Thermal printing head and printing method

Abstract

The invention relates to the technical field of application of thermal printing heads, in particular to a thermal printing head and a printing method, which can reduce heating logic control complexity, simplify a gray scale printing process and achieve fine gray scale control, and is provided with a thermal printing head and an external printing host, a heating substrate for the thermal printing head and a printing logic control part are arranged in the thermal printing head, an external printing host is connected with the printing logic control part, a heating resistor body is arranged on the heating substrate for the thermal printing head, and a plurality of heating points are arranged in the heating resistor body; a plurality of control units are arranged corresponding to a plurality of heating points on a heating resistor body, printing heating control data of each heating point are sent to the corresponding control unit at a time, and compared with an existing mode that multiple times of sending of printing data are combined with STB gating, the printing heating control data can be sent to the corresponding control unit at a time, and the printing heating control efficiency is greatly improved on the premise that gray level fine control is met. And the cost requirement on printer control resources is obviously reduced.

Description

Technical field:

[0001] The present invention relates to the technical field of thermal print head applications, and in particular to a thermal print head and a printing method capable of reducing the complexity of heating logic control, simplifying the grayscale printing process and achieving fine grayscale control. Background technology:

[0002] Thermal print heads are devices that print using Joule heat. In situations where grayscale printing is required, the print head must be able to accurately output the corresponding temperature or energy according to different grayscale requirements. Currently, the temperature or energy is generally controlled based on the printer's printing logic to control the opening time of the heating point of the print head, or rely on ICs with thermal history control to control the opening time of the heating point based on the heating logic of the front, back, left and right points for temperature compensation. The functions of traditional ICs are as follows: Figure 1 As shown, the traditional control logic is as follows Figure 2 shown.

[0003] The following prior literature is reviewed:

[0004] Patent document CN101242960B discloses a multi-color thermal imaging system in which different heating elements on a thermal print head can print on different color-forming layers of a multi-color thermal imaging member during a single pass. The line printing time is divided into segments, each segment being divided into multiple sub-periods. All pulses within the multiple segments have the same energy. By varying the proportion of sub-periods containing pulses, different colors are selected for printing during different segments. This technology allows the use of a single strobe signal line to print multiple colors using a thermal print head. The pulse pattern can be selected to reduce the uniformity of the pulses supplied to the multiple print head elements, thereby reducing the peak power requirements of the print head.

[0005] The invention with patent document number CN107073975B discloses a thermal transfer printer comprising: a thermal head having multiple heating elements, which prints an image on paper by causing the multiple heating elements to generate heat and transferring ink to the paper; a storage unit, which stores a first correspondence between the heating elements in the thermal head and the correction amount of energy applied to the heating elements, and a second correspondence between the concentration of the printed image and the adjustment coefficient of the correction amount, which is made based on the concentration of the newly printed image; and a control unit, which corrects the energy applied to the multiple heating elements based on the concentration of the newly printed image, and the magnitude of the energy is an amount obtained by multiplying the correction amount of each heating element obtained according to the first correspondence by the adjustment coefficient obtained according to the second correspondence.

[0006] The invention with patent document number CN111300996B discloses a method, device and computer storage medium for overcoming uneven heating of a print head. The method is applied to a print head including at least two heating elements, and the method includes: obtaining the average resistance value of all the heating elements; obtaining the individual resistance value of each of the heating elements; obtaining the target average power-on time of the print head under the average resistance value; and deriving the target individual power-on time of each heating element based on the average resistance value, the individual resistance value and the target average power-on time. This application obtains the target individual power-on time of each heating element by obtaining the average resistance value of all the heating elements of the print head, the individual resistance value of each heating element and the target average power-on time of the print head under the average resistance value. Therefore, this application ensures that the heating temperature of each heating element remains consistent by compensating and adjusting the power-on time of each heating element, thereby ensuring the printing effect of the printer.

[0007] The invention with patent document number CN118426720B discloses a simple grayscale level representation method for a thermal printer, including: obtaining a print image and loading it; generating a grayscale image from the loaded image; the printer's upper machine position maps the grayscale value of each pixel in the grayscale image to N-bit binary data; grading the grayscale image value range, mapping each pixel value in the grayscale image, obtaining a mapped grayscale value of each pixel value mapping, calculating the traversal point error, traversing the grayscale value of each pixel in the image in turn, and obtaining an updated grayscale value; based on the updated grayscale value of the pixel coordinate point, obtaining the grayscale printing binary data of each pixel point; the printer receives the data and heats until printing is completed; the grayscale image after the image is printed has a stronger grayscale level sense, thereby improving the printing quality. At the same time, during the printing process, the printed grayscale level can be appropriately adjusted according to requirements to better make the printing quality meet different needs.

[0008] Patent document No. JP1990188270A discloses a print head control circuit for implementing multi-grayscale thermal control, including: by dividing thermal resistors into blocks and using ROM to optimize the electrical heating time, this solution solves the problem of uneven resistance in the thermal control circuit.

[0009] The above existing technologies are all implemented using traditional ICs, and their execution principle is roughly as follows: the serial input data (DI) is shifted by the clock signal and input into the shift register (shift register) in sequence; then it is sent to the latch, and the data in the latch is output to the heating point through the selection signal STB to complete the heating of the heating point; and when performing multi-level grayscale control, it is necessary to use a method of sending data (DI) multiple times to achieve different grayscales or thermal control, which occupies more printer resources and needs to change the software to send different numbers of lines of data according to different grayscales. The control process is relatively complicated, which increases the difficulty for the embedded MCU where resources are already tight. Summary of the invention:

[0010] In view of the shortcomings and deficiencies in the prior art, the present invention proposes a thermal print head and a printing method that can reduce the complexity of heating logic control, simplify grayscale printing and achieve fine grayscale control.

[0011] The present invention is achieved by the following measures:

[0012] A thermal printing device includes a thermal print head and an external printing host. The thermal print head includes a heating substrate for the thermal print head and a printing logic control component. The external printing host is connected to the printing logic control component. The heating substrate for the thermal print head includes a heating resistor, and the heating resistor includes a plurality of heating points.

[0013] The control signal output end of the printing logic control component is connected to the heating resistor. The printing logic control component is provided with a clock unit, a latch unit, and a print strobe unit, wherein the clock unit is used to provide a system clock signal CLK, the print strobe unit receives the hot point strobe data STB issued by the external printing host, and the latch unit is used to latch the printing heating time control data Di issued by the external printing host. It is characterized in that the external printing host is provided with a grayscale data reading unit, a printing heating time data conversion unit, and a data sending unit connected in sequence, wherein the printing heating time data conversion unit is used to convert the energy corresponding to the dot matrix grayscale data generated by the grayscale data reading unit into the hot point heating time Ti, and convert the hot point heating time Ti into the number of printing pulses mi, the printing heating time control data Di includes the number of printing pulses mi corresponding to the current hot point and the hot point strobe data STB, and the printing heating time control data Di is sent to the printing logic control component by the data sending unit;

[0014] The printing logic control component is further provided with a frequency divider and a plurality of control units corresponding to the plurality of hot spots. Each control unit is connected to the data sending unit. Each control unit is provided with a counter. The strobe trigger end of the counter receives the hot spot strobe data STB forwarded by the print strobe unit. The output end of the counter is connected to the i-th hot spot. After the counter receives the number of print pulses mi corresponding to the hot spot, it executes a countdown triggered by the hot spot strobe data STB. When counting starts, the counter output turns on the i-th hot spot. When counting ends, the i-th hot spot is turned off.

[0015] The frequency divider receives the system clock signal CLK and outputs a frequency-divided clock pulse according to a printing grayscale requirement. The number of printing pulses mi is counted in units of the frequency-divided clock pulse.

[0016] In the present invention, i is the serial number of the heating point in the heating resistor.

[0017] The counter in the control unit of the present invention adopts 2 to 8-bit counting to meet the maximum 256-level grayscale printing requirements. That is, when the binary pulse number mi input to the counter is 11111111, the current printing performs 256-level grayscale control. Each pulse input to the counter through the divider corresponds to one grayscale, and each 2-8-bit data is written into the shift register in a serial communication manner.

[0018] The present invention also proposes a printing method using the above-mentioned thermal printing device, characterized in that:

[0019] Step 1: The grayscale data reading unit of the printer host reads the grayscale image to be printed and generates dot matrix grayscale values;

[0020] Step 2: For the grayscale value of each dot corresponding to the current row, the print heating time data conversion unit in the external printing host generates corresponding grayscale data according to the thermal history control requirements, and generates print heating time control data Di based on the grayscale data. The print heating time control data Di includes the print pulse number mi corresponding to the current hot point and the hot point selection data STB. The print heating time control data Di is sent to the thermal print head by the data sending unit;

[0021] Step 3: Start the clock unit CLK, and the printer host sends the printing heating time control data Di to the printing logic control component line by line. The printing heating time control data Di is sent in parallel to each control unit corresponding to each heating point, where i is the serial number of the heating point in the heating resistor. The printing heating time control data Di is latched by the latch.

[0022] Step 4: Execute printing. The i heating points in the heating resistor are printed in parallel under the control of i control units. The printing process of each heating point is as follows: the heating point selection data STB in the printing heating time control data Di is sent to the trigger end of the counter of the control unit corresponding to the current heating point, that is, the heating point selection data STB is used as the trigger signal of the counter. If the heating point is not working in the current row task, the counter is not triggered to start, and the preset value of the counter is 0. The control unit has no output to the current heating point, that is, no mi; otherwise, the counter of the control unit is triggered to start by the heating point selection data STB, and takes the printing pulse number mi as the preset value. Under the drive of the pulse signal input to the counter by the divider, countdown is performed. Each count outputs an on-pulse cycle to the corresponding heating point, and the heating point starts to heat up until the countdown is completed, the heating point is turned off, and the current heating point completes printing.

[0023] The printing heating time data conversion unit in step 2 of the present invention generates corresponding grayscale data according to the thermal history control requirements, which means that the grayscale data is corrected according to the thermal history control, specifically: logical operations are performed based on the N rows before and N rows below the current heating point and the left and right adjacent heating points, and the grayscale value of the current point is corrected according to the operation results; further, all point data in all rows are processed and corrected to obtain grayscale data with higher accuracy.

[0024] The number of print pulses mi corresponding to the current heating point in the print heating time control data Di in step 2 of the present invention can be selected to send 2-bit data as needed to achieve 4-level printing, and so on, 3 bits - 8 levels, 4 bits - 16 levels, 5 bits - 32 levels, 6 bits - 54 levels, 7 bits - 128 levels, 8 bits - 256 levels, to achieve grayscale printing of different levels.

[0025] In the present invention, it is considered that the data corresponding to each heating point is 2-8 bits of data, and multi-bit data is transmitted in the form of a shift register. Under the CLK pulse output by each clock unit, the multi-bit data of the previous point is shifted to the next point, that is, multiple Di are parallel inputs, and each Di data is 2-8 bits. Each bit is serially transmitted between each point. The number of CLK pulses corresponds to the number of heating points. Taking 8-bit data as an example, the corresponding grayscale is 256 levels, and the multi-bit data are respectively the 1st to the 8th bit. Each bit of data is serially transferred from the corresponding bit of the 1st heating point to the corresponding bit of the 2nd heating point, until the last heating point, that is, the 1st bit of data is transmitted from the 1st bit of the 1st point to the 1st bit of the last point, and the 2nd bit is transmitted from the 2nd bit of the 1st point to the 2nd bit of the last point, and so on until the 8th bit.

[0026] In step 2 of the present invention, the number of printing pulses mi corresponding to the current heating point includes preheating time data and formal heating time data, wherein the preheating time data is used to select whether to add a preheating function according to the actual printing effect and the need for thermal control of the current point. Generally, the appropriate preheating time is selected according to the thermal response characteristics of the print head, as well as the printing speed, the use of consumables, etc. The points to be printed are preheated before the formal heating time, and the clock unit CLK is started to send 2 to 8 channels of preheating time data. According to the number of hot spots on the print head, the corresponding preheating time data is sent for each line. For each CLK pulse, the shift register in the IC transfers the data from the previous point to the next point until it reaches the last point.

[0027] The present invention sets up multiple control units corresponding to multiple heating points on the heating resistor, and the printing heating control data of each heating point is sent to the corresponding control unit at one time. Compared with the multiple sending of existing printing data combined with STB selection, the cost requirement for printer control resources is significantly reduced while meeting the grayscale fine control. Description of the drawings:

[0028] Attachment Figure 1 It is a structural block diagram of the printer logic control component in the prior art.

[0029] Attachment Figure 2 This is a printing logic timing diagram of a thermal print head in the prior art.

[0030] Attachment Figure 3 This is a structural block diagram of embodiment 1 of the present invention.

[0031] Attachment Figure 4 This is a print control timing diagram of embodiment 3 of the present invention.

[0032] Attachment Figure 5 It is a structural block diagram of the present invention. Specific implementation method:

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Example 1:

[0035] This example provides a thermal printing device and method suitable for high-precision grayscale printing. The thermal printing device includes a thermal print head and an external printing host. The thermal print head includes a heating substrate for the thermal print head, an integrated circuit (IC), a circuit board, a heat sink, and a socket. The integrated circuit (IC) includes a multi-channel heating point control circuit. In addition to normal clock unit (CLK), latch unit (LATCH), selection unit (STB) and other signal inputs, the IC also includes a multi-channel control unit corresponding to multiple heating points of the thermal print head. Each control unit contains a counter module that meets 2- to 8-bit data input. The counter modules of the multi-channel control units all use the same clock pulse CLK. The clock pulse signal is a clock pulse generated by the clock unit through a frequency divider according to the printing grayscale requirements. The specific frequency division process is as follows:

[0036] S1: The printer host reads the grayscale image to be printed, generates dot matrix grayscale data, and outputs the print data (i.e., print heating time control data Di) by line. The energy of each grayscale level depends on the CLK frequency division number, i.e., the clock period of the counter. The clock period of the counter can be set by adjusting the frequency of the CLK sent by the printer. For example, the CLK of the printer is 10MHz, and each clock period is 0.0001ms. To achieve 128 grayscales, the internal divider parameter of the IC is set to 10, and the external 10MHz frequency is divided into 1MHz. The clock period of the counter is 0.001ms, corresponding to one grayscale. 128 levels are 128us, i.e., 0.128ms.

[0037] The printing host generates a corresponding grayscale value for the grayscale data of each dot in the current row, and generates heating time data to be sent to the print head according to the grayscale value (embodied in the form of print pulse number mi, the print pulse number mi is counted in units of the clock cycle of the counter). As needed, the heating time data can be sent as 2-bit data to achieve corresponding 4-level grayscale printing. Similarly, 3-bit data corresponds to 8-level grayscale, 4-bit data corresponds to 16-level grayscale, 5-bit data corresponds to 32-level grayscale, 6-bit - 54-level, 7-bit - 128-level, 8-bit - 256-level;

[0038] S2: Start the clock unit CLK, and the printer host sends heating time data to the printing logic control component. According to the number of hot spots of the print head and the printing task, the heating time data is sent to each control unit corresponding to each hot spot in parallel in rows, that is, multiple control units corresponding to multiple hot spots receive the corresponding data in parallel. Considering that the data corresponding to each hot spot is 2-8 bits, multi-bit data is transmitted in the form of a shift register. Under each CLK pulse output by the clock unit, the multi-bit data of the previous spot is shifted to the next spot, that is, the multi-bit Di is input in parallel, and each bit is transmitted serially between each spot. The number of CLK pulses corresponds to the number of hot spots. Taking 8-bit data as an example (corresponding to 256 grayscale levels), the multi-bit data are respectively the 1st to the 8th bit, and each bit of data is serially transferred from the corresponding bit of the 1st hot spot to the corresponding bit of the 2nd hot spot, until the last hot spot, that is, the 1st bit is transmitted from the 1st bit of the 1st spot to the 1st bit of the last spot, the 2nd bit is transmitted from the 2nd bit of the 1st spot to the 2nd bit of the last spot, and so on until the 8th bit;

[0039] S3: After the data is sent, the heating time data (printing pulse number mi) of multiple control units are latched with the same LATCH, and a counter is set in each control unit corresponding to each heating point inside the IC. The initial count value of the counter is the received data value of each point. STB is used as the GATE signal of the counter to start the output DriverOutput (DO) of the counter of each heating point. The opening time of DO depends on the size of the initial count value. DO drives each heating point to heat up. For details, please refer to Figure 3 ;

[0040] In this example, each heating point in the heating resistor uses the clock generated by CLK after frequency division to drive the down counter to count according to the received main body printing time data. STB serves as the Gate start signal of the counter. DO is turned on when the counting starts and turned off when the counting ends, thereby controlling the main body heating time of the current heating point.

[0041] Example 2:

[0042] In this example, during the thermal printing process as in Example 1, step S1 further performs grayscale correction processing as needed:

[0043] S1-1: The printer reads the grayscale image to be printed, generates dot matrix grayscale data, and takes out the print data row by row;

[0044] S1-2: The grayscale data of each dot in the current row is processed based on whether thermal history control is required. If thermal history control is required, a logical operation is performed based on the N rows before and N rows after the current dot, as well as the dots to the left and right of the current dot, and the grayscale value of the current dot is corrected based on the operation result. Thermal history control can be implemented in the following manner: taking a certain print head and a certain printing speed as an example, if the hot dot before the current dot is in an on state, i.e., in a heating state, the energy of the current hot dot is reduced to 60-70% of the original energy. If the second hot dot before the current hot dot is on, but the previous hot dot is not on, the energy of the current hot dot is reduced to 80-90% of the original energy. If any hot dot to the left or right of the current hot dot is on, the energy is reduced to 90-95% of the original energy.

[0045] S1-3: Repeat S1-2 to process and correct all point data in all rows;

[0046] S1-4: Generate heating time data to be sent to the print head based on the processed grayscale value.

[0047] In this example, by correcting the grayscale data, a printing effect with higher grayscale accuracy can be obtained.

[0048] Example 3:

[0049] This example provides a printing method that performs preheating before actual printing. Specifically, compared with Example 1, in Example 1, in step S2, the printer host sends heating time data to the printing logic control component. At the same time, whether to add the preheating function needs to be selected based on the actual printing effect and the need for thermal control. Generally, the appropriate preheating time is selected based on the thermal response characteristics of the print head, as well as the printing speed, the consumables used, etc. The points to be printed are preheated before the actual heating time. Specifically,

[0050] After step S2 starts CLK, first execute S2-1:

[0051] Send 2 to 8 channels of preheating time data. According to the number of hot spots on the print head, the corresponding preheating time data is sent at the beginning of each line. With each CLK pulse, the shift register in the IC transmits multiple channels of data in parallel from the previous point to the next point until it reaches the last point. When the line transmission is completed, the latch signal is activated to latch the data.

[0052] S2-2: Each point uses the clock generated by dividing CLK to drive the down counter to count according to the received printing preheating time data. STB is used as the Gate start signal of the counter. If STB is positive logic, the rising edge is valid, and if STB is negative logic, the falling edge is valid. When counting starts, the output DO is turned on and when counting ends, the output DO is turned off, thereby controlling the preheating time of the current heating point;

[0053] S2-3: After preheating, it is time for main body printing, and CLK is started again to send 2-8 channels of main body heating time data;

[0054] S3: Each point uses the clock generated by CLK divided by frequency to drive the down counter to count according to the received main body printing time data. STB is used as the Gate start signal of the counter. DO is turned on when counting starts and turned off when counting ends, thereby controlling the main body heating time of the current heating point;

[0055] S4: Repeat steps S2 to S8 in this way until all rows are printed.

[0056] The above process reference Figure 4 .

[0057] In the grayscale printing process of the present invention, the grayscale correction also includes the following measures: in order to achieve a better printing effect, a 1-fold margin is reserved for the grayscale levels in S1. For example, if 128 levels are to be printed, it is best to use 8-bit data; or, when actually setting the printing conditions, the initial value of the counter corresponding to the current grayscale can be appropriately increased or decreased according to the actual print density to fine-tune the density effect; in addition, in the case of 128-level control, since the number of bits of DI is 8, a margin has been reserved. When actually setting the printing conditions, if the 128-level print density is still light, the initial value of the counter can be appropriately increased to 129 or 130 to compensate.

[0058] The present invention sets up multiple control units corresponding to multiple heating points on the heating resistor, so that during the printing process, the printing heating control data of each heating point is sent in parallel to the corresponding control unit at one time. Compared with the existing multiple sending of printing data combined with STB selection, the cost requirements for printer control resources are significantly reduced while meeting the requirements of fine grayscale control.

Claims

1. A thermal printing device comprising a thermal print head and an external printing host, wherein the thermal print head comprises a heating substrate for the thermal print head and a printing logic control component, the external printing host being connected to the printing logic control component, the heating substrate for the thermal print head comprising a heating resistor, the heating resistor having a plurality of heating points; The control signal output end of the printing logic control component is connected to the heating resistor. The printing logic control component is provided with a clock unit, a latch unit, and a print strobe unit, wherein the clock unit is used to provide a system clock signal CLK, the print strobe unit receives the heating point strobe data STB sent by the external printing host, and the latch unit is used to latch the printing heating time control data Di sent by the external printing host. The external printing host is provided with a grayscale data reading unit, a printing heating time data conversion unit, and a data sending unit connected in sequence, wherein the printing heating time data conversion unit is used to convert the energy corresponding to the dot matrix grayscale data generated by the grayscale data reading unit into the heating time Ti of the hot point, and convert the heating time Ti of the hot point into the number of printing pulses mi, the printing heating time control data Di includes the number of printing pulses mi corresponding to the current hot point and the hot point selection data STB, and the printing heating time control data Di is sent to the printing logic control component by the data sending unit; The printing logic control component is also provided with a frequency divider and multiple control units corresponding to multiple hot spots. Each control unit is connected to the data sending unit. Each control unit is provided with a counter. The selection trigger end of the counter receives the hot spot selection data STB forwarded by the print selection unit. After the counter receives the number of print pulses mi corresponding to the hot spot, it performs a countdown under the triggering of the hot spot selection data STB; the frequency divider receives the system clock signal CLK and outputs the divided clock pulse according to the printing grayscale requirements. The number of print pulses mi is counted in units of divided clock pulses.

2. A thermal printing device according to claim 1, characterized in that: i is the serial number of the heating point in the heating resistor.

3. A thermal printing device according to claim 2, characterized in that: The counter in the control unit uses 2 to 8 bits to count to meet the maximum 256-level grayscale printing requirements. That is, when the binary pulse number mi input to the counter is 11111111, the current printing executes 256-level grayscale control, and each pulse input to the counter through the divider corresponds to one grayscale.

4. A printing method using the thermal printing device according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: The grayscale data reading unit of the printer host reads the grayscale image to be printed and generates dot matrix grayscale values; Step 2: For the grayscale value of each dot corresponding to the current row, the print heating time data conversion unit in the external printing host generates corresponding grayscale data according to the thermal history control requirements, and generates print heating time control data Di based on the grayscale data. The print heating time control data Di includes the print pulse number mi corresponding to the current hot point and the hot point selection data STB. The print heating time control data Di is sent to the thermal print head by the data sending unit; Step 3: Start the clock unit CLK, and the printer host sends the printing heating time control data Di to the printing logic control component line by line. The printing heating time control data Di is sent in parallel to each control unit corresponding to each heating point, where i is the serial number of the heating point in the heating resistor. The printing heating time control data Di is latched by the latch. Step 4: Execute printing. The i heating points in the heating resistor are printed in parallel under the control of i control units. The printing process of each heating point is as follows: the heating point selection data STB in the printing heating time control data Di is sent to the trigger end of the counter of the control unit corresponding to the current heating point. If the heating point is not working in the current row task, the counter is not triggered to start, and the preset value of the counter is 0, and the control unit has no output to the current heating point; otherwise, the counter of the control unit is triggered to start by the heating point selection data STB, and with the printing pulse number mi as the preset value, it is driven by the pulse signal input to the counter by the divider to perform countdown. Each count outputs an on-pulse cycle to the corresponding heating point, and the heating point starts to heat up until the countdown is completed, the heating point is turned off, and the current heating point completes printing.

5. The printing method of a thermal printing device according to claim 4, characterized in that: The printing heating time data conversion unit in step 2 generates corresponding grayscale data according to the thermal history control requirements, which means that the grayscale data is corrected according to the thermal history control. Specifically, logical operations are performed based on the N rows before and after the current heating point and the left and right adjacent heating points, and the grayscale value of the current point is corrected according to the operation results to obtain grayscale data with higher accuracy.

6. The printing method of a thermal printing device according to claim 4, characterized in that: The number of print pulses mi corresponding to the current heating point in the print heating time control data Di in step 2 is selected as needed to send 2-bit data to achieve 4-level printing, or to send 3-bit data to achieve 8-level grayscale printing, or to send 4-bit data to achieve 16-level grayscale printing, or 5-bit data to achieve 32-level grayscale printing, or 6-bit data to achieve 54-level grayscale printing, or 7-bit data to achieve 128-level grayscale printing, or 8-bit data to achieve 256-level grayscale printing.

7. The printing method of a thermal printing device according to claim 6, characterized in that: Taking into account that the data corresponding to each hot spot is 2-8 bits of data, multi-bit data is transmitted in the form of a shift register. Under the CLK pulse output by each clock unit, the multi-bit data of the previous point is shifted to the next point, that is, multiple Di are parallel inputs, and each Di data is 2-8 bits. Each bit is transmitted serially between each point. The number of CLK pulses corresponds to the number of hot spots. Taking 8-bit data as an example, the corresponding grayscale is 256 levels. The multi-bit data are the 1st to the 8th bit, and each bit of data is serially transferred from the corresponding bit of the 1st hot spot to the corresponding bit of the 2nd hot spot, until the last hot spot, that is, the 1st bit of data is transmitted from the 1st bit of the 1st point to the 1st bit of the last point, and the 2nd bit is transmitted from the 2nd bit of the 1st point to the 2nd bit of the last point, and so on until the 8th bit.

8. The printing method of a thermal printing device according to claim 4, characterized in that: In step 2, the number of print pulses mi corresponding to the current heating point includes preheating time data and formal heating time data, wherein the preheating time data is based on the thermal response characteristics of the print head, as well as the printing speed and the choice of consumables. The points to be printed are preheated before the formal heating time, the clock unit CLK is started, and 2 to 8 channels of preheating time data are sent. According to the number of hot spots on the print head, the corresponding preheating time data is sent for each line. For each CLK pulse, the shift register in the IC transfers the preheating time data from the previous point to the next point until it reaches the last point.

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