JPH04314554A - Thermal printing device - Google Patents

Abstract

PURPOSE:To permit a constantly satisfactory printing result to be obtained even with the use of any thermal paper. CONSTITUTION:A reading sensor 8 is provided to read out the coloring density of the printing of thermal paper, an optimizing part 14 changes the energy to be applied to the thermal paper via a head control part 6 when an optimizing action takes place and, from the coloring density of the thermal paper detected by the reading sensor 8 at that time, an optimum application energy is obtained and then stored in a data memory 12. The printing is performed according to the optimum application energy stored in the data memory 12. By the further provision of a temperature sensor 16 for detecting ambient temperature, the temperature upon printing is compared with that upon optimizing action and, when the temperature in difference therebetween is not below a predetermined temperature, the optimizing action is automatically repeated or a satisfactory printing can be maintained by changing the temperature through the correction of the optimum application energy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printing device equipped with a thermal head and using thermal paper as recording paper. Thermal printing devices are used, for example, in facsimiles, thermal printers, thermal video printers, and the like.

0002

2. Description of the Related Art Currently, there are many types of thermal printing devices using thermal heads on the market. Furthermore, many types of thermal paper are sold depending on the type of thermal printing device. On the other hand, a user using a thermal printing device using a thermal head must use thermal paper specified for each thermal printing device. This is because the applied energy differs depending on the type of thermal printing device, and the coloring characteristics of thermal paper also vary, so it is only possible to obtain a high-quality print screen if there is compatibility between the thermal head and thermal paper. It is from. Furthermore, even if the specified thermal paper is used, a good quality print screen cannot be obtained when the ambient temperature is extremely high or extremely low.

0003

[Problems to be Solved by the Invention] The present invention provides a method that allows a thermal printing device to determine the optimum energy to be applied to the thermal paper and always obtain good printing results even if any thermal paper is used. The purpose is to

0004

[Means for Solving the Problems] The present invention will be explained with reference to FIG. The present invention prints two prints on thermal paper according to print data.
Thermal head 2 and its head driver 4 perform gradation or multi-gradation printing, and the head driver 4 is operated by determining the applied energy based on a command from the optimization unit 14 or based on the optimum applied energy stored in the data memory 12. a head control unit 6 that performs a printing operation through the thermal paper; a reading sensor 8 that reads the color density of the print on the thermal paper; and a data memory 12 that stores the optimum applied energy.
The optimization unit 14 changes the applied energy to the thermal paper via the head control unit 6, determines the optimum applied energy from the coloring density of the thermal paper at that time by the reading sensor 8, and stores it in the data memory 12. ing.

In order to perform better printing, the present invention further includes a temperature sensor 16 for detecting the ambient temperature, and the optimization section 14 stores the temperature detected by the temperature sensor 16 in the data memory during the optimization operation. 12, and during subsequent operations, the temperature detected by the temperature sensor 6 is taken in and the optimization operation is automatically performed when the difference between the temperature and the temperature stored in the data memory 12 is greater than a predetermined temperature difference. It also has a repeat function.

In order to perform better printing, the present invention further includes a paper sensor 20 for detecting that the thermal paper has been replaced, and when the optimization section 14 receives a signal from the paper sensor 20 indicating that the paper has been replaced, It also has a function that automatically repeats optimization operations. In order to perform better printing, in the present invention, the head control unit 6 also takes in the detection signal of the reading sensor 8 during printing, and stores the data in the data memory 1 so that the color density becomes the optimum value.
It also has a function to perform a printing operation by modifying the energy applied from 2.

In order to perform better printing, the optimization section 14 also has a function of automatically repeating the optimization operation when starting the printing operation after a certain period of time has passed since the optimization operation was performed. We are prepared. In order to simplify the apparatus, if the applied apparatus is a facsimile, the reading sensor 8 can be replaced with a facsimile scanner unit. FIG. 1 also includes an optimization switch 24 for performing optimization operations at any time.

[0008]

[Operation] FIG. 2 shows the difference in color development characteristics depending on the type of thermal paper. A and B represent the color density when the applied energy is changed for different types of thermal paper. Optical density (O.D.
), a value of 1.2 is the density at which humans can clearly recognize the color development of thermal paper, and O. D. value 1.2
The applied energy required to obtain is the minimum required applied energy. In FIG. 2, thermal paper A requires greater applied energy. The optimum applied energy is, for example, O. D. The energy is set to be slightly larger than the applied energy with a value of 1.2.

FIG. 3 shows the difference in color development characteristics due to different ambient temperatures even when the same thermal paper is used. The ambient temperature of Ta is higher than that of Tb. The higher the ambient temperature, the lower the optimal applied energy. Therefore, for example, even if the optimum applied energy is determined and stored in the data memory 12 at the ambient temperature Tb, it is necessary to modify the applied energy to be smaller as the ambient temperature increases.

FIG. 4 shows the difference in color development characteristics depending on the type of thermal paper when performing multi-gradation printing. The horizontal axis represents the applied energy, and depending on the type of thermal paper, the O. D.
Different levels of value. Therefore, depending on the thermal paper, the optimum O. D. The applied energy indicating the level is determined and stored in the data memory 12.

FIG. 5 shows the optimization operation by the optimization section 14. Thermal head 2 while feeding thermal paper
A voltage is applied from the head driver 4 to. At this time, the energy applied every few dots in the direction in which the thermal paper is fed (sub-scanning direction) is changed continuously or stepwise. Changes in the applied energy are made to correspond to the application time, for example, while the voltage is kept constant. While such printing is performed on the thermal paper, the reading sensor 8 reads the optical density of each block printed with the same energy. The color density signal read by the reading sensor 8 is converted into a digital signal by the A/D converter 10 and taken into the optimization section 14, where the O.D. D
．． The applied energy resulting in a level is determined and stored in data memory 12.

The temperature at that time is detected by the temperature sensor 16, and the temperature value is also converted into a digital signal by the A/D converter 18 and stored in the data memory 12. Since the optimization unit 14 obtains the relationship between applied energy and color density as shown in FIG. 2 or 4, the data memory 12 stores the applied energy that gives the optimum color density in two-gradation printing as the optimum applied energy. When performing multi-gradation printing as shown in FIG. 4, the applied energy corresponding to each density level is stored in the data memory 12 as the optimum applied energy for each density level.

The printing operation will be explained with reference to FIG. At the start of the printing operation, the temperature at that time is detected by the temperature sensor 16, the temperature difference from the temperature at the time of the optimization operation stored in the data memory 12 is determined, and the temperature difference is determined as the preset temperature difference ΔT0. If it is larger, optimal printing cannot be performed with the applied energy stored in the data memory 12, so the optimization section 14 automatically repeats the optimization operation.

When the thermal paper is replaced with a new one at the start of printing operation, the paper sensor 2
The optimization unit 14 repeats the optimization operation based on the signal from 0. The optimization switch 24 is a switch for performing an optimization operation at any time, and the optimization operation is repeated even when the switch 24 is pressed. Furthermore, when a certain period of time or more has elapsed since the start of the printing operation from the time of the previous optimization operation, the optimization unit 14 automatically repeats the optimization.

When the conditions for printing with the optimum applied energy stored in the data memory 12 are established, according to the printing data, the optimum applied energy at that time is used for two-tone printing, or for multi-gradation printing. In this case, printing is performed using applied energy according to each gradation level. The color density of the printed thermal paper is read by the reading sensor 8, and it is determined whether it is the optimum printing. If the printing is optimal, the next printing data is taken in and the printing operation is repeated in the same way. if,
If some conditions are different and the printed density is not the optimum density, if the color density is low, the applied energy will be corrected to increase, and if the color density is high, the applied energy will be corrected to decrease. is repeated.

[0016]

Embodiment FIG. 7 shows an embodiment. Thermal paper 4
0 is sent by rubber rollers 36 and 38, and printing is performed while passing between the platen roller 42 and the thermal head 2. The printed color density is read by a reading sensor 8. The head driver 4 that drives the thermal head 2 is controlled by a control circuit section 30 including a CPU. The reading operation of the reading sensor 8 is also controlled by the control circuit section 30, and the read signal is converted into a digital signal by the A/D converter 10 and taken into the control circuit section 30. The thermal head 2 is provided with a thermistor 44 that detects the temperature of the thermal head itself, and the detection signal of the thermistor 44 is converted into a digital signal by an A/D converter 46 and taken into the control circuit section 30, and then The temperature of is also used as data to determine the optimal applied energy. A rubber roller 36 for feeding the thermal paper 40 is driven by a motor 34, and the motor 34 is driven by a motor driver 32. The motor driver 32 is also controlled by the control circuit section 30.

A detection signal from the paper sensor 20 that detects that the thermal paper 44 has been replaced is taken into the control circuit section 30 via the A/D converter 22. The data memory 12 is, for example, a RAM, and is connected to the control circuit section 30. A thermistor 16 for measuring ambient temperature is further connected to the control circuit section 30 via an A/D converter 18, and a switch 24 for starting an optimization operation is also connected. In relation to FIG. 1, the head control section 6 and optimization section 14 are realized by a control circuit section 30.

When performing the optimization operation, the head driver 4
, the paper feed motor 34, the motor driver 32, the reading sensor 8, etc. are all controlled by the control circuit section 30, so the block of print being read by the reading sensor 8,
The value of the applied energy in that block is determined by the control circuit section 30.
The relationship between applied energy and color density has been determined by the control circuit section 30.

[0019]

[Effects of the Invention] In the present invention, the relationship between the color development characteristics of the thermal paper and the applied energy is checked on the thermal printing device side, and printing is performed with the optimum applied energy for the thermal paper, so that two-gradation printing is possible. It is possible to print with good image quality on thermal papers with various coloring characteristics, regardless of the type of thermal paper, regardless of the type of thermal paper, realizing a so-called paper-free thermal printing device. be able to. If a temperature sensor is installed to measure the ambient temperature and the optimization operation is automatically repeated when the ambient temperature changes drastically, the optimization conditions can be set automatically regardless of changes in the ambient temperature. Good printing results. If the optimization operation is automatically repeated when the thermal paper is replaced, the user does not need to make any adjustments even if any thermal paper is used.

[0020] If the color density is always corrected during printing so that it is at the optimum value, good printing can be maintained even if the conditions change due to heat accumulation during printing in the thermal head. . The environment may change over time, so if the optimization operation is automatically repeated after a certain period of time, it is possible to respond to such changes in the environment. When the present invention is applied to a facsimile machine, the present invention can be realized at low cost by replacing the reading sensor with a scanner unit.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the present invention.

FIG. 2 is a diagram showing the color density characteristics of thermal paper during two-tone printing.

FIG. 3 is a diagram showing color density characteristics due to temperature differences.

FIG. 4 is a diagram illustrating differences in color development characteristics between thermal papers during multi-gradation printing.

FIG. 5 is a flowchart diagram showing an optimization operation.

FIG. 6 is a flowchart showing a printing operation.

FIG. 7 is a block diagram showing one embodiment.

[Explanation of symbols]

2 Thermal head 6 Head control section 8 Read sensor 12 Data memory 14 Optimization section 16 Temperature sensor 20 Paper sensor 24 Optimization switch 30 Control circuit section 40 Thermal paper

Claims (6)

[Claims] Claim 1: A thermal head and its head driver that perform two-tone or multi-tone printing on thermal paper according to print data, and an optimal applied energy stored in a data memory or according to a command from an optimization section described later. a head control unit that determines the applied energy and performs a printing operation via the head driver; a reading sensor that reads the color density of the print on the thermal paper; a data memory that stores the optimum applied energy; an optimization unit that changes the energy applied to the thermal paper through the thermal paper, determines the optimum applied energy from the coloring density of the thermal paper at that time determined by the reading sensor, and stores the optimum applied energy in the data memory. 2. Further comprising a temperature sensor that detects ambient temperature, the optimization unit also stores the temperature detected by the temperature sensor in a data memory during the optimization operation,
The claim further includes a function of capturing the temperature detected by the temperature sensor during subsequent operation and automatically repeating the optimization operation when the difference between the temperature and the temperature stored in the data memory is equal to or greater than a predetermined temperature difference. Item 1. The thermal printing device according to item 1. 3. The method further comprises a paper sensor for detecting that the thermal paper has been replaced, and the optimization section also has a function of automatically repeating the optimization operation when receiving a signal indicating paper replacement from the paper sensor. Item 1. The thermal printing device according to item 1. 4. The head control unit also has a function of capturing the detection signal of the reading sensor during printing, and performing a printing operation by modifying the energy applied from the data memory so that the color density becomes an optimum value. Claim 1 comprising
The thermal printing device described in . 5. The thermal printing device according to claim 1, wherein the optimization section also has a function of automatically repeating the optimization operation when starting the printing operation after a certain period of time has passed since the optimization operation was performed. . 6. The thermal printing device according to claim 1, wherein the applied device is a facsimile, and the reading sensor is replaced by a scanner unit of the facsimile.