interference of the low-temperature coloring layer on the high-temperature coloring layer. Compared with the fixed single-row heating element structure, the printing speed can be increased by more than 1.5 times.

[0026] The present invention sets two parts of the underglaze layer to respectively cope with the occasions of low-temperature coloring and high-temperature coloring, and at the same time improves the printing effect at two coloring temperatures, simplifies the control method, and has remarkable advantages such as reasonable structure, simple production process, reliable operation, and good printing effect compared with the prior art. Brief Description of the Drawings

[0027] Attached Figure 1 is a schematic cross-sectional structure diagram of the present invention.

[0028] Attached Figure 2 is a schematic surface circuit diagram of the present invention.

[0029] AttachedFigure 3 It is a schematic comparison diagram of the printing effect in the present invention.

[0030] Appendix Figure 4 It is a schematic diagram of the temperature rise and time curve of the heating resistor body during three-color printing in Embodiment 3 of the present invention, where Figure 4 (a) is the curve graph corresponding to the printed content with low-temperature color development, Figure 4 (b) is the curve graph corresponding to the printed content with medium-temperature color development, Figure 4 (c) is the curve graph corresponding to the printed content with high-temperature color development.

[0031] Appendix Figure 5 It is a schematic diagram of the printing effect comparison in Embodiment 2 of the present invention.

[0032] Appendix Figure 6 It is a schematic diagram of the printing effect comparison in Embodiment 1 of the present invention.

[0033] Reference numerals: heat dissipation base 1, insulating substrate 2, first bottom glaze layer 3, first heating resistor body 4, protective layer 5, second bottom glaze layer 6, second heating resistor body 7, rubber roller 8. Detailed implementation manners

[0034] The present invention will be further described below with reference to the drawings and embodiments.

[0035] As shown in Appendix Figure 1 and Appendix Figure 2 The present invention provides a multicolor printing thermal print head, which is provided with an insulating substrate 2. A bottom glaze layer and electrode leads are provided on the insulating substrate 2. A common electrode and individual electrodes are provided on the surfaces of the insulating substrate and the bottom glaze layer. The heating element is arranged between the common electrode and the individual electrodes. One end of the common electrode is connected to the heating resistor body, and the other end is connected to the power supply; one end of the individual electrode is connected to the heating element, and the other end is connected to the control IC. The control IC is connected to the other end of the power supply; the control IC is used to control the on / off state of a single heating point in the heating element. The above are all conventional configurations of the thermal print head and will not be elaborated here;

[0036] In the present invention, as shown in Appendix Figure 1 , 2 The heating element includes two rows of heating resistor bodies parallel to each other. Two bottom glaze layers parallel to each other are correspondingly arranged for the bottom glaze layer. The first bottom glaze layer 3 is arranged below the first heating resistor body 4, and the second bottom glaze layer 6 is arranged below the second heating resistor body 7. The first bottom glaze layer 3 and the first heating resistor body 4 are arranged near the paper feeding side, and the second bottom glaze layer 6 and the second heating resistor body 7 are arranged near the paper discharging side. The thickness of the first bottom glaze layer 3 is at least 1.5 times the thickness of the second bottom glaze layer 6, and the width of the first bottom glaze layer 3 is greater than the width of the second bottom glaze layer 6.

[0037] In the present invention, the distance range between two rows of heating resistors on the insulating substrate 2 is 0.75 mm - 2.0 mm. The precondition for setting this distance range is that the heating resistors R are all above the center of the bottom glaze layer. Therefore, the above distance is also equivalent to the center distance between two parts of the bottom glaze layer. The minimum width is to prevent the two parts of the bottom glaze layer from fusing during high-temperature sintering. At the same time, since two heating resistors share the same rubber roller during printing, if the distance between the two heating resistors is too large, the local pressure on the two parts of R will be small. Therefore, the distance should not exceed 2.0 mm.

[0038] In the present invention, the first heating resistor is located at the center of the first bottom glaze layer or deviates towards the paper outlet side, and the second heating resistor layer is located at the center of the second bottom glaze layer or deviates towards the paper inlet side. This is because the same rubber roller is used to increase the local pressure and contact area on the two parts of R and improve the printing density.

[0039] In the present invention, corresponding to the two rows of heating resistors, two control ICs are provided. The common electrode is arranged between the two rows of heating resistors and is respectively connected to the first heating resistor and the second heating resistor on both sides. The two control ICs are respectively arranged on the paper inlet side of the first heating resistor and the paper outlet side of the second heating resistor to be respectively connected to the first heating resistor and the second heating resistor.

[0040] In the present invention, the first bottom glaze layer and the first heating resistor are close to the paper inlet side and are used to print the low-temperature color-developing layer. The second bottom glaze layer and the second heating resistor are close to the paper outlet side and are used to print the high-temperature color-developing layer. The thickness and width of the first bottom glaze layer are greater than the width and thickness of the second bottom glaze layer. The thickness of the first bottom glaze layer is more than 1.5 times that of the second bottom glaze layer. Thickening the first bottom glaze layer can slow down the heat dissipation, and thinning the second bottom glaze layer can accelerate the heat dissipation speed and reduce the bleeding caused by the low-temperature color-developing layer.

[0041] An insulating protective layer 5 is further provided on the insulating substrate 2 of the present invention. The insulating protective layer 5 covers the surfaces of the heating resistors, the common electrode, and the individual electrodes. Two parts of control ICs and a printed circuit board are further provided on the insulating substrate 2. The insulating substrate is arranged on the heat dissipation base 1.

[0042] The present invention also proposes a printing method for a multi-color printing thermal print head as described above, which is characterized in that when multi-color printing is performed, the following steps are executed:

[0043] Step 1: Determine the multi-color printing content in the current printing line, and group the printing control data according to the multi-color printing content. Among them, the printing control data for low-temperature color development is divided into the first group, and the printing control data for high-temperature color development is used as the second group;

[0044] Step 2: The first set of printing control data is sent by the control IC connected to the first heating resistor to complete low-temperature color printing through the first heating resistor near the paper feed side; the second set of printing control data is sent by the control IC connected to the second heating resistor to complete high-temperature color printing through the second heating resistor near the paper discharge side. The second set of printing control data is delayed by a time of ΔT compared to the first set as a whole, where ΔT = L / V, L is the distance between two rows of heating resistors, and V is the printing speed. Whether the printing speed is the paper feed speed of the rubber roller;

[0045] Step 3: Repeat Step 1 to Step 2 until the entire page of printing content is completed.

[0046] In Step 1 of the present invention, when performing two-color printing, each row of heating resistors is only used to print one color. When performing multi-color printing, according to the color development temperature range, the printing control data for low-temperature color development and high-temperature color development is grouped, and the printing control data for the current printing line is divided into two levels according to the low-temperature color development temperature and the high-temperature color development temperature.

[0047] Example 1:

[0048] As shown in the Figure 1 accompanying figure, this example provides a thermal print head with two rows of heating elements and two rows of heat storage layers, including a heat dissipation base 1 and an insulating substrate 2. On the insulating substrate 2, there are a first underglaze layer 3 and a second underglaze layer 6. On the surface of the insulating substrate 2 and the underglaze layer, there are a part of common electrodes and two parts of individual electrodes. The first heating resistor 4 and the second heating resistor 7 are arranged between the common electrodes and the individual electrodes. One end of the common electrode is connected to the heating resistor, and the other end is connected to one end of the power supply; one end of the individual electrode is connected to the heating resistor, and the other end is connected to the control IC. The control IC is connected to the other end of the power supply, where the control IC is used to control the on / off state of a single heating point in the heating resistor;

[0049] This example provides a method for manufacturing the heating substrate of the above thermal print head:

[0050] As shown in the Figure 1 accompanying figure, the first underglaze layer 3 is printed on the insulating substrate 2 by screen printing and sintered at a temperature of 1200°C to 1300°C. Then, the second underglaze layer 6 is printed at a position about 1 mm away from the first underglaze layer and sintered at a temperature of 1200°C to 1300°C. The edges of the first underglaze layer 3 and the second underglaze layer 6 do not contact to avoid the two parts of the underglaze layer from fusing due to high-temperature melting, resulting in a change in the shape of the underglaze;

[0051] Print and sinter the conductive paste on the surfaces of the insulating substrate 2, the first underglaze layer 3 and the second underglaze layer 6. The sintering temperature is 800°C - 950°C. Then, use lithography technology to form the common electrode and the individual electrodes. The first heating resistor 4 and the second heating resistor 7 share the common electrode. One end of the common electrode is connected to two rows of heating resistors along the sub-printing direction, and the other end of the common electrode is connected to the printing power supply. Coat the first heating resistor 4 along the main scanning direction at the center of the first underglaze layer 3, and coat the second heating resistor 7 at the center of the second underglaze layer 6. Sinter into a solid at a temperature of 700°C - 1000°C. Print the amorphous glass glaze layer on the substrate surface of the heating element and the electrode as the insulating protective layer 5, and perform high-temperature sintering and curing at 700°C - 1000°C;

[0052] In this example, the thickness of the first underglaze layer is 1.8 times thicker than that of the second underglaze layer. As shown in the appendix Figure 6 When printing the low-temperature color-developing layer, use the feeding-side heating element and the underglaze layer in this example to print the low-temperature color-developing layer. The rows are continuous, and the overall gray value is high. Use the discharging-side heating element and the heat storage layer in this example to print the low-temperature color-developing layer, then there are obvious intervals between the rows, and the overall gray value is low. Therefore, choose to use the feeding-side to print the low-temperature color-developing layer;

[0053] As shown in the appendix Figure 6 When printing the high-temperature color-developing layer, use the feeding-side heating element and the underglaze layer in this example to print the high-temperature color-developing layer. The edges of the printed characters are not clear, showing the color of the low-temperature color-developing layer. Use the discharging-side heating element and the heat storage layer in this example to print the high-temperature color-developing layer. The edges of the printed characters are clear and neat. Therefore, choose to use the discharging-side to print the high-temperature color-developing layer. This is mainly because the structure on the feeding side reduces the heat dissipation of the low-temperature color-developing layer and increases the saturation of the low-temperature color-developing layer; the structure on the discharging side accelerates the heat dissipation of the high-temperature heating layer and reduces the bleeding of other colors in the high-temperature color-developing layer, effectively improving the overall printing effect.

[0054] As Figure 3 shown, the two rows of heating elements of the present invention require two parts of control circuits. The electrode leads include 2 parts of individual electrodes, sharing the same common electrode. An insulating protective layer is also provided on the insulating substrate, and the insulating protective layer covers the surfaces of the heating resistor, the common electrode, and the individual electrodes; two parts of control ICs and a printed circuit board are also provided on the insulating substrate, and the insulating substrate is arranged on the base.

[0055] Example 2:

[0056] As shown in Embodiment 1, both parts of the heating element are arranged at the center of the underglaze. To increase the local pressure on the two parts of the underglaze, the center of the rubber roller can be arranged in the middle of the two parts of the underglaze or near the second underglaze. However, if it is arranged near the second underglaze, it is likely to deviate too far from the first heating element, and the printing effect of the first heating element part will be reduced. If the rubber roller is arranged in the middle of the two parts of the underglaze, due to the relatively thick first underglaze layer and large local pressure, the local pressure of the second underglaze layer part is relatively small, and the printing energy needs to be increased. Increasing the printing energy will reduce the service life.

[0057] This embodiment provides another multicolor printing thermal printing head. As Figure 2 shown, two rows of heating resistor bodies are arranged according to the following rules: the first heating resistor body is located on the paper-out side of the first underglaze layer, and the second heating resistor body layer is located on the paper-in side of the second underglaze layer. In this way, the distance and height difference between the first heating element and the second heating element can be reduced, the local pressure on the two parts of the heating element can be increased, and in addition, the diameter of the rubber roller can be reduced, reducing the cost of the printer. In this embodiment, the center of the rubber roller is arranged in the middle of the two parts of the underglaze.

[0058] As shown in the appendix Figure 5 compared with Embodiment 1, the printing effect of the structure in this embodiment is more saturated.

[0059] Embodiment 3:

[0060] This example provides a three-color printing method, which is implemented by using the 3-color printing thermal printing head provided in Embodiment 1 or Embodiment 2, and specifically includes the following steps:

[0061] Step 1: Determine the three-color printing content in the current printing line, and group the printing control data according to the three-color printing content. The color development temperatures of the three colors are 90°C, 130°C, and 170°C respectively. The printing control data corresponding to the colors of 90°C and 130°C are used as the first group of printing control data, and the printing control data with a color development temperature of 170°C is used as the second group. Corresponding to the three-color color development temperatures in this example, to make the printing dots fully develop color, the highest temperatures should be 130°C, 170°C, and 210°C;

[0062] Step 2: Control the first heating resistor body and the second heating resistor body to generate heat respectively by sending printing control data to achieve three-color printing. Specifically:

[0063] Step 2-1: Complete the printing of the printing content corresponding to the medium and low temperature color development temperatures:

[0064] As Figure 4As shown, the first set of printing control data is sent by the control IC connected to the first heating resistor to complete low-temperature color development printing through the first heating resistor near the paper feed side. Among them, the first set of printing control data is sent in two times. The low-temperature color development printing content is printed through the printing control data sent for the first time in the first set of printing control data. As shown in Figure 4 Figure (a). The medium-temperature color development printing content is sent through the two-time data sending in the first set of printing control data. Under the control of the two sets of printing data, the first heating resistor accumulates to reach a temperature above the medium-temperature color development temperature and then prints and develops color. As shown in Figure 4 Figure (b).

[0065] At this time, since the first heating resistor in this example is used to print low- and medium-temperature color development content and its heat dissipation speed is lower than the heating speed, the opening time corresponding to the data sent for the second time in the first set of printing control data is at least 60% lower than the opening time of the first time. Otherwise, the temperature at the center of the printing point will be too high and the color of the high-temperature color development layer will be printed.

[0066] Step 2-2: Complete the printing of the printing content corresponding to the high-temperature color development temperature: After an interval of ΔT time, the second set of printing control data is sent by the control IC connected to the second heating resistor to complete high-temperature color development (170 °C) printing through the second heating resistor near the paper discharge side. In order to reduce the mutual interference between different colors and improve the printing speed, it is necessary to heat up to a temperature above the color development temperature at one time. As shown in Figure 4 Figure (c), where ΔT = L / V, L is the distance between two rows of heating resistors, and V is the printing speed, and the printing speed is the paper feeding speed of the rubber roller.

[0067] Step 3: Repeat Step 1 to Step 2 until the printing of the entire page content is completed.

[0068] By setting two parts of the underglaze layer, the present invention can respectively cope with the occasions of low-temperature color development and high-temperature color development, reduce the mutual interference between different color development layers in the same color development unit, improve the printing effect at two color development temperatures at the same time, and simplify the control method. Compared with the prior art, it has the remarkable advantages of reasonable structure, simple production process, reliable operation, and good printing effect.

Claims

1. A multicolor printing thermal print head is provided with an insulating substrate, on which a bottom glaze layer and electrode leads are provided. A common electrode and individual electrodes are provided on the surfaces of the insulating substrate and the bottom glaze layer. A heating element is disposed between the common electrode and the individual electrodes. One end of the common electrode is connected to a heating resistor body, and the other end is connected to a power supply. One end of an individual electrode is connected to the heating element, and the other end is connected to a control IC. The control IC is connected to the other end of the power supply. The control IC is used to control the on / off state of a single heating point in the heating element. It is characterized in that the heating element includes two rows of heating resistor bodies parallel to each other. The bottom glaze layer correspondingly has two bottom glaze layers parallel to each other. A first bottom glaze layer is disposed below the first heating resistor body, and a second bottom glaze layer is disposed below the second heating resistor body. The thickness of the first bottom glaze layer is at least 1.5 times the thickness of the second bottom glaze layer, and the width of the first bottom glaze layer is greater than the width of the second bottom glaze layer. The first bottom glaze layer and the first heating resistor body are close to the paper feeding side for printing a low-temperature color developing layer, and the second bottom glaze layer and the second heating resistor body are close to the paper discharging side for printing a high-temperature color developing layer.

2. A multicolor printing thermal print head according to claim 1, It is characterized in that the distance between the two rows of heating resistor bodies on the insulating substrate ranges from 0.75 mm to 2.0 mm.

3. A multicolor printing thermal print head according to claim 1, It is characterized in that the first heating resistor body is located at the center of the first bottom glaze layer or offset to the paper discharging side, and the second heating resistor body layer is located at the center of the second bottom glaze layer or offset to the paper feeding side.

4. A multicolor printing thermal print head according to claim 1, It is characterized in that corresponding to the two rows of heating resistor bodies, two control ICs are provided. The common electrode is disposed between the two rows of heating resistor bodies and is respectively connected to the first heating resistor body and the second heating resistor body on both sides. The two control ICs are respectively disposed on the paper feeding side of the first heating resistor body and the paper discharging side of the second heating resistor body to be respectively connected to the first heating resistor body and the second heating resistor body.

5. A printing method of a multicolor printing thermal print head according to any one of claims 1-4, It is characterized in that when performing multicolor printing, the following steps are executed: Step 1: Determine the multicolor printing content in the current printing line, and group the printing control data according to the multicolor printing content. Among them, the printing control data for low-temperature color development is divided into the first group, and the printing control data for high-temperature color development is used as the second group. Step 2: The first group of printing control data is sent by the control IC connected to the first heating resistor body to complete low-temperature color development printing through the first heating resistor body close to the paper feeding side. The second group of printing control data is sent by the control IC connected to the second heating resistor body to complete high-temperature color development printing through the second heating resistor body close to the paper discharging side. The second group of printing control data is delayed by a time △T as a whole compared with the first group, where △T = L / V, L is the distance between the two rows of heating resistor bodies, and V is the printing speed, and the printing speed is the paper feeding speed of the rubber roller. Step 3: Repeat Step 1 to Step 2 until the entire page of printing content is completed.

6. The printing method of the multi-color printing thermal print head according to claim 5, characterized in that, when performing three-color printing, the printing control data for low-temperature color development and high-temperature color development are grouped according to the color development temperature range, and the printing control data of the current printing line are divided into two levels according to the low-temperature color development temperature and the high-temperature color development temperature, specifically including the following steps: Step 1: Determine the three-color printing content in the current printing line, and group the printing control data according to the three-color printing content, which are divided into three levels: low temperature, medium temperature, and high temperature. The printing control data corresponding to the low-temperature and medium-temperature colors are used as the first group of printing control data, and the printing control data for high-temperature color development are used as the second group; Step 2: Control the first heating resistor and the second heating resistor to generate heat respectively by sending printing control data to achieve three-color printing. Specifically: Step 2-1: Complete the printing of the printing content corresponding to the medium and low temperature color development temperatures: The first group of printing control data is sent by the control IC connected to the first heating resistor to complete low-temperature color development printing through the first heating resistor close to the paper feed side. Among them, the first group of printing control data is sent in two times. The low-temperature color development printing content is realized through the printing control data sent for the first time in the first group of printing control data. The medium-temperature color development printing content is sent through the two data transmissions in the first group of printing control data. After the first heating resistor accumulates to above the medium-temperature color development temperature under the control of the two printing data, color development is printed; Among them, the opening time corresponding to the data sent for the second time in the first group of printing control data is at least 60% lower than the opening time of the first time; Step 2-2: Complete the printing of the printing content corresponding to the high-temperature color development temperature: After an interval of △T time, the second group of printing control data is sent by the control IC connected to the second heating resistor to complete high-temperature color development printing through the second heating resistor close to the paper discharge side. In order to reduce the mutual interference between different colors and improve the printing speed, it is necessary to heat up to above the color development temperature at one time. Among them, △T = L / V, L is the distance between two rows of heating resistors, and V is the printing speed, and the printing speed is the feeding speed of the rubber roller; Step 3: Repeat Step 1 to Step 2 until the printing content of the entire page is completed.

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