JPS63185657A - thermal printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a serial type thermal printer, and is particularly aimed at improving the printing quality thereof.

[Prior art]

Conventionally, in thermal printers, in order to prevent print quality from deteriorating due to heat accumulation during continuous use of the thermal head,
Various methods have been used, including the
5-48651, a method of determining the energization time by storing the previous data for each dot, and
A method such as No. 07 in which the energization time is changed depending on the driving cycle is used. As another method, which is generally referred to as a history control method, a method has been used in which the temperature of the surface of the thermal head is detected to determine the energy applied to the head.

[Problem that the invention seeks to solve]

These conventional examples are insufficient for serial type thermal heads, and it is impossible to actually suppress heat accumulation in the thermal head.

This is because in the history control method, even if the applied energy is determined while checking the history of each heat generating element, there is still heat diffusion to adjacent heat generating elements, and the status of all these heat generating elements is processed only by calculation. The conventional method of doing so was unreasonable. Furthermore, in a serial type thermal head that requires high speed, such complicated processing reduces the processing time and reduces the high speed.

Furthermore, the method of detecting the temperature on the surface of the thermal head using a heat-sensitive element has little effect on the -th line in serial printers due to the detection time delay from the heat-generating element. there were.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these problems of the prior art and provide a serial type thermal printer that is high speed and has excellent printing quality.

[Means to solve the problem]

The thermal printer of the present invention includes a base material made of ceramics on which a plurality of (n) heat generating elements are arranged;
The thermal head has a glass glaze part that raises a part of the base material to protrude a heat generating element, and a thermal head that is placed in contact with a part of the back surface of the base material on the opposite side of the glass glaze part. , further includes an energization width control circuit that determines a reference energization time to the heat generating element by the heat sensitive element, and a current flow width control circuit that determines the driving history of the heat generating element to a maximum of one basic character (m dot rows for a character in a matrix of nXm dots). [Embodiment] The present invention is characterized in that it includes a storage means for storing print data, and a part of the reference energization time is stopped to reduce the energization energy to the heat generating element based on the storage result of the storage means. FIG. 1 is a schematic diagram showing the configuration of a thermal head portion according to the present invention, in which (α) is a perspective view and (A) is a cross-sectional view, 1 is a base material made of ceramics, 2 is a part of the base material protruding from the base material, and FIG. 5 is a heat generating element; 4 is a flexible substrate on which an electrode 7 of the heat generating element is arranged; 5 is a thermistor which is a type of heat sensitive element disposed in contact with the back surface of the base material on the opposite side of the glass glaze part; 6 is thermistor 5
It is a resin agent that prevents contact between the glass glaze portion 2 and the air, and allows the temperature in the immediate vicinity of the glass glaze portion 2 to be accurately detected. A heat dissipation member may be further installed on the back side.

[Effect]

FIG. 2 (α>, (b), and (c) are explanatory diagrams showing differences in temperature detection characteristics due to differences in the installation location of the thermistor placed in contact with the thermal head.

FIG. 2(α) shows a circuit for checking a change in resistance value of a thermistor by a change in voltage, and 11 is a fixed resistor that is not affected by temperature, and 12 is a thermistor.

FIG. 2(b) shows the mounting position of the thermistor in the conventional example, and the thermistor 5 is installed on the surface of the thermal head 100. S is a heat generating element.

FIG. 2(c) shows the difference in the resistance value change of the thermistor between the thermal head according to the present invention shown in FIG. 1 and the conventional example, where the horizontal axis represents time and the vertical axis represents the voltage at the check terminal. I'm taking it. To is the time during which the same application pulse for printing is applied to the thermal head, and Tf is the rest time. 1
3 is a characteristic curve in the conventional example, and even after the energization pulse ends, the temperature of the thermistor further increases, and the delay time rwitd1 at that time reaches nearly 15 seconds. 14 shows a characteristic curve in the present invention. Since the influence of the outside temperature is small, the temperature near the heat generating element can be well detected, and the detection delay time td is approximately S Oms.

For this reason, conventionally, when printing continuously, the effect of a thermal element such as a thermistor was hardly visible on the first line, but with the thermal head used in the present invention, the response delay is extremely small, so the effect of a thermal element such as a thermistor is minimal from the first line. It is possible to use

However, due to the influence of heat accumulation on the glass glaze installed on the surface of the thermal head, the time required for heat conduction to the back surface, etc., there is a slight delay in response. The glass glaze portion was installed for responsiveness to paper, and instead of serving to rapidly raise the temperature of the heating element locally, it has a heat storage effect. For this reason, if the same heating element is continuously energized, the temperature on the surface of the glass glaze increases before the thermistor can detect it, causing a trailing phenomenon, disturbing the dot shape, and degrading print quality.

Conventional thermal printers using thermistors have been left with such problems.

In the present invention, in addition to detecting the temperature of the base material of the thermal head, in order to compensate for the temperature rise in the glass glaze part, the energization pulse width is varied based on the drive history of the heat generating element that has already been driven. method is used.

The correction based on the drive history is sufficient for a maximum of one basic character.For example, if the number is n dots vertically by m dots horizontally, it is sufficient to prepare a storage means for storing the number of minutes of m dots.

FIG. 5 shows an embodiment of the energization width control circuit for determining the reference energization time in the present invention, and the same parts as in FIG. 1 are designated by the same numbers.

34 is a thermistor, 33 is a variable resistor, 35 is a resistor, 31 is a capacitor, 32 is a transistor that instantaneously discharges the capacitor 31, 37 is a comparison circuit that turns on and off according to the charge level of the capacitor 31, and 36 is a charging circuit. Reference voltage Zener diode for determining the level; 58 is an inverter; 40 is a driver in which the power supply transistor to the heating element 2 is converted into a 10; 39 is a switching transistor that turns on and off the power supply terminal of the driver; 41 is a CPU. ing.

When trigger input Tg is applied to N terminal, thermistor 3
Charging of the capacitor 31 is started via the resistor circuit including 4. When a predetermined charge level is reached, a pulse with a pulse width TV is output from the output terminal OUT of the comparison circuit 37. This pulse width can be set to be appropriate for the temperature of the thermal head at that time, depending on the characteristics of the thermistor that detects the temperature of the thermal head. Since this output is directly used as the reference energization time for thermal power, it is possible to supply appropriate printing energy to the heat generating element 2 by turning on and off the power supply terminal of the driver.

FIG. 4 is a schematic block diagram showing the configuration of an embodiment of a thermal printer according to the present invention. Components that are the same as those in FIGS. 1 and 5 are designated by the same numbers and their explanations will be omitted. Reference numeral 30 is the energization width control circuit shown in FIG. This is a circuit that obtains the maximum current-carrying time. 42 is the third buffer, 43 is the second buffer, 44 is the first buffer, 45 is the CPU 41
50 is a RAM containing storage means for storing the drive history of the heat generating elements; 51 is next print data; 52 is previous past print data; indicate the registers that store the two previous past print data.

[Effect]

FIG. 5 is an explanatory diagram showing the operation of the present invention, which will be described in detail below.

Reference numeral 54 indicates each data stored in the storage means, and indicates a case where the number of heat generating elements is n=8. The drive history of each dot is represented by 1 or 0, with 1 indicating on and 0 indicating off.

Reference numeral 61 indicates the energization waveform of the first dot, and the shaded area indicates the rest period. to is the energization timing two times before, t,
indicates the previous energization timing, and t indicates the next energization timing.

Similarly, 62 indicates the third dot, and 63 indicates the fifth dot. 64 shows a detailed diagram of the energizing pulse, r,
is the start position timing of energization, which is the timing at which the data of the first buffer 44 is sent to the head driver,
r and 's are the timings for sending out the second buffer and the third buffer, respectively. e T4 indicates the end of the energization time determined by the energization width control circuit 30.

TIpTl+Tm indicates each energization period, and in the embodiment shown in FIG. 5, it is T1)T.

As shown in 61.65, when the previously driven dots are continuously energized, the current is applied for one section less, and when the current continues further, T! The interval is also reduced to T.

is applied only. Also, as shown in 62, if there is a one-dot pause in between, T! The interval is reduced.

In other words, the T7 section is made to correspond to the driving result of the two previous pasts, the 8 sections are made to correspond to the previous past, and if it was being driven, 1 section is combined with 1 section to create a rest section. Install.

In this way, the energization time after 2 consecutive dots is T3. The energization time after 1 dot is on is Tt + T. 3.2 dots before is on and 1 dot before is off is T.

10T, and the relationship is Ts <Tt + Ts <
By setting T and +T, it is possible to perform control that matches the temperature state of the heat generating element at that time, and it is possible to sufficiently improve the printing quality in a minute section in - line printing.

46 indicates the next energization data at each timing, and sequentially from the first buffer at a predetermined timing rl+
r! The data sent at +rS are shown respectively. A latch circuit or a shift register is generally used for the first to third buffers, but they can also be built into RAM, and the CPU only needs to sequentially read data from the RAM at a predetermined timing and send the data to the head driver.

As described above, r is the end of the energization pulse determined by the energization width control circuit 30. This energization width control circuit 30 accurately detects the temperature of the thermal head, which gradually rises even with the driving method based on the history described above, determines the reference energization time, further prevents heat generation, and is useful for improving printing quality. is set up.

Although the energization width control circuit is shown as a pulse generation circuit including a thermistor in this embodiment, it may also be a timer circuit built into the CPU or a delay time generation means using software.

In this embodiment, a method is described in which the thermal history is stored up to two dot rows ago, but the number can be increased to three dot rows and four dot rows, and the pause time can be changed to three or four types correspondingly. The effect is even more significant by increasing the number of data transmissions to four or five times. However, there is a limit depending on the printing speed and cptt processing time, and for normal characters and nXm dot matrix characters, it is possible to fully demonstrate the effect within m dot rows. As shown in Figure 1, the thermistor placed in contact with the paste substrate immediately after the glass glaze area where the heating element is located detects the immediate temperature of the glass glaze area extremely accurately and quickly, and the thermal head This is to provide feedback to the applied energy.

〔Effect of the invention〕

According to the present invention, it is possible to prevent print quality from deteriorating due to heat accumulation in a thermal head in a serial thermal printer, and to provide extremely good print quality.

This is extremely useful because it prevents heat accumulation in the thermal head, which is a drawback of conventional printing control methods based only on history control, and also solves the uneven printing caused by thermistor-based printing control methods.

In addition, by setting a pause section corresponding to the past drive point, there is no need to create a energization time corresponding to the number of cases in the past drive itM history, and with two types of pause sections, 2X
2 = 4 cases, 5 types of pause sections, 2X2
As in the case of X2=8, it is possible to configure a large number of energizing times in an extremely simple manner. The influence of heat accumulation due to past driving becomes smaller as you go back in time, so this pause time can be made smaller as the time goes further into the past.

Furthermore, since the appropriate applied energy required for printing is always supplied to the heating element, power consumption is saved and
The ripple effects are significant, such as making it possible to significantly extend the life of the thermal head.

[Brief explanation of the drawing]

FIGS. 1(α) and 1(A) are schematic diagrams showing the structure of a thermal head portion according to the present invention. 1...Base substrate 3...Heating element 5...Heat-sensitive element Fig. 2 (α), (b), (c) is placed in contact with the thermal head FIG. 3 is an explanatory diagram showing differences in temperature detection characteristics due to differences in the installation locations of thermistors. FIG. 3 is an explanatory diagram showing an embodiment of the energization width control circuit that determines the reference energization time in the present invention. FIG. 4 is a block diagram of an embodiment of a thermal printer according to the present invention. 10... Thermal head 30... Energization width control circuit 50... Storage means FIG. 5 is an explanatory diagram showing the operation of the present invention. Part 1 (α) Thermistors in line at home! (C) Second cause Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) It has a plurality of heat generating elements, and uses thermal paper or transfer film to move characters, symbols, etc. relative to plain paper.
Alternatively, it is a serial type thermal printer that prints image data, and has a storage means for storing drive data for the heat generating element for at least two previous times, and based on this result, the energy to be applied to the heat generating element is determined next time. In a thermal printer such as a thermal printer that controls the heat generating element, there is provided an energization width control circuit that determines a reference energization time to the heat generating element, and a rest period for reducing the next energization time based on the memorized result within the reference energization time. 1. A thermal printer, characterized in that the thermal printer has a control means installed therein, and the pause section is installed in correspondence with each of the stored past driving times.